I created one nice unit out of 2 parts rigs. My quest was greatly extended by user manual errors and rabbit holes I wasted a lot of time on. I put some photos in Photos.
What I fixed/replaced:
o Display board replaced with Elcon EL-31 – see Files for details.
o Added Elcon excellent vfo stabilizer – see Files for details.
o Fixed low SSB output problem after way too many rabbit holes
User Manual in wrong on Page 19. IF Board Q403 does NOT amplify the DSB signal. It is a 0.3 unity gain impedance matching stage.
The schematic is wrong on the IF Board. Both Q403 and Q404 drain connects are shown connecting back to the gates – dumb. They should be connecting to D404 8 vdc, one horizontal line below.
Removed the SSB filter on the NB Card and wired NB Card back to factory configuration for no Speech Processor. Even when RF Processor off, the path is through 2 series connected SSB filters. If the filters are not identical, one can never get the carrier set point right, one SSB will have low power out. I tried some filters from spare boards to no avail. I am going to use the MFJ-653 anyways so I don’t need screaming weeeeeemy DX audio anyway.
o I re-calibrated all except band pass, none were very far off so goodness.
o Cabinet – came out well.
I painted the trim ring with gloss black appliance enamel.
I over-sprayed cabinet with semi-gloss black enamel.
o I cleaned all switch wafers with DeOxit
o I cleaned all pots with DeOxit Fader Lube
o Power out can go up beyond 160 watts but I adjusted the pot on the NB card not to exceed 110 to be safe.
o Added 12vdc white LED to meter side light, looks nice, photo is exaggerated bright.
o Replaced burned out bulbs in the center indicator for VFO, Clarifier, EXT. This is a horrible job given Yeasu epoxied the the holder into the back of the face plate - stupid overkill.
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Summary
CONS
o Not many flaws, this is an excellent design and after mods is even mo better.
o Little plastic cover push fasteners are unobtanium.
PROS
o Internal speaker is the best I’ve ever heard, no need for external speaker.
o Carrier suppress (after fader lube applied to pot) is best I’ve ever seen on older radios. -70db
o AM is superb both XMT and REC with optional AM Board. My REA monitor shows 120% positive with a 30 watt carrier and perfect wave forms.
o Semi-breakin CW and VOX works well.
o SSB quality is excellent as long as carrier set point is 6 db down. With 50 watts output at 1,000Hz mic input, 2mV, 300 Hz mic in must be 6db down at 12.5 watts out. Set this ONLY after a long warm up because there is minor drift of the SSB oscillators on the AF Board.
o Small package and styled beautifully.
o Someone installed a CB crystal (41.5 MHz) in the AUX position and it works.
o NB works well and 60Hz pulse crapolla.
o REC sensitivity and selectivity are excellent – comparing to my FLEX 5000 and KWM-2A
Nick (N1CCK)