Saturday, July 29, 2023

Kenmore Elite Dryer Electronics...

 Oh boy, this dryer again... Over the years I've replaced 2 heating elements prior, but this time I think I got to the root of the problem. It's a typical electric dryer 10+ years old...the element burns out, you slap a new one in for $25 or so off of Amazon, and roll on. This time, however, there were several symptoms that made me think a bit more deeply. First, for some time, it had been presenting a "low air flow" alarm, but kept running. I cleaned the exhaust path and removed mucho lint. Seemed better, but still got that "AF" alarm from time to time. Didn't think much about it, until this element burned out. When I pulled the dryer apart, the heating element enclosure was pretty warped up from excessive heat. After studying how the air flows in this system, I discovered the blower actually draws air through the heating assembly, then through the clothes drum, then out of the unit. Air flow is measured in the heating assembly. The main drum has a leather and felt seal in the front and rear that had become very worn. This allowed air to be drawn from the cabinet area and in around the drum, reducing actual flow in the heating element assy. This caused the heater to run MUCH hotter than normal, and hence failure of that. OK, so I replaced the seals and element, and put it back together. I did notice that the element has struck against the inside of the heater enclosure when it burned in half, and made a big arc mark in there. Remember that....

OK, so all is back together and running fine. No AF alarm, but it's running really HOT. I put the dryer in "air dry" mode, put an ammeter on the 220v input, and it's still pulling full power from the service...even when no heat should be on. I pulled the control board from the head of the machine, and found the relay that modulated the heating element on and off to control heat, was welded "closed". When the unit was on, full heat was being applied. I ordered and replaced the relay, and the unit went back to controlling temp. Seems when the element broke and struck the housing, it destroyed the relay contacts at that time. 

All is back together and operating properly. I know this isn't radio, but maybe it'll help someone out there, one of these days :-) Here's a few pics...


Wednesday, July 26, 2023

Amp Supply LA-1000 Repairs & Upgrades

This is a LA-1000 sweep tube amp, made back in the 80's by Amp Supply Company. Amp Supply was a "spin-off" from Dentron, Amplifiers, and this is an upgraded model of their GLA-1000. This one was in need of work...bad caps, bad tubes, problems with the tuned input, T/R relay problems, etc. She's back up and running strong now, upfitted with Russian 6P45C tubes, new sockets and components. It'll run around 700-800 watts out, depending on band and mode. Here's some pics and a description of the work...

The first steps were to get this beast pulled apart in a way that it could be easily reassembled. Below are the tuned input board, plate choke, and main power supply boards.



Next, the rf board has to be pulled, and tube sockets replaced. The original used 6LQ6 tubes, and didn't use pin 9. The new 6P45C tubes are larger, and require the use of pin 9. The tube pins are also larger in dia, so a different version of the socket must be installed. 


The filter caps were toast, and blown due to failed bleeder resistors. This allowed the resting voltage to rise to a value above the rating of the caps, and that stopped the parade :-)  Caps were replaced, new sockets modified and installed, and the bottom of the rf board remapped to that needed for the proper pinout of the new tubes.

The above 2 pics are the tuned input board, and below is the RF board, ready to reinstall in the amp with new bleeders, caps, sockets, etc. 

The photos below show some mechanical issues to overcome. The tubes are larger in diameter, and taller. Various bits around the inside had to be moved to allow clearance from the tubes so as to not be touching the ends of screws, etc. 


Once everything was all reinstalled and tested, I had to cut an opening in the lid and fold a perforated riser, paint it, and install it in the lid. This provided additional clearance for the top of the taller tubes. 

Here she is, back on the air and ready for many more years of operation!