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Author Topic: Need assistance ID'ing a capacitor  (Read 2157 times)
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WA2SQQ
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« on: January 14, 2020, 09:50:31 AM »

Not directly AM related, but I need a quick answer to a component identification situation. I’m at the office and don’t feel like waiting till I get home to measure this. This USB dongle has 3 caps in parallel, labeled “1201J” I know the J is 5% tolerance. Caps usually have a 3 digit code, but this one appears to be 4. Anyone know about 4 digit cap codes?

Interesting circuit, from a device marketed to high end audio people – a USB line conditioner. Ground (pin 4) is separated from USB shell part of the connector. Simple RC network comprised of the 3 caps in series with a 33 ohm resistor between the shell and ground. Possibly it might improve a ground loop situation but hardly what customers who purchased it claim it does. Anyone want to guess what this sells for? $299 – No joke!


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N4LTA
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« Reply #1 on: January 14, 2020, 11:07:59 AM »

I'd guess 1200pF but I might be wrong. 1201 on a SMD resistor usually means 1200 ohms - usually...

Pat
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K1JJ
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"Let's go kayaking, Tommy!" - Yaz


« Reply #2 on: January 14, 2020, 12:00:11 PM »

I had a box of silver micas that were marked 39J, 202J, etc.  They were all picofarad, meaning 39 pF, 202 Pf....

So in your case this could mean 1200 pF =  the more common .0012 uF.

Just a guess though.

T

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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

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KD6VXI
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« Reply #3 on: January 14, 2020, 12:07:42 PM »

http://m.diytechstudio.com/apps/4-digit-capacitor-value/4-digit-capacitor-value-finder

--Shane
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