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Eico HF-81 Tube Amp to Restore

tube-a-lou said:
The tube sockets are not good, thanks for that info. I did take a ohm reading of the
OP transformers and I got readings, so I think there good. I'm going to put in a power
switch in the back to not use the front treble switch which it a odd design, I see a lot
of them with switches put in the front drilled in and it doesn't look that good. Dandy
I'm only at this point going to put in new .1 coupling caps and new electrolytics and
test the resistors and change some wiring.

Tube
Click to expand...

Turn the useless tape switch into a power switch....
 
ferninando said:
and my 2 cents is modify the heck out of it to your hearts content and make it the way YOU want it. These things are not made of gold, altho some seem to think so.
If a purist wanted it he had the chance to have it and didnt take it. Someone else did.
I say the owner has the right to do as he pleases. Let the purist get that crud encased piece of rust and just love the heck out of it. But Its never been modified!!!
You may can tell I have strong feelings on this issue. Sorry for the rant.
No offense to any purists either as I understand where they are comming from.
Went down same path doing old car restoration. Ended up with present feelings.
Click to expand...

No they are not made of gold....but if you rebuild it as designed with good parts IT WILL SOUND better then any modification on earth. Been there done it all.....
 
jaymanaa said:
I did an 85 all the way down too, I think they are worth it, and so is the 81. New sockets and all. You here folks talk about tube gear being high maintenance, but if you do it right, it's really not. I can't remember the last tube piece break down I've had.:scratch2:
Click to expand...

Isn't that the truth! I give lifetime transferable warranties (my productive lifetime) and see about 2 or 3 a year from 1000's of rebuilds over 12 years of business come back and at least half of those end up being a tube failure that the owner could not diagnose or the bad tube took out a resistor... do it once do it right and they last and last.

My favorite saying about new tube gear or properly rebuilt vintage tube gear when a problem arises is.....the problem with tube amplifier is almost always the tubes.....
 
GordonW said:
I used .039uf in my HF81 I just re-did (because I had some really nice polystyrene .039 @ 400v caps). It worked just fine. From what I heard afterward, I suspect it may have helped the bass response (the slightly larger cap value allowed the amp to maintain open-loop gain to a slightly lower frequency, which made for more available feedback at the lowest frequencies- which should act to lower bass distortion and make the bass response flatter).

In most cases, with most amps, as long as you don't go more than double the original coupling cap value, things are usually OK. These HF81s are not that particular about cap values, in that position.

Regards,
Gordon.
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In an HF81 I always raise the main couplers mildly.....when using a polystyrene in an HF81 you better raise it to offset the immense brightness those capos will cause. Sorry but I am not at all a fan of caps like that in any vintage piece.
But realize the cap he is asking about is in the phono section and I'd rather see him lower the value then raise it... rumble, rumble....
 
tube-a-lou said:
For now I'm going to use the F&T cap, I'm going to figure a way of putting it in
without drilling holes in the chassis.

Tube
Click to expand...

Just rough up the area that will be covered by the cap on the chassis with sand paper and then mildly rough up the surface on the F&T that will contact the chassis. Use some Loctite brand professional super glue and bang you'll break the plastic wrap before you rip that can off the chassis. Looks nice and clean...
 
tube-a-lou said:
Here's some pictures of some work so far, First picture is new switch and
cord which on the Eico is real easy because of the screws second pic is
the new 180 ohm resistors, I've read on the Earthlink website that 180 ohm
help the tube bias better, we'll see how this works out. The one thing I'm
doing is going over a lot of solder joints and resetting wires that they look
a lot neater.

Tube
Click to expand...

Its neat how those slide switches bolt right into the AC outlet spot. I've done it that way before but I usually use the useless Tape switch so its up front.
 
tube-a-lou said:
Here's some pictures of some work so far, First picture is new switch and
cord which on the Eico is real easy because of the screws second pic is
the new 180 ohm resistors, I've read on the Earthlink website that 180 ohm
help the tube bias better, we'll see how this works out. The one thing I'm
doing is going over a lot of solder joints and resetting wires that they look
a lot neater.

Tube
Click to expand...

You should raise those output tube cathode resistors to 200 or even 220 ohms 10 watt to cool the output tubes down a bit for todays higher wall voltages....
 
Well again the words did not say that.....I have no problem with mild improvements (RCA jacks, binding post, replace the selector switch and remove useless inputs ect..) your post did not look like that to me so I commented.

Sorry did not mean to rough up those feathers...I'm blunt and to the point because I simply do not have time to waste.
 
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mibag6 said:
I've found one of the most useful features of being a subscriber to this site is the ability to delete my posts that are off topic or snarky and have no relevance to the OPs thread.
I can see, without too much difficulty, a solid page of non helpful, unrelated banter here that really puts people off.
Personally, I enjoy tube's threads and wouldn't dream of mucking up his latest endeavor with supercilious non-sense, so I'm not going to leave this post up here very long but I do hope the posts which have no relevance will be deleted by the individuals making them.
Click to expand...

I agree hence my last post....useless information deleted.

There I think all my posts that do not apply are gone. Thanks for the words of wisdom.
 
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NOSValves said:
You should raise those output tube cathode resistors to 200 or even 220 ohms 10 watt to cool the output tubes down a bit for todays higher wall voltages....
Click to expand...

I'll be running it on a bucking transformer at 117 volts, I run all my vintage
Fishers on that.

Thanks
 
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Hi all,
The power supply caps came in the mail today, two F&T 30uf and a bunch
of Sprague caps for the other areas. I spend the day putting them in, changing
wires and cleaning things plus few of the pins broke off the sockets so I had to
replace them a simple matter of push in pull up. The kit builder did a okay job but
some of the soldering joints I don't like so I'm redoing them as I go along, will add
pictures later.

Tube
 
Lou,
Just wanted you to know I was looking in on you. You're getting better advice than I can give so I'm sitting on the sidelines. If it were me , I'd go with Craig on this. Experience is the best teacher. Need I say more? Keep up the good work.
 
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