bass guitar electronics problem

[James Porchik]

Hello everyone, this is my first post here. A friend brought his 1980's vintage aria bass to me to fix. It's an Aria Pro II. It has active electronics and the pickups are P-J combination. It also has a pickup blend knob, a volume knob that clicks when turned fully off, a mini switch, and what seem to be two eq knobs with multiple detentes. When I got it, it made no sound. I opened it up and several wires were broken due to loose pots and input jack. I soldered everything back into place and put in a good 9 volt (7.5 volts on my meter). The bass now sounds like I'm playing it through a fuzz box. For good measure, I tried a brand new 9 volt, but got the same result. As it stands now, the bass distorts, it has a huge transient when turning the volume on past the click point, and neither the eq's nor the switch do much at all tone wise. It has circuit board with an opamp, two transistors, and many capacitors and resistors. They are discrete, so they can be serviced separately. Can anyone suggest where I should start trouble shooting this?
thank,
James

 

[walter]

Broken wires inside? Did they all get back to the right place? May be mis-wired now. Can you get a schematic?

 

[seavote]

i was going to suggest a schematic and have a go at helping you . but your in good hands with guitar repairs with walter helping you.

 

[James Porchik]

I searched around for a schematic, but couldn't find one. I poked around aria's website and the only contact numbers that I could find were in the UK and Japan. Any suggestions as to where I might find one?
I wonder if I could have possibly miswired it too, but It's hard to know without the schemo. I'm pretty confident of the wires on the input jack, but for good measure, I tried switching the two broken ones and I went from distorted sound to no sound at all so I put them back. I will try reversing the two wires across blend pot. They appear to be correct, but I don't have a similar instrument to compare it to. My basses are very different.

 

[BYacey]

can you post a drawing of how you have it wired?

 

[James Porchik]

Yes, I will. I'm re-examining and drawing today.

 

[walter]

[quote author="seavote"]i was going to suggest a schematic and have a go at helping you . but your in good hands with guitar repairs with walter helping you.[/quote] Aw shuks. I did find this site.
http://www.guitarelectronics.com/category/wiringresources/
There's some diagrams (free).

 

[James Porchik]

my 3-in-1 scanner is not scanning today, so I'll try to describe what I did when I rewired. Firstly, only one of the three wires was attached to it's tabs on the output jack, so I looked at the jack on my old g&l and soldered the negative battery wire to the longest terminal, the common (-) to the shortest terminal and the output from the volume knob to the middle size terminal. If you held the jack with the female end away from you and the longest terminal at the top, the sequence is clockwise from battery to common to output. The other unattached wires were on the blend pot. The top row tabs are wired left to right: left-common, center-to preamp pcb, right-from bridge pickup to preamp pcb straight through.
The bottom row are: left-from neck pickup straight through to preamp pcb, center- to preamp pcb, right-common. The wires that were broken and resoldered by me on the blend pot were the common from the volume pot to the left top and the wire from the left bottom to the preamp pcb. I'm not sure if common is the right term here, but what I am refering to is the wires that connect to the shielding of the pickup wires as well as the casing of the pots. It is a single strand wire across the casing of the pots and it has no insulation. It sort of takes the place of the copper foil shielding that some basses have around the cavity. The wires that run back to the pcb go each to separate points on the board. I hope I haven't killed you with words or put you to sleep. Thanks for the link Walter, I'll check it out and see what I can find there.

 

[BYacey]

a schematic is worth a thousand words... I'm not sure which way is up after reading that. You most likely have a tip ring sleeve jack. signal goes to the tip terminal, Battery - (minus) goes to the ring terminal, all signal grounds go to the collar or barrel of the output jack. This ground should also be connected to the volume and tone pot cases. Pickup shield leads can be soldered to the pot cases as well. This is a start, until I see what controls / switch arrangement you have I can't offer too much more.

 

[James Porchik]

yes, I agree, a picture would have been much better. I actually have two sitting here, but I have uninstall/reinstall my printer/scanner (at least that's what hp's site is telling me). Anyway, if it helps, the description of the blend pot assumes that the shaft is pointing down so the top row is actually the back and the bottom row is the shaft side of the pot. I'm calling Aria's US distributor this morning to see if I can get a schemo. That's the easy way out.

 

[James Porchik]

Byacey, I took cell phone pic of my drawing. It's not a real schematic, but I think it makes sense. I can email it if you want to take a look.

 

[James Porchik]

I have found nothing online on this, though Walter's link had information for passive instruments. I drew out the circuit, but it is not a real schematic. I know how to read schematics, but have not drawn one yet. Can anyone suggest some rules of thumb for this, because I would like to make a real schemo for this bass.

 

[walter]

When I draw a schematic of an old tube amp this is what I do. Draw the tube sockets first, start at the input jack and trace each connection. If I don't know what the component is, I draw a picture of it with the wires going to the appropriate places. Like a multi position switch, and figure out the schematic symbol later. I fill in from tube to tube, power supply last. I get the values of the components as I go, and write them next to their symbols. I'll check again after I'm done, and re-draw it a couple times. I look at similar schematics to get an idea of what the layout should be. If you have drawn your bass already, try redrawing it like one of those diagrams, and double check with the bass. I'd like to see what you come up with.

 

[James Porchik]

Walter, that makes sense to me. I did make a preliminary sketch already. I simply treated the pcb as a black box, because it is so hard to get look at it in the cavity, but I am going to pull it right out of there and start tracing things around. I'd imagine that it might be time consuming, but the bass is probably a relatively simple circuit. I'll post it when I'm done.
thanks

 

[BYacey]

Start with a ground buss first on the bottom of the drawing, pickups on the left. I PM'd my email address to you. Did you try sending the photo?

 

[James Porchik]

BYacey, yes, I sent it, or at least I tried. It wasn't returned, so perhaps some soccermom got it. Maybe your spam filter didn't like it.

 

[BYacey]

please send it again. Label it as BASS or something that will catch my attention.

 

[BYacey]

Here's what I figure from the info you gave me:
http://img.photobucket.com/albums/v354/byacey/Basscopy.jpg

Because I don't know what the circuit is on the preamp board, I'm just guessing about the connections here. The two pots are ganged together as a balance control between the two pickups. There must be at least an additional control for volume and perhaps a tone control also?

 

[James Porchik]

thanks Bill, that looks like a pretty good start. I have a busy week of homework this week, but I'll start building on what you drew.