Drake T-4XC bias OK, but no plate current

[KI4IOV]

I recently obtained a set of Drake C-Line "twins". These units are in very good physical shape, and they were working when put into storage, I'm told (big surprise there). I have a set of original manuals and I've begun the tune-up procedure. I can set the bias just fine, but in the tune-up procedure I can't get any plate current. Nothing, gain, plate, load, nothing will make the needle move. All the voltages from the AC-4 check out, and the tubes have that cheery glow, but still no plate current.

Looking underneath, the carrier oscillator board had a broken coax shield and some really crappy solder work from an old repair. I corrected these, but still no joy. I'm planning on sending the R-4C off to Sherwood Engineering for a professional alignment, but I'd like to take a crack at the transmitter myself. I'm ready to start troubleshooting in earnest, but I'd like some advice on where to start.

I have a fairly well-equipped shack: Tek 'scope, Wavetek freq. generator, Fluke bench meter, well-equipped junkbox, etc. and I'm not unfamiliar with tubes. I learned electronics from an old ham in the early 70's before tubes were completely replaced by sand devices, so I do have experience working on glass radios.

Disclaimer: Yes, I understand there are lethal voltages inside the chassis; I promise I will be careful, but thanks for the warnings anyway.

These are the radios I lusted over as a kid, and got to play with in Gus' shop back in the day - I really want to get these guys back into good working order. Anyone have any ideas? Failing that, a recommendation for a reliable repair shop?

Thanks everyone!
73 de KI4IOV

[W0LPQ]

Take a look at the WB4HFN website. He has service info listed.

Bill, W0LPQ/9

[w9gb]

I have been very happy with Jeff Covelli (Ohio). Jeff has recently retired, and now has more time for Drake repairs.

I would send the entire "4-C" (both) to him for alignment, restoration and clean-up.

Here are his reviews
http://www.eham.net/reviews/detail/4908

Greg
w9gb

[W0LPQ]

Greg I have not checked into the net for a while, but was not aware that Jeff finally hung it up..! He is part of the Drake HF net on Sunday afternoons. As is WB4HFN and several others. Jeff does do quality work..!

WA8SAJ is Jeff's call, if those concerned want to look it up.

Bill, W0LPQ/9

[K3NOQ]

turn off the radio, unplug the ac cord and CAREFULLY discharge the p/s caps. Check for continuity from the power supply high B+ point to the plate cap. If no continuity, look for an open choke or other problem in the high B+ buss. Plate high B+ may be metered in the power supply so you would have good reading, voltage wise, but with an open feed to the tube, no plate current reading! Do NOT try to measure B+ at the PA tube plate, you could easily blow the voltmeter due to the high RF voltages also present. Hope this helps/ 73 John

[WA7KKP]

Look at the sideband selector switch, and you'll see one side marked with an X. It has to be on the X position to inject carrier into the finals for tuning.

Gary WA7KKP