[Hammarlund] kc5mip I re-cap the SP-600

[James A. (Andy) Moorer]

It sounds like there is a short in the B+ supply - either the 150V regulated 
or the
unregulated.
First thing to do is to isolate the short.

Try removing V18. That is the OA2 voltage regulator. The main power will
either go back to 288 or not. If it doesn't, then the short is not in the
regulated 150 volt line.

If removing V18 makes the voltage go back up, you can follow the red-white
wire that comes out pin 1 of V18. This goes all over the IF deck and up into
the RF deck. Remove the cap to T1 and unsolder the red-white wire. Does the
voltage go back up? If so, the short is in the RF deck. Too bad. If not, it
is in the IF deck. C167 is the obvious candidate, since it is directly
across the 150V supply. It is sometimes labeled C100. It is directly
connected to the red-white wire on pin 3 of E13. Note that some receivers
don't have this capacitor. In some others, it is way over on E14.

Oh - here's another one - switch the FCU into any one of the 6 crystal
positions. Does the voltage go back up? If so, the short is in the RF deck,
and it is specifically in the VFO tube, V4.

This is the sort of thing you have to do to find a short. In chasing one
short, I ended up disconnecting the red-white wire entirely before I found
the short. That was a pain because it goes everywhere through the IF and RF
decks. That's when I discovered C167 over on E14.

If none of these things make the voltage go back up, that is probably good,
since there aren't many parts left. Start disconnecting the wires from the
big filter chokes. Start with L52 and work backwards. One of these will
surely isolate the short. Now follow the shorted path from its endpoint back
to the filter choke. Disconnect it one pin at a time until you find the
short. Can't fail.

Good luck.
James A. (Andy) Moorer
www.jamminpower.com


----- Original Message ----- 

> Well I change  out  and re-cap all the caps in the under chassis of the 
> sp-600  jx-1 . The Bias supply for the AGC read around -45 volts and after 
> doing all of this the receiver does not work.   When ""S-9 "" is on the 
> "Send" position the main power supply read a good 288 volts and when I 
> switch "S-9" to received then the power is cut down to 104 volt. there 
> seem to be a bad  cap either inside of one of the IF can or God help me in 
> in the "T-1":can///////????? Help/ have anyone may have an idea where the 
> problems may be.