Williams Defender Power Supply

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Hello All,

I need some help on a Defender Arcade game.
I cant get the 5 v supply to work on the power supply board.
Now here is the puzzle , I bought another power supply board
rebuilt both with Bob Roberts kits. Both are still missing the 5 v
lights , but both have 12 , -5 volts.
I checked all fuses and resolder all pins and clean board.
Recconnect to machine (only plugging in the 4J1 connector :
>>> On Board Readings
>>> Pin 1-3 10.83 Acv
>>> Pin 2-4 10.83 Acv
>>> +12v and -5 v working
IC 1 pin 12 0 volts

I connected a 23 volt centertp Transformer and it worked (5 volts)
on both power supply boards

The main transformer has 23 volts ,

On the test bench with center tap transformer it works... 27vDC on pin 12 IC1

Connect to machine transformer IC1 pin 12 is at 1/2 volt ( both power supply boards)

Three circuits on the board 5 , 12,-5 volt , if there were a conflict neither or all would not work correct..??
But 12, -5 work and scope them out clean with no spikes..

I am puzzle by this simple circuit, I knew I had the all parts in correct... Now it turning out to be
Transformer.. or ??/
 
Check the transformer voltages at the connector. It may also be the header on the PS board. Reflow the solder on the input header.

ken
 
All votages between pins 1 , 3 23v Ac
Read pin 5,6 centertap 10.83 (pin 1,3) each

I did reflow the header plug , and read with meter - ohm check

I am puzzled , if I hookup the board to another transformer (small 23 v )
The 5 v works and the light goes on.. Looks clean with scope..
 
Transformer or not

I bought another Power Supply , Total of three boards -- all dont have 5v supply , but do you have 12 , -5v ..

On the Transformer pin 1 , pin 3 22v AC , pin 5 to either 1 or 3 reads 11 volts...
with boards not hooked up..

Ohm test 29 ohms between pin 1 , pin 3 -- now pin 1 , pin 5 0 ohms
and pin 3 to pin 5 29 ohms

Can someone confirm readings with a good one....

Does anyone know where I can get a transformer ??
 
Can you check the voltages going to to the wires going to the transistor on the big heat sink.

Blue wire (C) = +12.8DCV
Yellow wire (B) = +6.7VDC
White wire (E) = +5.3VDC

Also the voltages on the pins of IC2 (LM723 voltage regulator nearest to the +5LED):
Pin Voltage
3 = +5.1VDC
4 = +5.1VDC
5 = +51.VDC
6 = +7.3VDC
7 = ground
10 = +6.7VDC
11 = +27.4VDC
12 = +27.4VDC
13 = 7.9VDC

Those values are approximate as they are based on values listed the schematics.

The other thing to check are the values at the test points.
Test point 1 = +5.1VDC
Test point 2 = +12.8VDC
Test point 3 = -14.8VDC
Test point 5 = -5.0VDC
Test point 6 = ground

ken
 
Scrap the above. Check the AC voltage between either pad on fuse 1 to the maching pad on fuse 2. These should be about 20VAC. If you are not seeing this voltage, but you are seeing at the appropriate pins on the connector, then there may be something wrong with the AC connector.

Since you have tried this with other transformers and it works. And you are getting the correct voltages at the connector pins, it may be the connector.

ken
 
It is very common for pins 1, 3, 5 of 4J1 coming off of the trans to burn up making your 4J1 connector bad. Replace the connector at 4J1 on the trans and retest.
 
Yes , have resolder and replace pins on plug, I do have correct voltage from transformer and pins 1, 3 22vac

But this goes away when plug back to board , it drops to 11acv

When I connect it to a outside power supply all is well...5 vdc ..

readings I took earler are windings on the transformer.
Ohm test 29 ohms between pin 1 , pin 3 -- now pin 1 , pin 5 0 ohms
and pin 3 to pin 5 29 ohms
 
The other thing to check are the values at the test points.
Test point 1 = +0VDC
Test point 2 = +14.8VDC
Test point 3 = -14.8VDC
Test point 5 = -5.0VDC
Test point 6 = ground

Yes , have resolder and replace pins on plug, I do have correct voltage from transformer and pins 1, 3 22vac

But this goes away when plug back to board , it drops to 11acv

When I connect it to a outside power supply all is well...5 vdc ..

readings I took earler are windings on the transformer.
Ohm test 29 ohms between pin 1 , pin 3 -- now pin 1 , pin 5 0 ohms
and pin 3 to pin 5 29 ohms
 
See Pictures :

Do you think transformer is dead, or dying on 23vac side or could their be another problem?
 

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I am going to guess that this picture is your PS board hooked up to a separate 23VAC power source.

The only things that I can think of is that there may be a bad connection on the 23VAC wires from the transformer. Normally if a transformer shorts out internally you get a reduced voltage, plus there is usually the smell of burnt wiring and other hints that things are not right.

I have not seen this type of issue before, so I am just going on basic troubleshooting. I would get some 14 or 16 guage wire and create a new set of wires from the transformer lugs to a connector for just those 3 connections (pins 1, 3 & 5). Just like you did for the other transformer and see if the voltage still drops. If it does, then you may have a bad transformer.

ken
 
I have actually seen this a lot, and it is almost always burnt wiring from the trans. Let's see a pic of the trans and the 4J1 connector.
 
Dokert, your right, on this board I replaced the caps and rect ,I didnt do a deep cleaning on board (underside all flux and dust was cleaned), I didnt want add any new problems , I uploaded picture ..who knew it would look so small..I will redo the wires from the transformer to the connector.This a very clean machine ,all wiring looks new for its age.
Yes , I used another transformer to test the 5 v circuit ..
 
Update

Well , I change the wires on pins 1, 3, 5 of 4J1 - no Luck - So, I got 25v center tap
transformer ... Instead of 15v at pin 3 it is 18v .... but I now have 5+ , 5-
But another problem my screen has a pattern screen see pic ,
What do you think is wrong now ?

Thank you
 

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How bad is it ? You think replacing all the ram will fix it ??
I hope Yellowdog will know , This game ran two month ago for two hrs (off for a year)
and it went out on the next startup, I need to move it and wanted to sell it then it crap out.I guess she we were parting ways after 20+ years.
 
It is always hard to say when just looking at pictures, but my guess is that the MPU board is not seeing the correct voltages, so the CPU chip is not running. Jailbars like that are very common when the CPU is not running or is not able to address the watchdog reset memory address. This causes the watchdog to continually reset the CPU.

Replacing the RAM will probably not fix the issues.

The root cause needs to be found and fixed. My guess is that the power supply needs to be rebuilt and the MPU board probably needs some work.

If the power supply is rebuilt correctly, that will probably take care of the transformer issue.

ken
 
If the power supply is rebuilt correctly, that will probably take care of the transformer issue.

Problem is the powersupply board is OK (I have three of them ) all check the same , The problem I have is the main Transformer is 7v out instead of 23v , so I bought a 25 v center tap . I cant find 23 v -- so my output is pin3 18 volts instead of 12-15 volts.
They have a 20 volt center tap , should I try that ?

I can send you the boards and will see they are OK ?
 
It you are seeing the same issue on multiple ps boards, then the problem may be the connector pin(s) on the transformer connector. Transformers typically will not drop voltage as power is drawn. The usual failure mode is a short, in which case the voltage would be conssitantly low or would blow the fuse if it was the primary side.

The connector pins can become burnt or corroded and this will act as a resistor, limiting the amount of power that can be drawn. The voltage then drops as a result.

The biggest problem is that the higher voltage would raise the +12V & -12V unregulated voltages. That is not a siginificant issue as the only thing powered off the unregulated voltages is the sound board and it has its own onboard voltage regulator.

ken
 
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