Power supply issue after NIMH tests ok.

[61Wally]

Any Suggestions of where to go for service manual or parts. I thought I’d ask here before going to the classifieds, Thanks again for Everyone’s help.

[Badbaud]

You should be able to find a schematic of the power supply in Downloads.
There is a small filter for the 5 volts that goes bad and you can jumper across it to get the game going.

[UNIMAN]

Suspect failed noise filter in power supply.

Third post down describes removal of un-needed noise filter. /nlg/index.php?topic=177.0

[61Wally]

OK I will try and find the schematic for this. I took the power supply out and when I opened it I didn’t see any noise filter. In that area it looks like something was in there once upon a time. Unless this is a totally different type of power supply? ( Couple pics of it ).

[61Wally]

Thx for the reference material. I tested All of the pins that were listed and I’m Not sure if I’ve tested the pin#8 correctly. It’s supposed to be 9.5VAC. If I put a test lead on pin #8 to ground I get 4.1VAC. I also put lead in pin #8 to All the other pins and I don’t have 9.5VAC on any of those combinations. Only thing close was pin #8 and the “0” on the transformer. That gave me10.1VAC. If I put a lead on pin #8 where should I out the other one to test for 9.5VAC?
BTW My supply is a Yellow Dot, 5th picture.

[61Wally]

Sorry, My supply is Yellow dot, like the middle picture (3rd) one

[61Wally]

One other piece I’d like to ask about is this Gray switch that I must have snagged my shirt On and broke off part of the plastic housing. The Arm assembly solenoid was loose, So I tightened the screw. This was done in the same time frame that It died,(just noticed it).

[Pitts256]

The grey switch monitors the position of the pull handle unlock solenoid lever. If you still have the cover I'd tape or glue it back on to protect the electronics.

The power supply doesn't have the EMI filter, it's been removed.

The Yellow Dot power supply provides 24v to the fluorescent light electronic ballast. Are there fluorescent light starters on the backside of the main door? If so you have a RED Dot and the fluorescents are on 110v.

So if the fluorescent lights are on there's 110v power to the power supply.

Appears as though you're not getting +5VDC to the CPU and other devices.

That would be the 5amp fuse F3 (9.5VAC to +5VDC)

You can check the DC voltages at the 12 pin Molex plug CN-4 on the frontside of the power supply.

CN-4 pins
1) +5VDC PINK
2) +24VDC ORANGE
4) +12VDC RED
7) GROUND BLACK
11) +32VDC VIOLET

Check the voltages to ground, pin 7.

[61Wally]

When I checked the voltages on the power supply prior to this I did it with No load and power supply removed from the machine. I will reinstall it and I was wondering can I plug the Molex connectors back in and check those voltages right at each Molex connector pin?

[Pitts256]

I'll typically check the voltages with the Molex's plugged in so the power supply is loaded.



 

[61Wally]

OK, I appreciate All of Your input on this machine, I go see what results I can come up with. Thanks again.

[61Wally]

Here’s the results of the Voltages:
Pin#1)  1.49VDC
Pin#2)   22.21VDC
Pin#4)  12.43VDC
Pin#11) 35.75VDC

ALL of these readings were taken with Pin#7 used as ground.

[Pitts256]

There's low voltage on pin 1, should be +5vdc.

Do you get the same low voltage on pin 1 with CN4 unplugged? First double check that F3 fuse...still no +5vdc? The voltage regulator on the topside of the power supply has died. The voltage comes up with CN4 unplugged? There's probably a short somewhere in the chassis or maybe the MPU battery area?

[61Wally]

Ok here’s the Voltage readings for this Universal?
BTW how do I find the model number of this machine?

Pin#1)   1.49VDC
Pin#2)   22.21VDC
Pin#4)   12.43VDC
Pin#11)  35.75VDC

Pin#8)   5.23VAC

ALL of these were tested utilizing Pin #7 for ground.

[61Wally]

I get 6.59VDC on Pin#1+, Pin#7GND

[61Wally]

Time to troubleshoot the board issues, I hope there’s a fix for this that I can accomplish. I really appreciate the time and guidance You’re giving me, I enjoy ALL these different learning experiences.

[Pitts256]

The +5vdc needs to rock solid. So the the fact that the voltage is going from 1.49 to 6.59 tells me your power supply is tanking. I would disconnect the CN4 plug until it's fixed. Two things to replace, the large filter cap (22,000mf-16v) on the inside and the +5vdc voltage regulator on the topside. The capacitor will be easy to find, check Mouser. Replacing the capacitor may fix the issue so replace it first. First check the value to make sure it's 22,000mf-16v. It's attached to the wall inside of the power supply case, both leads attach to the voltage regulator. Take a screwdriver and short the two pins together to discharge any residual voltage before disconnecting the wires. Make a note of which wire connects to what terminal, it's polarized. Order a 22000 uF 16 VDC Aluminum Electrolytic Capacitor - Snap In. The part number for the +5vdc regulator is UA78h05SC with a TO-3 case. You could also post a want ad and see if there's a working RED DOT available from a NLG member too.

[61Wally]

I really want to THANK YOU SO MUCH FOR EVERYTHING. When I replaced the battery and everything worked, I sent video to my friend. It was his dad’s and they All had tears,( I heard) then it took a dump and I feel awful. I’d give him a machine but he the memories. That’s why I will do anything necessary to get this going.
After I replace the cap should I try it or wait until the mosfet gets replaced too? I have thousands of caps, and other electronic be parts. Do You happen to  b know the specs that I would need so I can look in my pile and see what’s what? Thx.

One last question, Do You know the model of this machine or where it’s hiding?

[61Wally]

Do You know if Ci can take a Very accurate 5v power supply and tap in/bypass the wiring in the machine and install it SOLO? I also have cases of every power supply made?

[Pitts256]

For a direct replacement order a 22000 uF 16 VDC Aluminum Electrolytic Capacitor - Snap In.

Or you can use a radial or axle polarized 22000 uF 16 VDC Aluminum Electrolytic Capacitor.

It's a 3 LINE MODEL 8938-0001 with an 8116 main board. The ID Label is normally riveted to the outer right side of the cabinet.

I can't recommend using an external supply, could be grounding and permissive issues. The main board appears to be functional, if we damage it...game over.