|
|
|
#1
03-26-2015, 09:20 AM
|
||||
|
||||
|
Aligning repaired IF transformer
Here's a fun (OK, maybe stupid question, sorry but it's got me wondering). I repaired a IF from a AA5 and was going to rough it in, out of the radio, alignment wise, off the chassis to keep from tearing up foils in case the frequency was too far off and I had to remove it again. I measured the capacitors (110 and 120 pf) and replaced them. I connected it to my frequency generator and started sweeping it. It appears to be 100 KHZ too low. I checked the generator with a frequency counter and it is correct. To double test, I connected a good 10.7 MHZ to the generator and it checks low also. I've read about checking IF transformers and ceramic filters out of the circuit so I am wondering if I am missing something. It would seem the IF would go up in frequency out of the chassis as the input capacitance to the next tube grid would parallel the secondary resulting in a lower frequency. I've rebuilt other IF transformers and reinstalled them and once aligned worked fine.
Any ideas? 
|
|
#2
03-26-2015, 10:21 AM
|
|||
|
|||
|
I have found this exact same thing as well and hope someone can provide some insight to this. I picked up about 200 old IF transformers at old radio auction and most are not marked. As I tried testing them I found the same thing.
Gregb
|
|
#3
03-26-2015, 10:48 AM
|
||||
|
||||
|
Is it from the radio originally, or a replacement? Lots of 262KHz (car radio) IF Cans out there being pawned off as 455KHz IF transformers. They wil work at 455, albeit with odd problems and lower output. DAMHIK...
__________________
Brian USN RET 22YRS (Avionics/Cal) CET-Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit!
|
|
#4
03-26-2015, 12:38 PM
|
||||
|
||||
|
It's an Ambassador 455KC REPLACEMENT! It seems you may have a lead on this problem. I still have to wonder why the 10.7MHZ was too low also. The radio has another different brand IF in it. A RI-Tran. It's a mess also so sweeping it may not give any leads. I guess another question is, has anyone swept a IF out of the circuit and had it pass 455KHZ as it should?
This radio has double foil boards and is requires real care not to damage the PC board.
|
|
#5
04-06-2015, 08:47 PM
|
||||
|
||||
|
How are you connecting the IF transformer to your test equipment? You could be adding capacitance to it from the cables and such.
|
| Audiokarma |
 |
|
|
Linear Mode
