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Author Topic: Rickenbacker TR25 Noise  (Read 1312 times)

aruption

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Rickenbacker TR25 Noise
« on: January 21, 2020, 09:14:11 AM »
Bought an old Rickenbacker TR25 guitar amp about a year ago. After a few months I noticed that there was a quiet distortion audible in addition to the clean signal. More noticeable at lower volumes. Someone suggested replacing the power supply caps, which I did, but that little bit of distortion didn't go away. Not worse, but not better either.

Left the amp alone for a few months, when I came back to it, it now makes an awful squealing and static noise. The noise increases as the volume is turned up and is silent when the volume is at zero. I haven't opened it up yet to check where I worked on it before, but I figured that should be the first thing I check. If not, any ideas what else it could be?

Jazz P Bass

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Re: Rickenbacker TR25 Noise
« Reply #1 on: January 21, 2020, 10:10:43 AM »
That puppy was manufactured in 1977.
So any interboard connections are suspect (wipe them with DeOxit).
The controls & reverb jacks should also be gone over.
As to the squealing: do any controls affect it?
Be careful in there as there are quite a few obsolete transistors in it.
The slight distortion may be a bad speaker. Try another one.

aruption

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Re: Rickenbacker TR25 Noise
« Reply #2 on: January 21, 2020, 10:49:08 AM »
I'll pop it open later and try some cleaning.

The squealing responds to the tremolo controls, just like it does to the volume control.

Enzo

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Re: Rickenbacker TR25 Noise
« Reply #3 on: January 21, 2020, 02:38:33 PM »
And please connect the amp to a different speaker for a test.   Sometimes a rubbing voice coil sounds as you describe.

aruption

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Re: Rickenbacker TR25 Noise
« Reply #4 on: January 21, 2020, 06:00:20 PM »
So the original slight distortion definitely is the speaker. I hooked the amp to a different speaker and that distortion did not come through the new speaker, but I could still hear the unhooked original speaker making that noise!

The squealing is there no matter what speaker the amp is going through, whether or not any instruments are plugged in, and even when a speaker is plugged into the external speaker jack.
Cleaned the boards and all of the connectors in the amp, to no avail.

This is a recording of the noise: https://drive.google.com/open?id=1U-GxBeajpkgCTpcbaDMDHah1X7hk2-wD

aruption

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Re: Rickenbacker TR25 Noise
« Reply #5 on: February 09, 2020, 04:36:48 PM »
Any thoughts? Bad transistor?

Enzo

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Re: Rickenbacker TR25 Noise
« Reply #6 on: February 10, 2020, 04:37:34 AM »
I don't have sound.  But in general I'd be more suspicious of a poor ground somewhere than a transistor.

aruption

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Re: Rickenbacker TR25 Noise
« Reply #7 on: March 31, 2020, 06:40:40 PM »
I ended up tracing the noise to the transistors near the inputs, replaced them with new ones, and the squealing noises seem to be gone. i might end up replacing the rest of the transistors anyway just to keep everything fresh. As far as the distortion from the speaker, I took the speaker out and manipulated the cone a bit until the distortion went away. Seems to be holding up, but I think I will look into getting a new speaker anyway.