I have recently acquired an Aria Pro Magna Series II Bass (MAB50).
The previous owner did say that he had had a problem with the electrics and that he had it repaired but didn’t tell me what the problem was.
I believe the that the blending control is not working as it should. Turning the control to one extreme has one pickup working only, middle has both pickups working and the other extreme also has both pickups working.
I took the back panel off and it was obvious that someone has had a go at the wiring to the blending pot.
Both pickups have been wired to the top blending pot terminals.
Next to the blend pot are three electrical poles/posts. These may connect to the bottom three lugs but I can’t tell without removing the circuit board.
I ran a multi-meter across the top three pot lugs while turning the control. I also measured the resistances across the three posts, again turning the control.
The results can be found in the attached sketch. (The pickups are active and there is also a red wire running between each pickup wire and the circuit board but I left these off the sketch for clarity. Also, with the pot lug values for L1 to L2, there was a gradual rise in resistance from 0 to 2.5k to midway then the value stayed at 2.5k for the rest of the control travel. I did not repeat this procedure for every measurement - just recording the readings at the three points on the pot travel A, B & C. Actually, I think I may have the decimal point in the wrong place throughout as the values should be more like 250k?).
I have also attached a photo of the circuit board.
I did manage to find a photo of inside another MAB50. The circuit board appears to be identical to mine but the white pickup wires are running to the posts adjacent to the blending pot instead of being directly soldered onto the pot lugs so something may well be wrong with my wiring.
I would greatly appreciate any advice as I am struggling to work out what I need to do, if anything, to get the blend pot working as it should.
Thanks for any help.
Comments
What I would do if I was working on it myself is to first remove the pickup wiring and clean up the terminals, and then see what you get from the pot readings, since it's possible it's been deliberately bodged in order to get around a faulty pot issue. The reading aren't likely to make much sense with the pickups still connected anyway.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
My thought is that the pickups should be soldered to the PCB somewhere out of shot. The soldering illustrated in the OP photograph is a bodge up.
The blend pot itself should have tapers upward from the opposing end of travel to the mid-point and full from there.
Looking at the OP photograph, the pot we can see is in the position where you would expect to find the master volume control.
If the PCB is well-designed, you only need three external connections, so the three copper posts should be all you need to connect to. The one furthest from the camera looks like the ground (large wide PCB trace) and the other two should be the pickup connections.
Regardless, the first thing I would still do is remove that mess of wiring and solder and see what you get from the pots.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
EDIT: Seriously, though, any bass balance pot wiring I've seen (which is not many!) have been as @ICBM and @Funkfingers said, with a dual-gang pot and each pickup going to each part of the dual-gang pot separately.
http://ariabasses.blogspot.com/2010/
It appears that the pickup hots (white and black) are connected to the two copper posts nearest the camera; the grounds (red wires at the top of the pic) are currently disconnected.
Interestingly, when the repairman reassembled it he connected the black and white to the third terminal and the reds to the two pickup posts. (Not sure why, but he sounds knowledgeable so it may be for better shielding.)
Hopefully that's useful, assuming your balance pot is OK.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
You're right to leave the ground where it is, it makes no difference electrically and there is (admittedly small, but not zero) a risk of disturbing something you don't want to.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein