> From: Ron Hooper <ab4ru@stc.net>
To: <amps@contesting.com>
> Date: Sat, 9 Aug 97 01:49:50 +0000
> Hi all,
> I guess some of my other posting was not clear. The 800 ma choke, is
> in the tank circuit not the power supply section of the amp. My B+ drops
> to something like 3600 volts under load, 2880 watts input, at 800 ma, is
> about 1800 watts out, with one tube. I got to believe the choke is under
> rated for 2 tubes.
If the choke had excessive dc voltage drop, it would be on fire or
glowing red hot...hi.
> Now the transformer in my unit is rated at 2.4 kva about the same as
> the one in my commander.
I gave up on figuring out where manufacturers get their kVA ratings.
The AL1200/1500/82 transformer is a 1800 VA CCS core, and it is the
highest kVA rated core available for that approximate weight. That
transformer weighs about 35 lbs. Smaller and lighter transformers are
rated higher (Amp Supply sold a 1200 VA core transformer and called
it 3 kVA).
In ICAS duty, you can push the transformer. But you'll find the ETO
transformer marginal. It uses up too much window area for the low
power windings and their insulation, so it has way too much copper
loss.
I also think putting the filament winding of a HV transformer, when
the PA is out of the low power or medium power class, is not a good
idea. It can cause inrush and voltage stability problems in the
filament supply.
> If your going to run 4kw out you will have to run about 6500 input,
> right. How long will even the SX's run at that level in a CCS duty
> cycle?
Not long with the stock one tube transformer.
> I havnt got into the xmitting caps yet, but all this talk about the
> door knobs are interesting. The caps are not much for handling current
> in the tank circuit. If thier temperture starts to rise the tank circuit
> tuning changes. The place to see this effect happening is the grid
> current changing while transmitting a carrier. I had a argument with the
> folks at Command Tech about this a few years back. Their solution was to
> put a negetive and positive coefficient door knob in series, so each
> could drift away and still be about the same amout of capacitance.
Sounds fishy.
I'm not sure you can get a positive temp coefficient
door knob of any value over a few pF unless the voltage rating is
very low. At least I've never seen or heard of one. You can get NPO
multilayer chips that will handle 20 amperes or more.
Besides....if they could build a positive temp coef doorknob cap,
they could also build a NPO type.
73 Tom
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