(Topic ID: 181077)

(Solved) Stern SDU-100 - missing 5v


By Fytr

2 years ago



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  • 30 posts
  • 8 Pinsiders participating
  • Latest reply 2 years ago by snyper2099
  • Topic is favorited by 3 Pinsiders

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#1 2 years ago

I have an SDU-100 that isn't producing 5v.

History is when I received the board first power up with 12V caused R50 to go up in smoke.

I replaced R50, and the main capacitors on the board, but the 5v regulator was outputing close to 12V still.

I just replaced the 5v regulator with a new one, but am now reading 12v on the input side to the regulator, and basically 0 on the output side.

The original regular was a "SG323", and the new one is a "LM323K". See pics below.

Old regulator
New regulator

As far as I can tell I connected the regulartor correctly, seems that the pins are lower on one side to avoid the possibility of incorrectly mounting it?

There was also a rubber (?) gasket between the old regulator base and the heat-sink that I kept between the new one and the heatsink, though the regulator schematics says the base of the case is the ground, so wouldn't that gasket keep it from grounding properly?

Any advice is appreciated!

#2 2 years ago

Okay, looking at it today I see the regulator still grounds via the bolt that mounts it, so the gasket isn't an issue.

I'm reading 11.74v on pin 1 of the 5v regulator, and 0.126v on pin 2. Defective 5v regulator?

#3 2 years ago

Make sure the regulator isn't shorting against heat sink, that'll stop things right quickly.
Could be due to some other part shorting the 5V line and the regulator isn't shutting down.

And I assume you replaced the burned resistor.
Did you do the ground mods to that board? Did you do the +5V mod of tying TP1 to TP3 at J3? If so, check for solderbridge?

#4 2 years ago

Okay, heatsink isn't shorting to the regulator, or to ground.

There is approx. 100 ohms resistance between the output of 5v regulator and ground.

The board is actually super clean, all I've done is replace the 3 caps (c23, c24, c26), the burned resistor (r50), and now the voltage regulator. I inspected the board under magnification and I don't see any shorts, hacked solder jobs, etc.

To test on the bench I've been connecting my power supply via ground to TP8, and 12v to TP5. The power supply seems to put about 11.7v out. Is this a valid setup?

Could the c23 cap. (tantalum) be damaged from when the r50 burned up? Would that even cause this?

#5 2 years ago

Tantalums can short when bad so that is a possibility.
Did you do the ground mods to this board?
http://www.pinwiki.com/wiki/index.php?title=Bally/Stern#Solenoid_Driver_Upgrades

#6 2 years ago

I have a spare tantalum cap I can try replacing it again.

I have not done the ground upgrades on this board, though I don't see how doing so would improve things in the short term?

#7 2 years ago

Short term: if you don't have good connections between the various ground circuits on that board then you will have a hard time trouble shooting this one.
You have an isolated ground to C23 expected to come from J3, pin 10 but if you are only connecting ground to the test point then the negative side of C23 is floating. You also have other grounds on that board that are isolated until J3 is plugged in (and J3 contacts are good). Doing ground upgrades takes care of the floating ground issues.

Regarding Tantalum - just clip one end of him and pull up. If it fixes things then replace him.

#8 2 years ago

So I replaced c23 and the other two .1uf caps in that circuit, tested the resistors and they were all fine, but still only seeing .126v instead of 5v.

So I pulled the voltage regulator and tested it in isolation, 11.6v in, .1 volts out. My "new" regulator is no dang good.

While I was at it I tested the original regulator that fried r50 and it was outputting 10v.

I'll look into picking up another regulator.

Thanks for suggestions, I'll also map out the ground upgrades and get those done.

#9 2 years ago

Interesting, I bought a 5V regulator last fall and mine was also faulty. Really pissed me off cause I ended up lifting a trace trying to remove that POS. I e-mailed the supplier to let him know about the faulty component but he wouldn't even respond.

#10 2 years ago

Curious -- where are these regulators coming from (other than China)?

#11 2 years ago
Quoted from G-P-E:

Curious -- where are these regulators coming from (other than China)?

Not sure. I got mine from a Canadian pinsider who sells eletrical components and such.

Markings are as below:

Screen Shot 2017-02-14 at 10.46.58 AM (resized).png

#12 2 years ago

ebay.com link » Lm323k Lm323 To 3 Voltage Regulator 5v 3a

lol

same date code even.

yeah that is likely a china fake. The transistors, voltage regulators, etc have way many more fakes out there than chips it seems.

The only regulators i would use from China would be used pulls with obvious markings from lock stars biting into the case.

#13 2 years ago
Quoted from barakandl:

ebay.com link ยป Lm323k Lm323 To 3 Voltage Regulator 5v 3a
lol
same date code even.
yeah that is likely a china fake. The transistors, voltage regulators, etc have way many more fakes out there than chips it seems.
The only regulators i would use from China would be used pulls with obvious markings from lock stars biting into the case.

What's annoying is the time and effort you waste using these bogus parts. I think we'd all happily pay a little more for ones that actually worked.

My guy is sending me an older unit that he'll test before shipping it out.
Luckily I'm not in a desperate hurry.

1 month later
#14 2 years ago

My new voltage regulator arrived a week awhile back but didn't have time to look at it until last night.

IMG_0978 (resized).JPG

I tested it alone via PC power supply and it output a steady 5.4V.

Once I had it installed on the board, I tested it again via 12V connected to TP5. TP1 showed 5.4V again, though TP6 and TP7 were 0. I assumed they relied on the connector being connected, etc.

However, once I installed the board into the game (which had been working fine with Bally boards borrowed from my Flash Gordon), readings were:
TP1: 3.4V (should be 5V)
TP2: 160V (should be 180V, but seems to work at this value when it is working with the other board)
TP5: 15.57V (should be 12V) - Is this too high?
TP6: 3.4V (should be 5V)
TP7: 3.4V (should be 5V)

IMG_0977 (resized).JPG

Any ideas?

Also, I think that I probably don't need the heat-sink with this new type of regulator, can anyone confirm?

#15 2 years ago

I used one of those and had r50 explode. hold on let me find it.
ah
https://pinside.com/pinball/forum/topic/lets-get-technical-ballystern-led-display-power-consumption/page/2

I think perhaps you must jumper r50 when using this puppy. Sorry if this muddles things more.

#16 2 years ago
Quoted from supermoot:

I used one of those and had r50 explode. hold on let me find it.
ah
https://pinside.com/pinball/forum/topic/lets-get-technical-ballystern-led-display-power-consumption/page/2
I think perhaps you must jumper r50 when using this puppy. Sorry if this muddles things more.

Thanks for the link! Had no idea. Ironically, it was R50 burning up that started me on this adventure. I replaced it with an overrated 2w unit, which is probably why it didn't fry when I tried it last night.

I'll replace R50 with a wire, hopefully I didn't damage the regulator.

#17 2 years ago

I still don't understand why notices aren't added somewhere on the product pages for known issues. I guess because it's a generic replacement and circuit considerations in whatever you're replacing are up to the end-user. Just seems like it wouldn't be a bad idea.. even if only for the PSU7 where a trace close to the mounting hole shorts to ground if saw-tooth washers are used.

#18 2 years ago
Quoted from acebathound:

I still don't understand why notices aren't added somewhere on the product pages for known issues. I guess because it's a generic replacement and circuit considerations in whatever you're replacing are up to the end-user. Just seems like it wouldn't be a bad idea.. even if only for the PSU7 where a trace close to the mounting hole shorts to ground if saw-tooth washers are used.

After I became aware of the issue I found this tidbit re: using the correct washers in the WPC Pinwiki topic:

5.15.16 Failed Voltage Regulator

Step 11: When all else fails...

The LM323K 5V regulator is a robust device, but it can drift over time to below the design requirement of 4.8VDC. If your 5VDC reads less than 4.8VDC at the test point, or less than 4.75V on the CPU board, you have to replace the regulator. Note that these voltages are compliant to the LM323K's spec. However, at the lower end of this spec, this lower voltage may be the cause of resets.

If you decide to replace the LM323K regulator you may wish to consider using an EZ-SBC PSU5 instead ([1]). The PSU5 is a 5V 3A high-efficiency switch-mode regulator that is a direct replacement for the LM323K in terms of form factor and current capacity; it is superior to the LM323K due to its reduced power dissipation. When using the PSU5 be sure to replace the KEPS nuts (nuts with captive lock washers) originally used to mount the LM323K with discrete #6 split lock washers and #6-32 hex nuts; the external tooth lock washer of the KEPS nut can contact one of the surface-mounted components on the PSU5.

Should add a similar tip/warning for the Classic Stern/Bally Wiki page as well.

#19 2 years ago
Quoted from Fytr:

Thanks for the link! Had no idea. Ironically, it was R50 burning up that started me on this adventure. I replaced it with an overrated 2w unit, which is probably why it didn't fry when I tried it last night.
I'll replace R50 with a wire, hopefully I didn't damage the regulator.

Someone on the other thread said they also removed R49.

Should I leave R49, remove it, or remove and also replace wth a wire?

#20 2 years ago

I believe you remove r49, otherwise your 5v would be connected directly to ground. I found another thread, too.
https://pinside.com/pinball/forum/topic/thoughts-on-preemptively-replacing-5v-to-3-regulators?responsive=0

#21 2 years ago
Quoted from Fytr:

Someone on the other thread said they also removed R49.
Should I leave R49, remove it, or remove and also replace wth a wire?

mimic the 5v regulator circuit on a wms sys 3-6 games. The two resistors Bally uses juices up the output voltage for a lm323k, often to a dangerous, MPU-U15 zapping voltage.

For the PSU5 switch mode regulator, it would be cut out r49 and change r50 to a jumper wire / 0 ohm resistor.

#22 2 years ago
Quoted from barakandl:

mimic the 5v regulator circuit on a wms sys 3-6 games. The two resistors Bally uses juices up the output voltage for a lm323k, often to a dangerous, MPU-U15 zapping voltage.
For the PSU5 switch mode regulator, it would be cut out r49 and change r50 to a jumper wire / 0 ohm resistor.

Okay, thanks!

1 week later
#23 2 years ago

Made some progress on the weekend.

Removed R49, replaced R50 with a jumper wire...

IMG_0984 (resized).JPG

Success!!

I now have solid 5V everywhere it should be.

Unfortunately, running the board in the game shows a problem with the high voltage section, when running the display digits are fading in and out instead of being sharp and bright.

IMG_0988 (resized).JPG

I adjusted the pot under the high voltage to max settings, didn't help, at least not much, and I'm seeing the following values on my MM:

TP4 177v
TP2 153v

I have already replaced the big caps on this board, so not sure what other components need replacing to resolve. Possibly another bad voltage converter on the high voltage section? *sigh*

#24 2 years ago
Quoted from Fytr:

Made some progress on the weekend.
Removed R49, replaced R50 with a jumper wire...

Success!!
I now have solid 5V everywhere it should be.
Unfortunately, running the board in the game shows a problem with the high voltage section, when running the display digits are fading in and out instead of being sharp and bright.

I adjusted the pot under the high voltage to max settings, didn't help, at least not much, and I'm seeing the following values on my MM:
TP4 177v
TP2 153v
I have already replaced the big caps on this board, so not sure what other components need replacing to resolve. Possibly another bad voltage converter on the high voltage section? *sigh*

Check the voltage at the rectifier board test point. If low there check the 1n4004 rectifier diodes on the power supply as maybe one is open circuit.

If looks good there, check the ground return and positive rail connector at driver board. They hv ground is isolated back to the transformer panel (unless you do the "ground mods").

#25 2 years ago
Quoted from barakandl:

Check the voltage at the rectifier board test point. If low there check the 1n4004 rectifier diodes on the power supply as maybe one is open circuit.
If looks good there, check the ground return and positive rail connector at driver board. They hv ground is isolated back to the transformer panel (unless you do the "ground mods").

Nice tip! The displays work perfectly when running with a known working SDB... but, I did the ground mods on the working board previously and have not done them on this Stern one yet. Maybe that's the secret sauce?!

Will have to figure out where the connections need to be made first, since vid1900 's example was for a Bally board.

#26 2 years ago

find the negative lead for the c26 230v filter cap. run a patch from the the negative lead to the nearby ground trace. Scratch off some solder mask on the ground trace so you can tack down your ground reinforcement.

Besides that.... I would suspect C26 being bad for low input voltage...

#27 2 years ago

Hooray! Mostly!

#28 2 years ago

I would suspect a bad (or not fully connected ) C26 too. I know you said it was new but still.... Depending on source, it could be a counterfeit part. I have seen photos of small value capacitors contained inside larger bodied cans. It's amazing how far they will go to make a few pennies.

1 week later
#29 2 years ago

Exciting news - I completed the ground fix and it's working 100% now!

IMG_1068 (resized).JPG

Many thanks guys!

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