Need help with my 1266x

[Digginrebel]

It has been a while since I have been able to swing a coil, but trying to get healthy enough to enjoy detecting again. I still own my original 1266x bought in the early 90's. I recently picked up another 1266x that looked little used at a good price, but they stored it with batteries. You know the rest of that story. I thoroughly cleaned the battery box, terminal connections and replaced the holders. I also inspected the wires and everything cleaned up nicely. To test it, i set both discriminators to the same settings and used a clad quarter. When I turned the machine on, I had to push the trigger forward several times to settle it down. My original machine settles without any issues or help. Air tested the quarter on 1st discriminator at maybe 2", but discriminator #2 air tested 8" or so. What is causing this? I'm not very knowledgeable in electronics, but know there has to be a solution. It's not like I need this machine as I still have my original 1266x and plenty of other good machines. Just hate to see this pristine machine not working properly. With the battery box being separated from the housing, could corrosion in the battery box cause the issue? Thx for any ideas and help.

 

[DizzyDigger]

The corrosion could have continued on to the circuit board...

 

[Digginrebel]

The corrosion could have continued on to the circuit board...

I was hoping that isn't the issue, but have been studying how to safely get inside the housing to look. I've been reluctant to go that route. With the battery box being totally separate and a fair distance apart, it seems it shouldn't be the issue. That said, I cannot come up with any other cause.
Thx

 

[Carl-NC]

Both discriminators use common circuitry and the only difference is really the pots, so I would guess that one pot is really dirty and results in a higher disc setting that you think. For the one that seems to work, set it to barely knock out zinc cents, then set the other to the same position. See if it also knocks out higher coins like copper cents or dimes.

 

[Digginrebel]

I will give it a try, thx

 

[Digginrebel]

I decided to eliminate any corrosion issues in the battery box by completely bypassing it. Since the battery holders have terminals that accept the snap on type, I carefully followed the wiring and spliced in 2 new snap on connections. Unfortunately, it didn't help improve anything. So, I guess the issue is on the circuit board in the housing. I don't see any easy way to access it. If anyone has any further ideas I more than welcome them.

 

[Carl-NC]

Remove the 2 screws on either side of the coil connector, and also the coil connector nut. Push gently on the coil connector and everything should slide out the front. There will be wires for the battery and the pinpoint switch that you will need to unplug from the board.

 

[Digginrebel]

Thx. I will give it a try. What should I look for? Corrosion? Anything else an untrained electronics guy can recognize? I'm good at wiring stuff, never tried circuit boards. Those tiny parts and my old eyes don't go well together. LOL.
Thx

 

[Carl-NC]

General dirtiness. Especially compare the 2 disc pots, see if one looks worse. Sometimes a pot will look like new but the carbon film used inside has deteriorated. Also see if the PCB looks dirty or filmy. Sometimes a good washing with alcohol will fix problems with charge leakage, which might be the cause of stability issues. Use only 90+% alcohol, the low-grade stuff has too much water.

 

[Digginrebel]

General dirtiness. Especially compare the 2 disc pots, see if one looks worse. Sometimes a pot will look like new but the carbon film used inside has deteriorated. Also see if the PCB looks dirty or filmy. Sometimes a good washing with alcohol will fix problems with charge leakage, which might be the cause of stability issues. Use only 90+% alcohol, the low-grade stuff has too much water.

Now that things have settled down after Thanksgiving and I finally got my nerve up to try and get into the housing, I found the time to do it. I removed the 2 screws holding coil cable connector. Then turned the piece a litte to get a better look at the nut and to my surprise the face plate with attached board fell out the front. I was expecting the housing to slide off. It was far easier than I expected. I checked everything best I could. Not really sure what to look for, though. Cleaned it with electronics cleaner. Blew it off with an electric keyboard cleaner and put it back together. Tested it with 3 different coils and no change. Disc#1 works, but only 1" air tested. Discriminator #2 air tests at an easy 10".
But knowing how easy it is to get into, I am more willing to continue to study it.
Thx