Ok i am at my wits end on this one. To put it mildly, HELP!!!!!!!!!

This is a Hammarlund SP120X. Here's what i have done to the unit so far:
Replaced all "Mica-Mold" and Black Beauty" caps with new moderd units,
Checked all tubes and power supply voltages. The problem is the IF strip. In
order to get anything to pass through the strip, i have to inject a 465Kc
(yes its a strange IF) into the grid of the first tube at a level of 20
millivolts. Thats what i call deaf..... each stage is weaker than the first.
I tried a quickie alignment and that made a very slight improvement.

The Plate voltages are fine (about 240 volts), but the screen voltages are
waaaaay off. What should be 110 volts is more like 30 volts, regardless if a
signal is injected or not. I checked all of the surrounding components, the
caps i installed and i have come up with nothing out of the ordinary. If i
remove all 3 of the tubes in the IF area (6D6's) my screen voltage returns.
For each tube i install, the voltage drops about 20 volts. Is there a
possibility of something being shorted in the IF cans?

Thanks in advance!
KC5KLQ

Paul M. Brady wrote:
Ok i am at my wits end on this one. To put it mildly, HELP!!!!!!!!!

This is a Hammarlund SP120X. Here's what i have done to the unit so far:
Replaced all "Mica-Mold" and Black Beauty" caps with new moderd units,
Checked all tubes and power supply voltages. The problem is the IF strip. In
order to get anything to pass through the strip, i have to inject a 465Kc
(yes its a strange IF) into the grid of the first tube at a level of 20
millivolts. Thats what i call deaf..... each stage is weaker than the first.
I tried a quickie alignment and that made a very slight improvement.

What did you replace the micamold caps in the IF strip with?

Was it this deaf beforehand?

The Plate voltages are fine (about 240 volts), but the screen voltages are
waaaaay off. What should be 110 volts is more like 30 volts, regardless if a
signal is injected or not. I checked all of the surrounding components, the
caps i installed and i have come up with nothing out of the ordinary. If i
remove all 3 of the tubes in the IF area (6D6's) my screen voltage returns.
For each tube i install, the voltage drops about 20 volts. Is there a
possibility of something being shorted in the IF cans?

Not unless all three are shorted, I don't think. Do the screen voltages
all come off one dropping resistor from the B+, with a shunt electrolytic
on it?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Hi Paul,
I suspect it's the screen voltage. Take a look in the power supply.
As Scott surmizes, there is a big droppping resistor in there for the
screen supply, and it probably has drifted very high in value, and maybe
if there's an electrolytic after it that could be the reason, it may be
leaky. (but maybe it had oil filled, I'm not sure, don't have a skem
close by.) When you remove the tubes, it removes the load on the dropping
resistor & the drop across it decreases. You might want to check the
current draw on the screen line, put a meter in series with that lead,
that'd tell you if there is a problem in the rcvr. Somewhere I have
recorded the various currents, perhaps it's on that webpage. The SP-120
will be close to the same.
I had very much the same problem in an SP-210LX a few yrs ago, you can
see some info on that on my website or on The Hammarlund Historian site.
73,

--
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.thecompendium.net/radio/
http://www.hammarlund.info


"Paul M. Brady" wrote in message
...
Ok i am at my wits end on this one. To put it mildly, HELP!!!!!!!!!

This is a Hammarlund SP120X.

The Plate voltages are fine (about 240 volts), but the screen voltages
are
waaaaay off. What should be 110 volts is more like 30 volts, regardless
if a
signal is injected or not. I checked all of the surrounding components,
the
caps i installed and i have come up with nothing out of the ordinary. If
i
remove all 3 of the tubes in the IF area (6D6's) my screen voltage
returns.
For each tube i install, the voltage drops about 20 volts. Is there a
possibility of something being shorted in the IF cans?

Thanks in advance!
KC5KLQ