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Drake Pages,TR-4Cw and AC4 PSU

Took delivery of this Drake TR-4Cw and AC4 in early April 2004. It looked a bit sad - over one week the following work took place to bring the unit to this level.

After switch on the RX worked OK, but loud hum from the Loudspeaker with the volume turned down..fix later. Note that RCVR / TCVR switch was in wrong position - meant the receiver was stone deaf

Take off knobs and clean front panel, replace marked case with newly repainted one from my other Drake projects. Polish dial skirt - actually rub down with wet/dry to remove pitting then use metal polish.. it shines now.

Reset S Meter, miles out and very optimistic

Check output tube cathode 15R resistors - as expected two are over 17ohms - replace later

Check operation with my good AC4 - no hum so AC4 that came with this unit must be faulty. Check 250V ripple on scope...very, very poor. Open the unit ARGGGHHH burnt wiring and bodged repairs (see the picture below). Tidy up wiring and change the three 250V line smoothing caps. 47uf 350V caps are very small and cost £1 each and fit under the chassis, do not parallel with the old ones. Fit 3 core mainslead and remove lethal mains flylead, presumably to run a 240V fan!!. Check this link for more info on Drake AC4 repairs

Fit the widely known fan mod using a small 12V fan on the back of the PA compartment and fire up to Transmit.

New Sylvania 6JB6's to fit and then go through full re-alignment, Happy to discuss any of this work - just email me

Material Copyright © 2002 {Steve Shorey}