"grupt" wrote in message
ps.com...
I have a Grundig tube radio - 4070U - which I love dearly. I bought it
almost five years ago and had it restored by someone who knew what he
was doing. I no longer live in the same area and can't benefit from
his services again.

It has two problems. The right channel cuts out intermittently. The
sound can be restored in two ways: if I turn the volume way up, or
(sometimes) if I give it a rap on the case. In both situations, the
sound is restored with a small pop. In addition, the sound also
returns if I do nothing, i.e., if I wait a few minutes. But then of
course it disappears again.

The other problem is that the sound in the left channel is extremely
weak. It is possible to hear it if the right channel has cut out, so
something is arriving at the speaker, but not much. This one is not an
intermittent problem.

The restoration in 2001 included replacement of capacitors. Not sure
if it included replacement of tubes.

Any suggestions received with gratitude.

The intermittent right channel will likely be something very simple, such as
a bad joint or dirty tube base, but the low level left channel is likely to
be something more challenging, and if you don't have any experience working
on this sort of kit, is probably best left to someone who does. Just one
quick thought though. Some of these old radios had a ' GRAM ' input on the
back for a record deck, and a selector switch, sometimes part of the
wavechange switch. If this were the case on yours, could be bad switch
contacts, particularly if you don't change band very often. Could even still
be this if it doesn't have a gram input. You might try giving the bandchange
switch a vigorous scrub back and forth if its a rotary type, or a good "
working " if it's the old Grundig piano keys.

As far as going inside yourself, the high voltages involved can be
dangerous, and I would hate for you to get a serious electric shock. If you
have any old mom and pop TV shops in your area, there's bound to be someone
there who is still tube-savvy, and could sort these problems for you.
Failing this, bit more of a long shot, but there are still lots of tube amps
in use by musicians. If you have a local musical instrument store that takes
in repairs, they will likely know someone experienced in tube equipment
repairs, that may be able to help.

Arfa