Belmont 1050 chassis after extensive rebuilding
 

It's (almost) back to original circuitry now. The 50K resistor you see
hanging off the chassis is connected to the cathode of the 1st. audio amp.
It doesn't belong there, but the radio will not play properly without it.
With it, the cathode voltage sits around 30 volts. Without it, it sits
around 70 volts, and the resulting grid bias cuts the tube off so far that
there's more signal at the grid than at the plate.

Any suggestions??

--
Say no to institutionalized interference.
Just say NO to HD/IBOC!

Belmont 1050 chassis after extensive rebuilding
 

That's confusing. Could you post a schematic?

Belmont 1050 chassis after extensive rebuilding
 

"William Sommerwerck" wrote in message
. ..
That's confusing. Could you post a schematic?

http://www.nostalgiaair.org/PagesByM...8/M0002028.pdf

Belmont 1050 chassis after extensive rebuilding
 

Hmmm... This is a totally unfamiliar circuit, so I'll limit my ignorant
comments to the following.

Based on what I can figure out, the plate current is 1mA. That should put
the cathode voltage at 60V, not 70V -- which still seems rather high.

I assume you've checked the obvious stuff like the resistor values.

Belmont 1050 chassis after extensive rebuilding
 

Brenda Ann wrote:
It's (almost) back to original circuitry now. The 50K resistor you see
hanging off the chassis is connected to the cathode of the 1st. audio amp.
It doesn't belong there, but the radio will not play properly without it.
With it, the cathode voltage sits around 30 volts. Without it, it sits
around 70 volts, and the resulting grid bias cuts the tube off so far that
there's more signal at the grid than at the plate.

Any suggestions??


Are you checking cathode E to ground? If so, it looks like R24 already
has 35V across it. Add the 50V from R18 to ground, you have 85V to
ground, not counting the E developed across R 15. The voltages given
look wrong, and they don't give a reading for the cathode. I would
select a cathode R to gnd that gave the correct current for good
operation. Ken

Belmont 1050 chassis after extensive rebuilding
 

"William Sommerwerck" wrote in message
. ..
Hmmm... This is a totally unfamiliar circuit, so I'll limit my ignorant
comments to the following.

Based on what I can figure out, the plate current is 1mA. That should put
the cathode voltage at 60V, not 70V -- which still seems rather high.

I assume you've checked the obvious stuff like the resistor values.



Indeed I have. In fact, every component but the tube itself in the circuit
is new, as I had to rebuild the power supply, first audio, driver, output,
detector and AGC circuits back to factory design. This one's a puzzle for
me. The voltages on that stage are strange. Plate voltage is quite high,
IIRC, around 240 volts, and the grid is at essentially zero. It's all
supposed to be a part of that squelch circuit, I'm sure.. perhaps it's
staying in the squelched mode for some reason.

Belmont 1050 chassis after extensive rebuilding
 

"Brenda Ann" wrote in message
...

"William Sommerwerck" wrote in message
. ..

Based on what I can figure out, the plate current is 1mA. That should
put the cathode voltage at 60V, not 70V -- which still seems rather high.
I assume you've checked the obvious stuff like the resistor values.

Indeed I have. In fact, every component but the tube itself in the circuit
is new, as I had to rebuild the power supply, first audio, driver, output,
detector and AGC circuits back to factory design. This one's a puzzle
for me. The voltages on that stage are strange. Plate voltage is quite
high, IIRC, around 240 volts, and the grid is at essentially zero. It's
all
supposed to be a part of that squelch circuit, I'm sure... perhaps it's
staying in the squelched mode for some reason.

I like to say that "science" is not about "facts", but about asking the
right questions. I think you've made the right observation -- the unit is
stuck in squelch mode.

One other possibility... double-check your wiring. (No offense intended.)

Belmont 1050 chassis after extensive rebuilding
 

"William Sommerwerck" wrote in message
. ..
I like to say that "science" is not about "facts", but about asking the
right questions. I think you've made the right observation -- the unit is
stuck in squelch mode.

One other possibility... double-check your wiring. (No offense intended.)


None taken. It was a total mess when I started, so it wouldn't be beyond
possibility that I made an error somewhere.

Belmont 1050 chassis after extensive rebuilding
 

"William Sommerwerck" wrote in message
. ..
"Brenda Ann" wrote in message
...

"William Sommerwerck" wrote in message
. ..

Based on what I can figure out, the plate current is 1mA. That should
put the cathode voltage at 60V, not 70V -- which still seems rather
high.
I assume you've checked the obvious stuff like the resistor values.

Indeed I have. In fact, every component but the tube itself in the
circuit
is new, as I had to rebuild the power supply, first audio, driver,
output,
detector and AGC circuits back to factory design. This one's a puzzle
for me. The voltages on that stage are strange. Plate voltage is quite
high, IIRC, around 240 volts, and the grid is at essentially zero. It's
all
supposed to be a part of that squelch circuit, I'm sure... perhaps it's
staying in the squelched mode for some reason.

I like to say that "science" is not about "facts", but about asking the
right questions. I think you've made the right observation -- the unit is
stuck in squelch mode.

One other possibility... double-check your wiring. (No offense intended.)


Well.... it's DONE!

Wasn't my wiring, per se, but it was something I hadn't yet bothered to
change. It was an extremely leaky C17. I couldn't believe it (though
obviously I should have just gone and replaced all the caps FIRST as a
matter of course.. but I'm the sort that loves the challenge of actually
troubleshooting a radio before shotgunning it.) I clipped it out of the
circuit, and the gain on the first audio stage came right up, all the
voltages are now within 5 volts of what they're supposed to be. I went ahead
at that point and replaced all the rest of the paper caps, cleaned the
controls, replaced the destroyed mounting grommets on the tuner mechanism,
and replaced the burned out dial lights. The thing works like new. Even the
squelch circuit works like it should. I'm a really happy camper (and my
friend who owns the radio will be even happier, since it's now up to snuff
after sitting in my basement for 3 years gathering rust and mold while I
looked and looked for a schematic under the wrong make....)

Belmont 1050 chassis before & after
 

Attached is a 1600x600 image containing Brenda's before and after
images of the Belmont.

On Wed, 16 Jan 2008 21:16:23 +0900, "Brenda Ann"
wrote:

Well.... it's DONE!

Wasn't my wiring, per se, but it was something I hadn't yet bothered to
change. It was an extremely leaky C17. I couldn't believe it (though
obviously I should have just gone and replaced all the caps FIRST as a
matter of course.. but I'm the sort that loves the challenge of actually
troubleshooting a radio before shotgunning it.) I clipped it out of the
circuit, and the gain on the first audio stage came right up, all the
voltages are now within 5 volts of what they're supposed to be. I went ahead
at that point and replaced all the rest of the paper caps, cleaned the
controls, replaced the destroyed mounting grommets on the tuner mechanism,
and replaced the burned out dial lights. The thing works like new. Even the
squelch circuit works like it should. I'm a really happy camper (and my
friend who owns the radio will be even happier, since it's now up to snuff
after sitting in my basement for 3 years gathering rust and mold while I
looked and looked for a schematic under the wrong make....)