Eico HF-81 Rebuild n Restificate Mini Thread

[Patrice B]

I love the look. Do you have pictures of the back?

Me too, I've told you about ugly gem in your other thread but you did improve the look.

BTW, on mine, treble pot switch broke the first day of ownership so I did the same: slide switch instead of the convenience outlet. Worst than that, one previous owner had converted it as a sort of guitar amp, drilling two holes to put 1/4 jacks on the side (still there). And, chhht! I kept the ceramics in mine...

 

[Patrice B]

A few more pics: Here's a few pics of the back showing modernization of RCA/binding posts. Once all the old riveted phenolic board was drilled out, worked great to use uncoated PCB board to mount everything on. Inside for the RCAs and outside for the binding posts to prevent output shorts. I extended out the binding posts with about 5/16" thick TV mount washers as the ones I got were extending into chassis a bit too close to EL84 socket connections. To get good spacing, only used 4+8 ohm taps as I never see having 16 Ohm speaks myself. with the spacing, it was tough to get original OPT leads to reach. Some had to be re-routed from factory and still barely made it. 16 Ohm taps are heat shrunk and coiled away, 32 Ohm taps still run to FB network as stock. This is all just a compilation of ideas that others have done before. The labeling using industrial strength label tape maybe not so pretty, but it's practical using stuff on hand. Same with the brass screws, not a fashion statement, just the best choice they had at local Ace Hardware.

I still am blown away at how my visualization of the looks was so far off once it was done in real life. Looks like two different amps front to back. But she plays beautifully, so I'm leaving it as is and enjoying to the max! Expanded metal look does not fit the style, but is real practical: a. Affordable enough b. Stainless low maintenance c. better cooling
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Ok hob, we could just swap our two amps, you would prefer my beat-up exemplar It came from here you said (Montréal) so it belongs to me

You will be glad to have this cage for cooling. Mine runs hot, I mean really hot with the original perforated cover.

 

[Patrice B]

Done! There is a bit of hum so if it doesn’t quiet down I’ll replace the can. Other than that, I replaced the 350 ohm screen resistor, the 25uf and 50uf lytics. Everything else checked out and the voltages are good so I’m not borrowing trouble. Nice sounding amp!View attachment 1825798

We are the three members of the HF-81 club... Kidding, I guess a lot of folks here own one of these. Glad I bought it more than 10 years ago. In good shape and unrestored, they fetch over 1000 Canadian bucks on Eprey.

 

[Patrice B]

You did the Brasso and clear coat on the front hob? BTW, you removed the "Focus" pot? You know that it was your balance pot?

**Oh well, read again your post: you replaced the volume pot so you should be ok. The focus pot on mine is used regularly as the old volume pot doesn't really track evenly under half course.

 

[hob]

Me too, I've told you about ugly gem in your other thread but you did improve the look.

BTW, on mine, treble pot switch broke the first day of ownership so I did the same: slide switch instead of the convenience outlet. Worst than that, one previous owner had converted it as a sort of guitar amp, drilling two holes to put 1/4 jacks on the side (still there). And, chhht! I kept the ceramics in mine...

Yes, slide switch is probably the best solution for that. Didn't even see if my treble one worked cause knew I was gonna be deep in there anyway and just ordered one with the caps. Man, bummer on the 1/4" jacks, doesn't seem like the HF 81 would be a very good gtr amp. You could always plug a high impedance mic into those and do karaoke though! Yeah if running other than ceramics made that amp better, it would almost be too good. Like you said it's a gem of an amp.

 

[hob]

You did the Brasso and clear coat on the front hob? BTW, you removed the "Focus" pot? You know that it was your balance pot?

**Oh well, read again your post: you replaced the volume pot so you should be ok. The focus pot on mine is used regularly as the old volume pot doesn't really track evenly under half course.

Yep, I was hoping to have good enough channel balance to bypass the extra of balance and also speak switch. New vol pot well worth it, 26 bux including the coupler.

Nope I messed up the spraying and wet sanding of clear coat. Kinda ran out of patience and wet sanded it back off. Then polished with that weird NevrDull wadding stuff it leaves a pretty decent protective coating.

 

[hob]

Ok hob, we could just swap our two amps, you would prefer my beat-up exemplar It came from here you said (Montréal) so it belongs to me

You will be glad to have this cage for cooling. Mine runs hot, I mean really hot with the original perforated cover.

Ah, let's see what's my excuse to not trade?? Oh yeah, coronavirus, that's it!! Our respective govs won't let us travel that far. And you know both of our amps are too pretty to trust to ups or Canada Post!

Yep function over form the 1/2" opening 18 ga is a good choice. It might blend better for looks with a paint finish that was a close match to eico color?

 

[hob]

We are the three members of the HF-81 club... Kidding, I guess a lot of folks here own one of these. Glad I bought it more than 10 years ago. In good shape and unrestored, they fetch over 1000 Canadian bucks on Eprey.

Yep, sounds like lots of folks enjoy this amp. Yeah these and everything tube now is rare and costly. I envy you and Blackdog61 for knowing to be on the lookout for stuff like this longer than I, a recent convert. I never find any at junk shops n stuff these days.

 

[Patrice B]

Congrats and happy listening!

 

[hob]

It had a nice quad of RCAs but I killed two of them but I managed to put together another RCA and RCA 7189. The plates are running at 350v so I’ll have to consider that. OK for now.

Ok this could be recommended, very cool. For a remote control setup I found a neat box called the McIntosh CR7, which you can use to automate any vintage system that doesn't have IR. Has 3 IR selectable stereo line ins and a ladder resistor IR volume control, when you power it on it goes to 40% volume every time.
So plug HF81 into switched outlet on it, hook CR7 between dac and HF81 input, turn HF81 volume 1/2 way up. You can learn the IR codes into a macro capable remote, insert the CR7 power on command in a macro it turns on your vintage amp at a perfect on volume of 40%, switches to input you want and you have nice transparent volume/mute control of your favorite sounding amp.
CR7 units sell for $80-350 when you find one, took 1 1/2 hr to install, programming included. You could even swap in/out different non IR amps easy with this and still have remote control. Haven't tried it yet, but CR7 could provide a minimalist pre with 3 input switching plus volume control in front of a power amp. Listened a couple hours and the McIntosh unit seemed to not degrade the audio quality, sounded HF 81-tastic! This is a great solution if you wanted to setup a system like this.