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Gottlieb System 80A Sound Board

JMP

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10 Years
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Aug 12, 2011
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Lancashire
Super Orbit almost working but no sound... and nothing from test button. Fuses, volume pot and speaker connectors checked. It's this version (1st pic) with dedicated PSU (second pic). New replacements available but in excess of 350 Euros (!) and shame to buy both if I only need one of them.

20200903_204522.jpg
20200903_204516.jpg

Something smoking in the centre of that PSU? 😄

As it's totally silent other than some white noise/buzz, I originally suspected the PSU and have re-flowed all solder and checked traces but nothing.... so suspect fault component on this or the sound board itself. I've ensured the wires are pushed home on the connectors.

Any way of diagnosing that the soundboard is at fault and not the dedicated PSU (I have no spares). Bit clueless with a multi-meter (!) but did read voltages coming from certain pins on the connector to the sound board.

Cheers.
 
Last edited:
So now I'm thinking the LM379S sound amp chip as appears a common fault. Anyone suggest a way of testing mine to clarify this?
 
First job is to check the PSB output voltages from the soundboard against the schematic.
Personally I would re-pin the connector A7-J1 and check the finger traces on the board are clean.
It wouldn't hurt to replace the capacitors if they are original.
Unless any of the components are unobtainium it doesn't look like it would cost the earth to replace all the components on the PSB.
At least then you can rule it out when diagnosing.

Sent from my SM-G960F using Tapatalk
 
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Cheers, I have cleaned the contact traces and could re-pin the connector when crimping tool arrives. Components are original AFAIK so will seek help to source these (this is where I get lost) @Arv
 
On that PSU replace:

R1 with a 1.5K 0.5W resistor
CR1 with a 1N4746A 18V 1 watt zener diode
 
In general the resistors are carbon film through hole type.
The one @Arv listed is a 1.5k ohm 0.5 Watt type. RS Components, Farnell and many other suppliers will carry these.
They should also have the diode. Just search for 1N4746A.
Don't forget the caps:-) They big ones are radial electrolytic. You need to get the same capacitance.
If you can't match the voltage its ok to go higher e.g. you need a 16V cap but can only get 20V- this would be OK. But don't go lower.
Finally get ready for the "Oh sh*t" moment when you realise you need one extra item when its too late to change the order :-)

Sent from my SM-G960F using Tapatalk
 
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You can test the 740x IC's buzzing them on diode test also at the pins in yellow.

1599213052378.png
 
Cheers all. Sound board PSU now tested out fine and ordered bits from Amazon to try keep it that way. Subject to re-crimping of new pins into some connectors still to do, sound board will likely go out for repair to ensure I don't make it worse.... like hen's teeth to source, never realised so many variations on System 80A's.
 
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