[R-390] R391 Audio Deck Question

[Roger Ruszkowski]

I have yet to locate the actual fault which is pulling the HT down, the reason 
for the initial investigation :o(

Pete
----------------------------------------
Pete,

I have not had much experience with the R391.

But the general procedures are in order to trouble shoot
any problem.

If you are not blowing fuses off the top check that what's in the 
holder is not largely over size, before you burn some thing out.


Likely a tube went bad and is pulling the B+ line down.
Once you pull a tube and try to measure B+ on the socket, 
the bad tube is out and you do not see the low B+.

It is likely that running all the tubes through a tube tester is in order.

Next choice is a cap has gone leaky short and is pulling the
line low.

If you still have tube rectifier in the power supply,
check these in the tester. The tubes can reach
and end of life and have low emission thus being
the source of the problem.

A real good eye ball from end to end may be in order.



Un plug a many modules as possible (IF RF Osc) 
then unplug as many tubes in the audio deck as possible.

See if you can unload the B+ line to where it comes back to a good value.

Then start adding things back in. 
This is not sure fire.
You can get the bad section powered up but because every thing
else is not on line, there is sufficient power to leave things looking OK
at that stage of investigation.

So get the audio deck and IF deck back together and run a signal 
through the IF and Audio to do stock signal to noise and gain test.
This is to make sure these decks really work.

Then you can add back in the RF deck.

Yesterday this receiver worked.
Today it does not work.
One and only one thing changed overnight.
The repair will be a single part.
This receiver does not need to be re engineered.
This problem does not need deep thought.
This problem does need good logical problem solving troubleshooting behavior.

This does not mean you will not find lots of things that should be fixed
along the way that are bad and should have been identified and
repaired prior to this point. Past prior problems from just old age still needs attention.
So as long as you are in it fix as many of the problems as you have time and parts
to resolve.

Please do stay with this R391 and get it operational again.

Roger AI4NI