Author Topic: About my Heathkit AA-121.  (Read 3082 times)

Offline HeathkitGuy

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About my Heathkit AA-121.
« on: June 05, 2018, 09:38:42 PM »
Hello! I scored a Heathkit AA-121 for free, it's in working condition! I fixed a couple issues on it, one was a bad solder joint between one of the 12 ohm resistors and the buss wire, this was making the bias voltage be EXTREMELY unstable, and too high. The other one was a bad power switch, and I replaced it with a heavy duty toggle switch. I  have a couple questions before I put the tubes back in it and power it on. Why is the voltage a pins 3 and 4 at 564 volts instead of 490 for pin 3, and 495 for pin 4? Is it because this amp doesn't have a regulated B+ supply? (If this is in the wrong section, I apologize. You may move it to the right one, if you need to.)

Offline Sir Thrift-a-Lot

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Re: About my Heathkit AA-121.
« Reply #1 on: June 05, 2018, 09:50:36 PM »
That's over my head, but welcome to VHiFi.   Hopefully Scott or one of the other tube experts can help you.

Offline HeathkitGuy

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Re: About my Heathkit AA-121.
« Reply #2 on: June 05, 2018, 09:57:46 PM »
That's over my head, but welcome to VHiFi.   Hopefully Scott or one of the other tube experts can help you.

Thanks!