Eico ST40 GW Find - Where do I start?

Use a large resistor before the first cap. This limits current, and lets even the most stubborn cap reform over MANY hours.. Without guess work.

Could you please be even more specific about that cap? I saw the - 100k, a couple of whats - suggestion, but I'm very new to this. Is that to say precisely 100k/2 watt?

On another note, I think for now I'm going to just bypass the cans altogether and use regular caps tucked underneath. I really want to get this running as inexpensively as possible until I can get the hang of it and make sure it works OK. I'll go through a second time and get some of those upgrades going.
 
Have you applied any power to the amp yet?

If so, It's a next time thing. No worries. The resistor replaces the B+ wire from the rectifier to the first filter cap. Some guys go as small as 1 watt, I use 5 or more, just because I have them lying around. Doesn't have to be 100K. Some have used as little as 22K, and I've used well over 100K. There can be other considerations....

A variac with diodes can totally work, but you're guessing either way, when you turn the dial. The resistor method may only take an hour or 2, and I know of 1 guy that says he saved one...after 36 hours. You just leave it on and wait for the voltage across it to get "close" to zero. The cap decides if it'll come back to life .... not you.

Gary's tube base/converted to diode solution is a nice plug and play one. I'd do it. Just not on a "time piece" amp, where having the original components can nearly double an amps value.(this is especially true with guitar amps that wind up in the $5K+ range, we're weird like that, and we'll pay through the nose for the original components.) You can learn an awful lot about saving caps on guitar amp forums, because stupid $$$ rides on doing just that. The "diode base" is a good all around tool to have in your arsenal, anyway. Assuming your rectification isn't a 5Y3(don't do it), and say, a GZ34? You can nudge your B+ a wee bit(add headroom), and hear what it sounds like with less sag.. You may hear the difference when you push the amp to the brink...

I thought it was fair to address your initial variac assumptions(as well as others). All you really needed was a resistor.(and some basic considerations) I used my variac "wrong?" for years, until someone gave a heads up. If you've already applied power?? I really don't think it's fair to you that we walk down this road in your post.... That's a 20 page circus...

If you haven't applied power.. That's different....We might be able to save your caps.. Otherwise, we should get back to your build(or at least post turn up procedure, elsewhere).



FWIW, Nerdvana? deserves a big ole hat tip, for stepping up to show you what he knows. Hands on is always priceless. Times 10 for the face to face. :)

-Bob
 
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I've always used a hammer and a file to re-form vintage can capacitors if I damaged them cutting the things apart to re-stuff. A little hammer and dolly work and the file or sandpaper to knock off the burrs from the saw do the job nicely. I don't bother with them electrically. I generally only re-stuff in a situation where I have no room to put new parts underneath though.
 
Antique audio sells most of the multi value can caps. Often cheaper than buying individual components. Just a thought
 
On another note, I think for now I'm going to just bypass the cans altogether and use regular caps tucked underneath. I really want to get this running as inexpensively as possible until I can get the hang of it and make sure it works OK. I'll go through a second time and get some of those upgrades going.

I would agree with that. If there is room, just leave the originals and use regular caps underneath. I like my Eico ST40, but don't think it is ever going to be a big $$$ heirloom. So, I rebuilt mine to use 6L6s, following Kegger's guidelines.
 
Maybe not a $$$$ heirloom, however I’ve seen fully restored EICO st 40s for sale on eBay upwards of $500.00!
 
The other can cap (20uf/40uf/40uf) can easily be replaced by this one:

http://www.tubesandmore.com/products/C-EC40-20X3-500

It has three 20uf sections and one 40uf- since you need one 20uf, and two 40uf, simply wire two of the 20uf sections in parallel, to create 40uf- use that to replace one of the original 40uf sections, and use the other remaining sections (one 20uf and one 40uf) to replace the corresponding other original sections.
Hi Gordon:

I am changing the chassis-mount can caps (C35 and C36) on my old Eico ST40 integrated stereo amplifier. I have a question.

I ordered a 40/20/20/20uF@500/500/500/500V capacitor to replace a 20/40/40uF@400/350/350V capacitor (C36). So I need to wire two of the 20 sections in parallel to create a 40.

Do I do this by simply soldering a wire between two 20s or is there more to it than that?

Thank you.
 
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Hi Gordon:

I am changing the chassis-mount can caps (C35 and C36) on my old Eico ST40 integrated stereo amplifier. I have a question.

I ordered a 40/20/20/20uF@500/500/500/500V capacitor to replace a 20/40/40uF@400/350/350V capacitor (C36). So I need to wire two of the 20 sections in parallel to create a 40.

Do I do this by simply soldering a wire between two 20s or is there more to it than that?

Thank you.

That is correct- just jump two of the 20uf terminals together with a wire.

Regards,
Gordon.
 
That is correct- just jump two of the 20uf terminals together with a wire.

Regards,
Gordon.
Thank you so much.
By the way, I started with the simpler of the two can caps -- the C35. I swapped out the old one with a 50/50uF@500V, and my Eico ST40 does not hum at all now. And it sounds amazing!
Since I bought it already, I'm going to change the C36 can cap tomorrow, and then do the loudness mod when those parts arrive from Antique Electronic Supply.
 
The first cap (C35) has to do harder work than the other cap (it's closer to the rectifier so it takes a lot more ripple current). So, that's usually the one that takes a hit first, in terms of degraded performance.

That said- the other cap (the three-section) is the same age- it is a very good idea to just replace it at the same time.

Regards,
Gordon.
 
I am finding that the JJ C36 cap from Antique Electronic Supply will not fit the existing opening in the chassis. (I haven't unsoldered the old one yet.)
Are people who face this problem cutting the chassis with a hack saw to enlarge the opening?
 
I did some chassis surgery when I modified my ST40. But I guess it might hurt its 'collector value'.
 
A Uni-bit (step bit) does a much cleaner job than a hack saw. Clamp the chassis to a bench before you drill. Using a drill press is an even better idea.
In my opinion having new filter caps, even with the enlarged holes, adds value to the piece.
 
I agree. These units are to be used. And, honestly, who would choose them for display only?
 
Thanks for the advice. I decided to change out the C36 can cap. To enlarge the hole, I used a dremel-type tool attached to a hand drill. It vibrated and chattered quite a bit, but I experimented with the cutting speed, and had success. (The tubes were removed during this process.)

90% of the hum is gone now, but a new problem has come up that I need to request your advice on. The loudness of the right channel is less than the left channel. And I noticed that all three of the transformers are cold, even when running for a while.

Were they always cold and I didn’t notice, or can you direct me to check on something specific?
 
I may not be of much help on the technical side of things, but have you tried the loudness switch modification? The instructions are in another post on this site. I did it and it made a dramatic difference. Also, sometimes I will get some humming or “popping” when turning the level, treble, bass pots etc. on occasion. However, I know right where the sweet spots are on them to get the desired listening preference. With all of its little quirks, I’ve managed a few work arounds and this is seriously one of the best sounding receivers in my arsenal. I’m driving a pair of Knight 280’s (50 watt) containing 15” Jensen subwoofers. The tubes offer lots of warmth, punch and crisp highs.

Good luck with your modifications. I’m sure your efforts will be rewarded.
 
Thank you for your reply.
Yes, I did the loudness mod, and it did improve things.
I have mine hooked up to Klipsch Cornwalls. They sounded great when it was working properly.
Do your transformers heat up? It might be hard to tell with the cover on because you might just be feeling the heat from the tubes, but you might be able to tell.
 
Update: I unplugged the power and removed the tubes. I cleaned every pin of every tube with DeoxIT D5 (non-lubricating type) using a Q-tip. The pins looked fine -- nice and shiny -- but I cleaned them anyway.
Then I cleaned the pin sockets with the same DeoxIT D5 using a pipe cleaner. (I sprayed it onto the pipe cleaner -- not into the socket.) I held the pipe cleaner with pliers that had rubber insulated handles to prevent a shock in case any stored energy from the capacitors might be conducted.
I sprayed air into the pin sockets with a dust remover aerosol can to make sure they were dry and to remove any dust.
I replaced the tubes in and out five times each, and let it sit for a couple of hours.
Then I powered it up and it sounds great. The volume from the right and left speakers seem to be equal!
 
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