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 Post subject: Realistic Clarinette II SS record player L channel noise
PostPosted: Jun Sun 23, 2019 3:54 am 
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Joined: Jan Wed 16, 2013 12:04 am
Posts: 1567
Location: 77001
Hello all,
I have a 1970's Radio Shack phono here that I've
completed restoring the BSR changer.

With some old Panasonic speakers, it sounds very good,
except the left channel is putting out a shushing or surf-like sound.
Sound is not really loud, but I'm wondering if it is indicating a coming
failure.
I know very little about SS amps, would there be
a logical troubleshooting starting point ?
I have a good DMM to use.
Thanks for bearing with me,
Hotwax


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 Post subject: Re: Realistic Clarinette II SS record player L channel noise
PostPosted: Jun Sun 23, 2019 4:26 am 
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Joined: Feb Wed 04, 2015 12:26 am
Posts: 940
Bad transistors


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 Post subject: Re: Realistic Clarinette II SS record player L channel noise
PostPosted: Jun Sun 23, 2019 3:53 pm 
Member

Joined: Jan Wed 16, 2013 12:04 am
Posts: 1567
Location: 77001
Okay, I figured it was a transistor.

I lucked out and found the schematic on the
bottom of the cabinet. Posting it.

I did some reading on transistors (npn, pnp differences
and how they appear on schematic)

Can someone now direct me on what to do next ?

Remember, this is my first foray into SS amps,
so be kind and detailed, ha !
H


Attachments:
Clarinette II Scheme.jpg
Clarinette II Scheme.jpg [ 260.24 KiB | Viewed 438 times ]
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 Post subject: Re: Realistic Clarinette II SS record player L channel noise
PostPosted: Jun Mon 24, 2019 12:21 am 
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Joined: Feb Wed 04, 2015 12:26 am
Posts: 940
Transistors consist of a emitter, base and collector. The legend is up at the top of the schematic. Start by taking voltage measurements with a vtvm. Unfortunately it needs to a sensitive meter such as this. The other option is that most modern meters have transistor checkers on them. The bad news is that you have to know the exact transistor number to find the replacement.


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 Post subject: Re: Realistic Clarinette II SS record player L channel noise
PostPosted: Jul Tue 16, 2019 1:46 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 9142
Location: Beaver Falls, PA. USA
It was made by Arvin; they also made similar units for Sears.

The preamp stage is an FET (field effect transistor). If you have an oscilloscope or signal tracer, the noisy component should be easy to find. Remember, you have one working channel to compare the noisy one to. As old as that unit is, it is possible to have a leaky electrolytic capacitor or noisy resistor as well.

In the shop, we would hit all of the transistors and other components with cooling spray, one at a time. That would usually reveal the culprit.

_________________
Tim KA3JRT


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 Post subject: Re: Realistic Clarinette II SS record player L channel noise
PostPosted: Jul Tue 16, 2019 2:06 am 
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Joined: May Sat 06, 2006 4:03 am
Posts: 3473
Location: ZIP 23831 South of Richmond, VA 25 miles down the pike.
Id'n that sound to a transistor is highly probable. But I would replace all the electrolytics before probing the transistors and possibly blowing one.

Bill J.


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