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 Post subject: WANTED: Schematic For Viscount 831 8 Transistor Pocket Radio
PostPosted: May Wed 15, 2019 12:10 pm 
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Hello Everyone,

Would anyone out there, have a Schematic Diagram for the above mentioned AM Receiver from around 1965? I would appreciate any help regarding this.


Thanks Very Much,

Steve


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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Wed 15, 2019 7:49 pm 
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I have the schematic but the quality isn't great.......... Any use?


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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Wed 15, 2019 8:22 pm 
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Hi Video Junk Yard,

Sure! Right now, I have nothing! I'm working totally blind! Thank You for your response :D

Steve


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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Wed 15, 2019 8:30 pm 
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Hi Steve,
PM me your email address and I'll get it off to you now.


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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Wed 15, 2019 9:18 pm 
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If the radio is silent, and you've made sure that the earphone jack tabs connect, then replacing the 4 or so Electrolytics should get it working again, and you really don't need a print for that.

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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Wed 15, 2019 9:30 pm 
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That's just it! The set is not silent. I replaced the electrolytics. The set plays at FULL volume! I lifted the detector diode cathode connection to the volume control, STILL runs at full volume. audio is very clear, but way too loud.


Regards,

Steve


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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Wed 15, 2019 9:44 pm 
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SJK wrote:
That's just it! The set is not silent. I replaced the electrolytics. The set plays at FULL volume! I lifted the detector diode cathode connection to the volume control, STILL runs at full volume. audio is very clear, but way too loud.


Regards,

Steve

If the VC doesn't lower the volume when rotated toward the on/off position, then I would replace it. First make sure that there is a ground connection to one side of it. Not unusual for a VC solder lug to become detached from a PCB solder landing.

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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Wed 15, 2019 9:58 pm 
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Yes, i'll check that. resistance does vary when I rotate the wiper.


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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Wed 15, 2019 10:02 pm 
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I was just about to suggest a defective volume control but Fifties got there first. Try shorting the wiper (center tag) to ground - that should kill the audio completely. If so, the volume control is likely open circuit at the grounded end, or as suggested has a broken ground connection. I had an Encore pocket radio with this exact fault just last week - the volume control track was open near the rivet securing the ground tag!


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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Wed 15, 2019 11:06 pm 
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I will definitely check this. Thanks so much! i'll post after I do this and see what transpires.


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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Thu 16, 2019 1:47 am 
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This is very interesting. I examined the pc board with an eye loop. found 2 solder bridges. They looked horrible, sloppy. I wicked them off, Now, the set is silent. I ran RF 455khz to the anode of detector. got a weak signal with sig gen cranked up. then ran pure audio at the cathode of detector. got a signal along with what sounds like to me Very Slow Motorboating. no reception though! I don't think I mentioned that the pc board mounting screws were missing. that's minor, I have those. I do believe someone before me worked on this set. glad I didn't pay much for it on ebay. I've never come across a problem like this one before. Turning into a "Tough Dog" and I mean TOUGH! I wish there was a Sams Photofact for this set.{no such luck} Replaced all electrolytics, and Osc and 1st IF transistor. When unit was loud, I checked IF alignment which was fine. I tested the volume pot and all connections are intact. {connections to resistor element inside volume pot. :(


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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Thu 16, 2019 2:50 am 
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Can you re-bridge the connections you eliminated, to see if it'll play again?

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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Thu 16, 2019 7:58 am 
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I installed a couple of jumpers and now set functions. I also bit the bullet and replaced the volume pot which was riveted to the pcb. No change. running loud and volume pot inoperative. 3am, and my brain is running 100 mph!


Steve


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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Thu 16, 2019 7:57 pm 
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Did you try shorting the wiper of the volume pot to ground? If that kills the audio, there has to be some problem around the volume control. The two solder bridges sound odd. I know you said it didn't work at all with them both disconnected, and is full on with them connected. Can you work out where the bridges are on the schematic? Can you try just disconnecting one of the bridges at a time and see what happens?


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 Post subject: Re: WANTED: Schematic For Viscount 831 8 Transistor Pocket R
PostPosted: May Thu 16, 2019 10:56 pm 
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Yes, I tried shorting the volume pot. nothing happens. this is by far the strangest problem I've ever seen. the set is playing fine{aside from volume control}. I decided {at least, for now} to insert a 300 ohm series resistance in the earphone/speaker circuit. now, plays ok with normal, comfortable volume. for now, its comfortably usable. what made this particularly tough was the lack of service data. I also replaced the volume pot. Had to desolder then drill out the switch rivets. Burned out my brain with this one. Perhaps, later on, i'll take it on again. Too bad there is no Photofact on this one.


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