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Re: [Amps] SB-200 circuit breakers

To: "Tom Osborne" <>, <>
Subject: Re: [Amps] SB-200 circuit breakers
From: "jeremy-ca" <>
Date: Sun, 26 Aug 2007 23:20:17 -0400
List-post: <>
Hmmm, Im not a fan of the Taylor label, Ive had several problems with them 
right out of the box. Im not sure how many Chinese factories are producing 
572B's and prints which label.

Leave the perforated cover off and the lid up and see if you can catch a 
tube starting to glow red when operating. If they stay dark and plate 
current doesnt sore they are likely OK,

I have put clip leads across those breakers while trying to find a problem 
but do so at your own risk  More than once Ive made a 2 handed grab for the 
on/off switch while a tube is approaching bright orange. Luckily the tubes 
survived the extreme abuse.


----- Original Message ----- 
From: "Tom Osborne" <>
To: <>
Sent: Sunday, August 26, 2007 9:35 PM
Subject: Re: [Amps] SB-200 circuit breakers

> Hi Carl
> Filter caps have been recently replaced. They are 100uf at 450 volts.  I 
> see
> in the schematic that the originals were 125uf.  I will do the 'heat' test
> and see if they do in fact get warm.
> Tubes were replaced just 3 or 4 months ago.  They are Taylor tubes.
> It is a problem that has just reared its ugly head in the past few weeks. 
> I
> used to run the amp around 300 watts on RTTY with no problems, but just
> lately it has started tripping the one breaker, and only at 200 watts.
> I guess I could just solder a wire across the breaker :-)   73
> Tom W7WHY
>> Three possibilities come to mind.
>> - Defective breaker. Possible but quite rare.
>> - Leaky filter caps. A very good possibility if they are original. Leave
>> the  amp on for a half hour or so and then shut off. Make sure t>he HV is
>> down to  zero and pull the plug. Feel the caps. If they are >more than
>> just barely  warm they should be replaced. The plate meter >will not show
>> the capacitor or  bleeder current. Get 220 MF 450V >Cornell Dublier 381LX
>> series caps from  Mouser. They are snap locks >but all can be oriented to
>> fit existing holes. Replace the 8 bleeder resistors with 75K 3W MOX, also
>> from Mouser.
>> - Bad tube or tubes. Actually not bad but not compatible with the SB->200
>> design. Some >Chinese and especially Russian tubes have different
>> interelectrode capacitances and lower mu than the original Cetrons >and
>> become unstable. Unless you want to install a neutralization circuit >and
>> possibly increase the operating bias the best step is to replace the
>>  >tubes.  There are still many good and even NOS Cetrons around. >BTW, 
>> what
>> brand are  they?
>> Carl
>> KM1H
>>> Hi All
>>> On my SB-200, the front circuit breaker trips after half hour or so of
>>> operation on RTTY.  If running RTTY, I usually keep it down to 200-250
>>> watts.  It is the same breaker, the front one, that always trips.  After
>>> it
>>> cools down a bit, it will come back on. The plate current is only 
>>> running
>>> about 300 ma or so.
>>> The tubes are fairly new (4 months) and don't run red when operating 
>>> RTTY
>>> at
>>> 200-250 watts.  I also have some muffin fans on top with the lid open to
>>> take out some of the heat.
>>> In looking at the schematic, the breakers are in the primary of the 
>>> power
>>> transformer.  What causes them to trip, heat?  There doesn't seem to be
>>> that
>>> much with the extra fans on top.  73 and thanks
>>> Tom W7WHY
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