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Faulty practice amp
Posted: Sat Feb 18, 2023 2:36 am
by Gasgano
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.
Re: Faulty practice amp
Posted: Sat Feb 18, 2023 2:09 pm
by laurie
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 (48.2 KiB) Viewed 3340 times
Re: Faulty practice amp
Posted: Sat Feb 18, 2023 2:12 pm
by laurie
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".
Re: Faulty practice amp
Posted: Sun Feb 19, 2023 12:24 am
by Gasgano
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.
Re: Faulty practice amp
Posted: Mon Feb 27, 2023 8:10 pm
by Gasgano
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!
Re: Faulty practice amp
Posted: Mon Feb 27, 2023 8:29 pm
by laurie
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!!
Re: Faulty practice amp
Posted: Mon Feb 27, 2023 9:27 pm
by Pepe
Very nice! Another piece of gear saved!
Re: Faulty practice amp
Posted: Tue Feb 28, 2023 2:15 am
by Gasgano
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
.
Re: Faulty practice amp
Posted: Tue Feb 28, 2023 2:57 am
by laurie
Gasgano wrote: ↑Tue Feb 28, 2023 2:15 am
... And then I turned the volume up on the bass
.
Ha!! You are in good company with doing something like that
Re: Faulty practice amp
Posted: Mon Mar 06, 2023 1:11 pm
by Gasgano
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?