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Post by raider on Nov 2, 2008 23:49:41 GMT -5
I have a d201 that was working very well. It seems that it hears almost as good at my 201a. Lately the smeter signals are much weeker that they used to be and far weaker than the 201a. I tested the green and white wire and it read.5v instead of .3. I even tried changing a diode behind d401 r 402. I changed the resistor on the on the bottom of the 401 tube. What should I do to get the smeter and the radio hearing a little better. any help would be appreciated. I have tuned and tuned and tuned all cans.
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Post by Marc on Nov 3, 2008 14:00:14 GMT -5
You say the sensitivity has not changed just the meter indacation. Have you calibrated the S-meter using a signal generator(not zeroing)
as per the service manual? After all the adjusting and tuning. Or if you have changed V300 or if you have been tuning it.
Also test if you can V401.
That could need to be done
Marc
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Post by 2600 on Nov 4, 2008 17:49:25 GMT -5
If you're hearing weak signals okay, then the problem will be with the receiver side of the meter circuit, rather than the receiver itself.
One or more drifted resistors is the likeliest bet. It's quitting time here, so I'll check back later after I look at the schematic. May have some notes about where to look first. If the meter will set normally on transmit, the tubes that run the meter, V401 and V602 are probably okay.
This IS a 23-channel radio isn't it? Makes a big difference. The meter in the 40-channel radio runs from a solid-state chip, and NOT from two tubes like it does in the 23-channel models.
There are a bunch of carbon-composition resistors that will change value in that radio and cause this kind of oddity, and a few others besides.
73
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