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Eico hf-85 volume pott

shelby1420

shelby1420

Enjoying the music.....
Hey all, I have one of these, only complaint I have is the volume pott, very touchy .......... What if anything do I need to be concerned with replacing this with a new one??
 
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That's the only complaint I have with mine too. I think part of it is just the sensitivity of the darn things (the pre itself). I'll see if I can dig up my schematic and maybe we can figure something out with some AK knowledge to help.
 
jaymanaa said:
That's the only complaint I have with mine too. I think part of it is just the sensitivity of the darn things (the pre itself). I'll see if I can dig up my schematic and maybe we can figure something out with some AK knowledge to help.[/QUOTE

Sounds good Jay, I preface this next question by stating up front I have limited knowledge about these thing soooo.........Could I not just take that pott out and swap it with an ALPS ( Blue Velvet maybe) and go that route??? Thats what I did with the Foreplay lll I had that had left and right attenuators( PITA) this won't do much for the amount of gain but....................
Click to expand...
 
Hey all, noticed a low level hum buzz ( only one channel, other is dead quite with 101db speakers......) , this would indicate ground somewhere ya?? I have replaced the cap can using the pegs from it to put my individual caps ( to replace) on two of those lugs, should I only have used one lug??? Figured it would be ok cuz the can is grounded......
 
I am not tech but I'm not sure there's any real solution for the gain, not without changing things drastically. It's hot, nature of the beast.

I do have the original manual w/ schematics. If you like, I can consult my tech who has rebuilt about 10 of these. He is a mod on the Yahoo EICO group.

Here's his site, you can email him directly rather than join the EICO group whcih can take days. However, you should consider joining.

http://sites.google.com/site/vintagetubeaudio/eicohf85page

My baby...

4495022452_a8193d617d.jpg
 
On the HF-85 does the tone circuit add a lot of gain to the signal and has
anyone tried to bypass and eliminate tone controls from this pre amp,
just curious if any one has modified these pre amps in that way.
 
BrokenHill said:
On the HF-85 does the tone circuit add a lot of gain to the signal and has
anyone tried to bypass and eliminate tone controls from this pre amp,
just curious if any one has modified these pre amps in that way.
Click to expand...

Good question, also wondering if 5751's in place of the 12ax7 might knock things down a bit, 100 gain to 70 should help, no??:scratch2:
 
shelby1420 said:
Good question, also wondering if 5751's in place of the 12ax7 might knock things down a bit, 100 gain to 70 should help, no??:scratch2:
Click to expand...

That would definitely help some. How much, would be a good thing to know. I even have some fairly weak 5751s I think.:scratch2: I can't remember if I left the tone controls in mine or not. I guess I should dig it out if we're going to play with them. I do remember though, that there was some reason I didn't change the volume pot when I overhauled mine, and it couldn't have been because the pot was great. Does it maybe have an extra tap at a certain %.:scratch2: Man, I hate getting old and senile. I just started taking B12 today as I noticed the bottle said "promotes normal brain function". I sure as hell hope it works.:yes:
 
jaymanaa said:
Man, all we need is a Nazi flag and we would be awfully scary.:lmao:

I'm going to look for that Eico stuff today.:yes:
Click to expand...

looking at mine I see two wires going to the loudness button ( have little to no use for it) so could bypass it easily, no? If yes then a straight dual gang 500k pott with extra long shaft should do, I think?? Already on the lookout for some 5751,s ..........
 
I searched the web on the 5751 tube and some People seemed to like it and
some don't, it would probably depend on what make of tube you try in that
circuit and hearing it for yourself to really know.
If you don't use the loudness function then a long shaft duel gang 500k pot is
going to be easier to find.
 
Getting a nasty hum/buzz when I engage the phono, all else is pretty darn good!!!! Anything I should look for, the hum/buzz increases with volume control, seems to me its picking up and then magnifying something, that make sense????
 
Hey Jay, using a step up, TT is grounded to that.... think the rca's are good, funny thing is the noise is the same with or without rca's hooked up to phono, wonder if its picking up noise from the mic, gonna try grounding some RCA's and filling up those extra jacks, hope that will eliminate some of that noise...... just changed the cap can for three individual caps, made a new ground lug to chassis, wonder if that is causing some type of ground loop, only to phono tho.................
 
Hmm, my TT grounds to the step up, which then grounds to the pre, but if it does it without the table....................................:scratch2: Sounds like a grounding issue to me.:scratch2: I put DC fils on mine.:yes:
 
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