Suddenly no video on a MS2930

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kryssss
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Re: Suddenly no video on a MS2930

Post by kryssss »

Hi Grantspain,

A friend of mine tells me I should take contact with you. Here I am. I hope you could help.

I own a Jaleco Pony Mark III and I should replace the chassis MS8-25A (mentionned on the label).
Two arcade fans who have seen pictures from my chassis tells me it is not MS8-25A, but a MS8-26A.
It is strange for me because I see the label model MS8-25A on it !!!

My question is :
should I check the yoke values to replace my chassis nanao model MS8-25A by a model MS8-26 ?
Or could I install a chassis MS8-29 ? In this case, should I replace the yoke to correspond with MS8-29 ?
What do you suggest me ?

As I am a newbee, do you know someone in Switzerland who can physically help me ?
Thank you for your help,
Cheers,
Chris
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grantspain
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Re: Suddenly no video on a MS2930

Post by grantspain »

kryssss wrote: May 12th, 2021, 9:09 pm Hi Grantspain,

A friend of mine tells me I should take contact with you. Here I am. I hope you could help.

I own a Jaleco Pony Mark III and I should replace the chassis MS8-25A (mentionned on the label).
Two arcade fans who have seen pictures from my chassis tells me it is not MS8-25A, but a MS8-26A.
It is strange for me because I see the label model MS8-25A on it !!!

My question is :
should I check the yoke values to replace my chassis nanao model MS8-25A by a model MS8-26 ?
Or could I install a chassis MS8-29 ? In this case, should I replace the yoke to correspond with MS8-29 ?
What do you suggest me ?

As I am a newbee, do you know someone in Switzerland who can physically help me ?
Thank you for your help,
Cheers,
Chris
start a new post, show some photos of the chassis and the tube number
Ioncannon
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Re: Suddenly no video on a MS2930

Post by Ioncannon »

I'm back; both happy and ****.

So I bought a "working used" flyback from TecknoService and plopped it into the board. To my excitement I didn't hear the normal crackle I usually did, and voltage was appearing from the EHT! After adjusting to 28kV I turned up the brightness and got crisp colour video too!

Then restarted the machine and the symptoms CAME BACK!!!! Gahhhhhhh.

Ok well from this we learn:

1) The tube isn't broken...
2) It was the flyback...
3) Unless I am the most unluckiest person in the world, something is killing flybacks on this board. The other option is it's not the flyback and me doing the swap nudged something that is causing the issue (so something in the neck or flyback area?).

So any idea what could be causing it? Oh yeah, I remember hearing short high pitch squeaks coming from the chassis. Couldn't pinpoint where; sounded like the yoke or neck board area but could've been the chassis board itself.
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grantspain
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Re: Suddenly no video on a MS2930

Post by grantspain »

try turning down the eht to 26kv
Ioncannon
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Re: Suddenly no video on a MS2930

Post by Ioncannon »

Like before, adjusting the HV isn't doing anything now. Hmm, I am inclined to think it's not the flyback but something on the board that I may have disturbed during the swap, temporarily fixing it. Besides just being unlucky; do you see a flyback getting killed by a chassis Grantspain?

I've read to test the internal capacitor of the flyback you measure the capacitance between the anode and pin 14; both flybacks show a reading of 1nf (my meter can't do decimals at that scale and this was done before I put the flyback in). Other readings match/look the same.

There are some really nasty resistors around that area with the ceramic casing chipped off... maybe I should try replacing those components.
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grantspain
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Re: Suddenly no video on a MS2930

Post by grantspain »

i have not seen a chassis kill a flyback, if you corrosion on the chassis then that could be the problem
Ioncannon
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Re: Suddenly no video on a MS2930

Post by Ioncannon »

Good to hear. Luckily no corrosion on the board itself. Alright, will start documenting the resistors and replace. Will replace that HV pot as well.
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grantspain
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Re: Suddenly no video on a MS2930

Post by grantspain »

only replace stuff that reads bad
you replaced the caps did you?
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Re: Suddenly no video on a MS2930

Post by Ioncannon »

Replaced all except the ones on the daughter board (two of them) as I had trouble removing it. Didn't want to put too much stress on the connect/board.
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grantspain
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Re: Suddenly no video on a MS2930

Post by grantspain »

the two little smd caps? they can cause problems
what i would suggest is checking every cap again for any track damage
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Re: Suddenly no video on a MS2930

Post by Ioncannon »

No, not U701, the other daughter card with a bunch of diodes, resistors, and 2 "can" capacitors on it. Not sure how to release the connector; was tugging on the card and it wouldn't come out.

MS2931 doesn't have this card; only 2930.

Will do.
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grantspain
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Re: Suddenly no video on a MS2930

Post by grantspain »

ah yes of course, ms2930- that board lifts off its header by removing the screw and gentle pursuasion using flat bladed screwdriver under each side
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grantspain
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Re: Suddenly no video on a MS2930

Post by grantspain »

have you checked the 180v video b+ line and neck card for bad joints etc?
Ioncannon
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Re: Suddenly no video on a MS2930

Post by Ioncannon »

B+ still 180v; didn't see anything broken on the neck card (socket was resoldered too).

I haven't had a chance to do much with that chassis yet. I did however fix a loss of blue in my other Blast City chassis; was a broken solder joint at the blue CRT pin; so at least something went well lol.

Do you know where the green gain pot is on the MS2930? I see the three cutoffs on the main pcb, and the remote board has a R and B gain.... but where the hell is green?
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nem
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Re: Suddenly no video on a MS2930

Post by nem »

There is no green gain, because technically you don't need it. You adjust contrast and then the other two gains to bring everything in line.
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