2nd Eico ST-70 Rebuild Thread

Great to see your progress with this rebuild. Congratulations on such thorough work. Has anybody here done something similar with an ST40?

~Sorry, I see I asked that question about the ST40 in the other thread. I guess I'll just have to dig out that schematic for myself.
 
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"Holy smokes Batman!" THAT is a complete REBUILD! The last one you did sounded that good? Did you also remove the tone controls on that one? I am impressed with the complete teardown and rebuild and wish I had the patience (and a tube amp worthy of the effort). I don't know how the EICOs sound, but I am guessing pretty darned good. Thank you for posting the progress. I can hardly wait to see the results (see? that patience thing again).

I get slightly better sound from my separate custom pre and a modified Dynaco ST-70, but IMHO a properly modified or "cleaned up" Eico ST-70 is really hard to beat as an integrated amp. To my questionable ears, it sounds better than Fisher, Sherwood, and Scott integrateds that I've auditioned. Having said that, it's hard to beat a Scott 222 on the top / midrange and I haven't heard a 299.

Is it worth the effort? I've done most of these mods for a friend and he's really happy with it. I haven't tried the CCS yet on the ST-70. Would my time be better spent elsewhere? Probably, but not clearly.

Hopefully, I'll be able to answer that question much better before long.
 
Just FYI, apex jr requires $20 min order.

They have other wire too -- I made my own speaker cables from other stuff they carry.

OTOH, $20 worth of that coax is 100'. Believe me, you'll find a lot of uses for it, and it'll go much quicker than you think!
 
Finishing the outputs, then going "backward" in the circuit.

The OPTs go in last, as this makes the chassis a bit easier to move about without their weight. I covered the bell with tape because these inevitably get scratched if you don't protect them while they're "belly up."

I'm implementing a lot of Steve Lafferty's mods. I decided to omit the adjustable resistors on the anode sides of the 6CG7s in favor of the CCS and equal resistors instead.

Quite a ways to go . . .
 

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Do you think you might consider making the new back and front panels available, maybe an AK group buy? I sure be interested in a set.

Great project.
John
 
Sorry I missed this post.

Contact me and I'll e-mail you the contact info for the company that made them for me, and you can buy directly from them.

Buzz
 
Almost there . . .

I have a few controls and the OPTs to wire in, and we're just about done with the construction.
 

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OK. Here's the rebuilt Eico ST-70, ready to power up, bias, and test before we add the panels and covers.

I've used all original Eico tubes, except for the 5AR4 which is a Mullard brand. Jim McShane did the 7591 current matching for me.

I'm excited to give it a listen . . .
 

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Really nice work. I'm glad you are sharing so much detail of your project.

Just an interesting note: the OPT's are different manufacture as are a pair I have. One has the bolt slot in the top of the lams and the other is solid (I think one is Essex, can't remember the code on the other). I've seen this in other ST-70 Eico's and also pairs that are brand matched. I'm sure Eico went back and forth with transformer vendors as they bid a new batch.

All the best,
John
 
I missed that altogether.

I bought a replacement transformer for one that was bad. I've got another matching set, which haven't been repainted yet. I wonder if there is any performance difference.
 
Glad to see this coming together Buzz, LOTS of great work.

Not to be a Buzz Kill, :) but yah after all that work I'd want the matching output tranny's.
(even if they got you the same performance per channel it would bug me there different)
 
Buzz,

Very nice work.

I was wondering if you could detail how you did the lettering. I have a Sansui 6060 faceplate that I washed the lettering clean off :(
 
Not to be a Buzz Kill, :) but yah after all that work I'd want the matching output tranny's.
(even if they got you the same performance per channel it would bug me there different)

BuzzK,
I apologize for mentioning it if, in fact, it does bother you. If you like, I'll trade you one of my mismatched pair for whichever you want. However, I imagine that Eico specified them such that the performance is the same and Eico delivered their amps with the mismatched pairs sometimes, as I've seen them on eBay.
John
 
Buzz,

Very nice work.

I was wondering if you could detail how you did the lettering. I have a Sansui 6060 faceplate that I washed the lettering clean off :(

The sheet metal was done as a turn-key operation by the metal fab shop that I use. They had it silkscreened.

For your situation, I have seen folks that do antique radio glass repair. It's not cheap. Probably the biggest challenge is to re-create the artwork, to prepare the silkscreen mask.
 
The sheet metal was done as a turn-key operation by the metal fab shop that I use. They had it silkscreened.

For your situation, I have seen folks that do antique radio glass repair. It's not cheap. Probably the biggest challenge is to re-create the artwork, to prepare the silkscreen mask.

Thanks buzz :thmbsp:
 
BuzzK,
I apologize for mentioning it if, in fact, it does bother you. If you like, I'll trade you one of my mismatched pair for whichever you want. However, I imagine that Eico specified them such that the performance is the same and Eico delivered their amps with the mismatched pairs sometimes, as I've seen them on eBay.
John

Hi John,

How incredibly kind and generous of you!

I'm sure I have a matching pair, which would leave me with one of each kind. Perhaps we could make 2 matched pairs?

Buzz
 
Fini!

Except for perhaps changing out the one OPT for a matching one, this project is done! Doesn't look much like the original ST-70, nor does it sound like it!

Buzz
 

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Totally sweet Buzz!

I keep contemplating what I may do with mine..:scratch2:
(keep thinking PP triode an different driver setup)
 
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