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Post by Trapper_267 on Nov 13, 2022 21:00:42 GMT -5
Since there isn'e a layout picture for a MK4. Where is C122 located in a MK4 Transmitter?
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Post by 2600 on Nov 13, 2022 23:56:16 GMT -5
The, uh "tin box" shield on the PLL circuit board has two holes in the top with a trimmer cap under each one. The factory snapped a tiny metal hole cover over each one. I'm pretty sure the one closest to the front is C101, that sets the 6 MHz reference crystal on frequency. The hole with C122 under it is closer to the rear of the radio, best I remember.
C122 serves to adjust the tuning range of the VCO in the PLL. I swore off supporting the original Mark 4 PLL in the 90s, and haven't touched one since.
We have a large carton full of factory-original Mark 4 PLL and channel select/display circuit boards we replaced back when I had an upgrade to sell. Guess I thought we'd salvage chips from them or something. Never did. Probably ought to find a new home for those. We'll never use them for anything.
Best of luck. That PLL has some knarly design quirks in it.
73
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Post by Trapper_267 on Nov 14, 2022 9:05:21 GMT -5
Thanks Mr. Nomad.
Whats the pot mounted on the bottom just to the rear of v205?
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Post by Trapper_267 on Nov 15, 2022 9:28:19 GMT -5
Found a picture on pg. 41 of the browning MK4 service manual from CB trick's that tell's it all. I just can't upload the picture.
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Post by 2600 on Nov 16, 2022 0:57:19 GMT -5
Thanks Mr. Nomad. Whats the pot mounted on the bottom just to the rear of v205? Should be R603, modulation limit control. 73 |
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Post by Trapper_267 on Nov 16, 2022 10:32:24 GMT -5
Thank's Sir.
Thank's for all you do for us.
Scott Hudson, CO.
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Post by 2600 on Nov 17, 2022 0:42:25 GMT -5
Hey, you're welcome. That's what we do here.
73
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