ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Help! I sold my 600 via eBay and the buyer is complaining that it doesn't get to the lower range in the FM scale. I wasn't aware as I only used it in the mid section.
He has said:
'VHF/FM works, but something is wrong with the r.f. alignment because it doesn't tune lower than 89MHz which means it can't receive Radio 2 at all.This is not caused by slippage in the drive cord, but something is off setting in the vhf alignment. Other than that VHF is ok.Also the lower part of the AM ranges is not working quite right, which is probably the same misalignment.'
and
'I am technical, but not familiar with vhf radio alignment. I do have a suitable sig. gen. and am willing to have a go. The radio is tuning fairly accurately at the upper end of the vhf band, but is out at the bottom (87.5 MHz) end. With the dial set at 88 MHz it tunes about 90.5 MHz. So it is the spread that is out, and it just can't manage to reach Radio 2.'
Can anyone offer any advice? He has a copy of the service manual.
Many thanks.
If you think nobody cares, try missing a couple of payments.
Before aligning anything check the dial cord.Maybe something in the cords travel (dial pointer?) or the way the cord has been fitted (or re-fitted ifpreviously serviced) blocks the travel before the tuning capacitor reaches its max rotational position.Tune as low as it will go and check if the tuning capacitor can go any further if rotated by hand directly at thepulley (carefully of course, not to snap the cord).
(Lowest tuned frequency = max capacitance = closed capacitor vanes).
Martin
Many thanks Martin, I'll pass that on. I was hoping you'd respond
Excellent answer and explained by Dillen, had similar problem with a BM900 and BM 1200 just recently. ended up with just same mechanicly problem, even if solved a bit different in the two cases, but it was solvable.
My re-capped M75 are my precious diamonds.
I've had a response....
"As far as I can tell, the dial cord is original and works ok over the whole length of the dial. The travel is not blocked at all, and the tuning capacitor goes smoothly goes from fully closed at the lowest freq to fully open at the highest. It's not possible to make it go down any further. I feel sure the problem is alignment drift, or perhaps something has aged out of spec in the rf section?I checked the dial setting against the actual VHF frequency:Dial set _ Actual Freq_Error %104 104.1 0101 101.3 +0.399 99.5 +0.596 96.8 +0.894 94.9 +1.092 93.3 +1.490 91.8 +2.089 91.0 +2.288 89.2 +2.6Minimum tunable freq is 89.2MHz, too high to get Radio 2.So the frequency alignment is OK at the top end, but the error increases as you go down in frequency. I need to adjust something that will reduce the tuning frequency only at the bottom end, but NOT at the top end…. i.e. the spread."
He clearly knows his stuff. Can anyone advise on the next step?
Steve
PM to you.