Did I damage my Eico HF-81 integrated?

[fazeka]

About 6 years ago I had an HF-81 I used to run through some old Toshiba speakers (I want to say that it said the word "Boston" in small letters underneath the Toshiba script on the square logo in the center of the grill; maybe that was the model?). Anyway, one day I was having a neighbor trying to drown me out with some lame hip-hop garbage. So I pulled out either my copy of Live at Leeds or Hendrix at Winterland (I forget) and I guess I basically had the Eico dimed.

At the time, after a while I noticed that one of the speakers went out. I gathered that I blew out the speaker. At least that's what I thought back then.

Fast forward to yesterday when I got a lead on some nice Klipsch Fortes thru the local CL. I scooped them up and proceeded to wire them to the Eico HF-81 I managed to keep and immediately noticed that one of the channels had a harshness coming through one of the Fortes. Then as I was about to turn it off, I noticed some hum coming through the same Forte. Needless to say, I turned off the HF-81 immediately.

Now, I flashed back on the last time I played the Eico and thought: did I actually blow one of the output trannies in the Eico, either as a result of cranking it up through the Toshibas or as a result of one of the Toshibas blowing and then the output transformer having no load and then going kaput?

I know at the very least I would need to recap the Eico, but I am wondering if I've also managed to f-up one of the output transformers as a result of that previous stupid stunt...

BTW, I now have the Fortes wired up through my Sansui AU-517. A little harsh in the midrange, that's why I am dying to get my HF-81 up and running.

Thanks,
Chris

[mhardy6647]

I doubt it... the former is extremely unlikely; the latter is certainly possible, but if you cooked the OPT, I think you'd get nothing.

The HF-81 has ceramic coupling caps (for better or worse), so the hum isn't likely bad coupling caps! Power supply caps (those two under the deck, especially) are worth evaluating if they're original.

My HF-81 has fairly significant background hum on sensitive speakers. Since most of these were made as kits, it can be a real chore to track down. Gary Kaufman and I spent an afternoon on mine, with no luck. At least one of his HF-81s, on the other hand, is dead quiet :-P

[NOSValves]

These vintage amps if still original are always running on borrowed time. They need to be rebuilt. I'd say 99% chance you do not have a transformer problem. Rarely will a transformer fail and the amp not blow a fuse pronto. The HF-81 just simply needs to be rebuilt and possibly some fresh tubes installed here and there. IMHO they always sound much better once rebuilt if done properly and the proper parts are used.

Craig

[gogofast]

HF-81 can be one of the sweetest sounding low power tube amp when properly restored.

have NOSvalves restore it properly for you. i think he had one done for an AK'er before.

here's one of websites with HF-81 mod: http://home.netcarrier.com/~rstevens/hf81.html

[fazeka]

Hi,

Yes, I guess I would start by replacing the electrolytics, cleaning it up in general and retubing.

I don't think I would mess with any significant mods, at least before recapping the 'lytics. In fact, I thought I remember somewhere that someone did something seemingly as innocent as shotgunning *all* the caps (maybe even the resistors?) and they reported back that the HF-81 lost some "magic"...

What are some of your favorite new EL-84s? JJ? Sovtek? Ei? I have a duet of JJs in an old Vox AC-15 that sound good to me... not sure how they would sound for hi-fi?

[mhardy6647]

I've used JJs in my HF-81 for years; I think they sound fine. More recently the quality of JJ tubes has been pretty roundly criticized.

As to the HF-81 magic, let me (yet again) go on record as saying that I think mine sounded a dang sight better with Orange Drops (716P) for coupling caps than the 'magical' ceramics that EICO used (and some folks rhapsodize over).

http://img.photobucket.com/albums/v223/mhardy6647/P1020749.jpg
http://img.photobucket.com/albums/v223/mhardy6647/HF81groundhighlight.jpg