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Re: [Amps] diodes wanted

To: "'Dan Hearn'" <>,"'kingwood'" <>,"'Amp Reflector'" <>
Subject: Re: [Amps] diodes wanted
From: "Robert Bonner" <>
Date: Sat, 23 Jun 2007 16:43:21 -0500
List-post: <>
Dude, is an air-pipe better than a water-pipe?

The stock Alpha 77 diodes are good to almost any reasonable power level.  I
ran my first power conversion to 5KW out with them without failure.  As far
as a 77SX goes, the diodes are the most rugged item.  Just like with any ham
amplifier every part in the darn thing as at the ragged edge of coming
apart, the Alpha no exception.  

However, those diodes just keep ticking unless something severe happens.  I
have had a filter cap short and even then didn't lose the diodes.  That was
with the Dahl external 3000V 1.5 amp transformer.  On my 77DD amps I used
VARO VC70's in the diode string, also never had a failure there with
considerably more diode.

And like I said Lon, I have 4 of the stockers in stock in my Alpha repair


-----Original Message-----
From: [] On
Behalf Of Dan Hearn
Sent: Saturday, June 23, 2007 3:01 PM
To: kingwood; Amp Reflector
Subject: Re: [Amps] diodes wanted

Hi Lon. I have a number of HV diode units for sale that would work. You can
see them at click for sale.
Items B,D,and I are sold and my email ads is not correct. It is I own an Alpha 77DX which was purchased from Texas
Towers, used inoperative, for a very good price, when I lived in Dallas. It
kept blowing the HV diodes. The problem turned out to be an arc under the RH
chassis where the bleeder resistors (2 in series) are located. The + HV wire
was arcing to the end of the bleeder resistor. Took  a while to find the
problem since it blew the diodes every time it was turned on. Fixed it and
has been working FB for 10 years. I give a 20% discount to TT buyers.
73, Dan, N5AR

-----Original Message-----
From: []On
Behalf Of kingwood
Sent: Saturday, June 23, 2007 11:21 AM
To: Amp Reflector
Subject: [Amps] diodes wanted

Greetings to all,

        Does anyone have a source for Semtech SCH5000 diodes, or happen to
have four of them.  These are the diodes used in the power supply of the
Alpha 77 DX/SX amplifier.

73 de K5JV

 Lon W. Cottingham
1110 Golden Bear Ln.
Kingwood, TX 77339

281-358-4234 FAX
281-795-1335 CELL

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