AA1214 output devices

[Karl Uppiano]

On Mon, 20 Nov 2000 00:25:25 -0500, George Osmundsen
<gosmund at BELLSOUTH.NET> wrote:

>Is it possible someone with a manual for the Heath AA-1214 amp would be
>kind enough to look up the JEDEC equivalent for the output devices,
>Heath p/n 417-298.
>I recently aquired this amp w/o the manual and one channel has had
>TIP-41C's installed.  The performance of this channel is noticeably
>degraded (clipping point very unsymetrical).
>I believe the output devices would be the same for the AR-1214 receiver
>and most probably the AA-1219 and AR-1219.
>Thanks for any help.
>George

George,

I see this is a very old message, but I have an AA-1214 that I built when
I was in high school in 1972. I still love this amplifier. I blew out the
output devices when it was still fairly new. Heathkit sent me replacement
output transistors, as well as updated drivers and emitter resistors. When
the output devices short, it's very likely that the emitter resistors will
burn out also.

Your amplifier might be suffering from a bad emitter resistor, since
almost any output transistor will work if it can handle the current and
voltage. I think a D44H would be an excellent choice. Your drivers might
also be damaged. The drivers Heathkit sent me to replace the original (non
complimentary pairs) are very similar to the current MJE243/MJE253
complimentary pairs.

I would replace all four output transistors, all four drivers and all four
emitter resistors. While you're in there, you might also consider
replacing all of the electrolytics in the power amp section. A dried-out
bootstrap capacitor can cause asymmetrical clipping. I wish I still had
the manual and schematics for that amp. I lost it when I moved out to
Washington State.

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