Rotary Encoder - Protek 9300 SPF05 Arb Function Generator

[reflowman]

I have just recapped the power supply of a "Sample Technologies" (badged Protek?) 9300 Series SPF05 Arb Generator (pic attached).

It works fine except for the rotary encoder which bounces all over the place; varying from infuriating to unusable depending on the mode the gen. is at the time.

I suspect it's slow/feeble firmware debouncing; it was pretty flaky when new (8ish years ago).

I can't find any schematics; the firmware is not updateable (easily) and I have little time for fault finding.

It drives me nuts having to punch in stuff on the keyboard all the time so:

Any help/pointers gratefully received!

[coromonadalix]

Dismantle it to know the part number if any written on it ? or show us a picture, it maybe a common part

ask Protek for a part number and or the possibility ot order it ?

[reflowman]

Dismantle it to know the part number if any written on it ? or show us a picture, it maybe a common part

ask Protek for a part number and or the possibility ot order it ?

Thanks for that @coromonadalix.
My guess is that the encoder itself is fine; as it consistently works better in some modes than others, I reckon the design (f/w, h/w or both) is suspect.
Sadly I have no time to mess about with the thing so I wonder if anyone with this type of ARB knows if it was a recognised problem and/or found a quick fix, otherwise I can buy something else.

[duak]

If the encoder is mechanical, it will have three pins.  I would try filtering the  quadrature signals by temporarily bypassing them to digital ground with 10n or 100n capacitors in series with 22 ohms.  These signals should be the outer two pins of the encoder.  You could use a voltmeter or oscilloscope to confirm by observing the voltages as the encoder is turned.

If the encoder is optical it will have more pins otherwise the above still applies.

Tell us what you find.  If the condition worsens, that's also a clue.

[reflowman]

The bouncing drove me so crazy I had to strip the thing down.
First thing I saw was an  unpopulated space for an MC14490.
I guessed wildly that this might have something to do with it as this chip is a "Hex Contact Bounce Eliminator".
They must have run out of stock when my gen. was made and someone had bodged things so the encoder output effectively went straight to the processor; no filtering at all. Nada!

Thanks all for the support.

[reflowman]

Just to complete this story:
I bodged a couple of 1uF caps directly from the encoder A and B tags to ground. No fancy RC filter here!
It now works perfectly. Much better than new.

Notes:
I'd never buy another SPF05 new (they're still sold it seems) but they'd be capable enough for audio work at the right price secondhand.
The only gotcha (on my old unit at least) is that someone got the meaning of Vpeak-to-peak confused in firmware. Punch in an amplitude of x Vpp and you actually get 2x Vpp ... sometimes ... other times you correctly get x Vpp - just depends on mode and where you are in the menu. Also, you can save 10 setups, but I get the feeling they're not always recalled correctly - that might just be me!

[lostman0077]

Hello sir do you happen to have the manual for the 9300, I have a 930120 and can't find a manual. The 9300 has the same front part. just need to know how to operated it.

[reflowman]

Hello sir do you happen to have the manual for the 9300, I have a 930120 and can't find a manual. The 9300 has the same front part. just need to know how to operated it.

Have attached my manual. F05_and_Protek_9300_user_manual.pdf
I hope it helps you!