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PSA: MS293X, faulty chassis can break the tube

Nothing's blown on my 2930 yet, but I'm a little concerned after some shrinking today. My chassis was recapped by GndZero when I bought the cab a couple years ago, I finished the restore this December so it's had about 6 months of use. I think there's always been a little bit of vertical noise in the picture. I'm not sure if it seemed a little worse today, but after about 5 minutes of playing, it started pulsing with a vertical shrinking to ~80% and back to full at about 1-2Hz. I didn't notice a clicking or anything. I immediately powered it down. I booted it back up and recorded the initial vertical noise, but didn't see the big collapse after 3-5 minutes of playing. Kinda terrified to turn it on now.

Here's a clip of the second boot up and the light background vertical noise (I think the on-screen shaking and sound towards the end is just a Matrimelee character charging an attack).

 
Looks more like cold solder on adj. pots or other area. Collapse it would shut into a line or be more aggressive.
 
advans14 said:
Looks more like cold solder on adj. pots or other area. Collapse it would shut into a line or be more aggressive.
Click to expand...
Thanks, hope that's all it is.

Here's an actual example of what happened. I think the picture didn't quite extend to the bottom throughout the whole first and second sessions, but when I booted it up again this afternoon, it was fine. I was able to play with no problems for about 10 minutes, then it went back to ~95%, so I started recording. It jumps to ~80% around 0:10 in this clip, and then back to full before I shut it off. During the first session, when it started pulsing, it was a little bit more severe, and pulsed in and out until I shut it off.

 
nem said:
I would like to remind everyone that getting a replacement tube for a MS2930 is a huge PITA. Best guess right now that for this chassis the problem is the two SMD caps on the MSPAC004 sub-board:

mspac004_1.jpg


Left cap is 2.2uF 50V, right cap is 22uF 6.3V. Both caps are 4mm.

I actually measured the old 22uF cap on the chassis that blew my tube and at least the ESR is way off:

mspac004_2.jpg


Here's a brand new 22uF that I measured just now for comparison:

mspac004_3.jpg


The 2.2uF cap seemed to be in spec.

If you've had your MS2930 "serviced", more than likely they haven't done jack shit to the SMD caps. Get them replaced!

Thanks to mufunyo on Arcade-Otaku for the tip.
Click to expand...

Sob... this has me worried cause I know for a fact when I got capkit I didn't change those.

Is there a website that sells better caps? I mean like best of the best or they all are generic?

I want to replace those asap.
And thank you nem for bringing this up, really crazy with these chassis.
 
Thank you nem.

There are so many versions of these caps... height, series, base, impedence ect,ect... kinda confusing. I usually just order pre-made capkits so all these searching for especific cap is intimidating.
 
tDRG said:
Thanks, hope that's all it is.

Here's an actual example of what happened. I think the picture didn't quite extend to the bottom throughout the whole first and second sessions, but when I booted it up again this afternoon, it was fine. I was able to play with no problems for about 10 minutes, then it went back to ~95%, so I started recording. It jumps to ~80% around 0:10 in this clip, and then back to full before I shut it off. During the first session, when it started pulsing, it was a little bit more severe, and pulsed in and out until I shut it off.

Click to expand...
I had that same shaking/pulsing in my Astro City for months. Very annoying. I intended to check out the potentiometers but never did. Eventually the problem went away on its own sometime last year. I still plan to at least clean the potentiometers but I’m being even more lazy about it now that the shaking doesn’t happen anymore.
 
So I finally got my 2 SMD capacitors today and decided to go ahead and replaced them. Took me about an hour and half after chassis removal and getting all my soldering tools together. Turned blast city on and everything worked perfectly. Now I can sleep knowing those possible tube killer caps are replaced.

THANK YOU NEM!!!!

Here is links of both caps I bought, if any one else wants to try it out.

2.2uf 50v https://www.digikey.com/en/products/detail/nichicon/UUL1H2R2MCL1GS/2550299

22uf 6.3v
https://www.digikey.com/en/products/detail/nichicon/PCF0J220MCL1GB/2549390

And this is the YouTube link of the method I used for removing those caps on the sub- board. There or other methods but these damns caps are so small this worked best for me. Magnifying glass with light is a must.

View: https://youtu.be/rEhYVyXYU9c?si=I3y63l2h1zLCptXJ
 
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