Eico ST 70

Here is a update.

Finished getting all the components soldered in.

Fired it up, no smoke and all the voltages looked pretty good, except the 6CG7 plate voltage they were high at 315 VDC.

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mock up 2.jpg
I've been trying to figure out what to do for a face plate. Here is a mock up, I think I still need to play around with the colors.
 
Very nice work! I see you didn't scrimp on parts.

One suggestion, though. The outer shell on those Russian PIO caps is conductive! You can isolate them with two rubber garden hose washers -- one at each end, or cover them with [clear] shrink wrap.

I'm sorry I haven't been more responsive on the forum -- busy with school & work.

Jon
 
Beautiful work on that rebuild!

As I previously wrote, it looks like you assembled a NOS kit you found somewhere in a climate-controlled chamber, untouched since EIOC put it in a box.
 
Very nice work! I see you didn't scrimp on parts.

One suggestion, though. The outer shell on those Russian PIO caps is conductive! You can isolate them with two rubber garden hose washers -- one at each end, or cover them with [clear] shrink wrap.

I'm sorry I haven't been more responsive on the forum -- busy with school & work.

Jon
Jon,
Thanks for the tip. I did make sure they were stable and both away from the chassis and bottom cover. Probably good insurance for me to go ahead and add some insulation like use suggest.
-Brad
 
Great work xbart. I took the cover off my modded ST40 to check an OPT number for another thread here, and was reminded of how pitted my chassis is, and also how I had to clean the sockets and replace those carbon comps to get mine quiet. But the chassis is built like a tank, e.g. that bottom plate with its 13 securing screws.

I'll be interested to see how you go with those tone controls and associated PECs. (Mine are marked Sprague 29751.) If you exclude them, you lose part of the goofy charm of the multiple controls, but probably gain sound quality. Another route is also have an input direct from from Tape 1 and Tape 2 inputs to the driver tube grids, for a power only option.

I found a part EICO 2536 schematic the yellow block is Spargue 29751.
 

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Nice work!
Somebody made up PCBs to replace the tone PECs.
(I think Sam Cogley?)
Maybe give a shout out if you're interested.
 
I measure the pin assignment.
My EICO 2536 one side sprague 29751 cracked.
But i can not find sprague 29751 on internet.
sprague-29751-pin.jpg sprague-29751-pic.jpg
 
See previous post.
Those pecs are no longer available.
If they were available and nos, they'd likely have drifted as much as the ones in the unit.
You can make your own with a small pieces of perf board.
1/4 and possibly 1/8w resistors would be fine.

I put very big heat shrink over ones I did so they don't touch anything they shouldn't.
Also keep leads as short as possible to reduce picking up noise.
 
Yes i will make a small board today.
But i am not sure the schematic show 47k UUF or 4.7k UUF.
The original image resolution too low.
sshot-8.png
 
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