[AMRadio] Sentnel Radio Co. Musicair Console, Help Needed

[Doxemf]

If you aren't already using a metered variac to bring up the AC line slowly then make up a simple lightbulb in series with the hot side of the ac line breadboard or box  using a 100watt +/- regular household incandescent lamp. If there is a short the lamp will light brightly and stay that way, etc. Normally it would flash bright at first turn on then dim down as the tubes warm up.
 In your case if the lamp starts to get brighter after a couple of minutes as the audio fades out then you have a leaky supply cap or a coupling cap that is reverse biasing a tube. Either way something will be getting hot.
You can also put a meter at the end of the supply divider chain and see if the voltage drops after a short period.
That's kind of the most common problems with the old gear and easy to check for a shorting condition.
Bill.
KB3DKS 






-----Original Message-----
From: Ronald Doering <wa9qnn at yahoo.com>
To: am radio <amradio at mailman.qth.net>; boatanchors <boatanchors at mailman.qth.net>
Sent: Sat, Mar 5, 2011 6:59 pm
Subject: [AMRadio] Sentnel Radio Co. Musicair Console, Help Needed


I am in the process of restoring a Musicair Console Radio.  Replaed several 
efective capacitors.
he radio plays now, but after warming up for 2-3 minutes, it fades out, no 
udio.
Turn it off, let it rest a few minutes and turn it on.  It plays and then does 
he same thing again.
Anyone have some advice on what to check?  Can a coupling capacitor do this?  
GC tube?
r, is it a tube?  All the tubes check out fine on a tube tester.  Something 
arms up and changes.
ny help will be appreciated.  Thanks,  Ron  100% DisAmerVet