Faulty practice amp

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Gasgano
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Faulty practice amp

Post by Gasgano » Sat Feb 18, 2023 2:36 am

Just bought a used IBZ10B from Ibanez to travel with.

I like the format, 10w is plenty for bedroom (or hotel room) volumes and it's a bass amp. It was cheap.

It does have an issue though: There is considerable white noise, even without an instrument and with the volume down. Tried into multiple outlets, even through a UPS to regulate power.

Even though I am inexperienced at those repairs, I opened the back, fiddled with some wires coming from the power (figured if it didn't need an instrument nor volume, it's a power thing) and after moving some of the wires, it stopped.

I narrowed it down to the wires coming from the power, going to the on/off switch and then back to the circuit board.

- What can cause such a noise? A short? A ground loop? There are a couple connectors involved. Could it be a dirty connector? A loose connector? Shall I simply rewire the power to the amp and back to the switch until I find the culprit?

I am traveling tomorrow, I left the back opened in case it comes back so I can fiddle again to mute it (was able to replicate the problem ad the solution a couple times) but any advice on what to look for or maintenance to fix it for good is appreciated. I'll make it my little project.
"People who are late are usually in a better mood than the people waiting for them to show up."

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laurie
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Re: Faulty practice amp

Post by laurie » Sat Feb 18, 2023 2:09 pm

That is weird. White noise usually comes from a failing component, not wiring.

It might be a faulty connector. Assuming the connectors are normal "quick connect" type, I would use needle-nose pliers to gently tighten the connectors and see if that helps.
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Connector1.jpg
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laurie
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Re: Faulty practice amp

Post by laurie » Sat Feb 18, 2023 2:12 pm

Gasgano wrote:
Sat Feb 18, 2023 2:36 am
Just bought a used IBZ10B from Ibanez to travel with.

I like the format, 10w is plenty for bedroom (or hotel room) volumes and it's a bass amp. It was cheap.
I found a similar one a while back at the thrift store:
http://www.bossareaforum.com/Forum/view ... f=12&t=582

I'm in perfect alignment with your sentiments. My comment then was "Of all the small amps I've found in the last couple of years, this one is the keeper".

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Gasgano
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Re: Faulty practice amp

Post by Gasgano » Sun Feb 19, 2023 12:24 am

laurie wrote:
Sat Feb 18, 2023 2:09 pm
That is weird. White noise usually comes from a failing component, not wiring.

It might be a faulty connector. Assuming the connectors are normal "quick connect" type, I would use needle-nose pliers to gently tighten the connectors and see if that helps.
.
Connector1.jpg
It's more of a constant hum than white noise per say.

It does feel like it's one of those connectors when I fiddle with them. I will undo them all, close the gap and see if it helps.
"People who are late are usually in a better mood than the people waiting for them to show up."

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Gasgano
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Re: Faulty practice amp

Post by Gasgano » Mon Feb 27, 2023 8:10 pm

So, as I mentionned, I played with the amp at a tradeshow I was at last week with an American colleague of mine that brought his guitar (in the hotel lobby). I could fiddle with the wires to make the noise disappear, but it would always come back after a couple minutes, likely due to vibrations. I could then fiddle with the wires again and eventually it would disappear.

Patch wire that went from the On/Off switch to the main board was loose and there seemed to be some grime on the male connector on the board (that I only noticed after I took the amp out of the cab).

Disconnected all connectors, used some contact cleaner on all contacts (also cleaned the pots at the same time), redid a new patch with wire and connectors I had laying at the office, used that instead of the wire that was originally used and voilà!

It's fixed! The noise is gone!
"People who are late are usually in a better mood than the people waiting for them to show up."

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laurie
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Re: Faulty practice amp

Post by laurie » Mon Feb 27, 2023 8:29 pm

Gasgano wrote:
Mon Feb 27, 2023 8:10 pm
So, as I mentionned, I played with the amp at a tradeshow I was at last week with an American colleague of mine that brought his guitar (in the hotel lobby). I could fiddle with the wires to make the noise disappear, but it would always come back after a couple minutes, likely due to vibrations. I could then fiddle with the wires again and eventually it would disappear.

Patch wire that went from the On/Off switch to the main board was loose and there seemed to be some grime on the male connector on the board (that I only noticed after I took the amp out of the cab).

Disconnected all connectors, used some contact cleaner on all contacts (also cleaned the pots at the same time), redid a new patch with wire and connectors I had laying at the office, used that instead of the wire that was originally used and voilà!

It's fixed! The noise is gone!
Nice!!

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Pepe
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Re: Faulty practice amp

Post by Pepe » Mon Feb 27, 2023 9:27 pm

Very nice! Another piece of gear saved!
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Gasgano
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Re: Faulty practice amp

Post by Gasgano » Tue Feb 28, 2023 2:15 am

Pepe wrote:
Mon Feb 27, 2023 9:27 pm
Very nice! Another piece of gear saved!
I feared it did not work as when I plugged the bass in there, no sound was coming out of it. Noise was gone, but I feared ALL SOUNDS were gone. I checked the wires again, fiddled with them again....
...
...
...
... And then I turned the volume up on the bass :lol: .
"People who are late are usually in a better mood than the people waiting for them to show up."

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laurie
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Re: Faulty practice amp

Post by laurie » Tue Feb 28, 2023 2:57 am

Gasgano wrote:
Tue Feb 28, 2023 2:15 am
... And then I turned the volume up on the bass :lol: .
Ha!! You are in good company with doing something like that :D

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Gasgano
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Re: Faulty practice amp

Post by Gasgano » Mon Mar 06, 2023 1:11 pm

Yeah... I'm pissed. The noise is back.

Tried the following:
- The black wire on the power cord is connected to the transformer via some kind of crimped marette.
- Disconnected it (it seemed a bit loose). Reconnected with a standard marette I had laying around. Noise is gone!
- Test it with the guitar. Noise is gone!
- Connect the bass to play: Noise is back again!
- Disconnect the bass. Noise is still there, even without any input (it was like that from the start).

I am starting to think this one is going into the trash.

I guess my question now is: What can make an intermittent white noise without any input that seems to go away temporarily when we fiddle with wiring? Power transformer? Capacitor? Where do I start if all I have are basic tools and a multimeter?
"People who are late are usually in a better mood than the people waiting for them to show up."

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