RCI 2950DX - 6 (Long Horn) PLL alignment issue/question

[Lkaskel]

Hi Everyone,
On the bench is an RCI 2950DX 6 the I needed to return the clarifier to stock (done) and align. The issue I am having is that I can align the AM Frequency to 10.1000MHz per the spec but but when I try the TX alignment the frequency oscillates or is unsteady. I am using the attached alignment doc for the 2950(70) DX. For the measurement I am using a scope probe attached to my HP 5335A Freq Counter and connected to TP16. The reading is rock solid on AM receive and is dead on. Any thoughts to why the reading is unstable or another way to verify the TX alignment? The frequency does change with VR 8 so I am sure the clarifier is back to stock. Here is a pick of the diode (D63) back in place as well as the black wire. I need to complete the alignment but one cuurect challenge is when the RCV alignment is set (10.1000MHz) the receive is off frequency when I test it with my bench radio.





Thanks as always!!

 

[nomadradio]

I suspect the radio's AM carrier is leaking into the counter input and disrupting the count that way. I suggest removing the "mirror" board, the small chip of pc-board material held in the three "fork" spring contacts just forward from the finals and driver. This will disable the power stages and should stabilize your count if I'm right.

73

 

[Lkaskel]

Thanks Nomad for your suggestion!!! The radio does not have a shorting board but I did turn the power to 0 and was able to align the TX.

I want to verify the bias as the radio sounds pinched on TX but the alignment directions I have show the shorting board. Any thoughts as to how I would align the bais without a shorting board?

 

[Lkaskel]

Thanks Nomad for your suggestion!!! The radio does not have a shorting board but I did turn the power to 0 and was able to align the TX.

I want to verify the bias as the radio sounds pinched on TX but the alignment directions I have show the shorting board. Any thoughts as to how I would align the bais without a shorting board?

View attachment 71384View attachment 71385

As a followup to this, I did find a thread that stated the drivers should be adjusted to 3.7vdc and the finals to 3.5vdc at the gate. That is how I adjusted them with no shorting board.

Thanks!!