verical ripple on a Philco 50t1400
 

Hi all, got an interesting issue with a newly recapped Philco 50t-1400.It's developed a vertical (intermittent)ripple when the volume is turned up.If you turn the volume down it disappears? strange.........any idea's? Thanks .I've changed tubes ,no effect......

I'd look at various parts of the power supply, maybe a supply is sagging when the audio amp is working hard.

Or maybe a dirty tube socket. test that by knocking on the TV cabinet, with the sound turned down.

It could also be caused by a "microphonic" tube... perhaps try tapping on the tubes in the RF/IF/video circuits to see if you can create the "sound bars".

jr

Very well could be electrically coupled , or it could be the vibrating speaker rattling something on the chassis like a bad solder connection (mechanical coupling of the sound to the problem)

If you disconnect the set's speaker and turn the volume way up , and the problem is still there , I'd guess electrically coupled . If the problem doesn't happen with the speaker disconnected and the volume way up then I'd be looking for a poor solder joint in the Vertical circuit or other microphonics as Jr Tech suggested . If it does turn out to be electrically coupled a somewhat gassy audio output tube could be throwing some strange stuff on the B+ line , I know you said you tried substituting tubes , does that include the audio tube(s) as well ?

PS , does lightly tapping on the set produce the picture distortion ?

Or maybe a decoupling cap in the audio out.
Also its before my time but does it use stacked B+
like a GE & some others ???

73 Zeno:smoke:

It appears that the audio output tube is stacked on top of several video IFs , a video amp and the CRT brightness pot... ample opportunity for audio signal to disrupt other functions. :scratch2:

jr

Got it! must have been a microphonic tube.I changed out all the audio tubes.It took care of that. Had to do another deoxit round on the pins of all of the tubes.Those loctals and miniature pins are a bear.Now, i want to add a fuse for the power trans.........which is the best location(point)? off the switch?

Factory would put it in one of the AC lines before ANYTHING like
chokes & line cap. Nothing there ?? Maybe a fuse wire ?

73 Zeno:smoke:

the vertical rippling is back........darn, thought I had it ! I've replaced -2- 6V6's now.If I put a new 6V6 in it's straightens right up.Are these tubes turning microphonic? If you lightly tap on the 6V6 it makes the vertical ripple.Kind of crazy if your watching something and when the scene gets louder it ripples.All the resistors are within spec on the 6V6 .I ended up putting the fuse on the center tap of the trans.This rippling is the only issue in an otherwise fine playing set.HELP.....lol

Bad "new' electrolytic cap!! a first for me after hundreds of re-cap's.....Thanks for all input!!