MVS MV1T power issue

BulletMag

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This post was originally in the general discussions thread, i didn't realise until after i posted that it was in the wrong place.....

Hi guys, I have just picked up a MVS MV1T board,
It was sold as not working "worked previously before being put into storage"
There was minimal battery corrosion but there does appear to be oxidisation on several components in the area where the battery used to be.

My issue is that I am using a Pc psu and have wired a fresh jamma connector with the ground, +5v and +12v (nothing else at this time) I have use the 4 pin PCs molex rather than the large connector on the psu but whenever I connect the jamma connector to the board the psu trips and turns off, I have to disconnect the psu to reset.

I have +5 and +12 on the connector in the correct pins while its disconnected from the board but as soon as I connect it ..... Psu turns off 😩

If I connect +12v only the psu stays on so the issue is with the +5v line shorting somewhere.... Trouble is I'm not sure where to start.

Could anyone help as to where I begin to troubleshoot this board? I can't seem to find much info regarding the mv1t revision board.

Any help would be greatly appreciated
 
UPDATE...

I hit the whole board wit some IPA and it cleaned up nicely,
I have been over the unit with a inspection lense and found no broken tracks at all
The components around the battery were a little green before I cleaned them up but I replaced them as a precaution (2 transistors, 2 diodes and 5 resistors) I have also removed and ordered replacement crystals and the ceramic capacitors that accompany them.
I noticed my 4990a had no markings at all and also had green pins so I ordered a replacement for this too.

Sadly the my PSU still powers off when I connect it to the board 😔 So I looked though my spares box and found an old external HDD PSU that supplies both 5v and 12v but it's only 35w but after hacking togther a connector I managed to get 5v to the board and I get a power led ... Yay!

I will rig the rgb up tonight and see if I get a signal
I'll keep you updated
 
Swapped the PSU for an old Amiga power supply i had, its handy as it provides both 12v and 5v.
Hooked up a scart cable to my jamma harness and powered on....

..... stayed on !

display on screen is grey but i can make out writing on the screen (looks like backup ram error) but its hard to read,
Im gonna mess around with resistors to try and get a clean display but for now i seem to have resolved my original issue.
 
Update ...
Decided to tidy up my Jamma harness so I rigged the Amiga PSU and a scart plug to the harness with all the required resistors etc,
On first boot I got a backup memory error at 000000 sent 5555 received 5540
Since then every boot is just garbage on the screen with what looks like feedback lines moving across the display,
If I click on dip 1 then I get the same garbage then the screen wobbles side to side slightly then it flashes and restarts the whole cycle again.
The garbage on screen is usually gray but can be different colours every now and then

This is the same with and without a cart, also the same with a universe bios and the original

Right now I'm a little lost on where I go from here so any help would be appreciated
 
Update...

After last update i left the unit off and disconnected overnight....

On first power up once again i got the backup ram error on a black background.. the unit then flashed then the garbage was back....

I thought to myself that this MAY be a power issue with the caps...
all of the caps look ok and using a multi meter they do seem to test ok .... oh how wrong i was.

While examining the board with a magnifier for broken/corroded traces i saw that there was dust and grime under the chips and between some components so i decided to clean the board in the sink :)

after scrubbing with a toothbrush the board looked lovely and clean, 30 mins at 80 degrees in the oven dried it off nicely..

The 470uf caps are all bulging (none of the others are surprisingly)
the stereo/mono switch melted in the process too (need to find a replacement)

Other than that the board looked tip top

As i now was committed i just thought i would try the board to see if there was an output or if i had killed it completely ...

The unit briefly booted to the unibios page then went black, after 5 mins disconnected i was able to repeat this with the same result :)

I have ordered replacement caps and will be shotgunning all of them.

If anyone can point me in the direction of a 2 position 12 pin switch it would be appreciated

Ill keep you updated
 
Welcome to the forums :)

For starters I wouldn't be attaching a PC PSU directly to a board like that. It might seem like it's working but there's no voltage regulation at all and it's likely to cause damage if it hasn't already.

You need to find yourself a supergun and this will take your PC PSU and turn it into something your arcade board can use (and regulate the voltage) as well as giving you a SCART output to your TV. These should be easy to find in the UK/Europe and you can get very reasonably priced basic boards that will do the job perfectly.

After this you've done exactly what anyone here would have suggested you do. Next step is to replace all the caps since they've clearly had it, remove the resistor that runs the charging circuit for the battery if you haven't already and report back.

To replace the switch (assuming the board ends up working ok) I would suggest buying a scrap (battery ruined is a good bet) MVS board with that same switch and pinching it from there. It'll also mean you have spare parts if you have any future failures.
 
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The psu I'm now using is an old Amiga psu that puts out +5v at 3a and +12 at 1a I have measured these at the board and they are consistent.
I read many other forums and posts re the ATX psu direct to board and there are as many who agree it's ok than there is those who don't, it was a quality cooler master PSU that gave constant readings so I don't think I have harmed anything.... Hopefully 😀 I will be grabbing a happ arcade switching psu this week though to be sure.

I have replaced all of the electrolytic capacitors with exception of the 470uf as my order was messed up so they should arrive tomorrow.
I do feel I will need to replace the backup and work ram so I have them on order too just in case

I have removed the switch and may just jumper the mono pins (RH six pins I think) but here in the UK these boards aren't too easy to come by with even broken ones going for £45 plus which seems expensive for one switch.

I am on the lookout for a short board mvs like an FZ but most are in Europe and p+p is a killer pushing a working board to around £80 to £100 !!

I took this board on as a project and I'm happy to chip away at it to get that satisfaction if I manage to resurrect it 😀
As always I'll keep you posted
 
Fair enough - I would still recommend trying to find yourself a supergun for working on boards (in case you decide to work on others) - since you can connect everything (buttons etc as well) to one board it makes life much easier, but back on topic

Why are you replacing the backup and work RAM? Even if you get this error from the board, the logic driving it may be at fault, have you removed the RAM chips and tested them off board?
 
Why are you replacing the backup and work RAM? Even if you get this error from the board, the logic driving it may be at fault, have you removed the RAM chips and tested them off board?

During testing i always get either a work error or backup ram error before the display turns blank, i do understand that indeed the logic chips driving the memory may be causing the issue (I'm waiting on my logic probe back from my brother) but the chips were only around £3 each so no big deal really (only ordered two at this time)

i do agree a supergun would be ideal but tbh the ones i have seen for sale look poor for the price, i may try and build my own from this http://hacks.slashdirt.org/hw/supergun/previous.html

I'm hoping my 470uf caps arrive tomorrow that way i should be able to power on the board without any issues .... hopefully
 
Update ...

Replaced 470uf caps ... although my 18w soldering iron didn't appear up to the job as it took a while to remove the original caps because of the large ground plane they are attached to (i have a new rework station on its way)

Turned on the unit... black display, then garbage (but not the same as before)

Turning on dip 1 the display stays black then after 40 seconds or so flashes then back screen again.

I went back over and rechecked my soldering and found that the two 470uf caps near the 5/12 volt line (the ones that gave me the most trouble to remove) don't seem to have a positive solder bond to the board, i have retried several times but i don't seem to be able to put enough heat into the pad for the solder to stick (and yes the pad is still there)
The rework station should help as it has a variable heat iron but for now I'm dead in the water until it arrives as i don't want to risk damaging the board by leaving the iron on the pad.

One step closer two steps back :(
 
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How did you get the old ones out that you said gave you trouble? Did you use a solder-sucker or solder wick? Or did you just heat the original solder and pull the old cap out?
 
How did you get the old ones out that you said gave you trouble? Did you use a solder-sucker or solder wick? Or did you just heat the original solder and pull the old cap out?

Mixture of solder sucker and wick, fortunately as there is a small gap under the cap you can heat from both sides, gentle pursuasion and it'll eventually yield.

just waiting on delivery of my desolder station and a few other components before i continue but ill keep you posted.

Unfortunately Pokemon GO is taking up a lot of my free time at the moment :) but hey at least I'm getting out of the house lol
 
Update ....

OK so i removed and correctly installed the two 470uf caps leaving the gap i had originally and checking the continuity above an below the board ... all ok.

Now when i power on the board i get a flashing display alternating between two images, one with garbage on one flash then the following info on the other....

EXCEPTION ERROR HANDLING

ADDRESS ERROR

ADDRESS: 61006100
AC ADDRS: 61006100
R/W: WRITE

--D/A/REGISTERS--

D0: FFF7BFFF
D1: EBFFFFEF
D2: FFFFAFFD
D3: FFEDFFFF
D4: BFFFEF5F
D5: BEFFFFFF
D6: FFFEFFDE
D7: DFFDFEFF

SSP: 5EFFFFF3
SP: 6100

Now i have no idea what the above means I'm using universe bios 3.2

i currently have no joystick hooked up (I'm in the process of building it) but i can hook up some buttons if that would help.

I feel I'm making progress but need pointing in the correct direction..
 
Update ...

Jamma PSU arrived today, I'm just making a wiring loom now, I'll report back soon......

.... No change other than the previous message is now intermittent, I'm getting garbage on the screen more than the error now.
I need reboot several times for the error message to appear,
Still a flashing garbage display though.

Reflow station arrives tomorrow I'm gonna remove and reseat the memory chips see if that helps.

Any pointers please let me know
 
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Update ...

My shiny new reflow station arrived today so I set about removing the backup ram from the board,

I removed the first (the one closest to the jamma connector on this board) and cleaned up the flux and contacts, checked for lifted traces and breaks but all looks good.

I re-fitted the original bios to see if it makes a difference, powered on and got a backup memory error .... Yay !
After a few seconds a few garbage blocks appeared on the screen and it began flashing again but the message was still there.

I removed the second backup memory chip and again after cleaning all appears perfect...

I have replacements for the backup ram (GadgetUK164 pointed to them in another thread I had read)

http://www.ebay.co.uk/itm/351620350753?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

I'll replace them both (I ordered another four just in case any of the others are defective too)

I did notice that my 68000 is slightly twisted like it's been caught on one edge, all of the joints look sound under a scope but it may explain the flashing so I may remove and refit this too.

I'll keep you guys posted but if you have any advice it would be much appreciated.
 
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Update ...

Ok 68000 removed cleaned up and replaced ... No change
The unit boots to flashing squares,

I don't know what to do next,
On first boot I'll occasionally get the exception error handling message but on subsequent boots just the flashing squares ( the board seems to need to discharge for the message to re appear)
I will say that the flashing squares do have the occasional letter or Japanese character among them and they do appear to be in the same positions every time so that may be relevant.

For the moment I'm truly stuck, is it worth me swapping out the remaining four ram chips?

I know the title of this thread my restrict the people who may view the thread but I really need help now
 
Post pics of the backup RAM and the area around the battery.
 
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