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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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9th Jun 2021, 1:26 pm | #1 |
Heptode
Join Date: May 2015
Location: Chatham, Kent, UK.
Posts: 965
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VRC 321 capacitor value?
Hi have a vrc 321 radio and the caps decoupling mic/ ptt line are leaky
the cap is marked 8n2p but a non sc one reads 14.5nf what is the right value ? by my reasoning it should be 8.2 nf but why 14.5 Mick |
9th Jun 2021, 10:27 pm | #2 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,536
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Re: vrc 321 cap value
A basic capacitance meter can be fooled by leakage resistance into displaying a higher capacitance than is actually present in parallel with said leakage resistance.
A "Megger" check of the suspect capacitor near its rated working voltage will confirm this!
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10th Jun 2021, 12:16 pm | #3 |
Heptode
Join Date: May 2015
Location: Chatham, Kent, UK.
Posts: 965
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Re: VRC 321 capacitor value?
Hi thanks yes it reads 472k on a dmm thanks. Changed them all this fixed fault thanks Mick
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10th Jun 2021, 10:26 pm | #4 |
Heptode
Join Date: Feb 2008
Location: Great Barr, Sandwell, West Midlands, UK.
Posts: 589
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Re: VRC 321 capacitor value?
Bit late now, I couldn’t find any detail in the 321 info I have here, but for info the audio RF decoupling unit in the PRC320 uses 68nF caps on each line with the ‘earthy’ ends all connected to the same rail, and that is then connected to ground via a 1Ω R.
Martin |