[Amps] Drake L7 issues- update

[RMead100@aol.com]

Thanks for the suggestions to date.

I have made a little more progress

Using a good light source, the existing caps look fairly bad. The one with 
the lead cut loose measures a dead short on the VOM, and two others look like 
they are slightly deformed at the top end with swelling inside. Cant see the 
diodes and resistors yet, but dont intend to take the boards out until I get 
the new parts. 

The good news is that the old Drake undersized (2 watt) glitch resistor didnt 
blow,  which I am reading as a sign that the immediate problem was upstream 
in the power supply, and not on the amp rf deck (scraping load cap not 
withstanding).   I never did hear any "noise" from the rf deck, and the 
initial power up reading on the plate meter shows that one leg of the voltage 
doubler was not operating to begin with. 

Looks like I can get some 105 degree computer grade caps from Mouser for 
about $9 each if I buy more than 10, and they are about 1/4 the size of the 
old ones. 

I wonder if I should replace the two giant 50k 50 watt dropping resistors 
which have the unusual mounting scheme at the top of the supply. They measure 
ok, about 10% low, but there was at least one thread on this board that i 
found which indicated that they sometimes give an arcing problem from the 
mountings. Seems like drake could have simply put another winding on the 
transformer instead of  using these things to get 120 volts from 2500.


73 Randy
K8BUX