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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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14th Jul 2020, 4:42 pm | #1 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Can't see the wood for the trees...? Hallicrafters S20 AGC.
Anyone know the purpose of R13 in the schematic in the link below?:
http://www.nostalgiaair.org/pagesbym...6/M0008856.pdf Its value is given as 100 Ohms, SW1 is the AGC on/off switch, so far as I can make out with the AGC switched off the AGC line is pegged to the +ve voltage that's developed across the 6Q7's cathode resistor (I get that bit) The other associated resistors are of a very high value compared to the value of R13. Lawrence. |
14th Jul 2020, 7:40 pm | #2 |
Guest
Posts: n/a
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Re: Can't see the wood for the trees...? Hallicrafters S20 AGC.
There is a somewhat tortuous path directly across some capacitors, the small 100R would stop the switch being hit by a large current when switched. An old dodge (best practice) to lengthen switch life. I still see reset switches on microcontroller circuits directly across 100nF or so, they don't last long.
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14th Jul 2020, 8:06 pm | #3 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Can't see the wood for the trees...? Hallicrafters S20 AGC.
The source voltage to the 100 ohm resistor will only be a volt or two at most.
Lawrence. |