Comments for page: Eico ST-84 Mods

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Posted by Steve L. September 10, 2012 - 11:04 am
Hi Paul,

Congratulations on getting your ST-84 out of mothballs! The Eico voltage chart is incorrect, in this case. Although the channels are different, in that only Channel-1 is being driven for the measurements, that should have only minor effect on the DC operating point. My own measurements of an ST-84 (at idle) showed:
        Pin-1   Pin-6
V1 173 66.3V
V2 172 68.2
(These were just an initial evaluation and should not be taken as ideal; just one data point.)

I have heard it said that Eico voltage charts are too often flawed. My own experience is consistent with this.

Note that these voltages should be measured with a high input resistance meter (like most DVMs and VTVMs) and not a VOM.

I will be happy to help if you have further questions.

Posted by Paul D. September 10, 2012 - 10:48 am
I am in the process of evaluating the ST-84 that I built 47 years ago. The pre-amp has not been used for about 30 years.

My question deals with the DC voltages listed in table 5-2 (page 12) the manual. The plate voltages are not the same for V1 and V2. Do you believe this is correct?

Thanks for any insight.

Posted by Steve L. July 05, 2011 - 10:51 pm
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