| Author |
Message |
    
W3faw
New member
Username: W3faw
Post Number: 1
Registered: 11-2012
| | Posted on Sunday, November 18, 2012 - 5:22 am: | 
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Hello, I am doing a complete alignment on this 2950. The PLL sets up perfectly according to the procedures posted on another web. The transmitter also aligns perfectly. The receiver aligns perfectly at 28.0000 but when you tune to 28.4000 the waveform on the scope is jumpy and the tone from the signal generator is fuzzy and distorted and when hooked to an antenna won't receive on 10 meters. It will receive on the CB band however. Thanks for any help. |
W3faw
New member
Username: W3faw
Post Number: 2
Registered: 11-2012
| | Posted on Monday, November 19, 2012 - 5:10 am: |
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I discovered today that the PLL is drifting in the higher frequencies. It is rock steady at 17.305Mhz PLL frequency (28.000Mhz), but when I move the radio above 28.200Mhz it starts to jump around on the frequency meter. Does anyone have any tips on stabilizing the PLL over the entire band? |
W3faw
New member
Username: W3faw
Post Number: 3
Registered: 11-2012
| | Posted on Monday, November 19, 2012 - 7:05 am: |
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I'm making progress. I have found that the adjustments of L24 and L25 are key to this problem, but I don't know how to set them properly. The RCI Service manual is no help at all. Here is a quote from the service manual:
"Set the oscilloscope for 50ns (.05µS) per division on the sweep selector and 10mV per division on the vertical input. Connect X10 probe to IC17 pin 13 and very carefully adjust L24 and L25 for the best waveform."
The question is; what is the best waveform? To me, the waveform looks the same at any setting. Does anyone have a clue to this adjustment? |
W3faw
New member
Username: W3faw
Post Number: 4
Registered: 11-2012
| | Posted on Monday, November 19, 2012 - 2:34 pm: |
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I found the solution. When you tune L24 and L25, it works better if you tune the transceiver to a higher frequency on the band, for example 30.0000Mhz and then adjust L24 and L25 for the appropriate equivalent frequency on the PLL which in this case would be 19.305Mhz (30.0000-10.695=19.305). If you do it that way all of the lower frequencies on the PLL lock right in. The oscilloscope method didn't work for me so I just kept adjusting L24 and L25 until the PLL locked in at the correct frequency. If this doesn't make sense, let me know and I will try to elaborate. 73, W3FAW |
Press_man
Advanced Member
Username: Press_man
Post Number: 694
Registered: 5-2008
| | Posted on Tuesday, November 20, 2012 - 6:59 pm: |
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BTW
Welcome to Copper! Glad you found the problem!
73
73 Pressman
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