Range Select madness

Satindas · Joined: Mar 26, 2011 Posts: 42 Location: uk

Hi, I just completed my Klee and everythings cool except the range select. The variable range was being selected at position 7 so I swapped 7and 8 at the plug end. So now in position 6 I get continuity between pins 1 and 8 on the plug and in position 8 I get nothing. Powered it up and the Variable range is now at position 6... WTF!!!!! Did some checks and I can't find any continuity through position 8, so it looks like what I actually swapped was 6 & 7. How the feck do I get VR to be at position 8? Been scratching my head over this.... please help before I start banging it on the wall. help

ps This is the switch: http://uk.mouser.com/ProductDetail/Alpha-Taiwan/SR2612F-0108-21R0B-D8-N/?qs=yA6kp8fx8Y6T0os%2fnPpMpA%3d%3d

Satindas · Joined: Mar 26, 2011 Posts: 42 Location: uk

A bit more info.. I put 7 & 8 back in their original positions and tried to do some calibration and this is what I get:

Position 1 selects R35 @ 0 - 0.66V
2 R36 @ 0 - 0.60V
3 R37 0 - 1.24V
4 R38 0 - 4.98V
5 R39 0 - 4.92V
6 R40 0 - 0.84V
7 VR 0 - 4.00V
8 R34 0 - 0.61V

What?.... Position 8 selects R34 ! It's like they all need cycling round a notch, but that doesn't sort out the voltage ranges which are not in the correct order either.
I've checked everything and the switch is wired correctly. What is going on here ???

Satindas · Joined: Mar 26, 2011 Posts: 42 Location: uk

I think I've sussed this. Part build error- part weirdness (wiredness!)
Firstly, the "odd" voltage at Position 6 (should be 7) is due to me using the equation for R33- doh! I wanted 5 octaves so used a 100K..... it should be about 8K6 Rolling Eyes

.
Secondly, that means if I just move all the cables along 1 slot on the housing it should be right.
But thats just plain weird because the switch is therefore... out of sync with itself dunno

State Machine · Posted: Thu Jun 23, 2011 4:52 am Post subject:

I have seen this happen to these types of Alpha rotary switches. They have a small mechanical "stopper" insert that basically "programs" how many positions the shaft can rotate. If this stopper is removed or inadvertantly slips out and you rotate the shaft, the rotary switch could become "unsynchronized" to it's true position (common connects to the wrong position). Sometimes removing this stop and rotating the shaft, you can re-sync the switch.

I hope I explained this well enough.

Bill

Satindas · Joined: Mar 26, 2011 Posts: 42 Location: uk

This was indeed a faulty switch but not quite due to the fault you describe State Janitor. The little piece of folded metal that acts as a bridge between the inner and outer tracks had been inserted backwards making all positions connect at 'position +1'. I tried to put it right but by the time I'd removed that piece of metal from its little melted mounting posts it was completely trashed. I eventually managed to make up a good switch from a rotor (the bit with the bridge contact) from a 3 pole 4 throw version of the same Alpha switch and the original casing (which contains the tracks) . That little piece of metal caused me a shitty headache .. really! It's all working perfectly now though and loving every minute of it Very Happy