Greetings Drake Aficionados, I have been working on refurbishing and updating a 1972 Drake L-4B since late March as time permits. This L-4B was a "closet find" and had not been in use for many years and has an unknown history.
The L-4PS was updated in April with the Heathkit Shop L-4PSR power supply board and a new R11 bias resistor was also installed. At that time, I decided NOT to replace the two 50K 50W bleeder resistors (R9 & R10)as they checked and looked OK and figured I could replace them later on. About three weeks ago I noticed the ALC stopped working and the Plate Amperes meter was "sticking" on transmit and of course the components for both of these circuits was the bleeder resistors and bias resistor. Yesterday I finally got around to replacing the 50K bleeder resistors and in the process of replacing them, I found that R9 had opened up entirely! Replacing both R9 & R10, and also the fuse resistor (R12) for good measure, fixed both problems. If you are interested, the replacement of the 50K bleeder resistors can bee seen on my web site, www.w1cc.net, under the Project menu under L-4B. So, I was very lucky indeed that there was no damage done to the L-4B when R9 opened and wish I had taken an extra 20 minutes to replace the 50K bleeder resistors three months ago. Just as you shouldn't trust 38 year old filter capacitors and diodes, you shouldn't trust 38 year old bleeder resistors! 73, Tom, W1CC _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
