Hello from the UK - and an IC-910 question...

[G8PEF]

Hi from the UK - and thanks for letting this pom join your forums

OK, I have an IC910 here (incl 23cm module) which has an odd problem. It's fine on both main and sub for 2m and 70cm, but with 23cm on the main, there is rritating noise on the audio as the tuning knob is rotated. It sounds like noise from the optical encoder - as if the pulses from the encoder are taking a bite out of the supply - but as I said, there is no such noise when tuning on 2m or 70cm

Any suggestions as to what this might be, whereabouts in the circuit the fault might lie, and/or how to fix, would be welcomed.

73 de John
G8PEF

[VK5PJ]

Hello John,
if performance is okay while the dial is still, then I would hazard a guess that the PLL for the 23cm module is on the verge of dropping out and changng frequency is causing the PLL to partially unlock on each step of the change, hence the noise when moving the dial. My 910 used to flash the main dial readout on cold morning as the PLL was going way out of lock on 23cm. I think in the service manual there are some voltage setting you can check for the 23cm module lock up and whether it is in normal range.

Good luck, having other issues with my 910 (pre-driver board)

Regards,
Peter.

[G8PEF]

Hello John,
if performance is okay while the dial is still, then I would hazard a guess that the PLL for the 23cm module is on the verge of dropping out and changng frequency is causing the PLL to partially unlock on each step of the change, hence the noise when moving the dial. My 910 used to flash the main dial readout on cold morning as the PLL was going way out of lock on 23cm. I think in the service manual there are some voltage setting you can check for the 23cm module lock up and whether it is in normal range.

Good luck, having other issues with my 910 (pre-driver board)

Regards,
Peter.

Hi, Peter

Many thanks for that - I hadn't cosidered a PLL lock problem, I had my blinkers on and was focussed on potential PSU problems, hihi.

Yes, rx performance (such as it is without an external pre-amp) seems normal when the dial is still, and my reports from other stations are good, suggesting that all is stable when txing.
I will get the lid off and have a probe around sometime in the next couple of weeks. I have downloaded a copy of the service manual, so should be able to compare what's in there to the reality. I have to be a bit careful, as the '910 doesn't actually belong to me (it's on long-term loan) so I need a clear bench and a clear head before I start to delve

At least the 23cm modue looks as though it'll be easy-ish to access.

Many thanks, once again, from the (currently) rainy and miserable North-West UK
73 de G8PEF