[SCCC] SB-220 Re-Build

[Dave Hachadorian]

I have an EBS-1H in my AL-1500.  A good quality schematic is attached (may 
not get through the reflector, but Joe should get it direct OK).

I stopped using the EBS after a while, because my shack can be quite noisy, 
with a window AC unit and two amp blowers, and some people mentioned that 
they could hear a "crunch" noise on SSB when the EBS was in transition 
between words.

Dave Hachadorian, K6LL
Yuma, AZ

-----Original Message----- 
From: Joe
Sent: Friday, May 17, 2019 10:30 AM
To: reflector SCCC
Subject: [SCCC] SB-220 Re-Build

I have been re-building this AMP.
Installed:
Harbach Soft Start,
Harbach RM-220 Meter Board,
Toroid HV Transformer,
New HV Filter cap's stack and resistors,

Now that the HV Transformer is close to 1 KV higher than Stock, The
diode string on the Harbach board did not supply a high enough Bias
voltage. Idle current was close to 250 ma. Thats almost 900 Watts of
power doing nothing really. And the tubes would turn orange just idleing
doing nothing amplifier wise.

So I added some more diodes to the string to get the Bias down to a more
reasonable level.

The AMP works great BUT.....

Before it let all it's smoke escape (the reason for the rebuild) it had
some sort of a Homebrew Bias circuit that shut off the Bias when the amp
was not needing it. the AMP ran MUCH MUCH Cooler!

But this Bias circuit must have had it's smoke escape also because it no
longer works.

So been hunting for a design of another one, and have actually found a
ready to install one. from Ameritron.

http://www.ameritron.com/Product.php?productid=EBS-1H

They will sell me one, but will not provide any support because it will
not be going into an Ameritron AMP.

They provide a downloadable schematic,,,, well kind of. it is of such
poor quality Very low contrast, and the resolution is soo bad, by the
time you enlarge a connection lead to learn what it is, the name of the
lead is un-readable.

So I am looking for anyone that has used one of these in a SB-220 with
the Harbach Meter board.

Joe WB9SBD

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