[R-390] FL101 Rebuild (R390)

[Jim Whartenby]

Barry
A lot has changed in the 70 years since the R-390 was released for production.  I haven't found the transfer curves for the line filter in the R-390 but we do know what frequencies the Schurter filter will attenuate.

Personally, I would mimic the 6 amp version which uses inductors close to what you report.  As for the smaller caps, lower leakage current perhaps won't trip a GFCI.  Check the attenuation curves for the 6 amp standard version, this is how the filter will attenuate line noise in the radio.

Regards,
Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy

-----Original Message-----
From: Barry <n4buq at knology.net>
To: Jim Whartenby <old_radio at aol.com>
Cc: R-390 Mailing List <r-390 at mailman.qth.net>
Sent: Sat, Oct 22, 2022 2:14 pm
Subject: Re: [R-390] FL101 Rebuild (R390)

Jim,

Apparently there some versions have four inductors and some have only two.  I suppose it depended on for which radio they were specified.  Interesting that those Schurter filters use 2.2nF capacitors which are significantly smaller than what I'm measuring from the original filter.

Thanks,
Barry - N4BUQ

----- Original Message -----
> From: "R-390 Mailing List" <r-390 at mailman.qth.net>
> To: "R-390 Mailing List" <r-390 at mailman.qth.net>
> Sent: Saturday, October 22, 2022 12:49:36 PM
> Subject: Re: [R-390] FL101 Rebuild (R390)

> Barry
> I looked on Mouser's site for AC Line filer, 125-250 VAC 10 amps. here is a link
> to the datasheet:
> 
> https://www.mouser.com/datasheet/2/358/typ_FMW_41-1275852.pdf
> 
> IIRC, there are four inductors in FL-101 so just duplicate the values given.
> 
> Regards,
> Jim
> 
> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy
> 
> -----Original Message-----
> From: Barry <n4buq at knology.net>
> To: R-390 Mailing List <r-390 at mailman.qth.net>
> Sent: Sat, Oct 22, 2022 11:38 am
> Subject: [R-390] FL101 Rebuild (R390)
> 
> After finding the connection between the input and output for the "A" connection
> was open in FL101 of my R390, I removed the filter, opened the lid (lots of fun
> there...), and found the problem.
> 
> Along with the ubiquitous wooden blocks and wax, I found that the connections
> for virtually all the capacitors were bad or going bad.  The caps in mine
> filter have three connections where the end points are the through connection
> and there's a center connection that serves as the third connection allowing
> the capacitor's ground connection.  Each capacitor was housed in its own cute
> little thick paper box - a rather unique configuration that I'd not seen
> anywhere else.
> 
> I'm not sure what caused it, but the endpoint connections were such that I could
> simply pull the wires away from the capacitor and the capacitor for the "A"
> connection was the worse of any of them.  I don't know if those are
> electrolytic and the electrolyte leaked (doubtful as they aren't really sealed)
> but something caused quite a bit of dark corrosion which had virtually
> destroyed the solder connections.
> 
> In any case, the inductors are still in great shape and I can rebuild it so a
> relatively happy ending for this once I get the necessary parts.  Anyone know
> the proper value to use for those caps?  The filter is stamped with FILTER TYPE
> 97JX56 and I wonder if those numbers indicate the inductance and capacitance
> value (e.g. possibly 56pF but that's just a guess).
> 
> Thanks,
> Barry - N4BUQ