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 Post subject: Scott Stereomaster 386 AM/FM Receiver
PostPosted: Oct Wed 09, 2019 5:35 am 
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Joined: Oct Wed 09, 2019 5:08 am
Posts: 6
Could someone help me understand why the Signal Strength Meter will not change at all when scanning AM or FM stations. However, the meter will swing to the right when the receiver is turned on. R603, a 5K pot in line will move the meter full scale either way, but wherever the meter is left, it will just stay there and not respond to the AM or FM signal changes. If you power down, the meter will go back to the left. I'm not a super techie, but am OK at it. I'm not sure where to start troubleshooting. (See attached)
The unit has excellent Sensitivity and Selectivity on both bands and works well.

Thank You

Attachment:
File comment: Portion of schematic showing S Meter in circuit.
20191009_002839.jpg
20191009_002839.jpg [ 726.8 KiB | Viewed 625 times ]


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 Post subject: Re: Scott Stereomaster 386 AM/FM Receiver
PostPosted: Oct Thu 10, 2019 12:44 am 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 1845
Location: Dallas, TX
You need to find a schematic with more detail, the circuit of the IF AMP board is probably where the problem is.

_________________
Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: Scott Stereomaster 386 AM/FM Receiver
PostPosted: Oct Thu 10, 2019 12:59 am 
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Joined: Oct Wed 09, 2019 5:08 am
Posts: 6
Thank You, I will review the Service Manual better.


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 Post subject: Re: Scott Stereomaster 386 AM/FM Receiver
PostPosted: Oct Thu 10, 2019 4:01 am 
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Joined: Oct Wed 09, 2019 5:08 am
Posts: 6
I was able to locate the HH Scott 386 Schematic


Attachments:
File comment: Scott 386 Schematic
Scott-386-Schematic.pdf [481.91 KiB]
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 Post subject: Re: Scott Stereomaster 386 AM/FM Receiver
PostPosted: Oct Thu 10, 2019 7:16 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3378
Location: Seattle WA US
Back around 50 years ago, I remember having much trouble with black plastic cased single-ended axial electrolytic capacitors in Scott products. Their failures were often intermittent. When I could focus the problem to a single circuit card, I would replace all the black caps on that card. New caps were cheaper than my time.

-Chuck K7MCG


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 Post subject: Re: Scott Stereomaster 386 AM/FM Receiver
PostPosted: Oct Thu 10, 2019 2:39 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 20719
Location: Utica, NY 13502 (USA)
Supersport wrote:
I was able to locate the HH Scott 386 Schematic
What is needed is a detailed schematic of the IF amp circuit board (part # 100-1331-013). The Scott service manual will have this. What you have shown in your PDF is a connection diagram for the unit's circuit boards.

Dave


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 Post subject: Re: Scott Stereomaster 386 AM/FM Receiver
PostPosted: Oct Thu 10, 2019 4:13 pm 
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Joined: Oct Wed 09, 2019 5:08 am
Posts: 6
Manual attached
Thank you


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Scott-386-Service-Manual.pdf [6.99 MiB]
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 Post subject: Re: Scott Stereomaster 386 AM/FM Receiver
PostPosted: Oct Fri 11, 2019 2:20 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 20719
Location: Utica, NY 13502 (USA)
Some schematics in the manual you provided were poorly scanned and this is one of them. But it is good enough to get an idea of the meter driver circuit. I would first check the condition the diodes in the circuit and the associated cap going to ground. Arrow is pointing to the meter output connection.

Attachment:
File comment: Click to Enlarge
Scott 386 FM IF Amp Schematic.JPG
Scott 386 FM IF Amp Schematic.JPG [ 267.07 KiB | Viewed 462 times ]


Dave


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 Post subject: Re: Scott Stereomaster 386 AM/FM Receiver
PostPosted: Oct Fri 11, 2019 2:37 am 
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Joined: Oct Wed 09, 2019 5:08 am
Posts: 6
Thank You Dave, I will look into it when I retun in a few days.
Thankfully, I was also able to procure an original Service Manual beyond that scanned copy.

Have a great weekend!

John


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 Post subject: Re: Scott Stereomaster 386 AM/FM Receiver
PostPosted: Oct Sat 26, 2019 5:51 am 
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Joined: Oct Wed 09, 2019 5:08 am
Posts: 6
Hi Dave
I went throught the diodes, cap and resistor on that meter circuit and all are fine. But, that test point where you have the arrow shows 1.18 volts (noise) there. I'm only getting .25 volts regardless if I am on a strong signal or just noise. It doesn't matter if I am on AM or FM, same problem.
Any idea where I should look next?


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