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R-390A Audio Mods - AM Window
http://www.amwindow.org/tech/htm/r390aud.htm
R-390A Audio Modifications. by. Chuck Rippel, WA4HHG Some of you may know that I restore R390A receivers as a hobby. Here is an easy "soft " (reversable) modification which I came up with that really improves the R390A audio by mellowing it out a bit. The audio tubes, V602A and V603 are coupled with 300V, .01mfd "Vitamin Q" type capacitors.
Chapter 11 – Upgrades, Modifications, Parts ... - r-390a.net
https://www.r-390a.net/Y2K-R3/11_Chapt_11.pdf
Capt. Lee’s Product Detector For The R-390/ R-390A – Revisited 31 AGC and Limiter mods 35 High-gain Product Detector 36 R-390A Upgrading: Panel and Frame 37 R-390A Upgrading: Audio Modifications by Chuck Rippel, WA4HHG 38 R-390A Upgrading: IF Sub-chassis 40 R-390A Upgrading: RF Amplifier Sub-chassis 40
Mods for Collins R390A
http://www.redwaveradio.com/11_d897569a063558ff_1.htm
For audio mods, you'll either want to 1) pull low-level audio off the "diode load" output on the back panel or 2) make the "Klerenomos" audio mod documented in "Electric Radio" magazine (I don't remember which issue). I haven't heard mention of significant differences in the audio chassis before between the R390 and the R390A.
R-390A Rebuild Audio Module - Dash Distributing
http://www.dashdist.com/1u2u/R-390A/Audio/Audio.php
Externally, you can't tell that the R-390A's Audio-module has been changed. The R-390A simply sounds better and works better. The squelch function, that was included in the R-390A's original design but omitted from its production, is included in my conversion because it required only a few, inexpensive components.
Productions Modifications, Field Changes, and ... - R-390A
https://www.r-390a.net/Pearls/mods-fcs.pdf
Optional Modifications for the R-390A This is a consolidation of modifications from the Production Modifications as listed in the Y2K Manual, various Navy Field Changes, Hollow State News, and various other sources. RF Deck Production Mod 2: Pin 7, V201, connected to ground instead of pin 2. Production Mod 2: C275 changed from 5000 pF to 3300 ...
R-390A Rebuild Part3
https://www.radioblvd.com/R390A_Rebuild_Part3.htm
July 16, 2016 - Ham & Hi-Fi, a vintage audio, vacuum tube and ham radio business in Sparks, Nevada, had its semi-annual Open House Sale today. Lots of bargains and "freebies." I was interested in a decent-looking R-390A that was priced at $70. Not complete by any stretch but I was pretty sure I had all of the missing parts.
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