10-13-2025, 09:37 PM
Ok so all that sounds good round two begins. I trust you checked #'s 18, 19, and 22, to be with tolerance.
When adjusting #17 (sensitivity control) does the IF stage oscillate? About 1/4 of a turn ccw from the point of oscillation is where you want to be. A little bit less than that the audio will sound rather bassy. Past that point (cw) it will squeal as you tune across each station. Be careful not to over tighten the fiber nut it cracks easily.
When adjusting #'s 11 and 15 do you get a reasonable peak at 460kc? Regenerative detectors are pretty sensitive and can be overloaded when applying a strong signal from a generator so keep level down to a minimum when aligning.
Is the spkr at fault? Stiff spider, off center cone, rubbing voice coil, or a dirty pole gap can limit the movement of the cone and decrees the volume.
Check chassis ground connections that use rivets. I haven't had any low volume issues but have had noise and hum problems.
The model 80, 81, 84, and a few the 50's and 600's use very similar circuits. These were entree level sets and had their limitation. It's a bare bones autodyne mixer, regen detector, and power amp. In one respect low sensitivity is a good thing as it only has one IF transformer to give it some selectivity. The design is balance between selectivity and sensitivity. Everything needs to be working well on these sets to get good performance. A weak tube, out of alignment or an out of tolerance resistor in the det circuit can ruin the performance.
Not sure what you are using for an antenna but the longer and higher the better. If you are using a couple of feet scrap hookup wire in the basement your probably not going to hear much.
When adjusting #17 (sensitivity control) does the IF stage oscillate? About 1/4 of a turn ccw from the point of oscillation is where you want to be. A little bit less than that the audio will sound rather bassy. Past that point (cw) it will squeal as you tune across each station. Be careful not to over tighten the fiber nut it cracks easily.
When adjusting #'s 11 and 15 do you get a reasonable peak at 460kc? Regenerative detectors are pretty sensitive and can be overloaded when applying a strong signal from a generator so keep level down to a minimum when aligning.
Is the spkr at fault? Stiff spider, off center cone, rubbing voice coil, or a dirty pole gap can limit the movement of the cone and decrees the volume.
Check chassis ground connections that use rivets. I haven't had any low volume issues but have had noise and hum problems.
The model 80, 81, 84, and a few the 50's and 600's use very similar circuits. These were entree level sets and had their limitation. It's a bare bones autodyne mixer, regen detector, and power amp. In one respect low sensitivity is a good thing as it only has one IF transformer to give it some selectivity. The design is balance between selectivity and sensitivity. Everything needs to be working well on these sets to get good performance. A weak tube, out of alignment or an out of tolerance resistor in the det circuit can ruin the performance.
Not sure what you are using for an antenna but the longer and higher the better. If you are using a couple of feet scrap hookup wire in the basement your probably not going to hear much.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got it!
Terry
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