Restoring Eico HF-22 pair

Morzh

Active Member
I acquired a pair less than a year ago, now that I am done with my last tube radio project I decide to put the twins on the bench.

First question: now that recapping is the 1st order of business, where exactly do you buy twist lock caps? The stock are 1" and I want them to be 500V rated, but all I can find even at 450V is 1-3/4" type which I am nor sure I could mount.

I could obviously leave the existing ones for looks and put the new regular hi-ripple cans underneath (and that would be a heck of a lot cheaper) but somehow I want to do my due diligence and see if I could buy a properly looking replacements.
 
+1 on hayseed hamfest, they will make you 1" cans with a high voltage rating!

The only thing is that the HH cans don't look as "original" as the caps from CE manufacturing. Hayseed cans have a very shiny mirror finish (I think they use stainless?) That being said they look great and their price is about the same as the cans from AES.

There is also a German company called authenticap, which get good reviews, but I don't think they have 1" cans, or take custom orders.
 
Have you considered restuffing the original cans? You can get 500VDC rated electrolytic caps with radial leads in 10uF to 150uF from Mouser Electronics which are under the 1" diameter of the can. The 150uF would probably be a tight fit at 22mm but the other sizes are 18mm or less.
 
Thanks guys, was not aware of these manufacturers.
Will try to research them.


Nerdorama,

I have restuffed twistlocks, for radios. And even that is borderline acceptable.
I do not know the ripple rating of the modern or vintage twistlocks, but I suspect that due to the sheer size it is more than that of even high-ripple modern can caps from Panasonic which is the highest I've found.
Even if I could stuff two in one can, I'd be worried if the amp were working at say 10W output.
If I were to use the modern hi-ripples, I'd use two 40uF in series to make one 20uF, this would give me over an amp rating. But it won't fit in the 1" can.
Regular GP cas should never be used in the rectifier filter, they are at best 1/3 of the required ripple and will, if used extensively, fail. They do in radios. And radios draw less power.
 
Even though the original can cap was larger than the modern cap, I think (I don't know this for certain) that the modern construction is actually lower ESR so should handle more ripple current. The can caps are also rated at 85 degrees C where many of the other modern caps can be had with 105 degree ratings.

I obviously don't have a definitive answer for you regarding this question.

Good luck with your project,
John
 
I just modeled the HF22 power supply in PSUDII- and it looks like the only cap with significant ripple, is C10 on the original Eico schematic (the first one after the rectifier- paralleled dual 20uf). And even that's only like 200ma ripple current, at idle, and around 250ma ripple current at full power.

Many modern "miniature" caps are rated in excess of one amp ripple current- that would be more than enough.

Given that the two sections of C10 are paralleled- I'd just re-stuff that one with a single 47uf cap, with as low of a DCR and as high of a ripple current as could be found. Mouser should have plenty of options.

Regards,
Gordon.
 
Gordon

You are right about the ripple that the HF22 filter cap will see (and only the first one which is 40uF), if they say it is 100mA as shown in the sch then the ripple is roughly double that.
However miniature caps that are rated in excess of 1A are not the 20uF ones. Or even 47uF ones.
EEU-EB2W220 by Panasonic, a 22uF 500V 105C cap is the best I found in its class, is the highest ripple-rated (surprisingly the Low ESR marketed caps are not the best in ripple ratings, but those marketed as Hi-ripple High frequency usually are). And it is 560mA but it has to be derated as it is given at 10kHz and a I think 0.8 factor is used for 120Hz (for some caps it is as bad as 0.5).
So since the ripple rating for the same type caps grows nearly proportional to the capacitance, 47uF 500V one, EEU-EB2W470 with 850mA@10kHz could be used alone instead of two formers in parallel. This will exceed the 5U4 rating which is 40uF. But maybe it's ok. Then again, I have a bagful of the 22uF I bought on sale.


Oh ... One more thing. The restuffed cap, at least in theory, has to lose some of the rating due to thermal insulation as there is an air gap between the inside caps and the old cap's shell. So the internal temp will rise faster than it would otherwise if they were exposed to the ambient air directly.
 
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I looked at the two caps in the two amps.
One seems stock, it is 2x20uF 450V and measures as 23 and 26 uF. May even get successfully reformed.
The other is exact same but seems to have been restuffed at so e point as it 1) has a somewhat mangled base and 2) measures at 80uF (2x40). Which is twice the rated load capacitance for the 5U4.


PS. Visited a friend, had a chance to listen to his pair of HF-22s, they are great sounding amps. And quiet. Which is surprising considering the output stage B+ is only filtered by that 40uF, no chokes or anything.
Oh....he runs them with G807 in the output instead of 6L6.
 
5U4s will run fine on 47uf, as long as the cap isn't terribly out of tolerance on the upside (more than 47uf).

Remember- electrolytic caps, in the old days, were usually rated at +30% / -10%. That means that 40uf could be 52uf, or 36uf, and still be within nominal spec. That's what the rectifiers were really rated for, when they said 40uf nominally.

Also, 375VAC isn't terribly close to the max voltage handling, and 100ma continuous isn't remotely close to the current handling of the 5U4GB. As a result, you can "push" the cap size further, than you could if it was running steady-state closer to its ratings in terms of voltage and current.That's likely how 80uf is running OK...

Regards,
Gordon.
 
I'm back!
Have finished recapping.
I went ahead with restuffing the twistlocks. The mentioned before high ripple Panasonic 22uF caps went inside. One of the twist tabs on each cap got soldered to the chassis.
I used Sprague Atom TVA series for low-voltage axial feedback electrolytic caps.
I used Vishay Röderstein film caps for the film caps that needed to be replaced. Which is all except 0.1uF interstage DC blockers, which were just fine.
I also replaced the 0.033uF Death Caps with X2/Y2 safety type.
Had to replace 220K resistors, were way out of spec, the rest seems very good.

Now to the tubes.
I will need full set of tubes for one amp and some for the other. However since tubes, at least the output, need to be somewhat mached, I think I'll go with full two sets.

Which brings me to the question: what mfrs would you recommend for ....all of them? Especially for the 6L6GC?

Also need shields for EF86.

And the last one: where could I get the RCA jacks, the panel mount type with two-screw mount? Mine are oxidized, I'd like to replace them.
 
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I'm not sure it's available. The load current of the rectifier is 100mA so the ripple would be about 200mA or so.
So to be on the safe side I'd use twice the rating, like 500mA. The cap I use, EEU-EB2W220 (Panasonic) has 560mA rating at 120Hz (no derating required), and to have two in parallel (which I have) will yield 1120mA which is x5, so it is quite safe.
I would go with a 500V cap (this one is 450V) but then this is what they used originally (the WV is 435V as shown in the sch).
 
I'm back!

Now to the tubes.
I will need full set of tubes for one amp and some for the other. However since tubes, at least the output, need to be somewhat mached, I think I'll go with full two sets.

Which brings me to the question: what mfrs would you recommend for ....all of them? Especially for the 6L6GC?

Also need shields for EF86.

And the last one: where could I get the RCA jacks, the panel mount type with two-screw mount? Mine are oxidized, I'd like to replace them.
I have a large stash of original tubes so i have no recommendations for current stock. For old stock you can't go wrong with any of the big 3, RCA, GE, Sylvania.
About rca jacks, you can revive them to a great degree by using a dremel tool with a wire brush, then follow with the polishing bonnet. the one made from plastic shaped like a donut. Lastly, put a drop of Caig Deoxit on the fitting to give it long term rust protection. I have rescued terminal looking rca jacks that way.
 
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No back to the amps:
Soon after the last post I contacted Jim McShane and ordered the tubes. Ordered in pair - Jim is good at that, always has matched supply. He also got me a couple of EF86 shields he happened to have. Being extra scrupulous guy, he said that the shields would need some polishing but I found no fault with them - I am not a "shine it all" type, but they were clean and unoxidized so I just left them be.
The tubes I put in are the Tung-Sol re-issue 6L6GC and EF86, plus a couple of used but testing as new 5U4 Philco tubes Jim had for sale.
I tested the amps on the bench using a small 7" 8 Ohm radio PM speaker. Just to check functionality.

Then I put in on the shelf. It took me about 3 weeks or so to fully test it as I was not willing to disassemble my primary system. What I did was buy another (this time - used but fairly new) SA-14S1 SACD player and C22 pre-amp (this time original) with a working set of tubes (uses some JJ and a couple of Fenders).

Here it is now:
IMG_20180429_194014_1525045321907_1.JPG

The speakers are the second pair of Klipsh Cornwalls I bought about 1-1/2 years ago cheaply (well, they are in great shape structurally but don't look too spiffy so I only paid $500 for them).
What could I say.....it sounds great. I listened to newly bought Tom Petty and Lynyrd Skynyrd CDs, then to some Bach organ from Orgelbuchlein. Very nice.
I ordered the new set of 12AX7 tubes for the C22 from Jim, this time B759 Genalexes and the LPS Sovteks (all Russian), the latter for phono input, plus some to experiment: ECC803S and a couple of good Mullard ECC83 (I want to see for myself if and how it affects the sound). I expect though it all to sound better as at least one of the Fenders tested kinda low (I have Hickok 600A). Maybe I will use them to place-hold the phono input when not playing vinyl to save the Sovteks from wearing unnecessarily.

Well, this almost concludes it.
 
Nice looking setup. Bet it sounds awesome.
Are you in North or South Jersey? There are are few of us tube guys in the state. A car load of us just went down to Western MD for an AK meetup. Good to see more more members on AK from here.

BillWojo
 
Bill,

It will sound even better when I put the new tubes in.
I am in Jackson. Still not sure if it is North or South, or even Center State. :)
We had one more guy from New Brunswick who worked with me until a couple of months ago, who was really into old HiFi, he pointed me towards HF-22 when I told him about the MC275 I got (went to Canada to pick it up. Or as we say in my native language, for a mad dog seven miles is not a detour. :) )
He has just retired though, quit the company and is about to move to CO. He runs his HF-22 with G807 (I think) in the output stage.

I am present more on radio forums, mostly on Philco; I restore lots of tube radios, mostly 30-s (you could see one behind the stereo - it is a Philco 41-280. Works too).
Will be happy to meet some of the local tubeheads :)

Mike.
 
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