System 7 vs. 11b/c Power Board - Transistors


By MaxAsh

3 months ago


Stats

  • 20 posts
  • 7 Pinsiders participating
  • Latest reply 3 months ago by G-P-E
  • Topic is favorited by 1 Pinsider

Find

Search this topic for posts matching certain words or written by a specific Pinsider. Or both!




Linked Games



Topic Gallery

There have been 6 images uploaded to this topic. (View topic image gallery).

FP2_Power_Back2 (resized).jpg
FP2_Power_Back1a (resized).jpg
FP2_GPE_Install (resized).jpg
FP2_Trans_Dia (resized).jpg
FP2_Trans_Schem (resized).jpg
FP2_PS_Trans (resized).jpg


#1 3 months ago

Hey All - I have a thread going about a Firepower II I'm working on, but it was suggested by another Pinsider that I start a separate post about a related question that is more general to System 7/11 Power Boards and transistors.

I'm rebuilding the power supply, and I've run into a question with the transistors Q1 and Q3. Based on research, my understanding is that most System 3-11 boards (aside from the late series 11b and 11c power boards) used SDS201 and SDS202 Transistors. With those unavailable, the replacements frequently used are MJE15030 and MJE15031.

Due to the different pinouts, per the instructions online like here: https://www.greatplainselectronics.com/Downloads/W3-11_HV_Kit.pdf , on most boards you need to "cross" the legs on the transistor to get the proper flow. As noted in the instructions, however, on late model boards this was NOT needed, as they already used the 15030 and 15031 transistors.

Now, here's my issue: When I pulled the board and prepared to replace the transistors, I noticed that they're already 15030 and 15031. See attached image of my board. But they are NOT cross legged as instructed. This leads me to believe either (1) The original board was replaced with a late model System 11 board or (2) Someone else replaced the transistors on the original board, but did it wrong.

Part Number on the Board: 5765-09466-01 (no revision letter)

The game was actually playing fine for a while before I started having issues with fuses blowing (solenoid fuse, then eventually the display fuse). It's hard for me to believe it would have worked at all with improperly installed transistors, but I'm not sure.

Thoughts and suggestions welcome. I'm ready to replace the transistors, but want to do so properly! Thanks in advance.

FP2_PS_Trans (resized).jpg

#2 3 months ago

Have you attempted to trace the traces attached to those transistors to their other components and see how it matches up with the schematic?

#3 3 months ago
Quoted from zacaj:

Have you attempted to trace the traces attached to those transistors to their other components and see how it matches up with the schematic?

No, good idea, I can take a look and see how it matches up. I really do think this is a non-late model board, just going by my gut, so I have to wonder if these are simply installed wrong. But again... wouldn't that cause all sorts of hell? So strange.

#4 3 months ago

Okay, so using the schematics I have from my FP2 manual, and testing all of the traces so I know where everything goes, here's what I found:

All trace checking from Q1 and Q3 matches the original schematic and diagrams, meaning that my board must require the original setup for the transistors (EBC). Just for reference, based on the schematics (if someone wants to double-check me), here's how the positions trace out:

Q1
E -> C2, R3, 3J5 Pin 4 (100VDC)
B -> Z2, Q2 (collector)
C -> D3, Z1, C1(+), R2

Q3
E -> C4, R6, 3J5 Pin 3 (-100VDC)
B -> Z4, Q4 (collector)
C -> D4, Z3, C3(-), R5

The replacements that have to be used are BCE, and need to be wired as shown in the link from my original post. As far as I can tell, that means that whomever last replaced these with 15030 and 15031 Transistors did them wrong, and never crossed the legs. I can't believe the game even functioned like that, but it did it seems.

Anyone object to my logic before I go ahead and replace with the cross-leg method?

FP2_Trans_Schem (resized).jpg
FP2_Trans_Dia (resized).jpg

FP2_GPE_Install (resized).jpg

#5 3 months ago

Wow, that's crazy! I've been assuming this whole time that wouldn't have worked at all...but I've never read any accounts of someone installing them wrong, so I'm not sure what would happen either. I'd rebuild the whole hv section as per GPE's instructions and see what happens.

#6 3 months ago

Can you shoot a photo of the bottom side so we can take a look at the traces?

#7 3 months ago
Quoted from G-P-E:

Can you shoot a photo of the bottom side so we can take a look at the traces?

I think this will spoil the magic trick

#8 3 months ago

I don't see any jumpering or altering of the original traces, but maybe I missed something? If the traces were changed or altered, wouldn't the tests I did not match the schematics? Here are some pics, I apologize for the back not being pretty/clean, but I snapped these quick without cleaning it first. The previous work done on it wasn't pretty. I marked Q1 and Q3.

FP2_Power_Back1a (resized).jpg
FP2_Power_Back2 (resized).jpg

#9 3 months ago

Wow... it is designed for the old TO-202 transistors.
OK -- so unless the transistors are internally shorted, I don't see how that could have possibly worked.
Board sure could use a bit of alcohol so we can see what is under that flux, maybe a solder bridge or two.

#10 3 months ago
Quoted from G-P-E:

Wow... it is designed for the old TO-202 transistors.
OK -- so unless the transistors are internally shorted, I don't see how that could have possibly worked.
Board sure could use a bit of alcohol so we can see what is under that flux, maybe a solder bridge or two.

I checked the board/traces with a meter, nothing seems to be bridged that shouldn't be, but I'll clean it off some more and see if that reveals anything unexpected. Assuming nothing is bridged, should I go ahead and cross the legs of the MJE15030/MJE15031 as directed?

I pulled the existing Q1 MJE15030 off the board and tested it. Definitely no good. Here are the results (marked with positive or negative for the test lead used):

Base (Pos) to Emitter (Neg) = Shorted
Base (+) to Collector (-) = 0.439
Emitter (+) to Base (-) = Shorted
Collector (+) to Base (-) = 1.450
Collector (+) to Emitter (-) = 1.432
Emitter (+) to Collector (-) = 0.388

I guess that short allowed the game to somehow work based on your comment? Guessing if I pull Q3 I'm going to find the same issue, or similar.

#11 3 months ago

Following up - pulled the Q3 (MJE15031) PNP that was on the board and it seems to test good:

Base (Pos) to Emitter (Neg) = OL
Base (+) to Collector (-) = OL
Emitter (+) to Base (-) = 0.552
Collector (+) to Base (-) = 0.555
Collector (+) to Emitter (-) = OL
Emitter (+) to Collector (-) = OL

I expected both to be shorted or test bad, but this one seems to be okay if I'm reading things properly. I will still replace it with the new GPE one I have, and I assume cross the legs as well?

#12 3 months ago

Yeah, both will need the crossed-leg modification according to the document i shared from gpe earlier. You can also use small pieces of heat shrink tubing to insulate the crossed leg from the others it passes under.

#13 3 months ago

Still amazed it was working like that for a while, but who knows. Okay, I'll go ahead and install the new transistors and see how it goes. Fingers (and transistor legs) crossed.

#14 3 months ago
Quoted from MaxAsh:

Fingers (and transistor legs) crossed.

Good luck, man!

#15 3 months ago

Success!!! Just finished everything up, reinstalled, and it's working. Including the pop bumper that was dead thanks to the new transistors on the driver board.

Thank you all for chiming in on the Transistor issue. While it's interesting to know that a shorted and improperly installed MJE15030 in Q1 and incorrectly installed MJE15031 in Q3 can somehow allow the game to work temporarily, it's clearly not a good thing and causes a lot of headaches.

Make sure you get the legs correct when replacing these! Whomever did this HV rebuild before I got the game failed that effort. Glad you all helped me correct it. Thanks!

#16 3 months ago

Good job! Glad everything's working properly again. That was an interesting discovery! Congrats on the fix!

#17 3 months ago

Glad you got this squared away

#18 3 months ago

Quick question regarding this generation P/S board. The Revision "D" version the MJE replacement transistors are installed straight (no crossing of the legs) correct? I'm fairly certain that's the case but I wanna confirm that before doing unnecessary work.

#19 3 months ago

My understanding is that the very late series boards were indeed different and used the newer transistors, without need for leg crossing. What game are you working on?

As noted above, and easy check is to compare the schematic to the board and check/trace connections to make sure everything matches. When I did this, it verified I had an older board.

You can post a pic too, might make it easier to tell.

#20 3 months ago
Quoted from chucktee:

Quick question regarding this generation P/S board. The Revision "D" version the MJE replacement transistors are installed straight (no crossing of the legs) correct? I'm fairly certain that's the case but I wanna confirm that before doing unnecessary work.

That was why I asked for bottom photo on post #6. There were boards that did use the MJE15030/15031 transistors.
Following the board routing shown in post #8 - his board truly was routed for the older SDS201/202 transistors.

Promoted items from the Pinside Marketplace
From: $ 9.00
$ 22.00
$ 21.00
From: $ 7.00
Playfield - Protection
Bright Lights Pinball
$ 25.00
Boards
German-Pinball-Modular
$ 200.00
Lighting - Led
PinballBulbs
From: $ 42.00
Cabinet - Shooter Rods
ModFather Pinball Mods
$ 99.99
Playfield - Toys/Add-ons
Lighted Pinball Mods
$ 4.95
Apparel - Unisex
ULEKstore
$ 74.99
Playfield - Toys/Add-ons
Tim's Pinball Mods
$ 18.99
Eproms
Matt's Basement Arcade
$ 49.99
Playfield - Toys/Add-ons
Lighted Pinball Mods
From: $ 42.00
Cabinet - Shooter Rods
ModFather Pinball Mods
$ 131.00
$ 7,199.00
Pinball Machine
Flip N Out Pinball
From: $ 9.95
Playfield - Toys/Add-ons
ULEKstore
£ 60.00
Playfield - Decals
Sillyoldelf Mods
$ 15.00
$ 219.00
Cabinet Parts
Tilted Pinball
$ 40.00
Lighting - Other
Rock Custom Pinball
$ 239.99
Lighting - Led
PinballBulbs

Reply

Wanna join the discussion? Sign up for a Pinside account, or log in if you already have an account.


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