Digimac Damaged Pot?

Single to Multi propo
Post Reply
NeilMac
Posts: 152
Joined: 04 Feb 2019, 22:07
Location: Nth Somerset

Digimac Damaged Pot?

Post by NeilMac » 11 Apr 2019, 22:30

I took my converted MacGregor Digimac 2 to the club this evening for a bit of show and tell. During the evening the transmitter took a knock whilst in my bag and I have now lost one channel.

A quick measure with a meter seems to show that the pot on the channel that is not working has dramatically different values to the working pot, I have only done a quick cursory check while having a coffee and will do things properly in the morning, but is it possible the track in the pot has been damaged? Are they ceramic?

It looks like a bit of a task to open the pot up, it also looks like a bit of a task to replace it.

Any ideas?
"I'm your huckleberry, that's just my game"

User avatar
Phil_G
Posts: 312
Joined: 15 Feb 2018, 23:32
Contact:

Re: Digimac Damaged Pot?

Post by Phil_G » 11 Apr 2019, 23:45

Hi Neil,
The pots are wired as potential dividers so measuring at the wiper wrt ground you should see a smoothly varying voltage somewhere between 0 and 5v, it doesnt matter what the voltage swing is as the calibration adapts to whatever but it should be smooth. Its unlikely you've damaged the stick but maybe the knock has dislodged some muck inside the pot, I always find a good squirt of "Electrolube" spray works wonders on pots. Another point is that the plastic can become brittle after 50 years so check that the pivot/bearing hasnt been damaged. Of course the first check is end to end across the pot outer tags, should be 5kΩ.

To prove that everything is electrically ok, remove the signal wire from the duff wiper and tag it temporarily to the other stick wiper. Both channels should follow the one stick.

Dont fret though, someone somewhere in retroland will have a spare.

Cheers
Phil

NeilMac
Posts: 152
Joined: 04 Feb 2019, 22:07
Location: Nth Somerset

Re: Digimac Damaged Pot?

Post by NeilMac » 12 Apr 2019, 06:42

Hi Phil.

Not being able to go to bed before I had done a proper check, I gave the offending pot a good squirt of our favourite fix all Servisol, left it 5 minutes to do its stuff, waggled the stick back and forth and measured the resistance with the stick unplugged and it looked OK, slightly different from the other, but close enough, after that I finished my coffee and headed to bed.

Tea's made, so time to check what's what.

I have just plugged the pots back into the encoder and ... we are back in business, with full throw on both servos. Goodness knows what the knock had done, but it is now undone.

BTW they guys at the WMS were really amazed at the idea of converting 'retro' RC to 2.4 ghz, but single channel button pressing was an idea too far. It did raise a lot of discussion though and I am hopeful that one or two of the well established flyers will out an old set up or two.
"I'm your huckleberry, that's just my game"

Post Reply