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Re: [Amps] Alpha 86

To: Paul Christensen <>, <>
Subject: Re: [Amps] Alpha 86
From: gudguyham--- via Amps <>
Reply-to: "" <>
Date: Tue, 8 Nov 2022 22:40:12 +0000 (UTC)
List-post: <>
I’ve got an 86 in for repair now and it had loads of problems wit pin diodes in 
the past. Finally someone put in the Alpha vacuum relay board that was made to 
do away with the pin diodes.

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On Tuesday, November 8, 2022, 4:52 PM, Paul Christensen <> wrote:

ETO's documentation of the Alpha 86 is sketchy at best.  The amp went through 
several re-designs during its production lifecycle, most changes of which are 
related to QSK performance and PIN diode protection.  The last design iteration 
added new circuit boards directly behind the front panel.  

From what I can determine, the 86 laid the groundwork for its successor, the 
model 89.  Only a couple hundred 86 models were produced by ETO before changing 
to the more robust model 89 design.  I own an early 86 with no design updates.

Paul, W9AC  

-----Original Message-----
From: Amps <> On Behalf Of gudguyham--- via Amps
Sent: Tuesday, November 8, 2022 4:31 PM
To: David Tenenbaum <>
Subject: Re: [Amps] Alpha 86

It’s odd that it works on 120 and not 240.  I looked in the manual but the 
terminal strip is not numbered on the schematic.

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On Tuesday, November 8, 2022, 3:24 PM, David Tenenbaum <> wrote:

Thanks for the feedback!
I am still on the clock at work but took a break to check R8 and I am seeing 
3.98K ohms, so the 4k resistor seems intact. Later tonight when finally done 
with work I will tear into it to look at the fuses and other resistors, confirm 
there is REALLY 220 v getting to the unit, and anything else that comes up.
Thanks all for the ideas!!!!

On Nov 8, 2022, at 2:33 PM, wrote:
Did you check R8 for open?

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On Tuesday, November 8, 2022, 2:20 PM, David Tenenbaum <> wrote:

Hi All,

I have an Alpha 86 that I have been using set up for 110v, and finally have 
access to 220v, so looking forward to seeing what it can REALLY put out. 
Unfortunately I have made the jumper changes (terminal in the back for 110 
operation has locations 1&2 jumpered, 3&4 jumpered, and 5&6 jumpered, but for 
220 only locations 2&3 are jumpered), and the unit fails to light up or come 
online. I hear a single relay activation when I hit the "On" switch, but no 
lights or fan.

Fearing I hurt the unit I restored it to 110v operation and all is good. I set 
it back to 220v and same problem. I checked continuity from the plug's ground 
to chassis ground, and the hot leads show continuity to the right places. I 
have been using a 220v SB200 on that outlet just fine.

Any thoughts or leads appreciated! Never thought I would have a problem just 
switching supply voltages.....Scan of schematic attached....


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