|[AMRadio] boat anchors heathkit etc|
w5jo at brightok.net
Thu Jun 22 22:42:47 EDT 2006
Good advice Phil. I am finishing an electrical restoration of a WRL Globe
Champion 300A at the moment. I replaced all electrolytics save one. It is
a 3 section 10 uf. 500 volt electrolytic. To be sure of it, I disconnected
it from the circuit and used a Sprague TO 6 cap checker to see how leaky it
was. The transmitter hasn't been used for years but the cap formed quite
nicely, reaching better than new specifications.
Watch for any TO 4,5 or 6 at hamfests. Last year I found a T0 4 for 10
dollars. I replaced some caps (electrolytic and paper) in it, and it worked
very well. Not only will it check value and leakage but will also check
power factor. That is important as well.
The Globe Champion had 4 Selenium rectifiers in it, which I replaced. I
don't want one of them to short and fill the room with that horrible smell.
One set was in the bias circuit, in which I put a zener. While you are
there check the resistors. In this set, I found two out of tolerance in the
audio chain. Both were cathode resistors in the second and third stages.
Another thing is to check for modifications and replacement parts. I
reverse all mods to get it going as the factory shipped and while looking,
found a resistor that had been replaced at some time with a wrong value. It
would work, but who knows how long. I was fortunate with this set and since
it did not have the AX 9909s, I modified it for 5894s. It is almost ready
to make RF and put on the air. The VFO and buffer stage work fine. I hear
it in my receiver.
All in all, this has been fun. Treat them with respect and they will give
> The safest thing to do when you decide to apply power to an old rig (after
> inspecting it carefully for frayed or burned wiring, obviously damaged
> parts, and other such problems) is to connect a 100 watt light bulb in
> series with the rig. If you have a Variac (variable autotransformer) for
> gradually bringing up the line voltage, so much the better. If any filter
> capacitors or solid state rectifiers are shorted, the bulb will glow to
> brightness and you won't blow any fuses or burn anything. Bringing up the
> voltage slowly will allow electrolytic filter capacitors to "form". It is
> usually a good idea to "shotgun" such capacitors, as they do deteriorate
> with age.
> I made up a test jig in a box with a standard light socket in series with
> receptacle. It has saved me a lot of grief.
> Phil K2PG
More information about the AMRadio mailing list
This page last updated 24 Feb 2018.