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2240 FM has a compressed tuning range - 88MHz - 106.5MHz on the dial

runningdog

runningdog

AK Subscriber
Subscriber
I'm unable to adjust the oscillator so that the FM tuning range goes from 88 to 108 on the dial scale. The low end can be adjusted so 88MHz is 88 on the dial scale. But the high end 108MHz signal can be adjusted only to 106.5 on the dial scale, no higher.

The full range of signals from 88 to 108MHz from the signal generator can be tuned in. But the pointer needs to be at 106.5 on the dial scale to tune in a 108MHz signal. The signal just falls off if the oscillator adjustment is turned to take it higher.

The tuner works great, if you don't mind the stations not matching the dial scale.

Is there another adjustment besides the oscillator adjustments that may affect this? Your thoughts appreciated.
 
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wlhd1610 said:
Isn’t L105/106 (not sure which on the 2240)the upper end adjustment?
Click to expand...

L104 and C106 for the oscillator adjustments. L104 can be adjusted so that the pointer is right on 88 but C106 will not allow adjustment beyond 106.5 on the dial scale the way it normally would.
 
I've had these variable caps need a small tweaking and when they are stuck hard and "pop" loose they can sometimes get out of their original range like you're experiencing. The only way I've ever fixed it is to put in whatever I have around that can be fit and try it. Usually it's pretty hard to adjust even if it's plus and minus of the 108 spot.

The ones I have are Mouse 659-GYA10000/5R000 and 22000 which were originally under $2 and are now up against $7. :yikes:
 
runningdog said:
The full range of signals from 88 to 108MHz from the signal generator can be tuned in. But the pointer needs to be at 106.5 on the dial scale to tune in a 108MHz signal. The signal just falls off if the oscillator adjustment is turned to take it higher.
Click to expand...
When you change the local oscillator, the other adjustments need to be changed also. Sounds like you need to adjust slightly up scale, then tune the other frontend adjustments for better reception, then go further up stream. Hard to say with out seeing it. Also, before doing any more adjustments, you might want to check out the sticky for cleaning tuning capacitors in the tuners forum.
The basic rules of thumb for adjustments are: inductors affect low and high frequencies about the same, capacitors affect high frequencies more. So adjust inductor and low FM frequencies, then adjust capacitors at high end of dial, then repeat, as adjustments interact. Steps 5 and 6 out of the service manual - they mistakenly called it AM adjustment instead of FM in the manual. Page 9 section 12.
 
Are you confident the the tuning cap is moving from stop to stop?
You want the tuning cap to move throughout it's range unimpeded by the dial pointer or anything else.

Tom
 
You're most welcome. I liked Tom's suggestion too as I've seen this. Danged if I remember what the hang up was but it was like the dial cord. Maybe a severely toasted plastic lamp housing? Ehhhh. I sure miss my memory ability!!
 
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