I looked at your pictures and have the following comments:
1) It looks like you painted the transformers. Bad idea. Why? Chances are
that the paint contains carbon. A lot of black paints do. I had a friend who
restored a Henry amp and didn't like the surface rust and spray painted them
black. Well he ended up buying both a new plate transformer and choke from
Henry. Some of the paint might have dripped into the windings. This is why
you might be loosing transformers. Once you painted them, there isn't a
really good way to remove the paint.
2) your use of a coat hanger for part of the tank circuit. I doubt that you
can get a good inter-metallic solder bond to the steel with standard RMA
tin/lead solder. It might "look" ok, but it will come apart with thermal
cycles. Go to you local hardware store and buy a piece of # 12 or #14 copper
wire. It will solder so much better.
I took another look at your photos and would say they appear to me to be
CSJs ( cold solder joints).
3) Put back the HV interlock!
It looks like you are not doing a 100% vintage restoration. So why bother?
There are plenty of good SB-220s out there that don't need this much work.
Good luck... Jack N8DX
On Thu, Feb 5, 2009 at 1:59 AM, Jim W7RY <w7ry@arrl.net> wrote:
> I think you have an intermittently shorted tube. This is why your old
> filament transformer smoked. There is a reason for re-wiring the antenna
> relay to keep from burning up the filament transformer. Details are on Rich
> Measures site. (I know I know....)
>
> If a tube shorts, it also shorts out the filament transformer. I don't
> remember the exact current flow but Rich explains it.
>
>
> 73
> Jim W7RY
>
> ----- Original Message -----
> From: "Jeff Carter" <amps@hidden-valley.com>
> To: <amps@contesting.com>
> Sent: Wednesday, February 04, 2009 8:51 PM
> Subject: [Amps] SB-220 and Xfrmr Smoke...Part 4
>
>
> > Okay, the replacement transformer is installed, and life is
> > good...except I'm beginning to think this amp is haunted.
> >
> > All voltages were checked and are present. Never again when working
> > on an amp will I assume that just because somebody sold me something
> > that it's good. I should have known better.
> >
> > The haunted part: At odd intervals, the meter needles will *twitch*.
> > The plate current, which is sitting on zero, twitches up to maybe 50
> > milliamps, the HV needles twitches down a few volts, and then, as
> > quickly as it started, everything goes back to normal.
> >
> > What's going on with this? Do I have another problem to find?
> > Nothing's hot, nothing's smoking like before, this just seems odd
> > behavior to me with no drive or anything.
> >
> > Has anybody seen this problem? Or is it just a normal thing when
> > everything is new like this, with things settling in?
> >
> > Thanks again,
> > Jeff/KD4RBG
> > _______________________________________________
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> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
>
>
>
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