Thursday, December 31, 2009

Drake Twins

Several years ago I picked up a set of Drake Twins and the Receiver seemed to work for a few month then developed an AGC/Muting problem where it was about 75% muted all the time and therefore would not receive signals.  This week I decided to try swapping out some tubes as I thought a tube might have become weak.  After swapping out V1, V4 and V5 the 1st RF and IF stages it seemed more like a mechanical problem so I started up with the tapping to try and isolate the problem.  With the bottom cover off I found a loose rivet on the RF gain pot.  Squeezing it with the heavy neadlenose 'fixed' this issure.  The speaker wire had broken loose from the MS4 Speaker so I removed the AC4 power supply and repaired this.  Now it was playing through the speaker.

After this success I decided it was a good time to finally unpack the transmitter and check out the power supply.  Everything seemed to light up and was even hearing the 'spotting' tone in the receiver but it sounded raspy with a bad tone like the power supply ......wait where is that smoke coming from ....holy....crap the AC4 looks like it is on fire.  White smoke was billiowing out of the power supply so I unplugged it and found the HV Capacitor was leaking smoking black goo out the bottom.

The Heath C-3 Condenser checker was fired up and the bottom taken off the AC4.

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