MV-1C Voltage Issues

Hey everyone. I've got an MV-1C board I'm working on consolizing. I had gotten everything up and working, but my PVM started going on the fritz which made me run some tests on the CMVS where I found there was voltage coming across the video lines even when the console was plugged in, but switched off.

I'd been using WulfsigeAK's daughter board, a NeoSaveMasta VMC (previously a NeoBiosMasta) as well as the stereo mod. After ensuring everything was grounded, I was still reading voltages roughly in these ranges:

MV-1C off and disconnected from power: ~0.1-0.2v

MV-1C plugged in to power, but switched off: ~0.6-1.5v

MV-1C plugged in and on: varies, between 1-2.5v

My next step was to remove just about all the modifications I've made. I removed the daughter board and the NeoSaveMasta VMC & cleaned up their solder. The stereo mod is still installed. I read these voltages directly from the JAMMA edge:

MV-1C off and disconnected from power:: ~.03v
-- Reading +5v and GND contacts: 0v

MV-1C plugged in to power, but switched off: .4-.9v
-- Reading +5v and GND contacts: 0v

MV-1C plugged in and on: Varies, haven't seen it higher than 2.5v / .5-.6v with no game/crosshatch
-- Reading +5v and GND contacts: ~5.10v


The +5v & GND contacts/connections always seem to read correctly (0.0v when plugged in & switched off, around 5.15 volts when switched on).

Here are some of the power-related parts I'm using:

Power supply: http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2256982_-1


Power port: https://www.radioshack.com/products/radioshack-size-m-coaxial-dc-power-plug?variant=5717483397

Switch: http://www.vetco.net/catalog/product_info.php?products_id=893

Does anyone have any suggestions on what the cause might be? I'm in the process of trying to track down another MV-1C to compare against, but ideally I can fix whatever's causing this issue on this board.

Thanks!

Anyone have any suggestions? I'm not sure where to go from here to try and fix it.

disconnect the backup battery and see what happens. The MV-1C's backup ram circuit is cursed.

Niko49 said:

disconnect the backup battery and see what happens. The MV-1C's backup ram circuit is cursed.

Click to expand...

Is that just removing the battery (which seems pretty stuck on this 1C)? Desoldering the battery holder?

kragit said:

Is that just removing the battery (which seems pretty stuck on this 1C)? Desoldering the battery holder?

Click to expand...

Yea, you would have to desolder it. I was only half way being serious though. I've noticed the backup circuit on the MV1C tends to leak current. Not much you can really do about it though. Other possibility for reading voltage while MVS is unplugged would be from the capacitors still holding a charge.

Reading voltage from the RGB lines is normal, I'm not sure what the normal range is, but 1v ~ 2.5v seems pretty harmless.

Niko49 said:

Yea, you would have to desolder it. I was only half way being serious though. I've noticed the backup circuit on the MV1C tends to leak current. Not much you can really do about it though. Other possibility for reading voltage while MVS is unplugged would be from the capacitors still holding a charge.

Click to expand...

I was able to get the battery out, but no change in voltage readings. I'll desolder the holder and test that too. At this point, I'm willing to try anything.

None of the capacitors are visibly bad (none are bulging) and the voltage doesn't slowly decrease once unplugged. It'll go from ~.7v when plugged in but off to ~.03v right when it's unplugged.

The board itself isn't the cleanest and it's completely possible there's some damage or otherwise uncorrectable issue, which would suck. I'm also trying to find a cleaner 1C to test against, but that's not been easy, unfortunately.

Niko49 said:

Reading voltage from the RGB lines is normal, I'm not sure what the normal range is, but 1v ~ 2.5v seems pretty harmless.

Click to expand...

Right, the voltage is normal for when it's sending out video, but I'm sure it shouldn't be sending out anything when the CMVS is plugged in, but switched off. The guys at Jamma Nation X have said 0.7v-1.3v is normal for when it's on/sending a video signal.

A quick update. Got a new, cleaner 1C board in. Haven't made any modifications to it. Still has the same exact issue.

I've had another individual suggest the battery backup may be causing the issue, so I suppose that's the next step if no one else has any suggestions.

If another board is doing it, I would think it's your monitor, the diodes could be going bad.

Xian Xi said:

If another board is doing it, I would think it's your monitor, the diodes could be going bad.

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Well, this second board hasn't been connected to the monitor at all. All I have connected is the power jack to a rocker switch which is run into WulfsigeAK's daughter board and I read the voltages (when the switch is in the off position, but the power supply is plugged in) from the JAMMA edge (on the 1C) and the screw terminals for the RGB out (on the daughter board). When I'm reading the voltages, they only appear on the R, G & B lines. Sync reads as 0v (when not plugged in & when plugged in and switched off) and as ~5v when on (which I believe you mentioned in our email correspondence is normal for the Sync line).

On the old board when reading these 'rogue voltages', I had tested without WulfsigeAK's daughter board and still read them, so that shouldn't be causing any issues.

Try shorting power and ground on the board with the board off. If it's just residual voltage in some caps/IC then the short should get rid of them.

Xian Xi said:

Try shorting power and ground on the board with the board off. If it's just residual voltage in some caps/IC then the short should get rid of them.

Click to expand...

Just shorted power to ground (on the board itself) when the board was (plugged in but switched) off, no change.

Few notes, this board is still unmodded, so the battery backup is still all intact (battery reads at 2.08v).

The voltage drops down to 0v as soon as the power is unplugged (the board has always been switched off, never switched on).

EDIT: Further testing seems to indicate JAMMA contacts 6/F (+12v), 8/J (Coin Counter) & 10/L (Speaker) also seem to have voltage running through them when the board is plugged in to power, but switched off (6 = ~0.127v / 8 = -0.50v / 10 = -0.19v). Capacitor AC5 shows ~0.127v under the same setup. None of these voltages dissipate when the power supply is disconnected and shorting GND to +5v on the board seems to have no effect (again, after the power supply has been disconnected).


At this point, it really seems like it would be something super simple, since no one else seems to have encountered the issue before and I'm pretty new to the modding/arcade/etc scene.

What meter are you using for these tests?

I just checked a few of the MV1Cs I have, they all have a very small amount of voltage. But I don't have problems with my monitor dude. You should really check your monitor to see what the problem is. Also keep in mind that some MV1Cs will require a sync cleaner. It happens rarely, but it does happen.

Xian Xi said:

What meter are you using for these tests?

Click to expand...

Mac Tools ET 332

Xian Xi said:

I just checked a few of the MV1Cs I have, they all have a very small amount of voltage. But I don't have problems with my monitor dude. You should really check your monitor to see what the problem is. Also keep in mind that some MV1Cs will require a sync cleaner. It happens rarely, but it does happen.

Click to expand...

How much voltage? The .4-.9v I read seems like it should be too high for a board that shouldn't be getting any power. One of the other individuals I've talked to who has built a few of their own CMVS' report that they don't have any voltage on their video lines when it's plugged in, but switched off.

I've tried to reach out to get support on the monitor as well, but as with the 1C, no-one seems to have any concrete ideas. I did get some suggestions on fixes, but the combination of the monitor being very compact and not knowing exactly what I'm looking at makes things very tricky to diagnose/fix.

Before the PVM went wonky, things were working/looking great. No issues with color or sync. The PVM was unplugged from the wall and the CMVS was left plugged in, but switched off and connected to the PVM via video cables. It sat this way for a week. At the end of said week, I plugged the PVM back in and turned the CMVS on, played for a little bit and eventually the PVM screen started to get a green tint, slowly started to show retrace lines and eventually got to this point (dropbox MP4). It's completely possible the PVM just happened to have issues that were completely isolated from the CMVS, but with the timing of everything, it's still very suspect.

I'm just being very cautious about it all because the CMVS will be sent to someone and I don't want to damage their equipment.

Per the JammaNationX tutorials/mods, caps AC5 through AC10, cap C6, & the VR1 potentiometer have been removed. The heatsync remains. NOTE: The mark in the last picture (the one that looks the lightest green) is sharpie.



The battery charging circuit has also been removed (R36, D5 and D6) as well as the old battery (no new battery holder has been installed yet).



Still read ~0.5v-0.6v when the CMVS is plugged in, but switched off.

Elsewhere someone advised me to measure resistance.

The multimeter I'm using is the Mac Tools ET 332. When touching the leads together, it most commonly reads between 0.15-0.25 ohms. I'll list the resistance as it's displayed and also list a zeroed-out resistance (zeroing the reading out at 0.20 ohms when the leads are touching).

JAMMA GND to Video GND:
-- Nothing connected: ~0.19 to 0.20 ohms (0.0 to -0.1 ohms)
-- Power and Ground connected* (AC cable unplugged): ~0.17 to 0.19 ohms (-0.2 to -0.3 ohms)
-- AC cable plugged in (rocker switch to off)**: 0.18 to 0.19 ohms (-0.2 to -0.3 ohms)
-- Console switched on ***: 0.81 to 0.82 ohms (0.45 to 0.46 ohms)

Daughter board installed and power/ground ran to screw terminals:

Screw Terminal Ground to the Screw Terminal Video Ground
-- Power supply completely unplugged: ~0.42 to 0.43 ohms (0.25 to 0.30 ohms)
-- AC Cable unplugged*: 0.43 to 0.44 ohms (0.15 to 0.16 ohms)
-- AC Cable plugged in**: 0.68 to 0.71 ohms (0.15 to 0.16 ohms) - [A future non-zeroed out reading was closer to 0.45 ohms]
--Console switched on ***: 13.2+ ohms (13+ ohms) -- [A previous non-zeroed out reading saw 19+ ohms]

* (R/G/B to video ground reads ~.003v)
** (R/G/B to Video Ground most commonly reads ~0.7 to 0.8v)
*** (R/G/B to video ground reads 0.168v -- should be crosshatch)

At no time is the CMVS plugged into a monitor or anything. Despite the difference in ohm reading with/without the daughter board when the console is switched on, I still read the voltage on the video lines when the console is plugged in, but off.

WulfsigeAK has mentioned that when he tested his CMVS', he didn't read any voltages. Xian Xi/JNX above has said the 1C boards he has have a small amount of voltage, but didn't mention how much. So I'm still stuck in a knowledge limbo.

I'm trying to figure this out, as I had a PVM kick the bucket while connected to my CMVS. Now, it could be a coincidence, but as I'm building this CMVS for someone else, I want to be 100% sure that the 'rogue voltage' wasn't the cause.

Oh, you should have mentioned earlier you were following jammanationX tutorials, might have answered you own question