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[AMPS] 866A replacement .... SEMTECH STR4B32 ... any data please

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Subject: [AMPS] 866A replacement .... SEMTECH STR4B32 ... any data please
From: (Walter Dail)
Date: Sat, 29 Sep 2001 14:05:07 -0400
OK, while on the Semtech subject, I've got two Semtech STR 577,
with "7624" underneath that number(probably a lot number??) They are about
the same height as a 572B (maybe a little taller) with the four pins and
anode cap.
Does anyone have any data on these rectifier replacements? Ratings? I've
the Semtech website with no luck.

Walter - KT4JA

----- Original Message -----
From: "skipp isaham" <>
To: <>
Sent: Saturday, September 29, 2001 12:54 PM
Subject: [AMPS] 866A replacement .... SEMTECH STR4B32 ... any data please

> -
> : From: "Wynand van Wyk" <>
> : Hi all,
> : I was today given two items at a flea market ... "you
> : are the only one I know that will appreciate and use
> : this in you amp projects" I was told.
> -
> At a flea market, it's most often the first indication that
> one should look for the attached anchor chain...
> -
> : It turns out to be two items with a 4 pin base (fits into
> : the 866A & 811A sockets) have hefty heat sinks and
> : anode cap on top.
> : About as tall as a 811A tube.
> : Markings ..SEMTECH STR4B32
> : My guess it is a replacement solid state rectifier for
> : the 866A mercury valve rectifiers.
> -
> Not limited to the 866a replacement. There is a non
> mercury similar tube to the 866a which from memory
> is the 3B28 or 3B29.... one of those two numbers I
> believe.
> -
> Solid state replacements are/were very popular as a
> viable retrofit in tube power supplies.   One must
> consider the original 866a has quite a bit of voltage
> drop while in operation. Same with the non merc
> tube (and most tube rectifiers).
> -
> It is interesting to know that some mfgrs often relied
> on the voltage drop as part of the circuit parameters.
> Replacement of the tube rectified raises the supply
> voltage, sometimes too high in certain circuits.  There
> have been failures from the elevated supply voltages.
> -
> For a block of time, equipment owners were replacing
> vintage vacuum rectifiers with the ssr replacements.
> Most "get away" with the higher output supply voltage.
> They are made in all sizes and types, you happen to
> have a common HV SSR 4 pin unit.  They are also
> manufactured for smaller supplies and popular in
> some Collins Amateur Equipment.
> -
> Some of us pull them back out of our amplifiers to
> restore vintage operation.  In the tube guitar amplifier
> groups I frequent, we consider the "sag" (operating
> voltage drop) a feature.  :-)  They do offer a measure
> of ruggedness and reliability vs glass packages. I've
> never had one fail. There is a very slight increase in
> amplifier power.  Extreme or marginal circuits might
> require adjustment of the zsac value.
> -
> I now run the non merc version in my 30-S1, the SSR
> units  work and work in lower profile power supplies
> (which are viewed less often).   Original 866a's
> still glow in circuits that allow their operational view
> from a safe position.  The Viking Valiant is such an
> example.
> -
> I'll look to see if I have a data sheet for your particular
> ssr replacement.
> -
> : Any info and how I can utilize this in my High Voltage
> : supplies appreciated.
> : Wynand
> : ZS6ARF
> Most of the installation instructions are basic plug &
> play, but some are smart enough to advise caution
> related to the resultant elevated supply potential(s).
> -
> cheers
> skipp
> -
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