Hello Boatanchor fans:
I have an Alpha 76A on my bench for repair from a friend
of mine but has no book. Am looking for a schematic covering
either the entire rig or at least the power supply as the
28 volt supply is out of it. Or, perhaps a website where
I might find one?

Thanks and 73

Doug, K7YD

"Doug" wrote in message
...
Hello Boatanchor fans:
I have an Alpha 76A on my bench for repair from a friend
of mine but has no book. Am looking for a schematic covering
either the entire rig or at least the power supply as the
28 volt supply is out of it. Or, perhaps a website where
I might find one?

Thanks and 73

Doug, K7YD

Doug -

Here are come Alpha 76A resources.
I have a 76A that I just refurbished beginning of year (new capacitors,
etc.)
http://www.alpha-amps.com/html/76a_pix.htm

BAMA has the Adobe Acrobat
http://bama.edebris.com/manuals/alpha/76a/

There are a couple of resistors on the HV board that Alpha recommends be
moved up to 1 watt in size --
opposite edge of PC board from 6 HV capacitors.

Matt Erickson, KK5DR has a "care and feeding guide" for the Alpha 76A
Guide was recently updated and is a 1 Mb file (Adobe Acrobat)
http://www.qsl.net/kk5dr/OLD76.pdf

Dick Byrd's web site
http://www.n4uq.com/

Alpha keying specifications
http://www.alpha-amps.com/html/ampkey.htm

Greg
w9gb

"Doug" wrote in message
...
Hello Boatanchor fans:
I have an Alpha 76A on my bench for repair from a friend
of mine but has no book. Am looking for a schematic covering
either the entire rig or at least the power supply as the
28 volt supply is out of it. Or, perhaps a website where
I might find one?

Thanks and 73

Doug, K7YD

If your 28 volt control line is "out" .. the meter bulbs will not light
For 28 volt control line - check these components:

D107 and D108 - rectifier diodes on PC board
C108 - filter capacitor
R115 and R116 -- R115 can "open". Alpha now suggests a 1 watt resistor
instead of the original 1/2 watt
[This was original problem with this Alpha in 1979 - when my Elmer owned it]

The tap from R115 goes to the Cathode Bias line for the 8874 finals

w9gb

"Doug" wrote in message
...
Hello Boatanchor fans:
I have an Alpha 76A on my bench for repair from a friend
of mine but has no book. Am looking for a schematic covering
either the entire rig or at least the power supply as the
28 volt supply is out of it. Or, perhaps a website where
I might find one?

Thanks and 73

Doug, K7YD

Doug -

So the prognosis ... was .....???

gb

Looks like the 28 volt supply is gone, nothing out of the
transformer, so guess the winding went open. This belongs
to a fellow ham and know he wont want to go the cost of
another trans, so will just sneak in a little trans to
make up the need for control voltage. It'll work fine.

Thanks for the interest

73

Doug, K7YD

"Doug" wrote in message
...
Looks like the 28 volt supply is gone, nothing out of the
transformer, so guess the winding went open. This belongs
to a fellow ham and know he wont want to go the cost of
another trans, so will just sneak in a little trans to
make up the need for control voltage. It'll work fine.

Thanks for the interest

73

Doug, K7YD

OK. Remember that this winding grounds the center tap (white wire).
I assume you checked for corrosion, etc. on Molex pins/plugs (and ruled
this out).

If this is a three- tube .. a Hypersil would be a nice changeout (Peter
Dahl).
I have talked to Alpha from time to time --
I think Alpha also uses a similar size one in the current amplifiers.

When sizing the add-on - remember that the 28 volt line:
Supplies the 8874 control grids and is used as a "bucked" winding for the
blower.

gb

Thanks for the info. I saw the configuration for the 28v
winding in the prints. No corrosion that I can find, and
nothing coming out of the trans on the 29v leads. Only
possibility is that it's open at the connection point.
So.....you're right, the hypersil trans would be a great
addition. This is the 2 tube model, but a good amp.

Onward, we'll see what he wants to do.

Thanks again

Doug, K7YD

"Doug" wrote in message
...
Thanks for the info. I saw the configuration for the 28v
winding in the prints. No corrosion that I can find, and
nothing coming out of the trans on the 29v leads. Only
possibility is that it's open at the connection point.
So.....you're right, the hypersil trans would be a great
addition. This is the 2 tube model, but a good amp.

Onward, we'll see what he wants to do.

Thanks again

Doug, K7YD

I just checked Peter Dahl's web site, for the 76A hypersil transformer -
looks to be a bit over $ 300 ... and its lighter than the "iron" in my 3
tube !!

Greg, w9gb

==================================================
ALPHA 76A POWER TRANSFORMER
FOR ALPHA MODELS 76A, 76PA, 76CA & 78
CORE) B-0393/ C-CORE STYLE #) 10 HIPERSIL C-CORE
PR) 120/240 VAC 60 HZ 1 PH

S1) 0-1200-1950 VAC @ 0.5A CCS

S2) 40 VCT @ 0.5A CCS

S3) 25 VAC @ 1A CCS

S4) 6.3 VAC @ 9.6A CCS

DM) HT = 6.000 WT = 6.325 DT = 6.281 MD = 3.625 MW = 4.000

PRICE) $310.00 Plus S&H FOB El Paso, TX WEIGHT) 23 LBS

I will send you a follow-up e-mail

"Doug" wrote in message
...
Thanks for the info. I saw the configuration for the 28v
winding in the prints. No corrosion that I can find, and
nothing coming out of the trans on the 29v leads. Only
possibility is that it's open at the connection point.
So.....you're right, the hypersil trans would be a great
addition. This is the 2 tube model, but a good amp.

Onward, we'll see what he wants to do.

Thanks again

Doug, K7YD