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Preamp or Input jack?

G

GospelBassMan

Apr 26, 2014
28
7
61
#1
Happy Thanksgiving to all,

I own a Yamaha TRB 6P, such a beautiful bass. I notice I hear a lot of static coming from the input jack and also when I turn the knobs. Not sure if its the input jack or the circuit board. Called Yamaha, they said they no longer make that circuit board or preamp. Does any one have an idea what it could be? The static progressively got worst and now there is no sound at all. Thank you in advance.
 
#2
I was thinking dirty pots until I realized you're saying it's completely dead now.

Unless you know a tech that can troubleshoot the preamp and make repairs to such stuff, you're looking at a new preamp.
 
#4
Does jiggling the cord in the jack make the sound cut out and/or come back? The jack is definitely the first place I would look. (I had to replace the jack on my TRB-6P back in 1996 and so did another guy I knew who had one.) That style jack is not the most durable and who knows where Yamaha was sourcing theirs for that production run? Good news is, that's an easy part to get and an easy job for someone with decent soldering skills (or even me).
EQ pots going scratchy are another common problem in older instruments (dealing with that in a 2000 vintage active axe right now...) If you're lucky, your tech might be able to access the pots and spray them with contact cleaner. Replacing pots when they're all soldered on to a board might be a hassle. (Definitely not as maintenance friendly as pots w/ wires.)
If a full preamp makeover turns out to be the least ugly option, all hope is not lost. I seem to recall Bartolini offers a piezo buffer as a component. And then you'll need a low impedance blend pot or two (can't recall if those magnetic pickups are active or not). It'll be a bit more complicated than normal but nothing that can't be figured out. May even be a thread here by someone who's done it.
Hopefully you won't have to do anything quite so drastic. I still have a mid-level Yamaha from that era and (knock on wood) the electronics are holding up surprisingly well.
 
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#5
Double E said:
I was thinking dirty pots until I realized you're saying it's completely dead now.

Unless you know a tech that can troubleshoot the preamp and make repairs to such stuff, you're looking at a new preamp.[/QUOT

Wouldn't it be completely dead even if the input jack was inoperable? I still have hope and looking for the cheapest solution first. Thanks Double E if you think of anything else let me know.
Click to expand...
 
#6
I suppose it could be the jack... however the scratchiness when turning the pots/knobs would not be explained by a bad jack.

I don't think these basses use a failure prone barrel jack... I am pretty sure this bass uses a football plate and a standard Switchcraft style jack which do not commonly fail but it is possible so I suppose and worth a look.
 
#10
GospelBassMan said:
Thanks for your help. I'm starting at the input jack first and working my way back. I really think that's the problem. Thanks Jefenator.
Click to expand...
Hope that new jack gets you back in business! :bassist:
Wouldn't surprise me in the least if the jack was kaput *and* the pots could use a little TLC as well. If cleaning doesn't work, you might just be able to live with a bit of scratchiness while turning if you're lucky. (Sometimes they do wear out internally & start cutting the signal. If pushing & pulling on the knob causes symptoms like jiggling the plug on a bad jack, that's not good...)
 
#11
lz4005 said:
Your bass does not have an input jack.
Click to expand...

True, but my friend's does:

Marco_BassCon2018_KorgBass.jpg
 
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#12
Check battery, the output jack and then the pots. Keep in mind the scratchiness of the pots may be a separate problem to the output issue, just go one step at a time.
It's unusual for a preamp to actually fail, it does happen but not often.
 
#15
GospelBassMan said:
Happy Thanksgiving to all,

I own a Yamaha TRB 6P, such a beautiful bass. I notice I hear a lot of static coming from the input jack and also when I turn the knobs. Not sure if its the input jack or the circuit board. Called Yamaha, they said they no longer make that circuit board or preamp. Does any one have an idea what it could be? The static progressively got worst and now there is no sound at all. Thank you in advance.
Click to expand...

The jack has switching terminals that turn the power on and off when you plug in a cord. It's possible the terminals are dirty, carbonized, bend, broken, or otherwise worn out. Inspect and clean the jack.

A dead battery can also cause static sometimes in active preamps. Install a fresh battery.

The nuts holding the controls on my TRB6P tend to work loose over time. This can allow the pots to move around a bit. Over time this can cause metal parts to fatique and break. I haven't taken my bass apart so I don't know if the pots are wired directly to the preamp or if they have flying leads. It could be as simple as a broken lead or bad solder joint.

If the preamp is relatively simple, a decent electronic technician will probably be able to repair it. It would be very helpful if Yamaha can provide the technician with a schematic. Unfortunately Yamaha does not have the best reputation for product support. I found it challenging to buy a replacement knob for my bass, when the bass was still in production. If the preamp cannot be repaired, there are after market preamps available that can handle the piezos.

Here is what the TRB6JP1 preamp looks like. I wouldn't be surprised if the TRB6P preamp has similar construction.
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As you see, the control pots are soldered directly to the circuit card. The problem could be as simple as a broken solder joint on the volume pot, or a bad volume pot.
 
#20
Wasnex said:
The jack has switching terminals that turn the power on and off when you plug in a cord. It's possible the terminals are dirty, carbonized, bend, broken, or otherwise worn out. Inspect and clean the jack.

A dead battery can also cause static sometimes in active preamps. Install a fresh battery.

The nuts holding the controls on my TRB6P tend to work loose over time. This can allow the pots to move around a bit. Over time this can cause metal parts to fatique and break. I haven't taken my bass apart so I don't know if the pots are wired directly to the preamp or if they have flying leads. It could be as simple as a broken lead or bad solder joint.

If the preamp is relatively simple, a decent electronic technician will probably be able to repair it. It would be very helpful if Yamaha can provide the technician with a schematic. Unfortunately Yamaha does not have the best reputation for product support. I found it challenging to buy a replacement knob for my bass, when the bass was still in production. If the preamp cannot be repaired, there are after market preamps available that can handle the piezos.

Here is what the TRB6JP1 preamp looks like. I wouldn't be surprised if the TRB6P preamp has similar construction.
View attachment 3613121

As you see, the control pots are soldered directly to the circuit card. The problem could be as simple as a broken solder joint on the volume pot, or a bad volume pot.
Click to expand...
 

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