[R-390] Arcing in 25Z5Ws

[Flowertime01 at wmconnect.com]

Dennis,

Now is the time for that trusty old tube checker.

First off you blew a fuse after the B+ 26Z5 rectifiers tubes.
This is not good. Most likely a tube shorted.
Second most likely a cap has shorted.

Then you see you have a dead 26Z5 with no light inside.

So you are only operating with 1/2 wave rectification.
Lots of hum from this state of operation.

As a 26Z5 did not light up in a known good socket (the other tube light up in 
that socket) you have at least one bad tube and need a replacement.

Run all the 26Z5s through a tube checker for shorts and minimum conducting 
current. A tube checker will do that for you.

It would be good to just push all the tubes in the receiver through a tube 
checker for shorts at this time. Using the receiver as a test device for shorted 
tubes is not considered good use of equipment or good service practice.

Once you find a set of tubes that pass the tube tester (I did not say a set 
of good tubes) and get them back into the receiver, you can apply power again. 
DO NOT over size the fuses. Watch for smoke and flashes. You could still have 
a bad cap. Likely a filter cap. Back when this was not a likely problem. For 
50 year old caps it is now a common problem. 

Fuses also just blow. No problem found. Likely once you get a couple good 
26Z5 back in the receiver it will work fine.

Have you considered just a couple good 400 Volt 2 Amp or better diodes as 
substitutes for the 26Z5 until you get the other problems sorted out?

You do not have to leave them in the receiver forever. Just something to help 
you get on with trouble shooting and problem solving until the post man 
arrives with parts.

Roger AI4NI   </HTML>