Rickenbacker International Corporation - Forum

McGuinn model compressor
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Author:  kvalois [ Tue Feb 21, 2017 9:53 am ]
Post subject:  McGuinn model compressor

Hi, everyone:

After some 27 years, the special compressor jack on my Roger McGuinn 370-12 is not only picking up radio stations, but causing loud "hums" when I play it. I brought the guitar to an electronics specialist-- an engineer who has worked on guitars and amps for years. He tested everything out-- except the "chip" itself.

He told me to call Rickenbacker to find out if I could get a new chip, or to get its number (someone at Rickenbacker rubbed out the original number). When I called Rickenbacker yesterday, I was told by the switchboard operator:

1) There is NO chip that I could buy
2) Nobody in the Service department would know the type or number of the chip
3) Rickenbacker no longer will service the RM 370-12 model

So, does anyone who also owns the McGuinn model have the same problem???
And, any suggestions???

Dr. Karl Valois

Author:  JohnHall [ Tue Feb 21, 2017 12:29 pm ]
Post subject:  Re: McGuinn model compressor

Unfortunately, that chip has not been made for many years now and there's nothing quite like it currently made. The good news is that if you hear anything, it's not the chip that's the problem; it either works or it doesn't.

The radio station problem suggests one of two things. Both relate to the fact that this chip was a bit unusual and the gain on the chip was controlled in an inverse fashion, that is, the gain goes up as the voltage on the gain lead goes down. Most often, the cause of the problem is the battery. Alkaline cells tend to drop in voltage as they go down, so a dying battery brings Radio Moscow in! The solution is to do as Roger McGuinn does, to use lithium batteries as you find at the camera store. They cost twice as much but last three time longer, so it's actually a bargain.

If it's not the battery, it's the circuitry surrounding the gain lead to the chip, either a resistor or a transistor failing, both of which are common, off-the-shelf components.

Author:  Micky [ Tue Feb 28, 2017 1:13 pm ]
Post subject:  Re: McGuinn model compressor

I think there is some Hendrix recording, can´t remember which, where this is audible. He is picking up some radiostation while playing. We´ve been discussing if it has something to do with his Wha-Wha pedal and the guitarstrings working as antennas. Ideas?

Author:  8MilesHigher [ Fri Nov 17, 2017 6:25 pm ]
Post subject:  McGuinn model compressor

I'm curious, did the Original Poster ever get his radio signal issue resolved, by changing to the lithium battery ?

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