V2000 vector issue

debaser138

Well-known member
Joined
Mar 1, 2009
Messages
1,029
Reaction score
64
Location
Grand Rapids, Michigan
I've got a V2000 monitor in an Asteroids machine that is on location. It was working great for about 2 years and then recently the HV diode crapped out. I installed a new HV diode and the monitor worked great for about two months and then it started having issues.

The monitor works but there are some weird vectors coming up and are originating from the middle of the screen. The monitor had been capped a few years ago. I checked all the caps on the HV board and found 1 that had high ESR so I replaced that along with the other caps on the HV board. I went thru all the caps on the deflection board and they were good.

I've uploaded a video for reference (I'm testing the monitor off my Omega Race cabaret):

https://www.youtube.com/watch?v=1qETbL0Rnho

Does this appear to be an issue with the Z circuit on the deflection board? Any ideas on what is going on would be appreciated. Thanks!
 
Can't say I've seen that one before exactly. Could be anything I suppose, but the most common thing with G05-802's and v2000's, *if* they have not had the resistor mod done, is that the resistors basically bake several of the small transistors in the upper corner. These usually cause dimming of the picture, but there is other Z functionality there as well. You want to remove the two large power resistors, replace them with pieces of wire, and replace the transistors in that upper corner near them.

Here's an old thread about it. (See posts 1 and 33). Not exactly your same behavior, but you want to do the mod anyway, if it hasn't been done, as it will cause issues eventually:

https://forums.arcade-museum.com/showthread.php?t=356350&page=4


Given that it's a curved type of noise, that almost makes me think it's maybe power related, maybe a bad filter cap or something. Hard to tell without digging into it.

If you want to trade it in for a rebuilt board, I have them available (or I can fix yours). PM for details.
 
Can't say I've seen that one before exactly. Could be anything I suppose, but the most common thing with G05-802's and v2000's, *if* they have not had the resistor mod done, is that the resistors basically bake several of the small transistors in the upper corner. These usually cause dimming of the picture, but there is other Z functionality there as well. You want to remove the two large power resistors, replace them with pieces of wire, and replace the transistors in that upper corner near them.

This deflection board has the jumper wires on the solder side for R100 and R101. The resistors are still in circuit. Should I cut those out or does it not matter since they are jumpered with thick wires?

Given that it's a curved type of noise, that almost makes me think it's maybe power related, maybe a bad filter cap or something. Hard to tell without digging into it.

Bad filter cap on the deflection board? I went thru the electrolytic caps on the deflection board and they were good. I know it's the monitor as it does this behavior on two different machines. I'll have to dig thru the deflection board some more and see what I can find. Thanks!
 
No, if the resistors are jumpered, that's technically good enough. But it doesn't rule out if damage (or more accurately premature wear) occurred on the components in that corner near them, before they were bypassed.

As for caps, how did you test the caps? You should ideally have a cap meter and ESR meter, as just testing capacitance alone often isn't enough. Also check all solder joints under a bright light, as cracked joints and traces are a common issue with these. (As it is, you always want to reflow all of the connector header pins, as they are always cracked if original).

Also, if you have time, turn the brightness up further, so we can see the retrace lines continuously, then post a pic. Also post a pic of the self-test crosshatch screen. Just to get more info, so I can better see what's going on, to narrow it down further, as it's hard to tell if it's X, Y, or Z at this point.

The fact that the lines are curved like that suggests to me that it's not just a Z issue, as if it was, we'd just see retrace lines, but not curved like that. So it makes me think it's something else. And there's always the possibility that there are multiple issues on top of each other.

I would focus on checking the small TO-92 transistors that are scattered around the board, mostly between the four fin heatsinks and the bypassed resistors. If one of those gets tired and fails partway, you can get weird issues.
 
I tested ESR on the caps with my ESR meter and tested capacitance with my Fluke meter. All header pins have already been reflowed.

I pulled out the deflection board and went thru all the transistors and diodes and they were good. I then went thru all the resistors and I found that R516 (which is in the brightness circuit) was measuring 75K ohms out of circuit. According to the manual this should be a 100K ohm +/-5% 1/4w carbon resistor. This is definitely out of spec.

The interesting thing is, in looking at the markings on the resistor that is at R516, they are Violet, Green and Red, which is a 7.5K ohm resistor. Not sure if the markings are just wrong on this resistor or what.

Andrewb, can you confirm that R516 should be a 100K ohm resistor? Thanks.
 
Yes, it is 100k, measured on two boards I picked at random from my pile.

I wonder what revision of the PCB you have.

Can you post pics of the entire board, both sides, including a close up of the R516 area? (Along with the other pics requested below.)
 
Yes, it is 100k, measured on two boards I picked at random from my pile.

I wonder what revision of the PCB you have.

Can you post pics of the entire board, both sides, including a close up of the R516 area? (Along with the other pics requested below.)

Ok good to know on R516. I replaced it with a 100k 1/2w as I didn't have a 1/4w in that value.

The deflection board is revision P299. Below are a couple pictures per your request. I'll reinstall the board in the monitor later tonight and take some pictures of the brightness cranked up showing the retrace lines. Thanks.
 

Attachments

  • IMG_6710.JPG
    IMG_6710.JPG
    142.4 KB · Views: 20
  • IMG_6711.JPG
    IMG_6711.JPG
    145.4 KB · Views: 13
  • IMG_6709.JPG
    IMG_6709.JPG
    147.2 KB · Views: 16
So I replaced D608 and D708. D608 was actually shorted - D708 was fine. I can't believe I didn't see that earlier. I must have skipped over that diode when I was checking them all.

I reinstalled the board and it's doing the same thing. I can't put the Omega Race (which is what I'm using to test the monitor on) in test mode right now as the wiring for that is a bit hacked up. I cranked up the brightness and took a picture.

Any other ideas what to look for?
 

Attachments

  • IMG_6715.JPG
    IMG_6715.JPG
    86.3 KB · Views: 23
Ok, progress.

If D608 was shorted, it's odd that the board was working at all. You may have a partially blown transistor on that axis, and they often won't register bad measuring them in or out of circuit (unless you actually test hfe). If it were me, I'd swap out the two heatsinked ones on that axis (the -U07 and -U57). Not sure if you have replacements handy though.

Also, have you measured your supply voltages? You should have between 35-40V (and -35 to -40V) on the two DC corners of the bridge rectifier. Just make sure they're both in that range, and approximately balanced.
 
I found some replacement U57's and U07's that I had in my inventory so I swapped out Q606 (U57) and Q607 (U07) but no change. I tested the voltages on the bridge rectifier and I'm getting -27v and 39v. Looks like the negative voltage is low.

FYI I'm testing this 19" V2000 using my Omega Race cabaret which powers a 13" G05. Not sure if this makes a difference but wanted to put it out there.
 
Yeah, looks like something's pulling down that negative side. That's why I was suspecting the filter cap originally. It may or may not be the cap, but in troubleshooting, that's where I'd start. Maybe pull the cap, and start measuring resistances, to see if something is shorted.

Also, I don't know who replaced the other pots on the board, but if it wasn't you, I'd be suspicious all of that work, and any other work done to the board. You may have already found one resistor that wasn't the right value, so maybe look at the solder side to see if/what other parts were replaced, and check to make sure all values are correct. I've seen that plenty of times, and it can take forever to figure out if you don't think to look for it.

These are the kinds of issues where having a second known-good working reference board can save you time, as you can do comparative measurements to try to narrow things down. But in lieu of that, you're just going to have to keep hunting. But you're on the trail.
 
Also, I don't think the 13 vs 19" should matter. (Though I'm speaking for Atari stuff, and I don't know if Omega Race could be different, but I'd suspect not.)
 
Yeah, looks like something's pulling down that negative side. That's why I was suspecting the filter cap originally. It may or may not be the cap, but in troubleshooting, that's where I'd start. Maybe pull the cap, and start measuring resistances, to see if something is shorted.

Which cap? Do you mean C100 and/or C101?

Also, if I'm only seeing -27v coming off the bridge rectifier, wouldn't that mean that side of the BR is bad? What's the part # on this? The manual does not say.

Also, I don't know who replaced the other pots on the board, but if it wasn't you, I'd be suspicious all of that work, and any other work done to the board. You may have already found one resistor that wasn't the right value, so maybe look at the solder side to see if/what other parts were replaced, and check to make sure all values are correct. I've seen that plenty of times, and it can take forever to figure out if you don't think to look for it.

A buddy of mine fixed up this monitor a few years back and it's been in an Asteroids that is on location running 12 hours a day for the last 2 years. The resistor at R516 that was 75K ohms (should be 100K ohms) was definitely original.
 
Which cap? Do you mean C100 and/or C101?

Also, if I'm only seeing -27v coming off the bridge rectifier, wouldn't that mean that side of the BR is bad? What's the part # on this? The manual does not say.


Low voltage could be any one of several things, including low AC from the brick (or a bad connector, cracked trace, etc). I suppose theoretically the BR could be an issue, but I've never seen one fail partially like that. They're just four diodes in a square, so they tend to either work or not, in all of the ones I've ever seen. (And most of the time they short and blow fuses.) You could remove it and test the diode drop across each leg. (And check the AC coming from the brick while you're at it.)

However most likely it's none of those things, but rather something weighing the supply down. Starting with the filter cap, and then possibly anything else downstream. (And yes, C100 in this case, as that's the one for the negative side.) Also, have you tested all of the TO-92 transistors using the DMM/diode test? (Base to emitter, base to collector, and collector to emitter)?

Maybe you could try swapping the two filter caps, and seeing if the issue moves to the other side, but it would be better just to swap the C100 with another known good one.
 
I did previously go thru all the transistors and test them with my meter. They all checked out ok.

I ordered up some new filter caps and will try replacing C100 first and see what happens. I also order some of the BR's to have on hand as well along with a bunch of MPSA05's. As soon as I get these parts and have a chance to work on it again I'll update the thread. Thank you so much for your help andrewb!
 
Ok so I made some progress on this deflection board. I replaced C100 with a new one even tho the ESR on the one installed checked out. I fired it up and I was getting the same thing.

So I replaced the bridge rectifier as the negative voltage was low (around -27v). After doing that I fired it up and the picture looked great! After about 10 seconds I saw a flash from the deflection board and the spot killer LED was on. F700 had blown which was the flash I saw. Pulled the deflection board and Q706 (MPSU57) was completed shorted. Also, Q708 (2N3716) was shorted in all directions and Q709 (2N3792) was open in all directions. These were all fine previously.

So I replaced all those components and fired it back up. The spot killer LED lights up instantly and F700 is blown again. All the parts I replaced except the fuse still test good. I tested the transistors in the 700's and everything looks good. D708 is good as well.

Thinking it might be possible Q707 is failing under load. What else should I be looking at?
 
Back
Top Bottom