Sterling SUB bass- active electronics stopped working

[Ken Baker]

Don't beat yourself up. I've screwed up more than my share of electronics stuff.

This is probably very repairable with a jumper wire running from the IC socket pin where the trace lifted to another point that the trace connects to. Little weensie insulated wire (24ga or so) and a fine touch with the soldering iron.

Ken...

[deltafred]

Don't beat yourself up. I've screwed up more than my share of electronics stuff.

This is probably very repairable with a jumper wire running from the IC socket pin where the trace lifted to another point that the trace connects to. Little weensie insulated wire (24ga or so) and a fine touch with the soldering iron.

Ken...

+1

I am still smarting from a mistake I made about 2 years ago but I don't want to talk about it. I still remember the muted 'phut' sound and the smell of burning components. It was a very expensive mistake, several £1000.

All may not be lost though. I would not throw in the towel for one track, it can be replaced with a piece of copper wire, if you don't have any thin enough then use a single strand from some multi strand wire. Then when it is working add a dab of glue if it looks like it could move.

If you look on this link http://www.musicmanbass.org/mycustompage0019.htm there is a track layout of the earlier 3 band preamp (4th picture from the bottom). If yours is this version then you can check it with this to make sure you have your repair in the correct place.

If you are unsure of where the track came from, or it is the the later preamp, and you don't want to post pictures on the site I will PM you my email address and send me it and I will draw on where it should go and email it back. What have you to loose!

fred

[bassman]

I appreciate the words of encouragement. I even have pictures that I have taken ready to upload and I can't find the USB cable for the camera!
I should say that during this whole process the bass is strung-up and in tune laying face down on my worktable. I have a guitar cable and test amp ready to go so that I can check my work.

Thanks for the picture reference of the three-band pre-amp from the MM site. Mine is a bit different. I have the volume and two pots on one board with the bass pot wired to a smaller, separate board. All of the pots are connected via the 3 metal stand-off support/connectors. The jack on a Sterling bass is a side-mount so it is not directly connected to the pre-amp board.

I went back to face the problem. I was able to run a jumper wire to fix the broken trace. I re-inserted the chip into the socket, reconnected the battery and connected the bass to my test amp- No sound.

I found two pins of the IC socket have continuity from sloppy solder. I fixed that problem.
I did the re-connection of everything and still no sound.

I am now wondering if I fried the replacement IC chip from connecting it with the bad solder job.

Is there any test for checking a chip other than inserting it into a circuit?

It occurs to me that I also don't know if the chip I got from Music Man was good from the start although that is probably the least likely cause of my problems.

[deltafred]

Bill

Sorry to hear that it is still not working.

It sounds like your preamp is the early 3 band, a bit higher up the page that I linked to.

Which 2 pins did you have linked, as some are more critical than others?

It will also be worth checking a few other things.

That there is 9v getting to the board when a jack is plugged into the socket. This will be between the red and black wires that run from the jack socket. Also across pins 4 and 8 of the IC, be careful not to short any pins with your meter probes. Set your multimeter to the 20v DC Volts range.

Have a really good look at all the solder joints, they should be a nice clean shiny cone with the solder sticking to the component lead (tinned is the techhnical term), not a doughnut with the solder seeming reluctant to go near the component lead, a 'dry' or 'cold' joint.

The joints should be clean and shiny, not grubby looking or dull (mat grey).

There is no real test for the opamp without building up a simple circuit, you would need another socket and probably 4 components, 2 resistors and 2 capacitors.

You could go down to your local component shop and get one of the following TL062, TL072, TL082, NE5532, LM833, 1558C, CA3240E, LF353, LF412, LF422. They are all pin compatible and will work but may have higher noise or battery drain but should all function in the preamp.

It is possible, but very unlikely that your replacement chip is DOA, I have never that I can remember had a dead one straight from a supplier.

fred

[bassman]

Which 2 pins did you have linked, as some are more critical than others?

The two directly opposite pin one. I guess it would've been pins 7 and 8.

I will check for 9 volts throughout the circuit and I will look for other chips as another test avenue.

thanks Fred

[deltafred]

Those are pins 7 and 8. 7 is an output and 8 is +ve supply, I am pretty sure you will have blown it. Any other pair of pins and you would probably have got away with it.

If you can find one of the chips locally then it will prove the board is ok and you can use it until you get a replacement.

[bassman]

Thanks for the reply, Fred.
I did a current test and I am getting power to pins 4 and 8.
So I probably fried the chip with my sloppy soldering job. That sucks , but live and learn, I always say.

I will look for another Tl 062 or a related chip to test the circuit.

I had to reassemble the bass with its dead circuit board in order to clean up my work area. I didn't want to lose any parts.

After I get another chip I will test it an d let you know if it works.

[bassman]

Update- After 4 years I finally decided to get this bass working. I had followed the advice to try to replace the chip and solder in a new 8 pin socket so that I could change it if this happens again, but I was not successful.
I called up MusicMan and they offered to replace the pre-amp for $75 plus 7.25 shipping if I send back the old pre-amp. I feel that is a reasonable charge for an out of warranty bass on its second owner. They mentioned that yes a battery in the wrong way will fry the pre-amp!!!
I have noticed on the current US made MM basses it is impossible to insert the battery the wrong way.

I have sent off the preamp, without pots attached since they said I could keep them and I am awaiting the arrival of my new 3 band MM Sterling US SUB bass pre-amp.

I will let you guys know when it gets here.

Thanks,
bassman Bill

[bassman]

The preamp arrived lat Friday. I spent a good amount of time connecting everything to it. It came with 3 out of 4 pots and I had to solder on the pickup leads directly to the circuit board ( MAJOR PIA). I did it right though, all connections were soldered and I used shrink tube over my mid wire splices.
I finally heard the bass again, and it sounds great, but I couldn't get this preamp to install correctly. The Volume pot wouldn't come through the body enough to get a nut on it. I finally stopped and measured the thread barrel on the vol pot and it was only 3/4 of the length of the other pots!

Time to return the preamp for a corrected version. At least MM admits their mistake.

What a pain in the ass. That's about 4 hours of work for nothing.

[bassman]

I contacted Music Man about my defective/replacement pre-amp. it was built with a volume pot that was too short to reach through the body.
They readily acknowledged their error and agreed to send out a new pre-amp free of charge but they want the old one back before sending out the new one.

I told them that this was a major pain in the ass! and the agreed to send me a set of strings and a t-shirt to placate me and to send it overnight as soon as they recieved notification from UPS that the old pre-amp was on its way so that I would get the repl. ASAP.

I went ahead and removed the second pre-amp from the bass and send it back to MM with a prepaid UPS label that they emailed me.

The new pre-amp arrived. I installed it more easily, because I am getting good at this by now and the bass is again working great. I have gigged with it several times since then and it is working perfectly.

During this experience I improved my soldering skills a great deal and I learned the value of a good soldering station. Ialso learned a lot about MM basses and pre-amps.

Thanks to deltafred and Ken Baker for the info and words of encouragement throughout this project.