Re: Need to fix old valve radio

On 5 Mar, 02:18, "hr(bob) hofm...@xxxxxxx" <hrhofm...@xxxxxxx> wrote:
On Mar 4, 5:18 pm, lafayettera...@xxxxxxxxxxxxxx wrote:



I have a very old valve radio from a company called Lafayette.
It has 6 valves which are
6v6 gt
6x5 gt
6sq7 gt
6sk7 gt
6sa7 gt

This radio was working fine but recently has developed the following
problem, when the volume is increased the sound is distorted
completely,
it can only be heared ok when the volume is very low, and putting the
ear onto the speaker. Any ideas?

Sorry, I accidently posted it to the wrong group.
To add to the above, it is a MW/LW/SW type
and the problem occurs on all of the bands.

Thanks in advance.

Got a model number? It sounds like a transformer powered all-band
1940's superheterodyne set. Later sets used 12, 35 and 50 Volt
versions of those tubes in series diretly across the AC power mains.
Then they were replaced by miniature versions of the same type of
tubes. The schematics for these sets are all almost identical, the
6say is converter, 6sk7 is IF amp, 6sq7 is detector and 1st audio amp,
and 6v6 is audio output, 6x5 is rectifier. Volume control is at input
to 1st audio amp. Do you have a scope so you can look at the signal
from that point to the speaker? If so, I can walk you thru the testing
needed.

H. R. (Bob) Hofmann

Bob, thank you. I don't have a scope.
I think you are right about the "series" thing. They are protecting
the valves these way, if someone takes one out everything stops
working.

Here is more information:

The model number is very faint, but it ends with E629, maybe IE629

There is also a 4 digits serial number, 2xxx
Probably not too many of those about today :-)
Made in America
Rated 110 to 125 Volts 50-60 cycles 40W
Yet (strangely) was always operated from 220V.

I need to change the power cable, it is probably the original and
is crumbling in a very dangerous way, so I might get a glimps
to the internal components. It looks like a big job simply to take
the unit out from the wooden box without damaging the tuning
mechanics. I wonder if it can simply slide out or if it needs to
be lifted out (bad).

Oh, and another interesting thing, the pickup coil doesn't use
ferite core like nowadays, there is a huge drum and on it the
coil is wrapped.

.

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