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Heath AA-1515,,,

knockbill

knockbill

Lunatic Member
Since I've been running into SS stuff recently,, I pulled this old dog of the shelf to mess with!!!! It's a Heath AA-1515,,, 60 or 70W/channel depending what ya read... It was built by an old buddy's FIL... I had it running maybe 10 years ago, but it always had some stupid issues,,, like sloppy selector switch,, loose speaker "jacks" , noisy controls/pots, etc... I remember liking its preamp in front of certain tube amps, and specially liked its phono stage...
I can't find a schematic for it, I think manuals are available tho...
This morning as I was looking again for schems/manuals/info,, I tripped over this great thread by @dlucy on the AR-1515,, the receiver that seems to incorporate this amp...

https://www.audiokarma.org/forums/i...upgrading-a-heathkit-ar-1515-receiver.891978/

So after pot/switch/jack cleaning, replacing shaft couplers for the mono/stereo controls & selector switch and securing the speaker jacks (which I plan to replace), I brought it up on the Variac/DBT, and it came back to life!!! Its still stone stock other than the shaft connectors I cobbled up,, which now securely connects the selector switch to the control knob,, and it doesn't occasionally drop the Right channel any longer!!!
This thing really sounds good, dead quiet even with original caps/diodes/transistors etc... But @dlucy effort with the receiver is urging me to at least recap this guy!!!
I'm sure I can just replace part for part, as its working fine,, (offset is 20mV Left/28mV Right), but a manual would sure help to disassemble it, and remove the boards without damage,,,
Here's a couple pics on the bench,,,
And thanks to @dlucy for the well documented thread!!!!
 

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Can the chassis be disassembled into its various panels? You may be able to disassemble it enough to lift the boards out enough to recap without removing too many wires. I've done this with a few pieces of equipment. With some of the Marantz gear I restored, I never removed a single board to replace caps and transistors other than pulling the amp boards loose and removing just a few wires to get to the back side. Hopefully someone has a schematic or knows where to get one. Someone probably has a SAM'S at leased.
 
The amp boards look pretty accessible,, and they seem to be attached by jacks/plugs and a RCA jack for the signal, they appear to come off with the heatsinks... But some boards are buried, and a manual would help getting them out without making a mess!!! Preamp/tone board looks like the whole front has to come off chassis...
I found picture of the output board schem, going to try to print it, but would like to find the others, but I guess others would also, as they aren't around...
 

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It's a nice looking amp. Was that one a kit or factory wired? From the pictures, iBooks like whoever built it did a dice job.
 
Its a kit,,, an old (he's in his 90s now) buddy's FIL built it... I guess my buddy got it when they cleaned out his house, and he gave it to me in the early 90s... IIRC, he was going to chuck it in another buddy's dumpster, and I saw it!!!!
Its a beautiful build,, not sure I can see well enough any more to do it justice!!!!
A manual would be helpful, then I could disassemble it properly...
 
I just had to try the phono stages,,, dont think I'll tear into this until, I find a schem or manual,,,
 

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Found a pic of the output amps....
index.php
 
Lol, ya, for some reason I can't see the pictures in the last two posts. Just the [ING] place holders. Maybe it's on my end. :dunno:
 
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Sorry, pics didn't work obviously... One pic of teh amp board,, the other of the schem for it,,, They are from the first page of the AR1515 thread I referred to in the first post in this thread,,, Maybe I didn't transfer them right,,, I can see them tho!!
I saw that site,, they want 37 bux for it,,,
 
Incl.shipping.

These days, I'm afraid we are no longer going to get Heathkit manuals cheaply. I have paid a bit for some of mine

Doug
 
Doug’s list of all components to replace for the AR-1515 contains a couple that are also applicable to the AA-1515, such as both output amp boards, and muting board.
I found the manual at the Heathkit site and it’s $27. I have recapped 4 AA-1515s and in one of them, I replaced all the resistors on the output amp boards with metal film low tolerance resistors. You will have remove the front panel (four screws total, 2 at each end of the side panels) and bottom cover to access the tone board. The knobs on the front panel pull off and the same for the bass, treble and balance controls. The plug for the panel lights unplugs and the wires for the meters just pull out of their connectors on the meter board. It’s best remove the walnut end caps before you take off the front panel.( remove the top 2 wood screws, the lower 2 screws are in slots. Four nuts with washers to remove the power supply and muting boards. Any questions don’t hesitate to PM me.

Larry
 
Thanks Larry,,, I looked at the AR1515 thread quite a few times and copied all the pics I could that applied here, along with the schematic for the output amp boards,,, I'd like to get a schematic for this guy before getting into it, as it plays very good now... Its hard to believe there isn't a schematic online for it... If I find one I'll put it in the AK schem thread, so others can see it if the search function ever gets fixed!!!

I doubt I'd shell out 27 bux plus shipping for a manual, as I'd rather put the money into the parts I don't have...
The phono stage in this amp sounds pretty good, and is very quiet... Been pushing my rebuilt OLAs with it, sounds like a good pairing... As I said earlier, DC offset is 20mV Left/28mV Right, which isn't terrible for an amp original condition,, and can be better with a couple parts replaced...

Thanks for the preliminary disassembly instructions, also...
 
How is the offset achieved whith that amp John? Is there a trim pot, or is it done with fixed resistors?
 
Resistors,, no trim pot on these... maybe matching the small transistors on the output boards a little better will get it closer??
 
20mV and 28mv is fine.

The DC offset on almost all Heathkit solid state amplifiers of the seventies is controlled by the differential preamp circuit. The two identical transistors and related parts keep the quiescent voltage at or near zero with no pots to adjust.

Doug
 
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