Those 3D printed replacements look great. With the blue color they look exactly like modern Sprague 36D electrolytics!
Interested to see what they would look like made from metallic filament. Also nice to see the latest design is easily restuffable and really applicable to almost any radio.
As to your oscillator problem, I wonder if something is seriously off with the oscillator coil. From your measurements, the oscillator tuning range is so far off that it looks like you have high side oscillator mixing at the lowest freqs (+175 kc) and low side at the top of the band (-175 kc). That would explain why you receive signals at the low end and high end but get no reception in the middle.
What you may be hearing is the normal high side mixing at the low end and the image response at the high end of the band.
(This post was last modified: 02-01-2022, 08:40 PM by Mondial.)
Mondial Mike, I schmoozed the IF back to 216 kc, made adjustments 1400 & 600, and we are back in business!
So, if I had a day to play with it, I could try IF at 260 but since it's working great, is it worth it?
-Simon
Bob Anderson,
Thank you for the Tube Shield, hope you are enjoying your chassis fixture. I made a video with some observations on the shield(s), as you will see if this link works.
I wonder if I have an uncommon variant of Model 90?
Yes, I've used the chassis fixture on several projects now with great success. You shield observations are very odd. I've seen a number of model 70 and 90 shields and they all have that screw hole. No clue about that second shield clip.
Something else odd I've noticed in both my 90 chassis and yours is the proximity of the 80 tube to the transformer. They almost touch when using an ST type and definitely touch if a globe is used. Didn't these come with globe tubes when new?
Yes, I'm sure they were all globe- that is what is pictured on the tube shield label, and I only have one remaining. The RF amp...
Maybe someone will recognize this particular shielding configuration
That is a fantastic stuffable replacement can, Simon! Rustoleum makes metallic gloss copper and aluminum paint that would possibly work for visual correctness instead of different filament. I don't know how much filament costs, but the paint is about five bucks. Just don't try to second coat with clear coat after painting with the metallic - it totally wipes out the gloss metal look. Don't ask how I know! Take care and BE HEALTHY! Gary
"Don't pity the dead, pity the living, above all, those living without love."
Professor Albus Dumbledore
Gary - Westland Michigan
Ah! that's what I need- I can easily have on lasered out. And, I see that 90 only has a 3-gang variable cap (mine has 4). Plus I have to admire your electrolytics, which are quite different also
Thanks,
Simon
Yes, this is a late version 90 with two 47s and a three gang tuning cap. The 90s that didn't the flat plate shield, used a round shield on the 27 tube on the left rear of the four tube group. The early Philcos came with either Mershon or Sprague filter caps, these are the Mershon. These have been re-stuffed with film capacitors.
Steve
M R Radios C M Tubes
(This post was last modified: 02-09-2022, 04:50 PM by Steve Davis.)
Boy you guys sure know your stuff! It is interesting though, how electronics evolved throughout the months and years back then, and we are here to preserve some of it.
-Simon
