Batboard

Can anyone relate to this happening? I searched the forum and couldn't find anything close to this. I haven't had the chance to disassemble the head. Its so jammed up that it won't turn anymore. Anyone know a part number for the rheostat? Thanks guys.

The best way to go is to get the VOL & ROTARY SWITCH Assembly. sure beats trying to solder on those damn flex connectors.

Motorola Part 0102709J83 VOL & ROTATY SWITCH A4 Control Head

Thank you W.E.C. for the quick response. $47 from Motorola and a 20 day lead. Looks like I'll buy one from them and get an eBay one and see who wins the race.

Has anyone ever experienced their A4 head rotary knob freezing?

Is it the control or the knob? The knob has that rubber gasket on it that fits tight down in the hole in the front panel, if something sticky gets spilled in there it can jam it up pretty good. If you haven't already, try taking the knob off.

Yeah I pulled off the knob immediately and saw the black gasket. Had a little bit of "juice" on it; looked like a dab of silicon. I wonder of that continuous rotary knob is servicable - if there is some sort of spring inside that keeps tension that needs to be adjusted.

I had this exact same problem on my A4 head. I am doing this entirely from memory but if my memory is correct the bushing is brass in the potentiometer. It had froze up against the stainless steel shaft that the knob attaches too. I completely disassembled my potentionmeter using various small tools and gave the shaft/bushing a nice cleaning with some lubricant (WD40). After that I cleaned the entire assembly with some contact cleaner to remove all residue. A little touch of some Mystery oil and this one has been working great ever since. The problem is the brass against steel connection on the shaft. I did not take any photos of mine but I am almost certain this is your problem as well... Mine was so tight that I thought I was going to break the shaft trying to "free" it up to get it to accept lubricant... If I can be of any assistance let me know.. This is what I would try before I would buy a used head etc..

KI4M good work, you nailed the problem right on the head.

After dissassembling everything, there appeared to be a small band of garbage on the shaft. Cleaned it off an everything was good. I should note that I had to work the shaft out twisting back and forth while spraying it with WD40. Reassembled everything and it works perfect! I even re-flowed solder on every point on the small flex cable and had to dab a little solder to replace the metal shield. Very simple.

Remember to note the position of the parts as you remove them so you don't put them in backwards.

Thanks everyone for your assistance.

chipjumper wrote: the shaft out twisting back and forth while spraying it with WD40. .

Make sure you get all the WD40 off the shaft/bushing. WD40 WILL jam it up again down the road WD40 IS corrosive...

A drop of lite oil without any aditives is good on the shaft.

oops. I guess I cheated on mine. I removed the knob and gasket, applied some 3-in-1 oil, and worked it back and forth with some pliers. It finally freed up. S o I guess I kinda cheated

Yeah I washed away the WD40 and put a dab of sil-glyde silicon grease. I just need this baby to work for a few years until the entire area finally goes to digital.