"like one case I saw the tuning gang in a Quad FM3 tuner. "

These days I apply it with a syringe right to the contacts. If the blades are really dusty I use stuff that is completely residue free, and I DO test it.

wrote:


"like one case I saw the tuning gang in a Quad FM3 tuner. "


These days I apply it with a syringe right to the contacts.
If the blades are really dusty I use stuff that is completely residue free,
and I DO test it.


** By "contacts" you mean the bronze bearings and fingers that ground the moving plates ?

A few drops of WD40 or similar works like magic and restores normal operation to AM and FM bands.

BTW:

Audio Generators often use a tuning gangs, not just old tube models but also modern examples with FET input sustaining amplifier circuits. The dual gangs used are the same as found in tube AM radios and give the advantages of infinite resolution and indefinite life compared to using a dual pot.

The circuit used is a Wien Bridge and to get down to 20Hz means using 20Mohm resistors in the network ( f = 1/2piRC ). The whole gang has to be isolated from ground since the two sections are connected in series.


..... Phil

"** By "contacts" you mean the bronze bearings and fingers that ground the moving plates ? "

Exactly. If the plates are clean that is all it needs and usually the alignment stays put enough that you only have to hit the trimmer caps a little bit to tweak it.

And realizing that when you clean a pot you are cleaning the contact to the wiper which is in the center, not the carbon element, I have successfully use LPS2 from the front. It gets through and takes care of it.

It is surprising how long it took for these tuning caps to become in need of cleaning. Back in the 1970s it was unheard of. Even now, alot of people who still have analog tuners just leave them on one station so they never move. Pots also, move them around all the time and they clean themselves.

Of course eventually there will be no such things, just buttons. Oh and rotary encoders. I have a bad problem with those but I am not going to ask you because you are in bumfukt Egypt or whatever. I need to source them here and not for twenty bucks apiece. They are not optical either. And I am serious unsure of how any I will need. I got 53 units and figure by cannibalisation probably get 35 or so of them up and saleable. These things, when the rotary encoder starts going the SOB will go down when you turn it up, up when you turn it down. That can be annoying and I don't want to see these things coming back with bullet holes in them.

On Sat, 16 Jul 2016 06:45:49 -0000 (UTC), gregz
wrote:

The r100 had a neat smell. Whatever I had left lost most of the smell.
Greg

Mine still reeks. Smells much like some form of naphtha. The
difference is that I know that the metal caps leak (from experience
with rubber cement and bicycle tire patch kits). My fix is to use
teflon pipe tape on the bottle, which offers a much better seal.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558