03-02-2025, 05:40 PM
I was planning on using motor run caps because the original electrolytic cans, which I believe were in cans, are missing, and motor run caps, if you have the space, are a more permanent replacement anyhow. I was comparing the two schematics, actually three, the one for my Grimes-Phonola made "Dictator", and the two U.S Radio and TV ones, are all called a model 27 by the way, and I couldn't really see the differences other then they substituted a .6 uf cap in place of a .5 uf cap as one of the bypass capacitors in the later version. Maybe they thought there might be an oscillation problem, or maybe they got a deal on some .6 uf capacitors? The originals would have been in side of some metal boxes filled with tar, but I can't say whether they had a terminal strip or just had a bundle of wires coming out of them, it's been five years since I had the chassis out to look at it.
I didn't notice the change in the volume control circuitry until you pointed it out, on the early version, which is the same as mine, the volume control is in the cathode circuit of the RF amplifier tubes, presumably to change the tube bias, in the later version the control is in the antenna circuit. I'm not sure why they changed it, maybe a cost cutting exercise since a wire wound rheostat would have cost more, where they could get away with using a carbon pot in the antenna circuit.
Regards
Arran
I didn't notice the change in the volume control circuitry until you pointed it out, on the early version, which is the same as mine, the volume control is in the cathode circuit of the RF amplifier tubes, presumably to change the tube bias, in the later version the control is in the antenna circuit. I'm not sure why they changed it, maybe a cost cutting exercise since a wire wound rheostat would have cost more, where they could get away with using a carbon pot in the antenna circuit.
Regards
Arran