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Roland Acoustic Chorus AC-90 dead
Roland Acoustic Chorus AC-90 dead
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Old 5th October 2019, 04:29 AM   #1
PhantomBox is offline PhantomBox  Venezuela
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Default Roland Acoustic Chorus AC-90 dead

Hello again.
A friend brought me a roland acoustic chorus ac-90. Amp is completely dead (no power when flipping the ON switch).
I opened it up (pain in the butt!) and checked power from the cord to the toroidal transformer primary winding. Tomorrow I will continue to search for the fault. It might be something stupid like a loose connector, or it might be more serious, like a blown secondary winding on the transformer. Who knows? I've seen both scenarios before on Marshall and Fender brand amps made in China.
Any suggestions as what else to look for?

Thanks in advance.
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Old 6th October 2019, 01:29 AM   #2
PRR is offline PRR  United States
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Location: Maine USA
I got no water at the bathroom faucet.

It is the same problem. You go through the pipes/wires step by step from bathroom through cellar to water meter to main water valve to street/well (or vice versa) until you find the clog/open. It sounds like you know how to check all the steps. Sometimes trouble-shooting is just tedious. (More tedious when products are not designed to be fixed.)
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Old 6th October 2019, 01:59 AM   #3
PhantomBox is offline PhantomBox  Venezuela
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Yes, I know. In this case, the fault is in the primary of the power transformer. Sometimes, these toroidals have some type of fuse built in the windings. I know someone who makes transformers for a living, and I just hope that he can rebuild it...
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Old 6th October 2019, 04:32 AM   #4
Enzo is offline Enzo  United States
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I find the simple test is to turn the power switch on, and measure the resistance between the main prongs of the mains plug. Obviously while the plug is not in a wall outlet. That way you are measuring both the primary winding and the power switch and fuse and wiring. If that reads open, then measure right at the primary wires. If the primary reads open, you will have to dig into the transformer to look for a possible thermal fuse that opened. And yes, the joint between winding wire and external lead could have failed.
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Old 7th October 2019, 05:30 PM   #5
javrolijk is offline javrolijk
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Quote:
Originally Posted by PhantomBox View Post
Yes, I know. In this case, the fault is in the primary of the power transformer. Sometimes, these toroidals have some type of fuse built in the windings. I know someone who makes transformers for a living, and I just hope that he can rebuild it...
Hello, have you sorted out the issue with the transformer? I have a friend with the same issue. He also has a Roland AC-90 with what seems like a dead transformer. Attached you will find a picture of the actual amplifier with its defect transformer.

If you have found a solution, we'll really appreciate your information.
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File Type: jpg IMG-20191006-WA0005.jpg (89.3 KB, 27 views)
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Old 7th October 2019, 05:36 PM   #6
javrolijk is offline javrolijk
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Join Date: Oct 2019
Quote:
Originally Posted by PhantomBox View Post
Hello again.
A friend brought me a roland acoustic chorus ac-90. Amp is completely dead (no power when flipping the ON switch).
I opened it up (pain in the butt!) and checked power from the cord to the toroidal transformer primary winding. Tomorrow I will continue to search for the fault. It might be something stupid like a loose connector, or it might be more serious, like a blown secondary winding on the transformer. Who knows? I've seen both scenarios before on Marshall and Fender brand amps made in China.
Any suggestions as what else to look for?

Thanks in advance.
Hello, a friend of mine is also having an issue with it's Roland AC-90. It seems that they were able to narrow the issue down to the Transformer as well. Attached you will find an actual picture of the amplifier with the presumed defect transformer.
If you were able to find a solution, we really appreciate the information.

Kind regards,

Jairo
Attached Images
File Type: jpg IMG-20191006-WA0005.jpg (89.3 KB, 27 views)
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Old 8th October 2019, 10:25 PM   #7
MAAC0 is offline MAAC0  Portugal
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I would start by unwrapping and checking the external wire connections, Then I would unwind a few turns until I found the damn fuse.
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