Vintage HiFi Audio Forum

Audio Discussion => General Discussion => Topic started by: HeathkitGuy on June 05, 2018, 09:38:42 PM

Title: About my Heathkit AA-121.
Post by: HeathkitGuy 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.)

Title: Re: About my Heathkit AA-121.
Post by: Sir Thrift-a-Lot 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.

Title: Re: About my Heathkit AA-121.
Post by: HeathkitGuy on June 05, 2018, 09:57:46 PM

Quote from: Sir Thrift-a-Lot 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.

Thanks!