Not working knob on Digitech bp-8

machine gewehr · #1 04-21-2011, 09:20 AM

For the people not familiar with the processor,

To the left of the pedal there are two knobs.One for Input and one for Output wolume controls.The Output knob stopped working (it's pretty old so it's normal),it's giving me a constant static/buzzing no matter how much I alter with the knob.

Question is,can I fix this myself?I'm pretty handy with electronics,nothing special though,little talent coming from my old man I guess.

Ba55Man1ac · #2 04-23-2011, 01:15 AM

Yeah crack it open if you're good with soldering & desoldering. I just popped mine open & it's a dual-gang 100kW 16mm potentiometer. If you can't find a W taper, you could use a linear but it will be a bit touchy at the ends of it's travel.

machine gewehr · #3 04-23-2011, 04:43 AM

Thank you for the answer.I don't really feel comfortable changing the potentiometer,don't know if I'm that handy.

Could it be a soldering issue,If I were to re-solder could it be fixed? If not I might go for the change however.

Edit:I opened mine too and it's not like what I think,I need to change it.Any tips?

alec · #4 04-23-2011, 06:57 AM

This sounds like a good thread to piggy-back onto.

I have a BP-8 which stopped working altogether. A multimeter reads 18vAC between the sleeve and any of the pins, and nothing between the pins themselves. The transformer says 9vAC.
So hopefully the problem is just the power supply and it hasn't damaged the unit.

Could someone who has the necessary equipment check for me what the voltages are between the different pins/sleeve? Then I can go about replacing it.

Ba55Man1ac · #5 04-23-2011, 11:29 AM

Quote:

Originally Posted by machine gewehr

Thank you for the answer.I don't really feel comfortable changing the potentiometer,don't know if I'm that handy.

Could it be a soldering issue,If I were to re-solder could it be fixed? If not I might go for the change however.

Edit:I opened mine too and it's not like what I think,I need to change it.Any tips?

If it was just a bit scratchy when you move it, a squirt of good quality contact cleaner/lube like DeoxIT inside the pot. usually does the trick. But you say it's a constant sound... even when you aren't moving it? If so, that sounds a bit more serious. Why do you think it is the pot?

machine gewehr · #6 04-23-2011, 11:54 AM

Quote:

Originally Posted by Ba55Man1ac

If it was just a bit scratchy when you move it, a squirt of good quality contact cleaner/lube like DeoxIT inside the pot. usually does the trick. But you say it's a constant sound... even when you aren't moving it? If so, that sounds a bit more serious. Why do you think it is the pot?

When I don't turn the knob,almost at all spots there is very little or non bass sound coming from it.

There were a few sweet spots of the knob that it worked perfectly but now those sweet spots are reduced to one and it is almost impossible to adjust to that spot.I managed to adjust to that spot just about now and it's a farty distorted sound.

Also I must have been mistaken,there's not a constant buzzing coming from it.

I opened it and tryed to remove the main board so that I can see the other side of the potantiometer so that I could decide if I can handle it or not.I couldn't remove the board and I felt like I could crack it...

Ba55Man1ac · #7 04-23-2011, 12:07 PM

Quote:

Originally Posted by alec

I have a BP-8 which stopped working altogether. A multimeter reads 18vAC between the sleeve and any of the pins, and nothing between the pins themselves. The transformer says 9vAC.
So hopefully the problem is just the power supply and it hasn't damaged the unit.

Could someone who has the necessary equipment check for me what the voltages are between the different pins/sleeve? Then I can go about replacing it.

Hi alec. Looking at the back of the BP-8: the 2 pins on the left side of the socket are shorted together & the 2 on the right are shorted together and also to the shell of the socket. So as long as you have 9-18V AC between those 2 'points' it should power up. Does it show any signs of life when you jiggle the plug? Maybe you have a dry/cold solder joint on the socket.

By the way, the socket on mine is the other way up to the one in the manual. Is yours the same?

Ba55Man1ac · #8 04-23-2011, 12:38 PM

Quote:

Originally Posted by machine gewehr

When I don't turn the knob,almost at all spots there is very little or non bass sound coming from it.

There were a few sweet spots of the knob that it worked perfectly but now those sweet spots are reduced to one and it is almost impossible to adjust to that spot.I managed to adjust to that spot just about now and it's a farty distorted sound.

Also I must have been mistaken,there's not a constant buzzing coming from it.

I opened it and tryed to remove the main board so that I can see the other side of the potantiometer so that I could decide if I can handle it or not.I couldn't remove the board and I felt like I could crack it...

Ah ok then. Definitely give the contact cleaner/lube a go. You might save yourself a whole lot of trouble.

machine gewehr · #9 04-23-2011, 12:54 PM

Quote:

Originally Posted by Ba55Man1ac

Ah ok then. Definitely give the contact cleaner/lube a go. You might save yourself a whole lot of trouble.

Thanks Ba55Man1ac.I got one of these right now,would it work as a contact cleaner?

WD-40 Lubricates, Cleans, Protects, Penetrates & Displaces Moisture

alec · #10 04-23-2011, 08:54 PM

Quote:

Originally Posted by Ba55Man1ac

Hi alec. Looking at the back of the BP-8: the 2 pins on the left side of the socket are shorted together & the 2 on the right are shorted together and also to the shell of the socket. So as long as you have 9-18V AC between those 2 'points' it should power up. Does it show any signs of life when you jiggle the plug? Maybe you have a dry/cold solder joint on the socket.

By the way, the socket on mine is the other way up to the one in the manual. Is yours the same?

Thaks for replying.

So you say that 18v is OK even though the unit says it wants 9v?

I get nothing when I plug the power in and give it a jiggle. I haven't taken it apart yet - I'll do that today.
And yes, my socket is upside down compared to the manual.

Does your wiring info ([Left pins] and [Right pins + Sleeve] being separate) sound like it should work with what the power unit is providing (18v between any one pin and the sleeve, but nothing between any two pins)?

bucephylus · #11 04-23-2011, 09:03 PM

Quote:

Originally Posted by machine gewehr

Thanks Ba55Man1ac.I got one of these right now,would it work as a contact cleaner?

WD-40 Lubricates, Cleans, Protects, Penetrates & Displaces Moisture

Here is the contact cleaner you want to use. Fry's electronics among others sells it.

Contact Cleaner

or you can Google it.

alec · #12 04-24-2011, 12:14 AM

I took the back off the unit and I can't see anything obviously wrong, other than several of the components being bent over to varying degrees.

One thing I noticed was that there is a 3v button-style battery (like a CMOS uses). I wonder if that has gone flat? I took it out, so I guess I've lost all my presets - no biggie. I don't have a multimeter but I just wired it up to a torch bulb. It glowed dimly and faded immediately. I did this about five times and now it won't glow at all, so I guess its flat. I should be able to get a replacement, they seem pretty common. Its a Sony CR2032.

Ba55Man1ac · #13 04-24-2011, 10:16 AM

Quote:

Originally Posted by machine gewehr

Thanks Ba55Man1ac.I got one of these right now,would it work as a contact cleaner?

WD-40 Lubricates, Cleans, Protects, Penetrates & Displaces Moisture

No, don't use WD-40. The lubricant it leaves behind doesn't last & actually makes the moving parts grip each other after a while. Not what you want when parts are meant to slide over each other!

Quote:

Originally Posted by bucephylus

Here is the contact cleaner you want to use. Fry's electronics among others sells it.

Contact Cleaner

or you can Google it.

This contact cleaner leaves no lubricant behind at all. Great for cleaning, no good for lubricating. This one would be better.

I highly recommend DeoxIT (no, they're not paying me!), but if you can't get it some other options are Electrolube EML, CRC, Super Lube.

Ba55Man1ac · #14 04-24-2011, 10:32 AM

Quote:

Originally Posted by alec

Thaks for replying.

So you say that 18v is OK even though the unit says it wants 9v?

I get nothing when I plug the power in and give it a jiggle. I haven't taken it apart yet - I'll do that today.
And yes, my socket is upside down compared to the manual.

Does your wiring info ([Left pins] and [Right pins + Sleeve] being separate) sound like it should work with what the power unit is providing (18v between any one pin and the sleeve, but nothing between any two pins)?

The thing with AC and unregulated DC supplies is that unloaded, the voltage will always be higher. When you start drawing current the voltage sags down towards the rated voltage. 18V does sound a bit high but maybe they use a barely adequate transformer & count on it sagging a whole lot!?

Re the pins... sounds like you might have something shorting in the DIN plug. Is it dismantlable or molded? With the power off, use the continuity checker on your multimeter to see if things are connected together where they shouldn't be (or not when they should be).

Re the battery... yep, you've almost certainly lost your presets, but good call on taking it out & checking it. Yep, they're commonly available.

alec · #15 04-25-2011, 05:06 AM

I put a new battery in, but no love.

The lead going to the BP8 is a bit loose where it connects to the PSU, so I'll find a triangle screwdriver and take it apart. Or find a new PSU that is wired the way you advised.

Ba55Man1ac · #16 04-25-2011, 05:59 AM

That sounds like a good plan. You might find something dodgy in there.

Make sure you don't plug it in with the cover removed!

BTW if you hadn't guessed, I don't have the original adapter for my BP-8. I made a power supply for it with a transformer in an aluminium box. I'll take some pics if you need to go down that path. Good luck!

alec · #17 04-27-2011, 07:59 AM

I picked up a tool bit set with some tri-toothed screwdrivers for the triangle screws but they were right pricks to get off and the last one got stripped before I could remove it completely. I was able to see inside though, and I couldn't see anything that looked wrong.

So a new power supply is in order. I'll take you up on your offer! Cheers.

machine gewehr · #18 04-27-2011, 09:28 AM

Quote:

Originally Posted by bucephylus

Here is the contact cleaner you want to use. Fry's electronics among others sells it.

Contact Cleaner

or you can Google it.

Quote:

Originally Posted by Ba55Man1ac

No, don't use WD-40. The lubricant it leaves behind doesn't last & actually makes the moving parts grip each other after a while. Not what you want when parts are meant to slide over each other!

This contact cleaner leaves no lubricant behind at all. Great for cleaning, no good for lubricating. This one would be better.

I highly recommend DeoxIT (no, they're not paying me!), but if you can't get it some other options are Electrolube EML, CRC, Super Lube.

Thanks to both of you.I'll go check out the stores on saturday hopefully.