MFA Lumi sings high-pitched tunes

[marknoir]

So far... so bad!

Hello guys

Finally had time to do some work

So far I have only replaced the photo flashes - 8 in the main chassis (decoupling) and 3 in PS (high voltage filters). Result: SEVERE low fr. hum AND high pitched noise, now loud. Checked old photo flashes - they all test good. So far this is a mystery, will try to get to it over the weekend. Unless the new Panasonics are bad, which is doubtful... Or all of the sudden regulator tubes and LV filters went bad overnight...

 

[kevinkr]

Recheck all of your work for cold solder joints and a missed connection or two.. Make sure if these caps have three lugs that you have used the correct two. (Ask me how I know this.. 😀 )

 

[marknoir]

Recheck all of your work for cold solder joints and a missed connection or two.. Make sure if these caps have three lugs that you have used the correct two. (Ask me how I know this.. 😀 )

Hello Kevin

Thank you

BTW, I lost all of our emails - had to restore computer :-( Pls re-send your e-mail address (PM I think is better?)

So far I can't find a problem with either solder or lost connections. Bewildering. And I don't even have a schematic for my particular vintage. It is quite different from the one I posted. I think in the early models they just used whatever was around. Hence, three photo-flashes in HV, instead of two little ones... I just resoldered all wires to new caps. I will get to it on Sunday (I hope!)

Rgds

Mark

 

[marknoir]

Welcome to the weird world of M.S. 🙂

Finally had time to get to it last night. Turned it on, and it's dead quiet. WTF????

Photo flashes perform as they should, AC ripple on phono filaments is about 40mv, on line - 85mv, it still sings it's high pitched songs. I guess it likes it this way. All this work and for nothing. BTW, all old grey photo flashes check out well. I guess only the CREATORS, that is Bruce Moore or Scott Frankland can solve this one! Scott mentioned he's got a solution for it.

M

 

[marknoir]

Up and running

So it is all re-capped now, running well, sounding a bit tight and dark, but I hope this will go away as it burns in. Still singing high-pitched tunes, but at least now I know it wasn't the caps! BTW, all old caps still check out totally fine! I had to get a bit creative with new cans, as they are all computer grade screw terminals, so some rehashing was necessary. In the main chassis the Russian teflons (stripped naked) are still in the temporary positions. I will try to attach some photos. As to high-pithed whine, it will require more attention...