Markbass Ninja Head Volume Pot. B50K or A50??

DanGR

DanGR

Jan 2, 2012
252
148
4,551
Grand Rapids MI
#1
I have a scratchy pot. I've opened it up and there is a B50k on mine. I went to order a replacement and the B50K is listed as most common on the eq and filter pots. O.K. Clicked on the A50K and they are listed on the pre, volume, and line out pots. This is all true on my except for the Volume. HELP! Thank you to those that know and post.
 
#2
I had a scratchy Master volume pot and was told to simply twist it back and forth from end to end multiple times and it cleaned up.
May save you a repair.
 
#3
SJan3 said:
I had a scratchy Master volume pot and was told to simply twist it back and forth from end to end multiple times and it cleaned up.
May save you a repair.
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I've done all of that. Now that I have it open, I have tested it. Twisting working for a while, now it just flat out needs to be replace. I don't speak Italian, and I'm thinking they don't share the schematics of their amp heads.
 
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#4
I have ordered both, had to confirm with my credit card's fraud division that I ordered something from Italy....Sheesh on the shipping. Total cost is nearly $18 a pot. I just need to know if I'm supposed to replace with the original B, or if A really is the correct one. Someone just loaded them incorrectly?
 
#5
Replace it with what is in the amp. You may have misunderstood the description, or it may have been inaccurately described.

Did you try ordering from the service agent locally?
 
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#6
agedhorse said:
Replace it with what is in the amp. You may have misunderstood the description, or it may have been inaccurately described.

Did you try ordering from the service agent locally?
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I bought it used and it was less than a year old. I am the "service guy" here lol. It's out of warranty and the only local shop I would trust taking it to won't touch it--they are overloaded with warranty work as it is. I'm a DIY who's taken electronics classes. Years ago when I was recovering from surgery I did some buy/fix selling on the side and did quite well on some.
 
#7
I was talking about sourcing the parts from the local MarkBass authorized service organization, they would know the correct part without the challenges of translation from their native language?

Both A and B taper pots ban be used in volume control circuits, it depends on the designer's intent as well as how the part is used.
 
#8
I get it, but local place won't even deal with you unless your item is under warrantee. They really are that busy. I was hoping someone else had one and maybe thought it would be time to open it up and clean it anyways and take a look. It's an upper one and not difficult to see.
 
#9
DanGR said:
I get it, but local place won't even deal with you unless your item is under warrantee. They really are that busy. I was hoping someone else had one and maybe thought it would be time to open it up and clean it anyways and take a look. It's an upper one and not difficult to see.
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I'm not talking about a local service shop, I'm talking about the factory service agent in the US. They may not sell to individuals however, I do not know their policy, but they are the service agent of record in the US.

Virtual Sound Technology
11901 Goldring Road Unit C
Arcadia, CA 91006

(626)-239-0044
 
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#10
I got both pots today, finally. They actually came from France. A good friend of mine used to be the electronics repair guy for a now defunct Music Store. He said he could do it, but lives a ways away now and gave me advice on how to do it knowing that I have some knowledge in this area. I will try replacing with the original one first and post on how it goes. Need this done by June 27th, my band's first gig after the shut down of venues.
 
#12
2 different parts, use the one that MarkBass used in YOUR amp, in that position.

This is why I suggested contacting the manufacturer directly.
 
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#13
UPDATE: So here's the skinny from a real electronics pro who ended up replacing my sealed pot. A is a "Logarithmic" pot, and B is a "Linear" pot. It was explained to me that B tends to start at about 45% and climbs rapidly. A is more of an audio taper and climbs gradually. He also said that there might be something else in the circuit that makes B act more like A but to try it out and let him know if I'd like to try A. I don't have to, this is my third MB head and I know that I almost reach full volume by the time it's at 3.5. Thanks everyone for your input and hope it helps someone out there. I guess I'll do another update if I decide to have the A installed. Cheers!
 
#14
UPDATE #2: So I have plugged everything in with the same everything I normally use. It's even worse! It goes from 0-100 in an instant. This has me thinking that the original pot was actually an A and mislabeled a B. Going to have my guy install the A that I ordered with the B. There's more $ and time down the drain.
 
#15
DanGR said:
UPDATE #2: So I have plugged everything in with the same everything I normally use. It's even worse! It goes from 0-100 in an instant. This has me thinking that the original pot was actually an A and mislabeled a B. Going to have my guy install the A that I ordered with the B. There's more $ and time down the drain.
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No, there's likely something ELSE wrong. That's NOT how a pot taper affects things.

Also, a B taper pot does not start out at 45%... ALL pots start at 0% and end at 100%, the taper affects the SLOPE of what happens in between.

I wonder if he forgot to solder one pin, OR the pot was damaged, or it was defective.

Man, I see these kinds of failed repair attempts all the time, which is why the flat rate program does not apply to amps that have had repairs attempted. It's a lot more work trying to sort out and correct somebody else's work. It's why I suggested VST (MarkBass's authorized service facility) to begin with, they have the parts in stock and know how to repair them right the first time without second guessing which part MIGHT have been right... they KNOW.
 
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#16
agedhorse said:
No, there's likely something ELSE wrong. That's NOT how a pot taper affects things.

Also, a B taper pot does not start out at 45%... ALL pots start at 0% and end at 100%, the taper affects the SLOPE of what happens in between.

I wonder if he forgot to solder one pin, OR the pot was damaged, or it was defective.

Man, I see these kinds of failed repair attempts all the time, which is why the flat rate program does not apply to amps that have had repairs attempted. It's a lot more work trying to sort out and correct somebody else's work. It's why I suggested VST (MarkBass's authorized service facility) to begin with, they have the parts in stock and know how to repair them right the first time without second guessing which part MIGHT have been right... they KNOW.
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This was a professional, not a home DIY. His day job is at an Electronics company. His 2 very nice homes attest to him knowing what he is doing. He tested the pot before he ever installed it. I myself having some electronic schooling, inspected the work before I ever put it back in. All pins were soldered. We unplugged the harness and so he wouldn't have to take the whole amp with him, so he never got to hear it. Funny how the amp reacted just the way he described?? I will update when I have the A pot installed.
 
#17
Silly me for trying to help, you already know it all.

Forget tried since obviously I don't know as much as you and your friend do (in spite of having not repaired the amp).
 
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#18
agedhorse said:
Silly me for trying to help, you already know it all.

Forget tried since obviously I don't know as much as you and your friend do (in spite of having not repaired the amp).
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Not old school "Taper" pots--either one. One is Linear, one Logarithmic. Played a 5 hr outdoor gig Saturday. No scratchy pot--at all. I just couldn't go much above 1, this is a 1,000 watt amp only used as a personal monitor amp. I will now have him put the A pot in and I'll bet my house it'll work like new.
 
#19
That's not the symptom of the difference in taper, but what the f do I know. I only design with them every day.

Have him test the pot when he removes it, I'll bet the pin 1 connection is open. Or, he damaged the PCB's plated through holes...

Depending on how it is used in the circuit it may be a better choice, but it could be worse too. If a b taper pot was used originally and it worked fine, the replacement will work exactly the same.
 
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#20
agedhorse said:
That's not the symptom of the difference in taper, but what the f do I know. I only design with them every day.

Have him test the pot when he removes it, I'll bet the pin 1 connection is open. Or, he damaged the PCB's plated through holes...

Depending on how it is used in the circuit it may be a better choice, but it could be worse too. If a b taper pot was used originally and it worked fine, the replacement will work exactly the same.
Click to expand...
Agedhorse, I'm glad we're adults and can agree to disagree, based on your "Like" of my comment in a different thread. My electronics tech was on vacation to his lake house for a week and messaged me yesterday. He said he had my job done and had also tested it out. He said I'd like it (A) much better. I'll be picking it up today and installing it tonight or tomorrow. I respect Mesa Boogie gear, and a band I just left last October had me playing bass behind an old rock bassist fronting who had played through it all. He still says his old Mesa was THE best head he ever had and how he'd like another one sometime. He said it was because when he adjusted the eq knobs, he could really hear a difference unlike any other head he has played through.
 
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