RE: Heathkit AR-15 and Eico ST-40

Vintage Asylum

Classic gear from yesteryear; vintage audio standing the test of time.

Posted by Eli Duttman (A) on November 9, 2013 at 13:11:36

In Reply to: Heathkit AR-15 and Eico ST-40 posted by spindoctor on November 9, 2013 at 12:31:32:

IMO, the ST40 is definitely worth rebuilding. The magnetics should be decent and current production EH 7591s are quite satisfactory.

The unit employs self biased output tubes. Hence the 20 WPC claim. I don't know if the O/P "iron" is robust enough to permit a switch to "fixed" bias circuitry that would yield approx. 30 WPC.

I find myself making the same recommendation, over and over again, for units with Tape Head I/Ps. Replace the source selector switch, hard wire a single set of I/Ps to the phono section, and make all other I/Ps line level. Switches in the lines that carry mV. level signals are NOT good and Tape Head I/Ps are totally passe. AC heating of the low level preamp section tubes MUST end.

BTW, I also recommend the use of the passive EQ tweaked RCA phono circuit in place of the OEM active EQ setup. Scan the archives for the tweaked RCA schematic. I've uploaded it many times.

Eli D.

EICO ST40 Schematic (Open in New Window)

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Follow Ups Full Thread

Topic - Heathkit AR-15 and Eico ST-40 - spindoctor 12:31:32 11/9/13 (16)

RE: Heathkit AR-15 and Eico ST-40 - airtime 14:42:17 11/10/13 (0)

RE: Heathkit AR-15 and Eico ST-40 - Michael Samra 18:23:25 11/9/13 (0)

RE: Heathkit AR-15 and Eico ST-40 - dadbar 14:39:19 11/9/13 (0)

both have "redeeming social value" ;-) - mhardy6647 14:28:52 11/9/13 (1)

just a little more on the ST-40 :-) - mhardy6647 16:52:50 11/9/13 (0)

RE: Heathkit AR-15 - spindoctor 14:13:13 11/9/13 (0)

RE: Heathkit AR-15 and Eico ST-40 - Eli Duttman 11/9/1313:11:36 11/9/13 (0)

RE: Heathkit AR-15 and Eico ST-40 - Mossback 13:06:17 11/9/13 (8)

RE: Heathkit AR-15 and Eico ST-40 - Michael Samra 18:26:59 11/9/13 (6)

RE: Heathkit AR-15 and Eico ST-40 - vinnie2 12:22:31 11/10/13 (0)

Thanks Mike - Mossback 23:45:45 11/9/13 (4)

You should take a look at this... - realistico 07:16:30 11/10/13 (3)

Thanks, Matt - The Bored 16:25:57 11/11/13 (1)

You're welcome (nt) - realistico 17:24:18 11/11/13 (0)

Matt: - The Bored 07:57:10 11/11/13 (0)

RE: Heathkit AR-15 and Eico ST-40 - Eli Duttman 13:16:06 11/9/13 (0)

Follow Ups

RE: Heathkit AR-15 and Eico ST-40 - Eli Duttman 11/9/1313:11:36 11/9/13 (0)

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