Yaesu FL-2100Z Conversion

 This is an old Yaesu FL-2100Z that needed repairs and tubes. Considering the availability of _good_ quality 572B tubes these days, I gutted the PA and converted it to the Russian ceramic GI7B tubes.

Conversion is a bit involved, requiring new tube sockets in a different location to preserve the band-switched tuned input system, relocation of several capacitive pads gor the Load control, 4 new fans, high voltage interrupter (to allow filament warm-up without HV on the plates), new bias regulator,  new cathode fusing, hv glitch protection, tank circuit re-tap, new DC supply for controls, and modification to almost all of the L and C components in the tuned input system. Here's a few pics of the process...

Finished unit, about 800w out with 65w drive.

Cathode fuse added in case of a flash over.

A little rig I built to work the C values out for the tuned input. The tuned input is basically a bunch of Pi networks, one for each band. I adjust the 2 air variables to find best match, measure the results with a C meter, and install fixed values on the board. Works great!

33K for resting bias of about 60vdc.

Voltage doubler on the 6vac winding for the 12v fans and controls. The 12vac winding can't be used, as it is directly coupled to the GI7B filaments and has bias dc floating on it. 

HV interrupter and HV glitch resistors. The interrupter opens the lower bridge connection in the HV supply. Glitch resistance is 10ohms @ 50w.

Cathode fusing at 1a, brought to outside connection.

Zener that control the heatsinked bias regulator out back...

Rear mounted bias reg seen on heatsink, here.

About 2400vdc at idle...

Filament pin cooling fans seen in the rh side of this Pic. Absolutely required!

Placement of the tube coolers...notice each has its own dc cooling fan.

The RF compartment is full!

Wiring the sockets. I reuse the filament choke from the 572b setup...

DC fans installed on a bead of silicone adhesive.

Adapter plates and sockets installed in the old fan locations, with a bit of outward offset.

Gutting the old PA, old tube socket locations seen here.

C pads, sockets, plate caps, etc have to come out.

Getting started on the overhaul...

D&A Maverick Amplifier updates...

 This is a D&A Maverick that I repaired and updated with Russian 6P45C tubes. The Maverick originally had 4 small 6JG6A tubes driving 4ea 6LQ6 tubes. The PA was much like the Dentron GLA-1000 and the Amp Supply LA-1000 (designed for 100w drive). The Maverick essentially added a 100w driver stage with the 4ea 6JG6a tubes.

I replaced the 110v plate relay, and made a few repairs to this amp. Next, I rewired the sockets and converted it to the much larger and more robust Russian 6P45C tubes, in a 2 driving 4 configuration. The Maverick has a stout power supply, with 2 plate & filament transformerscin phase. 

This can now be driven with 30w pep, but with the little 3 watt radio I use on 29.000 AM, is doing about 650 pep on AM. With my IC-756 limited to 30 watts on SSB, it'll do about 800 on 10m SSB. Here's a few pics and a video...

Tank moved inboard to reduce coupling with the outer cover.

I relocated the PA tank more inboard, from this location, due to interaction with the outer cabinet when installed.

Yaesu YD-844 Microphone

 This is a Yaesu YD-844 mic that a friend in Western NC sent to me for repairs. He bought it on eBay for his Yaesu FT-901...but when it arrived, it didn't work on his rig.

I checked it over and found it incorrectly wired for his rig, found broken wires in the base of the mic, discovered some unknown "goo" where the cord entered the mic, and the 4-pin plug was missing a locking screw. On the bright side, the mic was in good cosmetic condition, the mic cartridge was in good shape, and the cord was fine.

I cleaned the sticky goo from the cord and mic, repaired the broken wires, rewired the connector, and replaced the missing locking screw. 

I also disabled the Yaesu "lift to talk" switch. I've found most hams hate this feature, and in my opinion, it was a horrible idea. A sprint loaded post extends out the bottom of the mic, and connects to a switch, inside. When the mic is lifted off the table, it keys the transmitter. It also keys the transmitter went bumped over on it's side for some reason. 

Here's a vid and a few pics. It's back at its new home, and being used on a FT-901. Great mic!