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Gottlieb sys1 psu repair?

Ok the 7912!does not read shorted off the board, across r9 in situ is zero ohms, I can’t get at the pins for scr201 or c5 but c5 was replaced , I will need to split the pcb from the frame to fit a new 7912 anyway

Couple pics of the psu I know the new c1 is a bit overkill but I had them to hand!


R13 looks a bit scortched but it was like that when I first looked at the board?



ECB9C6D4-2482-4111-9CD9-CFEE6EDFA58E.jpeg4BFFD10E-AAC2-45A9-BB90-0CFF77DC41A1.jpeg
 
Ok, if it isn’t shorted off board it may well be fine after all. Lift one leg of R9, see if that makes a difference (unlikely). Probably C5 or the crowbar SCR (this is what is there for after all). As the latter has been soldered flush, you will have to take the board off again to unsolder/test.
 
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drhex said:
Ok, if it isn’t shorted off board it may well be fine after all. Lift one leg of R9, see if that makes a difference (unlikely). Probably C5 or the crowbar SCR (this is what is there for after all). As the latter has been soldered flush, you will have to take the board off again to unsolder/test.
Click to expand...

Ok problem found! I stupidly bridged the traces of C5 with solder! Once I sorted that I think my short is gone, the SCR seems ok measured in situ, and R9 is reading ok in situ, Is there anything else I should check while I can get to solder side? remove SCR to test maybe?

Thanks for your help, I would be stuck otherwise

Ronnie
 
Ok, put the 7912 back in and report. Underfusing is fine for that.
 
Thanks, the 7912 has it's legs cut off, only have about 1mm of leg tio play with, have ordered some new one's.

Will also need to buy some new Molex pins for the psu and other edge connectors, can get from RS components for 10p each but min of 100 plus carriage, smaller amounts on ebay but more expensive

Thanks Ronnie
 
what kind of soldering iron are you using? 1mm should be plenty. Tin both sides and put it on.
 
Lol I have a Weller TCP iron, tbh would rather fit a new one before I put it all back together
 
Actually I might try that, what with postal strikes I could wait long enough!
 
Right soldered the 7912 back on, all seemed good short wise, I had found the correct fuse but on power up it blew again! So if the scr is bad what do I need to get to replace it?

Thanks Ronnie
 
S107Y1 or NTE5452. So you power on with nothing connected downstream? No more short across any of the voltages?
 
No only the AC feed into psu, no shorts I can find in respect of the 5v and -12v, could not find any shorts on the scr across it’s pins but it’s tab reads short to ground?

Thanks Ronnie
 
Any shorts on the incoming end, ie either across the windings or winding to ground?
 
If that isn’t the case, take the 7912 out again and see if a 500mA holds.
On another note, did you recap post shorting it out or past?
 
The fuse stayed intact with psu removed that transformer also feeds the sound board and it was working without the psu so sure the windings are ok, I checked all the diodes for shorts they were ok

The shorted c5 happened whilst I was recapping the psu, prior to this the pinball was working,

Will have another bash at removing the 7912 tomorrow and try another power up. I hope that scr is ok as I could not find any in the uk!

Thanks Ronnie
 
So the story is

Psu was working but after recap -12v was missing due to shorted c5. But all other voltages were good,

Me checking pins of 7912 with my meter probe slipped and shorted out something nearby? Fuse blew, there is a diode right above the pins but not sure what I shorted to where!
 
The diode is CR23

I removed the 7912 again but it's still popping the fuse 500ma fitted, it lights like a lamp lol, would the sound board overload the fuse?

Thanks Ronnie
 
Ok I removed the connector to the sound board, still pops the fuse, should the tab of the SCR be connected to ground?

Thanks Ronnie
 
Would not expect that as it was working before. Easy test: Does the fuse stay in if the power board is disconnected? CR23 is one of the drop diodes for the 4V - you may have shunted -12V into the regulator pin of IC1. That won't like that very much.
On SCR: Yes, may well have a grounded tab. Depends on the actual device installed.
 
Yes fuse intact and sound working with psu removed. So likely a bad SCR or IC1? The SCR's look hard to find and IC1 looks like it might also be hard to find!

Thanks Ronnie
 
So when I had solder bridged C5 by mistake the fuse was not blowing and all volts good bar -12, I had my meter grounded to casing and + lead on one of the 7912 when it slipped off and touched either CR23 or one of the output pins of the psu, not sure how it could have shorted anything! the probe end is tiny
 
The SCRs you can remove to test without impacted functionality (Overvoltage protection will be gone). SCRs tend to fail shorted though so if you don't have a short across them they are unlikely culprits. With the 7912 gone SCR102 is out of action anyway. Leaves the 5V side of things - you could remove SCR101 to see if that keeps the fuse in. IMPORTANT: Without anything connected on the secondary as overvoltage protection will be gone!
 
Just touching something should not kill anything.
Anyway, to recap:
- Fuse blows with PSU connected
- You have no shorts on input plug across transformer connections or any transformer connection to ground
- You have no shorts from any of the output voltages to ground
- 7912 is out of circuit
If all of the above is correct, I'd remove SCR 101 next in the hopes of keeping it running to probe around further without the fuse blowing.
 
Thanks, so with the 7912 removed SCR102 would not blow the fuse if faulty? I never checked SCR101! Time to split the pcb again lol

Right! The SCR's are marked 10212 H1279

SCR 102 only reads to ground on pin 2
SCR101 only reads to ground on pin 1

That's with them both in situ

Thanks Ronnie
 
That makes sense as the polarity is reversed between the two. If there is no short across they should be fine. Now if SCR101 gets switched on as voltage regulation is shot it will burn the fuse. You can either take it out and see what happens next, again WITHOUT ANYTHING CONNECTED DOWNSTREAM. You could also lift one leg of CR101 which switches SCR101 on if the voltage is too high. What circuit is the fuse in question in (EDIT: Figured it out, newer games have a primary fuse for the small transformer, guess this one has it)? Can't see it in the diagrams. There are three windings connected, 11.5VAC, 14VAC and 69VAC. The latter should have a separate 250mA fuse in the bottom of the box. I hope it isn't that one burning up? I assume you disconnected the display connector from the PSU.
 
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Thanks again, the fuse that's blowing is in the AC feed (primary) to the smaller transformer, I think earlier games did not have this fuse, not got anything connected to the psu at this point only the AC in, it's getting complicated lol.

Maybe my shorted C5 was fine for a time until something went, maybe my probing was coincidence?

Thanks Ronnie
 
Could well be. I'd suggest adding in secondary fuses for the 11.5VAC and 14VAC feeds to protect the transformer. 2A/750mA should do nicely (and would provide separation on this issue). Again, removing the overvoltage protection on the 5V track would be the next thing I'd try to see if that keeps the fuse in. Again, you have no short between any of pins 1-2-3 on P1 to each other? CR1 and CR2 aren't shorted? Same for pins 3-4-5 and CR3 and CR4?
 
Ooops! CR3 and CR4 are reading short in situ, the only 2 diodes I never noticed! Sorry!

I plan to add in those 2 fuses once I fix my mess up!

Thanks Ronnie
 
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That would explain it. Lift one leg of each, remeasure to make sure and try another fuse with them disconnected.
 
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