Yaesu: Yaesu FT227R frequency knob issue

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VA7SDO

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When the Yaesu FT227R transceiver is turned on, the display shows 7.000, which I guess is 147.000 MHz. Mostly, turning the tuning knob causes the frequency display to increase, whether the knob is turned clockwise or anticlockwise. I read a relevant post on this forum by techman210 on 8 January 2020: "If you can change frequencies in one direction only, then there is an optical coupler attached to the backside VFO wheel. That is either bad or just dirty." The manual says the two photo-interrupters are PS-4001. I can see them like disk brakes, on each side of the disk on the knob axis. I blew the area out with compressed air, with no improvement. I would be grateful for advice about this. Is replacing the PS-4001s likely to fix the problem? Is procuring and replacing them in the radio straightforward? I'm moderately handy but not a professional electronics repair person, by a long shot.

Is running a 13.8v radio at 12v a bad thing?
 
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VA7SDO

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VA7SDO said:
When the Yaesu FT227R transceiver is turned on, the display shows 7.000, which I guess is 147.000 MHz. Mostly, turning the tuning knob causes the frequency display to increase, whether the knob is turned clockwise or anticlockwise. I read a relevant post on this forum by techman210 on 8 January 2020: "If you can change frequencies in one direction only, then there is an optical coupler attached to the backside VFO wheel. That is either bad or just dirty." The manual says the two photo-interrupters are PS-4001. I can see them like disk brakes, on each side of the disk on the knob axis. I blew the area out with compressed air, with no improvement. I would be grateful for advice about this. Is replacing the PS-4001s likely to fix the problem? Is procuring and replacing them in the radio straightforward? I'm moderately handy but not a professional electronics repair person, by a long shot.

Is running a 13.8v radio at 12v a bad thing?
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Update: the photo-interrupters are easily accessible. PS-4001s are hard to find but an almost-equivalent part MCA81 is available from several sources. I can risk that the MCA81 output will work.

Incidentally, the power spec in the manual is 13.8v +/- 10%, ie, 12.4 - 15.2v ... so 12v is out of the range. What can be the consequences of too low voltage?
 
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techman210

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As I recall, there is a diode matrix inside (undocumented, but I believe you can find it in an old issue of QST or 73 Magazine, internet, etc.) where you can cut diodes to have it default to any 10 KHz step. There's also a mod where you can install a 9V battery and diode for memory retention. As my memory serves me, it can be modded to cover up to 149.99 MHz (RX only, of course!) as well.

On the photo-interrupters, there's always the chance that they are good, I would check continuity into the PLL board from the output before digging into that old radio. Maybe re-flowing solder on whatever pins in the PLL IC that those signals ultimately terminate into.

12VDC should make everything work, most of the internals of the radio works at 8VDC, so I would suspect at 12.0V it will just have diminished TX power.

You might also want to be a bit more aggressive in cleaning, maybe some no-residue contact cleaner and a modified Q-tip and see if that works.
 
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