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FWIW, I have a copy of Lou's "Construction and Operation, Tri-Power Mobile Linear Amp" publication from 1979. It's written very well with pics & diagrams.

Goes way back

Me too but my DX-70T is unfixable due to the BPF filter board unavailability. I prepared to attempt replacing the SMT diodes (even purchased replacement diodes). After I saw how microscopic they were, it was obvious the required soldering work was beyond my skill set. Tweezers, an smt camera...

Lightly used EMS-14 desk mic. This is an Alinco mic not the look-alike clone. Purchased new in or about 2010 (I probably have original packaging and probably the Receipt too) been in the original box since for but 2 years use max. I do recall that the removable foam element cover (windscreen)...

Audio Note Kit 4 clone board 2x 12ax7 driving 2x 6sn7 driving 4x 6v6's into Ultra Linear OTP's for 16w clean sound. This is a temp layout to get it working. 12ax7's has separate DC Heater circuit & xfrmr

I'm going to take a guess by your handle here (Guitar_1999) that you are interested in audio amps, no? I spent the last few months working a 6v6 stereo amp, you work on music amps?

I have the same meter but it’s setup for -0- center so it shows negative current. Same plastic case. I glued a heavy piece of scrap metal inside to weight it down. I’m at the theatre now but I’ll attach a pic when I get home. It was dirt cheap for a zero center meter big enough to read across...

All bands (10-15 and 40-80) work well (5w in 500 out) but 20M remains a problem where output about 200w under same drive. Roller subject to arcing hoping para board helps.

Yes a turns counter would be useful. I have a page of notes to recall settings for each band. The top mesh cover allows me to see the roller and V caps for some setting info but it’s tedious to change bands. 10-15 and 40-80m input inductors set set. Still tuning 20m but I’m in the...

Thought I had too much stuff for an amateur / non-radio pro but the preceding pages made me feel a bit better. Next thread along this theme should focus on how big a collection of Parts & Supplies needed to keep the equipment going. How do you organize it all? I'm swimming in zip-lock baggies.

Why does a vacuum variable have bellows? If the concentric circles that mesh together and apart control the capacitance, and; There is a vacuum inside the glass tube itself, why is there any need for bellows? Bellows also look like copper. Having a quality capacitor helped me rank my...

Looks like it was packaged by Khrushchev himself. The foam inserts rotted and fall apart at the touch. A greasy mess but the cap is in a sealed plastic bag. Did they even have plastic back then? Package insert has several dates. A rubber stamp of 1991 and other handwritten and pre-printed...

The lowest Tune capacitance I can apply with an Air Variable is about 15pF. That minimum Tune C reduces PO by nearly 80%. Yet, with no Tune C connected at all (L network Tank) I see about 1:100 PO w/ reduced plate volts/mA. The RF Input parallel resonance revisions appear to work fine...

I assumed that the 750R RF swamping resistance was reduced by the .01uF bypass cap so it's closer to 450. I'm considering dividing one of the 1.5k resistors (the 2nd one after the trifilar on the way to band switch/tube grid) into 1.2k and 300. The 300 would be in series on the way to the grid...

OK I have some reading to do. I briefly saw that t match can also aid impedance matching. Is it feasible to use the pride’s swamping resistance of 750R as one of the T-pad’s resistance values? It’s already there

My FT891 only goes down to 5 watts and shuts off if I lower the VDC below 12v. A series resistor sounds like trouble. How far can I reduce the 750 ohms 'swamping' resistance to ground without altering the input impedance a'la Pride formula? It would make tuning & trouble-shooting easier if I...

The picture (above) of an external roller looks absurd and was a last resort. Fortunately, I don't need to pursue that route b/c the fixed inductors are working. It was the T-R relay compartment that precluded 10-20 meter operation (when reassembled). I did sample the input swr with the...

I was too fast to conclude total success. There was overall improvement but the same general pattern of too much C in pi network for 10-20 meters remains. This picture is an abomination but I’m hoping to rule-out inductance as an impediment to 10-20 meters. The last round of testing showed...