Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Closed
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Coronado Oscillator problem
#3

+1 on Arron's comments, something is wrong with the oscillator tanlk circuit. The oscillator seems to be running at a much higher frequency than it should be. This is kind of a stumper. A few things to look for (IMHO, and I do mean humble)

Does either the oscillator coil or the main tuning cap look like it was replaced? Is the tuning cap Osc section the same size as the RF section? (The older ones were, the newer ones have smaller plate on the oscillator section

If you have a digital all band radio like a Sangian or a Grundig, use it to validate the signal generator.

If memory serves, the local oscillator should be at 465 KHz above the desired frequency. Calibrate the tuning dial (With cap fully meshed, set the pointer to 535KHz, with cap fully meshed, scale should read 1650 KHz (or whatever the highest broadcast frequency is). Tune the radio to a known station on the lower end of the scale. Use your digital radio to test for the frequency of the local oscillator. tuning the digital radio, it should squeal, then get quiet at 465 KHz above the frequency tuned on the Coronado. My guess is that you will find something to be way off.

More to the puzzle:

Nost adjustments to RF, IF and Local Osc allow only minor adjustment. For example, if the IF Frequency is 465 KHz, you shouldn't be able to adjust both primary and secondary of both IF Xformers to resonate at 200 Khz. If the oscillator is running at 1000KHz higher than it should, you should not be able to adjust RF resonance to correct for this much difference.

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis

Best Regards, 

MrFixr55


Messages In This Thread
Coronado Oscillator problem - by Tom45acp - 03-10-2023, 07:39 PM
RE: Coronado Oscillator problem - by Arran - 03-10-2023, 11:31 PM
RE: Coronado Oscillator problem - by MrFixr55 - 03-11-2023, 06:21 AM
RE: Coronado Oscillator problem - by Tom45acp - 03-11-2023, 11:15 AM
RE: Coronado Oscillator problem - by MrFixr55 - 03-12-2023, 03:40 AM
RE: Coronado Oscillator problem - by Tom45acp - 03-12-2023, 10:31 AM
RE: Coronado Oscillator problem - by RodB - 03-12-2023, 11:07 AM
RE: Coronado Oscillator problem - by MrFixr55 - 03-12-2023, 05:44 PM
RE: Coronado Oscillator problem - by Arran - 03-13-2023, 02:41 AM
RE: Coronado Oscillator problem - by Tom45acp - 03-13-2023, 08:24 AM
RE: Coronado Oscillator problem - by Tom45acp - 03-14-2023, 06:13 PM
RE: Coronado Oscillator problem - by Tom45acp - 03-21-2023, 08:02 AM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
PT 6 chassis screws size???
Have this done except for missing chassis screws. It looks like 1 inch 6/32 sheet metal screw may work but can anyone s...bridkarl — 10:32 PM
Philco model 38 code 121 not receiving signal.
Hello Stormlord, Well done on rewinding that coil it turned fairly good for your first one. Sincerely Richardradiorich — 09:12 PM
Philco model 38 code 121 not receiving signal.
Well here it is. It ain't pretty, but hopefully it'll work. I checked it with my DMM on continuity and it keeps and r...Stormlord5500 — 08:56 PM
Philco 42-345 Restoration/Repair
Yes, 57 is an electrolytic cap that should be 12 mfd 400 volts according to the parts list from the Phorum library schem...RodB — 06:01 PM
Philco 42-345 Restoration/Repair
Looks like if I am reading it correctly it looks like the silver capacitor#57 that appears to be a replacement is of a l...osanders0311 — 05:09 PM
Philco model 38 code 121 not receiving signal.
Thanks Arran. Yeah this plastic is pretty thin. It's a little thinner than the original stuff. It kinda reminds me of p...Stormlord5500 — 04:37 PM
Testing a speaker and output transformer Trutone A2-G
The equivalent of one short turn is basically the same as that of a shorted load. If it is the primary's turn, then the ...morzh — 03:53 PM
Testing a speaker and output transformer Trutone A2-G
I've never had an output transformer become shorted, the failure mode is usually an open primary, or in a center tapped ...Arran — 03:52 PM
Philco model 38 code 121 not receiving signal.
As long as the plastic sheeting isn't too thick, I think that the thickness of photographic film would be just about rig...Arran — 03:19 PM
Philco model 38 code 121 not receiving signal.
Well why not! :lol:Stormlord5500 — 03:14 PM

[-]
Who's Online
There are currently no members online.

>