[Collins] re: newbie question

[Rodger]

If it is actually dropping almost 200 volts across choke L-123 you 
either have a problem in the choke or a significant drop in your 
resistance to ground downstream of the choke.  Before going further, 
disconnect L-123 to preserve it if it hasn't already been damaged and 
check your resistance to ground at pin 5 of C-217, it will take a few 
seconds to get a valid reading as C-217 charges up.  Hopefully you just 
have a capacitor with severe leakage and nothing else.  If the 
resistance to ground is normal at the capacitor, check the resistance 
across the choke and also from the choke terminals to ground (with the 
both leads to the choke disconnected) in case the choke has developed 
internal leakage.

Does the R-388 have the proper fuse in it?  With the current draw it 
takes to drop this much voltage across a good choke I would expect a 
properly sized fuse to open.

Rodger WQ9E

T

 wli wrote:
> Recently, I picked up a cosmetically clean R-388 Order 25067-PH54-55
> Had all the tubes and both covers
> Not able to test before purchase at a busy local hamfest (lame excuse)
> It was almost deaf on all bands when I tested it initally at home.
>
> I replaced the power cord with a new 3-wire cord and replaced weak/wrong tubes. Both 47µF electrolytics seemed OK (both leak <0.1µA at 250v). Slowly brought it up on a Variac, passed the smoke test. No internal components seemed discoloured or broken. 
>
> Funny thing: B+ at pin5 of C217B was only 50V, whereas it was 240v at pin3 of C217A. Next move could be to break the B+ line at C217B and measure the mA draw...
>
> Does this make sense?
> What other things should I do before that?
> What are the weak areas to look at in a R-388?
>
> Thanks
>
> W. Li
> Mercer Island, WA
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