[ARC5] Burned out R-78 on BC-457-A

[J Mcvey]

Not too many choices on that one!
I believe the bypass is a mica type. I don't remember changing one, but it might be bad.
The other choice is some kind of tube meltdown that I have never seen either. 
The good news is that it's not hard to fix!

Do change/ re-stuff the .05 X 3 cap in the rear of the transmitter as a "given".

     On Tuesday, May 26, 2020, 02:17:31 PM EDT, Bill Cromwell <wrcromwell at gmail.com> wrote:  
 
 Hi,

I don't have any of the command transmitters of any flavor. I have had 
the screen bypass get leaky enough to burn the screen resistor. Check 
C-64 (screen bypass?) at operating voltage for leakage or a short. It 
might be possible for the 1625 tube itself to have an internal short at 
operating temperatures. We don't know what sort of abuse it took during 
handling and shipping.

Good luck with your transmitter.

73,

Bill  KU8H

On 5/26/20 1:43 PM, Dave Merrill wrote:
> Since many of us don't have much to do these days, would anyone care to 
> speculate on why R-78 in the 1625 screen supply is charred?  Seller has 
> no clue, calls it a 'diode.'  Can't tell for sure from the photos, but 
> most of it looks original.  Someone has labeled the rear power connector 
> so that might be an indication of tampering.
> 
> Possibly shorted C-64?  Anybody ever find a bad one?
> 
> https://www.ebay.com/itm/164218971890
> 
> 73, Dave N9ZC
> 
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-- 
bark less - wag more
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