[Heathkit] SB-200 issues.

[Kenneth G. Gordon]

On 17 Jan 2008 at 23:45, James M. Walker wrote:

> Ken,
> Ola, I know you are familiar with the unit, but I have to ask, is the
> AC line to the amplifier stiff enough?

Yup. It is a dedicated line, using #10 wire, and goes directly 
back to a new 200 amp panel with nothing else connected to 
that line. The line voltage is nominally nearer 130 VAC than 
125 some of the time, but mostly hangs around 126 VAC, even 
at key-down.

> Reason I ask is if it sags
> going in that effects the filament voltage as well as the high
> voltage.

Yup, thanks. I was aware of that.

> 
> Also I may have a left-over fan motor with the blades that goes on
> that I would have to check. It is the same fan used on the TX-1
> Apache. which is also in my Johnson thunderbolts.

I think that all I have to do to mine is take it out and lube it 
properly. Actually, I think what I am going to do is to replace it 
with a "muffin" fan which has a lot more air-flow. One can't 
really have too much cooling for an amp, IMHO.

> 
> First place I would look is the AC line, then check the resistors
> cold, and again after warm-up.

Thanks. I'll do that. SOMEthing is changing drastically with 
heat...all I have to do is figure out which "thing" it is.

> 
> Also is this the rig with the 572Bs in it?

Yup. The two that I have in it are NOT a matched pair either. 
One is a lightly-used Cetron and the other is an almost new 
Chinese one...at least they were about 6 months ago. :-)

When everything is working as it should, I can easily get 500 
mA at 2100 VDC, which is a little over a KW input.