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Gottlieb sys1 psu repair?

ronnie63

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Ok I have been checking over this non working buck rogers and have found I have no +5v output to the cpu, pin repair suggests replacing C1 filter cap to 6800 to 10000uf 20v, I have a new 12000uf would that do? Also any help to find the 5v fault woulb be great.

Also the 4v and 8v to the displays are reading 12v and 15v unloaded! Don't think that's good?

This is a new tech to me so any pointers would be great.

Thanks Ronnie
 

Ashbo

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Ok I have been checking over this non working buck rogers and have found I have no +5v output to the cpu, pin repair suggests replacing C1 filter cap to 6800 to 10000uf 20v, I have a new 12000uf would that do? Also any help to find the 5v fault woulb be great.

Also the 4v and 8v to the displays are reading 12v and 15v unloaded! Don't think that's good?

This is a new tech to me so any pointers would be great.

Thanks Ronnie
Hiya, never worked on a system 1, but replacing the caps and transistors on a faulty PSU usually does the trick. I don't normally have a problem getting a cap with a higher voltage, but don't normally replace with a different capacitance
 

drhex

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Hi Ronnie,
so you have nothing on A2-P2 1/2 where the 5V should be? On the 4V/8V, are you measuring them against A2-P3 5? Different ground. The 4V are actually generated from the logic 5V, so strange you're not seeing any voltage there. 12000 uF should be OK otherwise.
 
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ronnie63

ronnie63

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Hi Ronnie,
so you have nothing on A2-P2 1/2 where the 5V should be? On the 4V/8V, are you measuring them against A2-P3 5? Different ground. The 4V are actually generated from the logic 5V, so strange you're not seeing any voltage there. 12000 uF should be OK otherwise.
Thanks, for the 5v I was using the ground pin on same plug. for the 4v 8v I used the neg end of the cap below the plug so not C1, I will try the ground pin on those pins

Cheers Ronnie
 
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ronnie63

ronnie63

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Just checked again using ground pin on the actual plug if the bottom 2 pins are 4v and 8v I'm reading 12v on both? not sure what the pin is below the common? I'm reading 5.7v on both pins of Q1, C1 looks bloated one end!

Thanks Ronnie
 
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ronnie63

ronnie63

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Right I messed up testing the voltages buy using wrong ground for reference! All voltages from psu are correct now.

So title changed to cpu repair, Started out by replacing the 5101 ram, no change! Of to look at pinrepair and see what I can learn.

Cheers Ronnie
 
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ronnie63

ronnie63

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Right bit of a result! The AC in on the psu plug was flaky cutting the power to the displays, once this was wiggled a bit the game booted! I can start a game but no sound but pressing the switch on the sound board cycles the sounds?

Switch wise on the playfield they all seem to register but coil wise it seems only the target resets are firing! No flippers, pop bumpers the 1 slingshot etc, but the hole kickout worked, so really 4 coils work. The 3 taget resets and the hole kickout. all the fuses are good inc the one on the bottom of the playfield, the 2 bridges are reading around 24v DC

I know there are lots of jobs to do with these crappy connectors, the ground mods. and sort out some fancy choc block mods to some of the coils! re cap the psu and sound board but I want to make sure these spider chips are good before I go much further,

Advice from those in the know warmly welcomed?

Thanks Ronnie
 
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ronnie63

ronnie63

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Ok further digging

If I activate the T relay under the playfield the flippers work so that relay is not energising in the game.

The sounds according to the chart in the head are Q26,27 and 28 listed as chimes but mine has a sound board, I tried grounding their tabs but all 3 seem to energise the playfield relay or relays so a bit lost with that? I guess I need to pull the driver board an test the transistors, but nothing looks scorched at this point

Pin repair says the 3 sound switches are controlled by a rockwell chip that's obsolete, so that's a worry R3272-12 although I can't find it!

Thanks Ronnie
 
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ronnie63

ronnie63

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Ok ignore all that above! I stupidly left the right connector off the driver board when I re attached the head! it was still hidden in the base! DOH!

Most everything is working apart from the trough kicker which the owner said was a problem before it died. I'm chuffed so far but much to do
 
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ronnie63

ronnie63

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I re capped the whole psu, but now lost my -12v! I'm reading -15v to the tab of the -12v regulator, I replaced C4 with a 220uf 250wv cap, and I'm reading 97v across it, all other voltages are fine, is it possible the 7912 is bad all of a sudden, I have double checked the polarity of all the caps and they are fine!

Thanks Ronnie

From the repair guide

The negative voltage -12V is created by rectifying two times 14 volt AC transformer windings with diodes CR3 and CR4, and filtered by cap C4 (200 mfd 150 volts). Then a 7912 voltage regulator is used to keep the -12 volt DC output right at -12 volts.
 
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ronnie63

ronnie63

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Things gone from bad to worse! I was probing round the 7912 and my probe slipped! Not sure what it touched but board is dead now! fuses all intact I have ac coming in on the bottom of the psu, no idea what I killed!
 

drhex

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Please disconnect the output of A2 first so nothing further down gets damaged. OK, so you have all AC voltages measured on A2 P1 vs pin 3 there? Nothing anywhere else, e.g. all outputs are dead incl 60V and 42V?
 
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ronnie63

ronnie63

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Sorry to update! I missed a fuse for the small transformer it was blown, replaced it but as soon as I connect AC plug to psu it blows again, the 7912 is short to ground all pins so guess that’s the issue ?


Thanks Ronnie
 
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ronnie63

ronnie63

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Please disconnect the output of A2 first so nothing further down gets damaged. OK, so you have all AC voltages measured on A2 P1 vs pin 3 there? Nothing anywhere else, e.g. all outputs are dead incl 60V and 42V?
Thanks for reply have updated above
 
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ronnie63

ronnie63

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Yes, that is toast then. Snip out and see what happens.
Cheers have ordered some 7912’s I’m guessing it was bad before I shorted it as I had -15v on the tab but nothing on the output ? I think I used my last 1 amp slo blo , will need to have a rake around but might need to order some of those too

Thanks Ronnie
 

drhex

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Just stick some smaller fuse in, you're testing it unloaded after all. -15V sounds like it didn't regulate, so yes, probably broken beforehand.
 
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ronnie63

ronnie63

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Just stick some smaller fuse in, you're testing it unloaded after all. -15V sounds like it didn't regulate, so yes, probably broken beforehand.
Thanks for that, got plenty 500ma so will bung one in tomorrow and check it with the regulator snipped, don’t fancy splitting the pcb from the heat sink again so will probably try soldering the new one on component side.

Thanks ronnir
 
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ronnie63

ronnie63

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I snipped the 7912 but I'm still reading short to ground on pin 3? So pin 1 is ground pin 2 the input and pin 3 the output, I can't see the solder side of the pcb but maybe the remaining legs have crossed somewhere?

Thanks Ronnie
 

drhex

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1 and 3 counted as ? 3 should be the input and be connected to CR3/4. you wrote above that it is the output. That would mean SCR201 or C5, maybe R9.
 
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ronnie63

ronnie63

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Sorry I looked at the pin outs for a 7912 and first pin ground middle pin input last pin output, last pin has continuity to the -12v pin on top connector of psu I must have that wrong! I can’t even find the 7912 on the schematic lol

So for clarity the outer pins where the 7912 goes on the pcb have continuity to ground.

Thanks for your help I’m a bit stuck with it. Annoying as it was working fine before the recap!

Cheers ronnie
 
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ronnie63

ronnie63

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And I’m using backbox metal as ground? This could also be wrong? I know you need to use different grounds to test the voltages the negative of c1 and the other big cap
 

drhex

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It is the thing called LIC1 on the schematic. So pin 1 ground is correct. You‘r saying that output has continuity to -12V pin as well as ground? If so, see above.
 
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ronnie63

ronnie63

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Thanks so I should check SCR201 or C5, maybe R9. I think I will need to pull the pcb off the heat sink after all

Cheers Ronnie
 
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