Good progress on my Gates BC-1T this evening... A friend at work loaned me a
really big modulation transformer that may be from a Gates 1F. It say it is
intended for two 833s into a 5k PA load. It doesn't have the driver winding,
but even so I gave it a try...
Eureka! Finally - I get to see
I wrote:
> In that case I was using my Fluke 70-something: RMS reading with flat AC
> response in the audio range.
Make that a Fluke 87.
Steve WD8DAS
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[EMAIL PROTECTED] writes:
> I mounted my BC1-T mod xfmr on ceramic standoffs and put a spark gap across
>
> the primary, each side of midtap to modulator plate. Those xfmrs look a
> little anaemic to me.
I did the same to my transformer as soon as it got here. I remember watching
the spark
Jim wrote:
>Steve, I'm sure your getting frustrated. Hang in there
>since the solution is close now. When it is all over and
>we all look back on it, it needs to make sense.
That's one reason I'm going over it on the mailing list - I'm sure it has
educational value to a number of folks.
[EMAIL PROTECTED] writes:
> So what you are saying is that the total voltage across the 4 K resistor
> load was 5 x 200 or 1 kV rms audio? I assume you drove it midband (1 Khz or
> 400
> Hz etc).
That's correct.
> If you have a good HV scope probe, you should look at the plates of the
> mod
Mr. T., W9LBB said:
"As a last ditch effort... in the W9LBB Surplus Heap I have a modulation
AUTOTRANSFORMER (Wilcox was big on those) that matched a pair of 450THs to
Gawd only knows WHAT in the final! The primary CT is internally tied to the
B+ supply side of the secondary, near as I can figu
[EMAIL PROTECTED] wrote:
Deep in the bowels of my junk I found some resistors for a test of the whole
modulation section of the Gates BC-1T. I put five large-ish (each like a roll
of quarters, maybe 50 watts?) 800-ohm wirewounds in series across the
secondary of the modulation transformer. Th
Deep in the bowels of my junk I found some resistors for a test of the whole
modulation section of the Gates BC-1T. I put five large-ish (each like a roll
of quarters, maybe 50 watts?) 800-ohm wirewounds in series across the
secondary of the modulation transformer. Thaty would seem a good loa
At 03:34 PM 2/25/2007 EST, you wrote:
>
>I just confirmed that the grids of the 833s are indeed being fed 180 degrees
>from each other. One signal had more RF from the driver (only low B+ was
on)
>than the other, but otherwise all seemed normal.
>
>Steve
>
>
>
>
Howdy, Steve!
OK. Thinking ahe
ating!
73 de Bill, AB6MT
[EMAIL PROTECTED]
- Original Message -
From: [EMAIL PROTECTED]
To: amradio@mailman.qth.net
Sent: Sunday, February 25, 2007 12:34 PM
Subject: Re: [AMRadio] Low modulation Gates BC-1T
I just confirmed that the grids of the 833s are indeed being fed 180 degrees
I just confirmed that the grids of the 833s are indeed being fed 180 degrees
from each other. One signal had more RF from the driver (only low B+ was on)
than the other, but otherwise all seemed normal.
Steve
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[EMAIL PROTECTED] writes:
> I still suspect a phasing problem, perhaps a double error.
I know what you mean, but I did use a dual-trace scope to confirm that the
grids of the push-pull 1st audio stage are getting signals that are 180 deg out
of phase from each other. I will do the same on the
That is flat-out wierd that the winding contacts are ripping up the insulator
plate or whatever it is. That's the second time
recently that someone has talked about mod transformer terminals that came
loose.
If the windings are really ripping the terminals on the back plate like that,
then the
Subject: Re: [AMRadio] Low modulation
My Gates BC-1T still resists my troubleshooting efforts. For the mod
reactor
I substituted a big power transformer's secondary which measured 45 H - no
difference. I temporarily substituted a 1 uF 4000v cap for the 2 uF @ 3
kVon
the low end of the modulation
My Gates BC-1T still resists my troubleshooting efforts. For the mod reactor
I substituted a big power transformer's secondary which measured 45 H - no
difference. I temporarily substituted a 1 uF 4000v cap for the 2 uF @ 3 kVon
the low end of the modulation xfmr secondary - no difference, st
Don, thank you very much for the great ideas on testing my Gates mod
transformer and reactor using the HV supply in the transmitter. I'll hopefully
get
back to it again in day or two and we'll see what the results are.
Steve WD8DAS
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[EMAIL PROTECTED] writes:
> Try applying 122VAC to the secondary through a 1K, 20 watt power resistor.
> The voltage to the windings should not drop much
> from the no-resistor readings.
Thanks for the suggestion. There was little difference with a resistor in
series, however, so still not s
>I notice from the schematic, that there is also a tertiary winding which is
>fed to the the driver stage. Seems a long shot, but could it be out of
>phase?
Good thought - I tried it both ways, no difference.
>Also, what are you using to measure the capacitor. A digital capacitance
>meter will
still be
open. Can you substitute another?
Bill
- Original Message -
From: [EMAIL PROTECTED]
To: amradio@mailman.qth.net
Sent: Monday, February 19, 2007 3:38 PM
Subject: Re: [AMRadio] Low modulation
[EMAIL PROTECTED] writes:
> Mod Reactor shorted?
Ohms-out OK on a Simpson 260,
[EMAIL PROTECTED] writes:
> Mod Reactor shorted?
Ohms-out OK on a Simpson 260, but perhaps a problem under higher voltage?
> The cap to ground off the bottom of the Mod secondary good?
It measures the expected 4 uF value.
Bob wrote:
>Does that thing use feedback?
Yes, and I've tried it wit
radio@mailman.qth.net
Subject: [AMRadio] Low modulation
Now an end to a long day of work on my Gates BC-1T transmitter. After
cleaning, painting, and reinstallation of the removed parts, the RF sections
had
shaped up nicely, but today I tried modulating the old girl. No matter
what I
did I onl
Thanks for the heads-up on that one.
Healthfully yours,
Don W4BWS
- Original Message -
From: "Gary Schafer" <[EMAIL PROTECTED]>
To: "'Discussion of AM Radio in the Amateur Service'"
Sent: Monday, February 19, 2007 11:16 AM
S
TECTED] [mailto:amradio-
> [EMAIL PROTECTED] On Behalf Of D. Chester
> Sent: Monday, February 19, 2007 11:24 AM
> To: amradio@mailman.qth.net
> Subject: Re:[AMRadio] Low modulation
>
> To test the modulation transformer for sure, try high voltage a.c. on it.
> The insulation may be brea
be closer to the no-resistor readings. But
if the transformer acts like a short, then there
is a problem.
Bacon, WA3WDR
- Original Message -
From: <[EMAIL PROTECTED]>
To:
Sent: Monday, February 19, 2007 2:09 AM
Subject: [AMRadio] Low modulation
>
> Now an end to a
To test the modulation transformer for sure, try high voltage a.c. on it.
The insulation may be breaking down at higher voltage, while appearing
normal at 110 v.a.c.
Using some clip leads or temporary wiring, set the mod transformer on the
floor away from the transmitter, so that it cannot ac
Steve,
Mod Reactor shorted?
The cap to ground off the bottom of the Mod secondary good?
Bill
KB3DKS/1
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Now an end to a long day of work on my Gates BC-1T transmitter. After
cleaning, painting, and reinstallation of the removed parts, the RF sections
had
shaped up nicely, but today I tried modulating the old girl. No matter what I
did I only got about 10 - 15% modulation as indicated on a sco
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