Help with Mushihimesama PCB--- repairs??

dpful · Post by **dpful** » Sat Jun 13, 2009 7:51 pm

I've just gotten a mushihimesama pcb, and there's something wrong with the colors. (It's not a cab prob, ibara and other boards works fine- jamma edge not a problem either)

Symptoms:
1. in one cab, the image shows no blue (all white is yellow, all bullets are red, etc.), and the color test shows a black bar where the blue should be.

2. in another cab, the image is awash in blue-- and the color test still shows a black bar where blue should be (even though the whole screen is tinted blue), it's as if the blue output is all fucked up- out of the parameters for one monitor, and picked up on the other as an overload.

3. also, on this second cab, you can see that it's not just a simple wash, but as the screens change, you can see that the screen starts proper, and then VERY quickly (as it brightens) flashes to blue, over some objects in clear-cut vertical stripes, as if it was a problem with the chips rather than the signal path (don't know what I'm talking about

) I had a turboforce pcb that had pale blue stripes coming off of some objects, and flexing and tightening connections seemed to have an effect-- on that one it was only on some objects, on muchi it's everything... same color of blue, though.

Does anyone have any ideas? Could I even dream of a way to FIX the board or have it repaired? I really went out on a limb to buy it and I don't want to send it back! It's got me feeling awash in blue

thanks

Koma · Post by **Koma** » Sat Jun 13, 2009 8:49 pm

I have the same problem with my board too.No blue at all!It's appears with no reason couple days after the purchase.

PC Engine Fan X! · Post by **PC Engine Fan X!** » Sat Jun 13, 2009 9:36 pm

Sounds like you need your Mushihimesama needs to be serviced by a professiona arcade PCB repairer. ^_~

If you can find one based out of the USA, that would be your best bet right there. As much money that some of these modern-day Cave shmup PCBs costs, sometimes if they are performing at 100% capability, then it's time to call in the pros & see if it can be revived to full working condition. You could always send it back to Cave and have them fix it for you but that would incur a serious repair bill indeed. They do service what they sell, y'know that right, dpful? ^_~

PC Engine Fan X! ^_~

IronGiant · Post by **IronGiant** » Sun Jun 14, 2009 10:55 am

Two boards with exactly the same fault indicates that it's either coincidence or a common point of failure on the PCB, such as a dodgy IC or poor solder connection.

I've repaired a few 'recent' boards of a similar integrated and customised nature and some are easy, some not. As in all cases, it depends on the nature of the fault. If it's a dodgy custom chip then you're scuppered (unless you send it back to Cave). Then again, it might be something far simpler.

As the problem has just occurred I assume that nothing has changed in the board's environment? Also, I assume that the voltages have been checked and are correct?

Presumably the edge connector is making good contact?

dpful · Post by **dpful** » Sun Jun 14, 2009 2:27 pm

voltages are good, edge is good. Could have gotten hot or cold at some point in the box?? I'm supposing there's no way to really troubleshoot the fault over the internet. Does anyone know what would be involved if I sent it to cave for repairs? (or what it would cost? Is that even possible?)

IronGiant · Post by **IronGiant** » Sun Jun 14, 2009 2:32 pm

Can't think of anything else to suggest I'm afraid - have never dealt with Cave but you could try contacting them. I would though imagine that they will charge a small fortune for a repair, but at least you can be certain that it will be repaired as they have all that's required at their disposal (schematics, replacement custom chips, etc).

Sending it to a repairer other than Cave (such as those repairers who frequent this forum, myself included) won't guarantee a repair, but if one of us does fix it then it will almost certainly be cheaper than sending it to Cave.

Up to you.

BTW, Cave's contact page:

http://www.cave.co.jp/contact_e/index.html

dpful · Post by **dpful** » Sun Jun 14, 2009 7:26 pm

Thanks guy!

On another return to the pcb, tapping and flexing to make double sure (I was hoping beyond hope that I could locate a mechanical failure), I decided to hold a pot between blue and ground (I had grounded out blue before on the color test screen with no result-- blue open=black bar, blue grounded=(of course) black bar), I turned the pot and............ purple bullets! The pot went about half way, and then the blue wash snapped to normal! (the second half of the turn slowly reduced the blue from normal to zero).
So I guess I do know what I'm talking about regarding pcb repair; total 100% hunch driven expensive pcb fixing magic powers!
I did have G-net mobo that had a fucked up image (all colors), and it was a fault with the signal path of the video ground.

Koma, if you still have that board, stick leads in the back of the jamma harness on blue and video ground, hold them to a pot and give it a turn (I used a pot from my tupperwear of old guitar parts- probably between 500k and 1 meg). After I get mine soldered proper, I'll measure the exact resistance needed to get it to snap into shape and I'll post it.
Holy shit I'm stoked!

CStarFlare · Post by **CStarFlare** » Sun Jun 14, 2009 9:14 pm

Haha, you're stoked

This is valuable information, since it seems like this is not unheard of on Mushi boards (or maybe SH3s in general?)

dpful · Post by **dpful** » Thu Jun 18, 2009 4:03 pm

in response to a PM, here's a rough pic of the mushi fix.

I was able to solder the pot (I had a small pcb mount variety- I think the final setting was around 30 ohms- it was a 1 meg pot), right to "blue" and "video ground" traces just above where the jamma harness reaches.
I used another value pot in the first expiriment, that seamed to snap the blueness away, but this one's was more appropriate and actually gave me a lot of control over how much blue there was. Third leg of pot bent up and out of the way.

When I was expirementing with pots, I jammed stiff wires in the back of the jamma harness on those spots and then held the ends to the pot tabs.

Koma · Post by **Koma** » Sun Jun 21, 2009 9:18 am

Thx dpful but it aint works.The only pot i had was a 1kohms.Maybe it is not enough...

dpful · Post by **dpful** » Sun Jun 21, 2009 7:18 pm

I might have misread the multimeter as 30 instead of 30k-- I'll go check again.

I suppose, just to test without the pot, those two leads (blue and video ground) touched together should eliminate all blue from the picture.

.......just checked again, mine's a 1 meg pot at about a quarter turn which reads at just 33 ohms. I'd try another pot- or even a 30 ohm resister if you had one. Other than that, it could be a different problem than I had; mine was no blue on one cab and all blue on another (both due to an overload of blue from the board), where yours could actually have a LACK of blue? (although I think that's less likely). Could you test it was another monitor and see if there's a blue overload? ----I'd really hope you just had to try another pot.

rtw · Post by **rtw** » Sun Jun 21, 2009 8:09 pm

Locate S2 (DIL SWITCH) on the PCB. Make sure all switches are turned to the ON position.

Is this your first SH-3 PCB ?

dpful · Post by **dpful** » Mon Jun 22, 2009 5:11 am

rtw wrote:Locate S2 (DIL SWITCH) on the PCB. Make sure all switches are turned to the ON position.

Is this your first SH-3 PCB ?

Is this a fix? I didn't try that on mine before I put the pot on.

rtw · Post by **rtw** » Mon Jun 22, 2009 5:26 am

dpful wrote:Is this a fix? I didn't try that on mine before I put the pot on.

I was meddling with these switches at some point in time and discovered I was suddenly lacking a colour.

But once again, is this your first SH-3 board ?

Post by **Dave_K.** » Mon Jun 22, 2009 5:27 am

dpful wrote:
rtw wrote:Locate S2 (DIL SWITCH) on the PCB. Make sure all switches are turned to the ON position.

Is this your first SH-3 PCB ?
Is this a fix? I didn't try that on mine before I put the pot on.

When you flip one of those tiny switches (assume S2) on Ibara it messes up one of the colors for some reason. I think mine turned all blue...so I don't think this would fix yours, but you should see if either of the dips were flipped.

dpful · Post by **dpful** » Mon Jun 22, 2009 2:11 pm

rtw wrote:
But once again, is this your first SH-3 board ?

Sorry, I have this one and Ibara.

edit-
I see now that one of those switches makes everything blue (no red or green included)- that could be your problem. Does your screen go black when you short blue and video ground? (the switch is the one closest to the jamma edge)

Koma · Post by **Koma** » Tue Jun 23, 2009 6:04 pm

Check the S2 switch was the first thing i've done.The screens goes to black when the swtich 1 is on off but i assume is it the same on every SH-3.
Tested on a supergun and my 3 others cabs,no blue at all.Check the +12/+5 all good.
I need to check with a new pot just in case it works.

dpful · Post by **dpful** » Wed Jun 24, 2009 2:19 am

That would mean you've got the same prob as mine perhaps-- that switch is supposed to leave only blue (so your blue's being overdriven and not picked up by the monitor as mine was?)

Try another pot-- go to radio shack and get your hands on a couple.

kernow · Post by **kernow** » Wed Jun 24, 2009 2:57 am

I never understood why those dipswitches are on SH3 boards.

Koma · Post by **Koma** » Wed Jun 24, 2009 6:13 pm

dpful wrote:That would mean you've got the same prob as mine perhaps-- that switch is supposed to leave only blue (so your blue's being overdriven and not picked up by the monitor as mine was?)

Try another pot-- go to radio shack and get your hands on a couple.

Yeah i will.
I think that is the last thing i can do,for now on i only use it as a pcb test,what a sadness.
Thx dpful for your support