Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems G91A Volume Control Knob 'Noisy'

RS offer an alternative part number EC11B15244A7. It is the same size and mountings but has 15 pulses per revolution instead of 20. I think I can live with that so I've ordered one. I'll report back on what happens

I can now report that the RS Stock No.: 623-4079, Alps part number EC11B15244A7, is a direct mechanical replacement for the original Alps part fitted to the G91A.

RS - Alps Alpine 15 Pulse Mechanical Rotary Encoder Flat Shaft (Not Indexed), Through Hole

The difference between the replacement part's 20 steps per revolution and the replacement's 15 steps is simply not noticeable.

Getting the old encoder off the display board was a bit tricky, I couldn't get enough of the solder out of the plated through holes because the pins were sucking all the heat away. In the end I managed by getting the large mounting holes clear. Then I used the side of my soldering iron bit to heat up all the pins on one side simultaneously and pushing the top to lift that side a bit. Repeat on the other side. After 2 or 3 repeats, I got it out. the holes were then easy to clear.

I've dismantled the old encoder to see what was wrong with it. There are 4 staked legs on the sides. A small screwdriver and a pair of thin pliers lets you straighten out the legs, the the base can easily be pushed off. The green base then just lifts off. Inside is the encoder disc.

Some Pics

The disc has grooves round it, the green base has 'fingers' on fixed wipers that run in the grooves. I'm pretty sure that the grooves are manufactured as there is no sign of a great big pile of dust that would be the result if they were due to wear. Looking at the grooves with a magnifying glass they are pitted in places which could cause intermittent connections. I think there is also some discolouration which might be worn plastic dust in the lubricating grease. That could also cause intermittent connections. Washing in alcohol, as suggested in a post above, could wash that dust and grease off.

But I'm not going to try any experiments cleaning the encoder as I've now got the new one installed and its working fine

Thanks for everyone's input.
Adrian

Impressive repair.

Locus.