Qbert - Arcadeshop Switching power supply

pinballdirec

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I was having problems with my Qbert so I replaced my old power supply board with a Arcadeshop switcher kit, that didn't resolve the issue so it has been setting for a while.

I started working on it again and the problem is that it boots up to a frozen screen with small blocks on it. If I press the test button on the sound board I do get a beep. But that is all it does.

I was checking the grounds and I noticed that the Filter Board Grounds were not tied to the power supply ground, Does anyone if they should be?

Thanks Kevin
 
You're with Gobels? Fun arcade. Friend of mine had his birthday there last year. I snapped a photo of how it's supposed to look (minus soundboard). The bundle of grounds does not go to the filter board.

Check voltage at the PCB, perhaps across one of the electrolytic capacitors. If the voltage is good then it's possible you have a board problem. If you get over to the east side of the state bring your board; thats my qbert you see in the photo.
 

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Thanks Joey, My setup looks just like yours, but I have the switching power suppy kit instead of the board like you have.

I want to run all new ground cable and I was wondering the best way to do it. I wasn't sure if all the boards should be grounded together.

thanks Kevin
 
Mmm do what you want, but I'd suggest you test with a DMM before you start hacking. There's no reason to guess the ground wiring is bad -- it's easily proven good or proven bad.

Check the +5v supply at the legs of an IC or across a capacitor on the PCB. If it's below 5.00v then make an adjustment. If it's at 5.00v then you're fine and you might be barking up the wrong tree.

Check voltage drop between ground (at the PCB) and ground (at the PS). If you see a significant voltage drop then there's an issue (and it's probably a burned-up connector, not wiring). If you don't see much drop then you're fine and it makes no sense to replace wiring.

It would be useful you're able to test that Qbert PCB in another known-good machine to be sure the PCB is known-good or known-bad.
 
I was having problems with my Qbert so I replaced my old power supply board with a Arcadeshop switcher kit, that didn't resolve the issue so it has been setting for a while.

I started working on it again and the problem is that it boots up to a frozen screen with small blocks on it. If I press the test button on the sound board I do get a beep. But that is all it does.

I was checking the grounds and I noticed that the Filter Board Grounds were not tied to the power supply ground, Does anyone if they should be?

I've been having the exact same problem! I picked up a Qbert from a klover up in Reno, and have been struggling with it ever since. I thought I had grounding or power issues too, but tightening the grounds, and replacing a missing ground strap had no effect.

I was able to get my board to come up and play once or twice by manipulating the voltage on the Arcadeshop power supply. That worked once and the game played for an hour or two, and hasn't worked since.

I've had the boards 'repaired' by El Dorado, but I know now that they weren't bad cause I had the same exact problem when they came back (it seems EDG took my money, exchanged the board, even though most likely nothing was wrong with it. Fortunately I do have a friend (elevenstrings) who lives nearby with a qbert. Popping the board into his cab, it came up just fine! Taking it back to my house, and plugging it into my qbert machine, it's back to the frozen rom garbage screen.

I've also tried using a known good stock power supply board to no avail. I'm suspecting the small filter board above the sound board or the PCB connector but I'm definitely losing patience.

I'll check the voltages on the main pcb and post back tomorrow. Maybe between all of us we can put our collective heads together and figure this one out.

-BAZ-
Tom Bazzano
 
I had a chance to do some testing tonight, and with the Arcade Shop switcher set to 5.05 (measured at the switcher), the PCB main connector was getting 5.05 volts DC, and at the 2 obvious capacitors on the board, I measured 4.85 volts DC. Adjusting the voltage has no real effect on the gardbage displayed on screen.

Pindirec - Did you have a way of running your board in another cab to verify it works? Have you had a chance to check your voltages at all?

-BAZ-
Tom Bazzano
 
Hi Tom, I reflowed the soldier on my interface without any luck. I spot checked a few voltages and they were around 5.10. Any ideas where are the best points to do a voltage test? I attached a picture of my screen...
 

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Any ideas where are the best points to do a voltage test? I attached a picture of my screen...
Easy peasy lemon squeezy. Check 5v supply:

- Across C27 on the top-left side of the board.
- Or on the 8088 processor from pin40 (top right, 5v) to pin 1 (top left, gnd)

Check 12v supply:

- Across C26. Check the schematic, it's a tiny diode/resistor sized one right near the battery.

You doubted your wiring, so use the testpoints described above and check:

- From ground on PCB to ground on the power supply. Just tested my board and it said 0.001v. Not bad.
- From 5v on the PCB to 5v on the power supply. Just tested my board and it said 0.190v drop across the wiring. That makes sense because I read 5.0v on the power supply and 4.8v at the board. My connectors are a little burned-up, add some resistance, and need replacing.

You said the spot checks are 5.10v, so you're pretty close to eliminating the power as a problem. You should pursue finding another machine to test your boards in.
 
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Kevin,

The output on your screen is near identical to mine, and when I put the board in a known good Qbert cab, it worked. I still haven't figured out what's causing this on my machine, but I do know that to get 5.0V on the board, I had to crank the arcadeshop switcher up to 5.15 Vdc.

There's a big voltage drop from the board connector to the test points I used, but nothing out of the ordinary from other Working Qberts I've seen. Unfortunately, I won't be able to troubleshoot my board/game much further right now, as I've fried a diode while being careless. Once I get that fixed and re-verify that the board is again good (in another qbert) I can contribute to the thread a bit more. Till then I'll just be reading in case you're able to get it fixed.

-BAZ-
Tom Bazzano
 
Hi Joey, I took some voltage readings tonight...

1. Across C27 4.51 volts

2. intel 8088 with the postive on pin 1 and negative on pin 40 it read -5.15 volts ????

3. Across C26 .09 volts ???

4. Pin 1 on intel 8088 to power supply +5 was 5.18 volts

5. Pin 40 on intel 8088 to power supply Ground was 5.28 volts


It looks like I have a couple problems... Kevin
 
Hi Tom, My game played ok until the original power supply died, The install for the New powersupply looked pretty straight forward. Maybe I missed something. My volt appear to be backwards on the CPU..
 
Kevin, I had it written backwards in my previous email. I'm going to try to edit and correct the post right now. On the CPU pin 1 is ground, pin 40 is +5v. As a result it looked like a negative voltage (probes were opposite what was expected). But you saw 5.15 which is fine. Try it again the correct way and the numbers will make more sense.

You might want to investigate that +12 though. Double check that you measured the correct part. It looks like +12 comes in on the edge connector pin 27? Follow it with the schematic.
 
4.799 across C27
4.824 at the 8088 processor

They're both a little lower than I'd like to see, but my game runs fine. As I commented earlier it's probably because my connectors are in nasty shape. I'm not sure why your C27 read so low but I would suggest to double-check at additional points (power/ground on the EPROMs or RAMs) before you stress about it.
 
Qbert is finally going.... It was missing the 12volts to the logic board, someone had modified the harness when it had the original power supply board in, when we replaced the power supply board with a switcher it wasn't getting the 12 volts.

Thanks to Joey & Tom for all your help.... attached is a picture of the connector that was modified.
 
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