[Drake] TR-4Cw RIT restoration (I)

Sat, 13 Apr 2002 22:29:45 +0200

Hello!

Well, I have spent several hours cleaning the TR-4 set (TR-4Cw RIT S/N
45445, RV-4C, MS-4, AC-4). Now they shine like new :-)!. It is incredible
how smoke deposits over panel, knobs, chassis, tubes and so on. Covers were
specially dirty; as a sample, TR-4 side lettering was brown...

I had been told TR-4 troubles were a large attenuation (50dB) in all bands
and a large (about 280kHz) tuning frequency error. First trouble should be
located in a common circuit, so I started to look in the schematics from
the antenna connector. First thing, after the relay, was a '#12 fuse lamp'
and, yes, you guessed it, was broken. I put a temporary wire jumper on it
and checked the set. It received in all bands and seemed to perform well
(no large attenuation at all). So, although I will later align the set,
first trouble was gone :-)!

Then I looked for frequency accuracy, connecting my trusty HP8640B at
21.150 and -73dBm. And, yes, the set was really out of frequency, as it
received the signal at about 21.400 dial indication. And the frequency
tuning was not completely stable; I got an slightly warbling sound instead
of a constant tone. 

As I also had the RV-4C external VFO, I connected it to the TR-4 and it was
dead accurate and, best of all, there was no warbling... So it seems the
trouble is located in the TR-4 PTO assembly; I will check it when I have
some time.

So things sound promissing!. I plan to get the PTO out of the set and
connect it by means of an extension cable to the set, so I can make
measures with it working. I will look first for dead / value changed
components and then, if there is no evident trouble, I will check it with
the set powered. More to come!

BTW, if somebody has an spare #12 fuse lamp, I will be interested in
getting one. I need also the two non-standard crystals (42.5 and 43.6 MHz),
as they were missing. Thanks!

Regards,

JOSE
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  73 EB5AGV / EC5AAU - JOSE V. GAVILA
     La Canyada - Valencia (SPAIN)

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