[amsat-bb] FT-736 power supply part.

Jim Walls jim at k6ccc.org
Fri Aug 7 22:06:35 UTC 2020


On 08/07/2020 15:04, Vince Fiscus, KB7ADL via AMSAT-BB wrote:
> Hi All,
>
> I walked into the shack about a month ago and smelled something
> really hot like the smell from a hot resistor.  Turned off all
> the equipment waited a while then turned everything back on.
>
> The FT-736 didn't come back on, so I assumed the power supply,
> as this is a common problem with the rigs as they get older.
>
> Bought a repair replacement kit for the electrolytic caps
> in the power supply, which is normally the problem. They get
> baked and fail.
>
> Got the power supply out last night to do the repairs and
> I discovered it was the SCR in the power supply that had
> totally burned up. Weird.
>
> Does anyone here have or know a Digi-key or Mouser part
> number for the SCR or an equivalent compatible part?
> It labeled SCR21 on P.C. board.


Vince,
Please either post results here or privately to me about fixing your 736 
power supply.  I am in the same position except that I have not done the 
caps & resistors replacements yet.  Therefore, I am in an information 
sponge mode as I do want to get mine working again. I expect to do the 
caps and resistors replacement.

According to the writeup I found for repairing the power supply, there 
is a schematic from DL7VHF that shows the SCR that appears to be part of 
an over voltage crowbar circuit to be a part 6P4M.  When I did a Google 
search for that, there were lots of hits.  This page may be very useful.

https://category.alldatasheet.com/index.jsp?components=scr%25206P4M

Good luck with your repair...

-- 
73
-------------------------------------
Jim Walls - K6CCC
jim at k6ccc.org
Ofc:  818-548-4804
http://members.dslextreme.com/users/k6ccc/
AMSAT Member 32537 - WSWSS Member 395



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