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First tubes! Eico ST-70 and ST-97

jessdw

jessdw

Active Member
I picked up an Eico ST-70 and an Eico ST-97 at an estate sale over the weekend. They came installed in a nice corner cabinet with a Voice of Music 1552 turntable and built in record storage. They wouldn't sell me the equipment without the cabinet so I took the whole setup for $50. :banana:

I am as new as can be to tube equipment so I've been trying to read up here. I know I should proceed cautiously and I could use some advice. Do I need to do some recapping as a first step? I don't have a tube tester or a variac.
 
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jessdw said:
I picked up an Eico ST-70 and an Eico ST-97 at an estate sale over the weekend. They came installed in a nice corner cabinet with a Voice of Music 1552 turntable and built in record storage. They wouldn't sell me the equipment without the cabinet so I took the whole setup for $50. :banana:

I am as new as can be to tube equipment so I've been trying to read up here. I know I should proceed cautiously and I could use some advice. Do I need to do some recapping as a first step? I don't have a tube tester or a variac.
Click to expand...

GAAAAAH.

Where am I when these amazing deals come up? :tears:

-D

Oh, and before I forget...

:worthless
 
I don't know anything about when the last time these were used. I'm really itchin' to try them out, but I guess I need to wire up a poor man's variac, get some bulbs, and do it right. Do I really need to put it in the oven first? And can I wait until after I try it out to test the tubes?

















 
$50?! Man, that's some BIG Karma you got there! Those are beautiful! You're really gonna like that setup. Get a pair of efficient (<95dB spl) speakers and you'll hear sound like never before. Really worth recapping and replacing some diodes. :thmbsp:
 
What's going on with those output transformer laminations on the right side of the picture?
 
Hiya,

What's going on with those output transformer laminations on the right side of the picture?
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Bad shuffle out of the shoe ?? :)

Nice cab and awesome find. You gonna have fun with this.

Frannie
 
JonL said:
What's going on with those output transformer laminations on the right side of the picture?
Click to expand...

I looked at it again last night and I think the picture makes it look worse than it is. Hopefully it doesn't affect performance.
 
Those two units are beautifully clean. Congratulations. The Eico Yahoo groups fanclub is knowledgable and friendly if you want to talk about Eico stuff in detail. It is at http://tech.groups.yahoo.com/group/eico/

As both units have probably been stored dry and indoors, I would rig up a lamp limiter to give the amp a quick test. It's just a 60W lightbulb in series with with the power cord. If it lights up brightly the amp is drawing too much current somewhere.

You could also check that all the heaters are working in the amp by removing the rectifier tube (5AR4/GZ34 probably) and checking that all the other tubes heat up. I would also check and clean the tube sockets. The sockets on my 7247 tubes are all in poor condition and noisy!

If it passes both tests, I'd risk a quick test with full voltage. My old Eico ST40 worked without replacing the can caps. I just replaced the 8 coupling caps all 0.1uF at 400V, (C15-22 on the ST40 schematic),and a 30uF electrolytic (C37 on the ST40 schematic).

Once you are sure the amp is working, you can do a rebuild of the amp, such as is described here: http://sites.google.com/site/vintagetubeaudio/eicost70page-1

If none of this makes any sense, please take care and ask for more help :)

Great find!
 
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sculptura said:
If it were me, I'd place the restored pieces back in the custom cabinet and use it just like the orig owner did in the 50's. This is super cool and you stole it.
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I'm still trying to figure out where I can fit the cabinet in my house. Ideally, I would love to put the Eico gear back in there as it was designed. SWMBO likes the cabinet which puts it in the realm of possibility... I told her how much I saw the same amp go for on that auction site the other day and now she thinks I should keep the cabinet and sell the amp. :no:

Dandy said:
As both units have probably been stored dry and indoors, I would rig up a lamp limiter to give the amp a quick test. It's just a 60W lightbulb in series with with the power cord. If it lights up brightly the amp is drawing too much current somewhere.
Click to expand...

I've read a little bit, here on AK, about bringing the unit up slowly so the caps can reform. Like everything there seems to be various opinions on this. I'm thinking it couldn't hurt, right?

Dandy said:
You could also check that all the heaters are working in the amp by removing the rectifier tube (5AR4/GZ34 probably) and checking that all the other tubes heat up. I would also check and clean the tube sockets. The sockets on my 7247 tubes are all in poor condition and noisy!

If it passes both tests, I'd risk a quick test with full voltage. My old Eico ST40 worked without replacing the can caps. I just replaced the 8 coupling caps all 0.1uF at 400V, (C15-22 on the ST40 schematic),and a 30uF electrolytic (C37 on the ST40 schematic).

Once you are sure the amp is working, you can do a rebuild of the amp, such as is described here: http://sites.google.com/site/vintagetubeaudio/eicost70page-1

If none of this makes any sense, please take care and ask for more help :)

Great find!
Click to expand...

The problem is it makes just enough sense for me to get myself in trouble. :D I'm pretty sure I can handle what you've outlined. And thanks for the links. I joined the Eico group and that rebuild link has some great info! I'm pretty sure I'll be back asking for more help soon. :yes:
 
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