Author Topic: GTB Sys 80 diodes  (Read 176 times)

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Offline Retropin

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GTB Sys 80 diodes
« on: November 08, 2008, 05:54:06 PM »
can anyone confirm that the diodes on a sys 80 game for the coin door switches are 1N4004??

Offline Pinball Fixers

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Re: GTB Sys 80 diodes
« Reply #1 on: November 08, 2008, 08:29:58 PM »
From memory they are Gavin.

Being switch matrix, anything from 1N4002 to 1N4007 should be fine.

Offline Strangeways

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Re: GTB Sys 80 diodes
« Reply #2 on: November 08, 2008, 10:49:25 PM »


Gav - I have a few in the garage I can check for you, mate - I'll look tomorrow - or check the schematic on the Rocky.

From memory, they are germanium 1N914... But you can use 1N4148. I use them on switch matrix for system 1 machines..
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Offline Pinball Fixers

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Re: GTB Sys 80 diodes
« Reply #3 on: November 08, 2008, 11:13:32 PM »


Gav - I have a few in the garage I can check for you, mate - I'll look tomorrow - or check the schematic on the Rocky.

From memory, they are germanium 1N914... But you can use 1N4148. I use them on switch matrix for system 1 machines..

Hmmm, you could be right there Nino... maybe my memory is failing me  :lol :lol

Offline pinnies4me

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Re: GTB Sys 80 diodes
« Reply #4 on: November 09, 2008, 06:09:01 AM »
IN270 ???
“If you wanna escape, go up to a pinball machine. There’s a magic button on the front that makes the whole universe disappear.”

Offline Mr Pinbologist

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Re: GTB Sys 80 diodes
« Reply #5 on: November 09, 2008, 08:33:02 AM »
1n270 is a germanium diode, which may be hard to get. any of the silicon diodes mentioned above (1n4004, 1n4148 etc) will work fine. I too have used 1n4148 (1n914) in the switch matrix of my own system1 games and they work fine.
« Last Edit: November 09, 2008, 08:37:41 AM by mitch »

Offline Strangeways

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Re: GTB Sys 80 diodes
« Reply #6 on: November 09, 2008, 09:33:57 AM »

1n270 seems to be the diode used in the switch matrix on system 80s. Confirmed in the Spirit Manual.

I recall trying to get these a while ago and as stated, the 1n4148 has a similar characteristic - I can't exactly recall - but I think it needs to be "Fast Switching"..
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Offline Retropin

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Re: GTB Sys 80 diodes
« Reply #7 on: November 09, 2008, 09:52:51 AM »
Thanks everyone!!

I couldnt get the schematic to download off marvins site. I didnt think they were 1n4004 as these are used throughout  the PF, but the coin door switches are glass type and so i wondered why the difference.
 You know after extensive searching on the web, i couldnt find these labelled as what type they were.

All i got was " if door switch diodes fail then replace" and other such generic statements.
VERY irritating non specific information!

Ive follopwed marvins guide to the earthing upgrades on this machine and also re earthed the whole cabinet etc - no  more shocks!

However, this has not stopped the faults..

Previously the zener had gone on the power board for the 8.2V, ive replaced this and done the upgrades as mentioned. Game does not boot ( it did sometimes previously). Testing voltages on power board reveals them all to be slightly too high.

5V - cant get below 5.5v
 8v - is 11.5v ( zener is good)
42v (?) - is a whopping 60v
60v is  something like 75v

Any clues?? all help appreciated as this will save me some time..

Thanks  gavin

Offline Strangeways

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Re: GTB Sys 80 diodes
« Reply #8 on: November 09, 2008, 10:50:02 AM »

Gavin,

TP1 is your 60V rail
TP2 is your 42V rail
TP3 is ground for this part of the circuit.

If TP2 is reading 60V then the Zener CR6 is shot (1n4756a). Check R5 (10K). Until these are right - you will get no 42V and the Zener drops 18V.


At the junction "E5" - you should measure 5.6V. R12 (labelled as 0.33, 10% 5W) drops the 5.6V to 5V, at junction "E5". so check for the voltage drop across R12.

The 60V line measuring 75V could be Q1. Collector should measure 76V, Emitter 63.1V - Test Q1

If Q1 is playing up, then 76V -18 = 58V - which is close to the 60V you are seeing at TP2..

Sounds like Q1 Emitter / Collector short..

also check J1 Pins 7 and 8 for 60V AC.


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Offline Retropin

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Re: GTB Sys 80 diodes
« Reply #9 on: November 09, 2008, 11:09:45 AM »
Thanks Nino,

Such a simple board, and yet as i replace one part another fails. should have just rebuilt the whole lot at start.

OK then - time to do this properly...

Offline Pinball Fixers

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Re: GTB Sys 80 diodes
« Reply #10 on: November 09, 2008, 11:19:01 AM »
Thanks Nino,

Such a simple board, and yet as i replace one part another fails. should have just rebuilt the whole lot at start.

OK then - time to do this properly...

Always best to just rebuild the boards and be done with them. Once done properly, they should be reliable for a long time... I prefer this, rather than constantly having to repair one thing after another.

Offline Strangeways

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Re: GTB Sys 80 diodes
« Reply #11 on: November 09, 2008, 11:53:22 AM »
Thanks Nino,

Such a simple board, and yet as i replace one part another fails. should have just rebuilt the whole lot at start.

OK then - time to do this properly...

Always best to just rebuild the boards and be done with them. Once done properly, they should be reliable for a long time... I prefer this, rather than constantly having to repair one thing after another.

Yep - Best advice is to rebuild any boards that are in a "condition alone"...

I might to a "Guide" on the System 1 and System 80 PSU and the Bally Transformer Boards.. Sounds like fun !



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Offline Retropin

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Re: GTB Sys 80 diodes
« Reply #12 on: November 09, 2008, 11:58:43 AM »
Bally Transformer Boards..


...My pet hate

Offline Pinfan

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Re: GTB Sys 80 diodes
« Reply #13 on: November 09, 2008, 02:10:58 PM »
Gav let me know if you have trouble finding IN4148's... Have a few laying around...

Some people have big HEADS !