[BrendaAnnD]

Does anyone know how I could verify the adjustment of what a modern schematic would call the "Do not admit" compensators (the back two on the tuner itself)? This set has had the cover for these adjustments removed some time in the past, which says to me that perhaps someone has done some tweaking with them. How would one verify that these are at factory settings, or reset them to factory settings?

[Chuck Schwark]

That says DO NOT ADJUST, not admit. It's not reproduced clearly in those Riders scans online.

BTW, your packet mails out today.

Chuck

[BrendaAnnD]

Chuck,

I know it says do not adjust. It's just that I'm pretty sure someone HAS adjusted them, as the cover used to block them is missing.

I used "do not admit" because that term is used in more modern equipment to denote an adjustment that should not be tampered with (especially in transmitting equipment).

[BrendaAnnD]

Bump? Still need help with this...

[Ron Ramirez]

Brenda

Sorry, I missed this previously.

The back two screws that originally have the metal piece over them stamped "DO NOT ADJUST" are antenna trimmers for the 4th/5th band and for band 2.

Numbering the four trimmers, from front to back, we have:

1 - Band 4/5 oscillator, to be adjusted on band 4 at 10.8 mc and then checked on band 5 at 21.6 mc.
2 - "Police" band (band 2) oscillator, adjust at 3.6 mc.
3 - "Police" band (band 2) antenna, adjust at 3.6 mc. Bear in mind that this will affect the sensitivity of the set on the three lowest bands, so check for proper operation on all three after adjusting.
4 - Band 4/5 antenna, to be adjusted on band 4 at 10.8 mc and then checked on band 5 at 21.6 mc.

I trust you have the alignment procedure which outlines the adjustment of all trimmers save for the "Do not admit" trimmers?

[BrendaAnnD]

Ron,

Yes, I bought the service literature on this radio, so have the alignment procedures, etc.

Still no love getting bands 4 and 5 to oscillate below the middle of each band. There doesn't seem to be any resistance between the rotor of the tuner and the frame, but I'm going to see if bonding the rotor with solder wick to the frame helps.

Of note is this:

Looking at the LO output on my scope (cathode follower, no load on the LO), the BC band is strong, but quite distorted, with the bottom of the waveform truncated and flattened. Band 2 is similar. Band 3, 4, and 5, where they oscillate at all, are much closer to a natural sine wave, but are much lower in amplitude.

[BrendaAnnD]

Here's the update...

I got in the new 76 tube a few days ago. Tonight I installed it in the radio. After doing this, and making all modifications suggested in service notes, I now have the complete Band 4 working. Unfortunately, band 5 stops working below 13.5 MHz. If I raise the plate voltage to 100 volts or so, I can bring that down to 12.5, but it will not oscillate any lower. I've been offered a replacement LO coil for the SW bands, I'll see if that helps when it gets here.

In the meantime, does anyone have any suggestions as to things I can try?

[Ron Ramirez]

Mica capacitors associated with Band 5? Or it could be when you replace the coil, that the entire band will return?

[BrendaAnnD]

Here's one to make a crazy person sane...

Last night, I put a new power cord on this radio (the old one was only about 3' long). After doing this, I lost about 2MHz at the bottom of Band 4 and almost 3MHz off of band 5. Odd thing is, I was working nowhere near the LO circuits..