(Topic ID: 160312)

Replacement caps for AFM Strobe Board?


By ForceFlow

3 years ago



Topic Stats

  • 57 posts
  • 18 Pinsiders participating
  • Latest reply 3 years ago by BowlingJim
  • Topic is favorited by 17 Pinsiders

You

Linked Games

Topic Gallery

There have been 20 images uploaded to this topic. (View topic image gallery).

P1010002.JPG
7._Complete_back_(resized).JPG
6._Complete_Front_(resized).JPG
5._cap_&_diodes_soldered_(resized).JPG
4a._Attaching_Diode_to_Cap_leads_(resized).JPG
4b._connection_closeup_(resized).JPG
3._Diodes_Marked_(resized).JPG
2._Caps_Removed_(resized).JPG
1d._bulging_C1_(resized).JPG
1c._Original_Back_(resized).JPG
1b._Original_Top_2_(resized).JPG
1a._Original_Top_(resized).JPG
Caps-appguide.pdf (PDF preview)
caps_(resized).jpg
AFM_Plate_&_Repro_PCB_(resized).jpg
Power-On_and_Power-Off.png

There are 57 posts in this topic. You are on page 1 of 2.
#1 3 years ago

I was going to help someone with their AFM, and it sounds like one problem area on it is that the strobe isn't flashing. Since the game is unshopped, it seems like a problem area would be the 100uf 100v non-polarized caps on the strobe board.

Since I would prefer to repair it just once and not have the 100uf 100v caps fail again because of the 140v being thrown at them, is there a go-to option for replacement? I seem to be having trouble finding non-polarized caps that are more than 100v.

I did see this article where two polarized filter caps are tied together, and the traces on the board tied together: http://kcpins.com/archives/63 I wasn't sure if that was basically the only option or not.

#2 3 years ago

great plains electronics
axial
https://www.greatplainselectronics.com/proddetail.asp?prod=CEA-100uF-100V-RMD

radial
https://www.greatplainselectronics.com/proddetail.asp?prod=CER-100uF-100V

edit:
doh! just re-read your post about not wanting to use 100uf - 100v caps

#3 3 years ago

axial 100uf - 160v
https://www.greatplainselectronics.com/proddetail.asp?prod=CEA-100uF-160V-RMD

dammit! these are polarized

have you thought to give ed a call and ask him?

#4 3 years ago
Quoted from j_m_:

edit:
doh! just re-read your post about not wanting to use 100uf - 100v caps

Right, they're probably just going to fail again at some point in the future since the caps are underrated for what they are actually used for. I'd like to try to bulletproof it.

Quoted from j_m_:

have you thought to give ed a call and ask him?

I imagine someone around here has replaced them already, so no need to reinvent the wheel if it's already been done. I may contact Ed later if nothing pops up in this thread--he's just a busy guy and I'd hate to bother him too much if I didn't have to

#5 3 years ago

You can use two 200uF 250v polar caps in series. connect the terminals + - - + or - + + -. The end result is a 100uF bipolar cap, im not sure if extra ceiling on the voltage rating is needed in that setup. The capacitance is halved though.

#6 3 years ago

Not sure how physically big this is, but this should work well.

amazon.com link »

Need to check the caps on mine!

#7 3 years ago

Even better - $3.19 with free shipping:

amazon.com link »

#8 3 years ago

I have been asked several times regarding this cap and have not had luck finding them.

I have seen lots of posts regarding the back to back caps and there is a lot that can happen if you don't do this right (yes, there is a lot of room for human error in this one especially in the future when somebody else looks at this solution and "simplifies" it). I have decided not to suggest that one. But it does seem that as long as you go much higher in voltage with the replacements (as barakandI said) then this seems to work ok. It is somewhat space limited which makes it difficult to fit in even more caps.

I am working on a large capacitor order right now. I'll see if they still make axial non-polarized caps (not many companies make any axials anylonger). If they are available, will probably add in some 100uF, 160V caps. I do know they make these in radial style so we may need to go there.

Can you take a quick measurement of lead spacing for the C1/C2 caps so I can determine the max length? And measure C3/C4 if you can.

Ed

#10 3 years ago

Yeah, I see they have the enhanced strobe board back in stock. At $35 it really is a no brainer. Built to last and the strobe is much brighter.

#11 3 years ago
Quoted from G-P-E:

Can you take a quick measurement of lead spacing for the C1/C2 caps so I can determine the max length? And measure C3/C4 if you can.

Sorry, I don't have access to it any more until another day. Finished fixing what I could and got it flipping again, minus the strobe.

#12 3 years ago

I had pinbits rebuild my AFM strobe board. Works great and I know they changed some parts so it won't fail again. You might want to check with Martin.

1 week later
#14 3 years ago

OK, I have some really good news for us AFM owners: You can repair/rebuild your strobe board with normal, inexpensive electrolytic capacitors instead of impossible-to-find non-polarized caps. Each 100uF/100V NP capacitor can be replaced by a commodity 100uF/250V capacitor and a 1N4004 diode.

Here's the link to the how-to: https://pinside.com/pinball/forum/topic/replace-caps-on-afm-strobe-board#post-3184588

The rest of this post is background on this modification and proof-that-this-is-not-a-crazy-thing-to-do:

We know there was a big mistake in the original design: C1 is rated at 100V, but C1 sees about 145V in normal operation. But there was another "mistake" (really more a missed opportunity) in the design that will eliminate the need for these impossible-to-find non-polarized caps.

The problematic circuit is this:
Original Schematic

C1-C4 and D1-D4 form what is known as a "voltage doubler" (in this case a voltage quadrupler since they employ the technique twice in series). This circuit takes the 50Vac input and turns it into about 290Vdc. I'm not going to explain how voltage doublers work, but there's plenty of info here: http://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/voltage-multipliers/ and on google.

Here's a simulation of that circuit (ignore diodes D5 and D6 for now):
Simulation of voltage quadrupler

I believe the designer of the original circuit used non-polarized capacitors because it seemed like the right thing to do in a doubler, particularly if you don't fully think-through the design. In the original design, C2 does need to be NP, because when the circuit is starting up (when power is first applied) the voltage across C2 (which is the voltage at point B minus the voltage at point A, or "V(b)-V(a)", the gray trace) does go to -30V before it goes positive and settles at about +70V:
Startup of original design

But note that except for the bottom of the first 60Hz (or 50Hz) cycle, the voltage across C2 is always positive. That means we could use a normal, polarized electrolytic capacitor for C2 if only we could get rid of that one-time -30V dip. Well it turns out that's not going to be hard to do. If we put a diode (D5) across C2 as shown, it will allow as much positive voltage as we need, but will clamp any negative voltage to about -0.7V. And -0.7V for 1/60th of a second every time you power on your AFM is not going to hurt a polarized cap (electrolytic caps are designed to withstand -1V to -1.5V specifically so they can be protected by a diode).

Here's the simulation with the diode:
Startup with Schottky diode clamp

I put a diode across C1 as well (D6), but it's really not necessary because the way the circuit works, C1 will always be positively charged.

When you're analyzing circuits with large capacitors, it's important to see what happens when you turn OFF the power as well, because unexpected things can happen. Fortunately in this circuit, everything just gradually discharges to 0V:
Power-On and Power-Off

So my recommendation is to replace C1 and C2 with 100uF / 250V polarized capacitors, add D5 (and D6 if you want), and enjoy a very robust Strobe Board.

Here's a good cap choice:
http://www.newark.com/illinois-capacitor/107tta250m/aluminum-electrolytic-capacitor/dp/28M9179

Use a standard 1N4004 diode for D5 and D6.

Hope this helps. If there are any questions let me know and I'll answer/update the post.

#15 3 years ago
Quoted from yonkiman:

If there are any questions let me know and I'll answer/update the post.

Sure...I've got a question.

WTF does this all mean? My head hurts.

So this is the reason the Pinbits strobe doesn't work without strobe board modifications?

#16 3 years ago

SPICE for simulator? Looks like a much different version than what I last used.
I saw the negative on C2 originally but never even considered putting a shunting diode across him to take care of the negative voltage. Excellent post, Would be nice to somehow work this into pinwiki.

#17 3 years ago
Quoted from G-P-E:

I saw the negative on C2 originally but never even considered putting a shunting diode across him to take care of the negative voltage.

#18 3 years ago

To simplify what he said:
For both C1, C2 caps -- use 100uF, 200V axial electroltyic caps. Could also use 100uF, 160V caps but that is cutting it close.
In order to use these more common caps - you need to protect capacitor C2. Install a protection diode directly across C2. Anode of diode to negative lead of C2, Cathode (banded end) of diode to positive lead of C2. SB140 is a good choice.

#19 3 years ago

I couldn't have said it better myself!

I don't have time right now but will work on the TL;DR summary soon.

#20 3 years ago
Quoted from G-P-E:

SPICE for simulator? Looks like a much different version than what I last used.
I saw the negative on C2 originally but never even considered putting a shunting diode across him to take care of the negative voltage. Excellent post, Would be nice to somehow work this into pinwiki.

Yep - ltspice. http://www.linear.com/designtools/software/ Free and fairly easy to use. I believe it's really nice on Windows - the Mac version I used has a very painful GUI (you can memorize all the keyboard shortcuts to avoid).

Is pinwiki editable by anyone? I'll try to clean up the explanation here first...

#21 3 years ago
Quoted from beelzeboob:

Sure...I've got a question.
WTF does this all mean? My head hurts.
So this is the reason the Pinbits strobe doesn't work without strobe board modifications?

Yeah, I'm not an engineer either. I'll have to read through it more carefully to fully understand it. Nevertheless, I cetainly fully appreciate the initiative, time, and effort yonkiman put into coming up with a possible solution

However, like I mentioned in your other thread beelze, a common cause of the strobe not working is bulging caps. You'd have to inspect them to determine that.

#22 3 years ago

Or just send it to Martin at Pinbits - he will fix it with better Caps that will improve the board and he doesn't charge much money. It made a world of difference in mine. My strobe was still working but it wasn't flashing very much before I sent it to him.

#23 3 years ago

Can anyone post or send me a highish-res photo of both the front and the back of the strobe board? That would speed up my how-to write-up (I won't have to pull mine from my machine).

#24 3 years ago
Quoted from ForceFlow:

Yeah, I'm not an engineer either. I'll have to read through it more carefully to fully understand it. Nevertheless, I cetainly fully appreciate the initiative, time, and effort yonkiman put into coming up with a possible solution
However, like I mentioned in your other thread beelze, a common cause of the strobe not working is bulging caps. You'd have to inspect them to determine that.

I haven't had a chance to get back there and look at it...and I'm leaving on a trip Thursday. I have a laundry list of post-restoration things to tweak, and I've decided (for the time being) to just ignore it all and make the wife happy with yard work. That AFM was one problem away from fueling a dumpster fire, so I needed a break. Worst part of a restoration is the troubleshooting, IMO.

#25 3 years ago

Two caps "back to back" work perfectly well. I did a lot of research when making these replacement boards and found a very good article by a capacitor manufacturer that basically said it is a valid way to use polarised electros *OF THE SAME VALUES AND VOLTAGE RATINGS*.

It has already been mentioned that, connected in series you HALVE the value of capacitance but ADD the voltage. In the case of the board we make below, we use 220mfd @ 250V so, with two in series, we end up with 110mfd @ 500V.

AFM_Plate_&_Repro_PCB_(resized).jpg

#26 3 years ago
Quoted from Homepin:

Two caps "back to back" work perfectly well. I did a lot of research when making these replacement boards and found a very good article by a capacitor manufacturer that basically said it is a valid way to use polarised electros *OF THE SAME VALUES AND VOLTAGE RATINGS*.

No question, two caps back-to-back can work.

It has already been mentioned that, connected in series you HALVE the value of capacitance but ADD the voltage. In the case of the board we make below, we use 220mfd @ 250V so, with two in series, we end up with 110mfd @ 500V.

Agree on the halving of the capacitance, but not on the doubling of the voltage. Look at it this way: if you had two 250V caps back-to-back in series and you put 500V across the string, you could have 250V across each cap (in which case one cap would have +250V across its + to - terminals, but the other would have +250V across its *-* to *+* terminals, which is verbotten), or you could have +500V across one cap and 0V across the other (to prevent reverse biasing the cap), but then you'd obviously be exceeding the max 250V spec of the cap.

Adding voltages works when they are non-polarized caps (and can therefore split the voltage evenly), but not for polarized. At best you'll end up with a 110uF @ 250V cap.

#27 3 years ago
Quoted from yonkiman:

No question, two caps back-to-back can work.

Agree on the halving of the capacitance, but not on the doubling of the voltage. Look at it this way: if you had two 250V caps back-to-back in series and you put 500V across the string, you could have 250V across each cap (in which case one cap would have +250V across its + to - terminals, but the other would have +250V across its *-* to *+* terminals, which is verbotten), or you could have +500V across one cap and 0V across the other (to prevent reverse biasing the cap), but then you'd obviously be exceeding the max 250V spec of the cap.
Adding voltages works when they are non-polarized caps (and can therefore split the voltage evenly), but not for polarized. At best you'll end up with a 110uF @ 250V cap.

You are partially correct. One cap will have the full voltage BUT only at the moment of power application in an AC circuit (50/60hz). In any case, the caps we use at 250V are each more than double the originals at 100V. See the attached info from the cap manufacturer, a short excerpt is also here:

caps_(resized).jpg
Caps-appguide.pdf

#28 3 years ago

I've had Mikes's (Homepin) strobe and strobe board in my AFM since building it in 2014. Works great!
https://pinside.com/pinball/forum/topic/theres-one-more-afm
http://www.johns-arcade.com/#!product-page/c1cs/6e4d3d6a-895c-fa32-47aa-42170ddb50b9
Wally

#29 3 years ago
Quoted from Homepin:

You are partially correct.

What was I partially incorrect about? My only point was that a 250V electrolytic cap back-to-back with another 250V cap doesn't give you a 500V cap - it becomes a non-polarized 250V cap. I guess you could argue that it's 500Vp-p, but that's not how max capacitor voltages are spec'd.

In any case, the caps we use at 250V are each more than double the originals at 100V.

I agree. Though I'd rather use silicon diodes to control the current flow than rely on the characteristics of a reverse-biased electrolytic. If I *was* using the two caps back-to-back solution, I'd still put a 1N4004 across each cap to guarantee no reverse biasing and have a high-current path that doesn't go through a reverse-biased capacitor.

If you break it down, the back-to-back solution only ever (except for the bottom of the first 50/60Hz cycle on C2) uses 1 of the 2 caps used to form C1 and/or C2. The other capacitor in each pair is basically just acting as a diode, as well as cutting the total capacitance in half. The back-to-back solution apparently works, but it's certainly not as good from a cost, physical size, and design elegance perspective as this new modified design. I suspect the modified design (by not using electrolytic caps as diodes) is additionally also more reliable as the caps age over time, but I don't know enough about reverse-biased electrolytics to know for sure.

I'm not saying anyone should worry about their boards if they are currently working. But if you're repairing/restoring a board you might want to consider this modified design.

#30 3 years ago
Quoted from yonkiman:

What was I partially incorrect about?

If you read the application notes I attached they describe the resultant max voltage of the back to back pair as equal to one of the caps BUT only for the first half cycle - after that the total voltage is much higher than a single cap although not the sum of the two.

We are nitpicking anyway as the application notes clearly suggest that it is a perfectly sound method of creating a non polarised part and that is the point I was making.

#31 3 years ago
Quoted from Homepin:

If you read the application notes I attached they describe the resultant max voltage of the back to back pair as equal to one of the caps BUT only for the first half cycle - after that the total voltage is much higher than a single cap although not the sum of the two.

I just reread both notes for the fourth time and still can't find anything mentioning the total voltage being any higher than that of one cap. But I may have a blind spot - can you quote just the part where they say that? The closest I can find is:

Article #1: "When voltage is applied, the correct polarity capacitor gets the full voltage." That's exactly what I've been saying: with one polarity voltage, the cap in the "right" direction gets the full voltage (250V max in our example), then when the polarity is reversed, the voltage across that cap goes to zero (actually more like -1V) and the max of 250V is applied to the other (now the correctly-biased) capacitor. At no point do you ever get more than 251V across the two capacitors (the additional 1V comes from the reverse biased cap acting as a diode).

Article #2: the closest I can find to a relevant passage here is the exact same sentence that's in article #1: "When voltage is applied, the correct polarity capacitor gets the full voltage." (Almost makes me wonder if there's a little plagiarism going on.). Again, the "full voltage" is the max voltage of one capacitor, and it applies not only for the first half cycle but for any amount of time the voltage is that polarity.

BTW, what the last sentence of article #1 is saying is that the only reason the back-to-back capacitors don't overheat and explode in our AFM application is because they are seeing DC most of the time - one is always reverse-biased and acting like a diode, and the other just sees a large DC voltage. They only see any AC during startup, before they settle to their DC values, and after the strobe fires, where the voltage across C3 and C4 is depleted causing the C1/C2 voltage doubler to have to supply current again to charge them up. The modified circuit I'm proposing never subjects the capacitors to any of the excess heating and corresponding short life the article mentions, which is one of the reasons I consider it a better design.

We are nitpicking anyway as the application notes clearly suggest that it is a perfectly sound method of creating a non polarised part and that is the point I was making.

Sorry if I seem nitpicky - I just genuinely want to understand your point because if what you're saying is correct, it contradicts a lot of what I know about electronics/physics/mathematics and I'd like to correct my understanding if it's wrong.

#32 3 years ago
Quoted from beelzeboob:

So this is the reason the Pinbits strobe doesn't work without strobe board modifications?

This is just not true. I bought the Pinbits enhanced strobe(the small board with the u-shaped tube) and it has worked perfectly with my stock strobe driver board. Zero problems and much brighter than the original board.

#33 3 years ago

Thanks for the clarification. I was just under the impression that more than a few people were having problems getting it to work without strobe board modifications.

#34 3 years ago
Quoted from beelzeboob:

Thanks for the clarification. I was just under the impression that more than a few people were having problems getting it to work without strobe board modifications.

I have restored two afm's using pinbits enhanced strobe with original board combo with zero issues. That's why I though you may have crossed up the plugs. If it was working before, it in theory should have worked after.

#35 3 years ago

Okay...haven't spent any time looking into it. Waiting for my Pinbits shipment and trying to keep wifey happy with some yard work in the interim. I'll report back here and on my restoration thread when I find out what my issue was. (But I'm leaving tomorrow on a trip, too!)

#36 3 years ago
Quoted from ForceFlow:

I did see this article where two polarized filter caps are tied together, and the traces on the board tied together: http://kcpins.com/archives/63 I wasn't sure if that was basically the only option or not.

Not going to argue about theory, just report my experience. You've linked to my site, I've done the modification I detailed on three different AFM strobe boards. Two of the games have been on location, turned on 12+ hours a day. One is on location now. The method I detailed works fine and is still working.

Nice to know adding a diode is also an easy solution.

11
#37 3 years ago

OK, here's the *practical* how-to guide to replacing the NP (Non-Polarized) 100uF caps on your AFM strobe board with readily-available Polarized 100uF/250V electrolytics.

- Order 2 (or 4) 100uF/250V axial capacitors. You probably only really need replacements for the 2 NP caps, but I replaced all 4 since the game's 20 years old and I don't want to have to go back in the strobe box anytime soon. I bought these: https://www.digikey.com/product-detail/en/illinois-capacitor/107TTA250M/1572-1310-ND/5410816, but any 100uF/250V axial cap from a reputable manufacturer should work fine. Also you'll need two 1N4004 diodes (https://www.digikey.com/product-detail/en/fairchild-semiconductor/1N4004/1N4004FSCT-ND/1626118 if you don't already have them on hand.

- Make sure your AFM is powered off. The high voltages in the strobe board will discharge in less than a minute after it's turned off.

- Remove the board from your AFM. Remove the cover around the board first (4 corner screws), unplug the connectors from either side of the board, then unscrew the remaining screws (2 on top and 1 on the bottom) to remove the PCB and the backing plate.

- You should now have this on your workbench (minus the cable that I left on for a few photos):
1a._Original_Top_(resized).JPG

- Pry the PCB off of the backing board by twisting a large flathead screwdriver against each mounting pin between the backing plate and the PCB so that all the pressure on the PCB is applied right next to the mounting post. If there is any distance between the mounting post and the pressure on the PCB, you could damage the PCB. Put the backing board aside. Now we're here (front and back):
1b._Original_Top_2_(resized).JPG
1c._Original_Back_(resized).JPG

- If you look carefully, your C1 may also be bulging from being overstressed:
1d._bulging_C1_(resized).JPG

- Next, desolder C1 and C2 (and C3 and C4 if you're replacing all 4 caps):
2._Caps_Removed_(resized).JPG

C3 and C4 have "+" marks to identify the positive side of the capacitor. C1 and C2 do not, because the caps were non-polarized. Since we're converting to polarized, we should add "+" marks, and since we're also adding a diode to each cap, let's draw that on as well:
3._Diodes_Marked_(resized).JPG
Note that the positive end for C1 and C2 is on the bottom of the board while C3 and C4's positive is on top. MAKE SURE YOU GET THAT RIGHT! Otherwise the caps will explode when you power it on. (I'm not saying there's any *extra* risk with this technique, just that any electrolytic cap installed backwards can explode when power is applied.)

- Install the caps (and the diodes) for C1 and C2 (and C3 and C4 if you're replacing them as well). It's easiest to do C1 and C2 one-at-a-time because we're attaching the diode on the back at the same time. So first, install C2 by sliding the leads through the holes (and triple-checking the polarity). Then turn the board over and wrap the ends of the diodes around C2's pins (triple-checking the polarity of the diode as well - the diode band should be on the bottom of the diode, closest to the big copper rectangle (which is a tiny heatsink for the power resistor R9). It should look like this before you solder:
4a._Attaching_Diode_to_Cap_leads_(resized).JPG
4b._connection_closeup_(resized).JPG

Before you solder, make sure:
- The capacitors are flush with (or a few mm higher than) the PCB
- Neither the capacitor or diode lead are touching the copper rectangle)
- The diode's body should be in-between the two PCB traces that connect to the diode (in the example above, if the diode was closer to the top instead of closer to the bottom, the bottom lead of the diode MIGHT short to the trace connected to the top of the diode - you want to avoid that).
- The diode's leads are wrapped around the capacitor's leads (I use needle-nose pliers to make a good mechanical connection), and
- The diode's leads are flush with the PCB.
- The band on the diode is on the bottom.

- Solder the leads to the pads. I'm not going to teach soldering here but if you're new to it, make sure the solder wicks around the cap leads, the diode leads and into the hole on the PCB. When you're done, you should see a nice solder joint on the other side of the board as well (compare it to the other solder joints on the board if you're not sure).

- Clip the capacitor leads and repeat for C1. The back of the board should look like this:
5._cap_&_diodes_soldered_(resized).JPG

- Install C3 and C4 if you're replacing them.

Front and back should now look like this:
6._Complete_Front_(resized).JPG
7._Complete_back_(resized).JPG

You're basically done - reverse the removal steps and fire it up. The only other tip I have is that when you mount the PCB back onto the backing plate, I recommend you push the PCB down over each mounting point with a 1/4" socket (or similar) - that will apply equal pressure around the PCB while allowing the mount to pop through. It's a tight fit and you don't want to risk damaging the PCB.

My board fired right up strobed away as expected. I played for about 30 minutes (including one Strobe Multiball where I made exactly 9 hits before I drained ), and everything seemed fine. If there were any serious issues with the modified design or the board work I did, they would have shown up (in the form of loud pops and smoke) within the first minute or two.

Hope this helps (and was less cryptic than my first contribution to this thread: https://pinside.com/pinball/forum/topic/replace-caps-on-afm-strobe-board#post-3178085 )!

1 week later
#38 3 years ago

Homepin: I just realized that the Homepin I was having the capacitor discussion with was *probably* the Homepin that made that beautiful replacement strobe board shown in https://pinside.com/pinball/forum/topic/replace-caps-on-afm-strobe-board#post-3178339 with the www.homepin.com URL printed on it. (I really need to start paying more attention to handles. )

I want to make sure everyone reading this thread knows that I agree that your board is a solid design and will work fine in their AFM. It's a much better board/better design than the original. It remains the best solution to the original problem: how to replace an unavailable NP capacitor with an even higher voltage (and even less available) NP capacitor.

When I analyzed the issue, I realized that the design didn't actually need NP capacitors, so I was able to suggest an alternative solution. I did not mean to suggest that your solution/board was inferior - we just had a little back-and-forth about how to make NP caps out of P ones. The design needs 160V caps, you believe you created 500V caps, I believe you created 250V caps, but whichever one of us is right you have at least 56% voltage margin (which is very safe) vs the -37% of the original design (which is really inexcusable).

TL;DR (which is what I should probably change my handle to): No one should have any qualms about purchasing the Homepin strobe board, and it would be what I recommend to people who don't do board work or just want to buy a well-engineered solution that works.

#39 3 years ago
Quoted from yonkiman:

Homepin: I just realized that the Homepin I was having the capacitor discussion with was *probably* the Homepin that made that beautiful replacement strobe board shown in https://pinside.com/pinball/forum/topic/replace-caps-on-afm-strobe-board#post-3178339 with the http://www.homepin.com URL printed on it. (I really need to start paying more attention to handles. )
I want to make sure everyone reading this thread knows that I agree that your board is a solid design and will work fine in their AFM. It's a much better board/better design than the original. It remains the best solution to the original problem: how to replace an unavailable NP capacitor with an even higher voltage (and even less available) NP capacitor.
When I analyzed the issue, I realized that the design didn't actually need NP capacitors, so I was able to suggest an alternative solution. I did not mean to suggest that your solution/board was inferior - we just had a little back-and-forth about how to make NP caps out of P ones. The design needs 160V caps, you believe you created 500V caps, I believe you created 250V caps, but whichever one of us is right you have at least 56% voltage margin (which is very safe) vs the -37% of the original design (which is really inexcusable).
TL;DR (which is what I should probably change my handle to): No one should have any qualms about purchasing the Homepin strobe board, and it would be what I recommend to people who don't do board work or just want to buy a well-engineered solution that works.

Hello Yonkiman. I appreciate your technical input in an area that I certainly do not claim to have intimate knowledge of. All discussions, lively or not, are perfectly OK IMO until they become personal attacks and I don't believe there is/was any of that in our discussions.

I researched an area of electronics and decided to use a solution that I was taught to use 30++ years ago. At that time there was no technical justification for using electros in this way but I knew it worked, was safe and a valid way to create an NP cap.

I appreciate your very valid input to the discussion and your suggested repair method is certainly the way to go for repairs to existing boards. I ALWAYS advocate repairing original boards where possible rather than simply replacing. Interestingly, almost all of the replacements I have sold have gone into machines where the original board is missing or into new builds such as Wally's brilliant "ground up" AFM build (I wouldn't have the patience for a project like that).

#40 3 years ago

Hey Mike (Homepin)
Thanks for the nice compliment.
Big thanks to you from me and all the others that have scratch built AFM's and use your Strobe Board. Sweet design!
Wally

2 weeks later
#41 3 years ago

Tried my second Pinbits strobe and that didn't work either, even though the stock one still does. I'm guessing I need the bigger caps in my strobe board? Would it be the lack of a charge strong enough to light the strobe?

I'm not versed enough in electronics theory to understand this, but I know it's not a cable or strobe problem since the original works.

#42 3 years ago
Quoted from beelzeboob:

Tried my second Pinbits strobe and that didn't work either, even though the stock one still does. I'm guessing I need the bigger caps in my strobe board? Would it be the lack of a charge strong enough to light the strobe?
I'm not versed enough in electronics theory to understand this, but I know it's not a cable or strobe problem since the original works.

Sometimes the trigger needs replacing. Little blue rectangular box with super-thin leads.

#43 3 years ago

Can you provide a link to that part? I'm assuming I can get it at GPE? And if someone can post a link to the correct upgraded caps and/or diodes I'd appreciate it greatly.

#44 3 years ago
Quoted from beelzeboob:

Can you provide a link to that part? I'm assuming I can get it at GPE? And if someone can post a link to the correct upgraded caps and/or diodes I'd appreciate it greatly.

It's in the stobe board kit, and separately:

https://www.pinbits.com/index.php?main_page=product_info&products_id=214

https://www.pinbits.com/index.php?main_page=product_info&products_id=213

4 weeks later
#45 3 years ago
Quoted from yonkiman:

OK, here's the *practical* how-to guide to replacing the NP (Non-Polarized) 100uF caps on your AFM strobe board with readily-available Polarized 100uF/250V electrolytics.
- Order 2 (or 4) 100uF/250V axial capacitors. You probably only really need replacements for the 2 NP caps, but I replaced all 4 since the game's 20 years old and I don't want to have to go back in the strobe box anytime soon. I bought these: https://www.digikey.com/product-detail/en/illinois-capacitor/107TTA250M/1572-1310-ND/5410816, but any 100uF/250V axial cap from a reputable manufacturer should work fine. Also you'll need two 1N4004 diodes (https://www.digikey.com/product-detail/en/fairchild-semiconductor/1N4004/1N4004FSCT-ND/1626118 if you don't already have them on hand.
- Make sure your AFM is powered off. The high voltages in the strobe board will discharge in less than a minute after it's turned off.
- Remove the board from your AFM. Remove the cover around the board first (4 corner screws), unplug the connectors from either side of the board, then unscrew the remaining screws (2 on top and 1 on the bottom) to remove the PCB and the backing plate.
- You should now have this on your workbench (minus the cable that I left on for a few photos):

- Pry the PCB off of the backing board by twisting a large flathead screwdriver against each mounting pin between the backing plate and the PCB so that all the pressure on the PCB is applied right next to the mounting post. If there is any distance between the mounting post and the pressure on the PCB, you could damage the PCB. Put the backing board aside. Now we're here (front and back):

- If you look carefully, your C1 may also be bulging from being overstressed:

- Next, desolder C1 and C2 (and C3 and C4 if you're replacing all 4 caps):

C3 and C4 have "+" marks to identify the positive side of the capacitor. C1 and C2 do not, because the caps were non-polarized. Since we're converting to polarized, we should add "+" marks, and since we're also adding a diode to each cap, let's draw that on as well:

Note that the positive end for C1 and C2 is on the bottom of the board while C3 and C4's positive is on top. MAKE SURE YOU GET THAT RIGHT! Otherwise the caps will explode when you power it on. (I'm not saying there's any *extra* risk with this technique, just that any electrolytic cap installed backwards can explode when power is applied.)
- Install the caps (and the diodes) for C1 and C2 (and C3 and C4 if you're replacing them as well). It's easiest to do C1 and C2 one-at-a-time because we're attaching the diode on the back at the same time. So first, install C2 by sliding the leads through the holes (and triple-checking the polarity). Then turn the board over and wrap the ends of the diodes around C2's pins (triple-checking the polarity of the diode as well - the diode band should be on the bottom of the diode, closest to the big copper rectangle (which is a tiny heatsink for the power resistor R9). It should look like this before you solder:

Before you solder, make sure:
- The capacitors are flush with (or a few mm higher than) the PCB
- Neither the capacitor or diode lead are touching the copper rectangle)
- The diode's body should be in-between the two PCB traces that connect to the diode (in the example above, if the diode was closer to the top instead of closer to the bottom, the bottom lead of the diode MIGHT short to the trace connected to the top of the diode - you want to avoid that).
- The diode's leads are wrapped around the capacitor's leads (I use needle-nose pliers to make a good mechanical connection), and
- The diode's leads are flush with the PCB.
- The band on the diode is on the bottom.
- Solder the leads to the pads. I'm not going to teach soldering here but if you're new to it, make sure the solder wicks around the cap leads, the diode leads and into the hole on the PCB. When you're done, you should see a nice solder joint on the other side of the board as well (compare it to the other solder joints on the board if you're not sure).
- Clip the capacitor leads and repeat for C1. The back of the board should look like this:

- Install C3 and C4 if you're replacing them.
Front and back should now look like this:

You're basically done - reverse the removal steps and fire it up. The only other tip I have is that when you mount the PCB back onto the backing plate, I recommend you push the PCB down over each mounting point with a 1/4" socket (or similar) - that will apply equal pressure around the PCB while allowing the mount to pop through. It's a tight fit and you don't want to risk damaging the PCB.
My board fired right up strobed away as expected. I played for about 30 minutes (including one Strobe Multiball where I made exactly 9 hits before I drained ), and everything seemed fine. If there were any serious issues with the modified design or the board work I did, they would have shown up (in the form of loud pops and smoke) within the first minute or two.
Hope this helps (and was less cryptic than my first contribution to this thread: https://pinside.com/pinball/forum/topic/replace-caps-on-afm-strobe-board#post-3178085 )!

Just did this board mod. Fixed my strobe issue, but now every time the drop targets is hit the sounds cuts out and seems to reset. Any ideas?

#46 3 years ago
Quoted from beelzeboob:

Just did this board mod. Fixed my strobe issue, but now every time the drop targets is hit the sounds cuts out and seems to reset. Any ideas?

Are any wires getting getting hit when the drop target moves?

If you knock down the drop target in switch test, does anything else go off along with it?

#47 3 years ago

No and no. When we unplug the strobe board, the sound behaves normally. Got a PM in to Yonkiman, hoping he can tell me what would cause that.

#48 3 years ago

Okay...the strobe...and game...are finally working properly.

This was a tough one. My friend and I went through the following permutations:

Stock strobe board + Pinbits strobe=not working
Stock strobe board + stock strobe=working
Capacitor upgrade + Pinbits strobe=strobe working, sound cuts out on drop target hit
Pinbits rebuild kit + Pinbits strobe=strobe working, sound cuts out

Now, here's the incredible part: I'd been having opto issues (top left popper would go off during attract mode, Return to Battle would trigger for no reason). When my buddy was rebuilding the high voltage board, he found that diode D7 had been reversed! And it was a stock board...it didn't look like anybody had ever replaced that diode. Go figure.

Diode flipped, board rebuilt and caps upgraded with diodes, strobe working, sound working.

Thanks to all in this thread for your input!

#49 3 years ago

Wow, that was a good catch.

#50 3 years ago
Quoted from beelzeboob:

When my buddy was rebuilding the high voltage board, he found that diode D7 had been reversed! And it was a stock board...it didn't look like anybody had ever replaced that diode. Go figure.
Diode flipped, board rebuilt and caps upgraded with diodes, strobe working, sound working.

Great catch!!

Remember what I said in my PM about pinball electronics flagrantly ignoring the laws of physics? I just looked at the schematic, and if you'd asked me "What would happen if D7 was reversed?", I would have said "That's easy: *nothing* would happen. The board would simply never fire the strobe because a reversed D7 would just block the trigger signal for the opto isolator, so as far as the board could tell, players just never made it to Strobe Multiball. Very basic diode theory.

But you saw it working fine and shutting down the sound board.

My head just exploded. Again. From freakin pinball electronics.

Promoted items from the Pinside Marketplace
There are 57 posts in this topic. You are on page 1 of 2.

Hey there! Got a moment?

Great to see you're enjoying Pinside! Did you know Pinside is able to run thanks to donations from our visitors? Please donate to Pinside, support the site and get anext to your username to show for it! Donate to Pinside