[DSP-10] Problems Loading UHF3x35A.HEX

[kd7ts]

On Thu, 17 Dec 2015 10:25:02 -0800, Rich Miller via DSP-10 <dsp-10 at mailman.qth.net> wrote:

> I am now trying to figure out what is going on with the PLL lock issue. As I told Mike, it only seems to happen when I do a RX to TX transition. When I leave in RX it seems to be stable. The only other odd thing I am seeing is the D/A level also seems intermittent. It will go away, and then reappear, and go away again. I am not certain if the bridge on the ADSP caused damage elsewhere to the device itself,or something else.

Hi Rich,

On Fri Dec 4 19:26:30 EST 2015, Bob mentioned the resistor change, but I missed if you had checked that.

quoted from the message from Bob:

One more thought.  Do you have the R108 change?  From the DSP-10 main
page, under "Hardware Information, "R108 should be 4.7K Ohms (not 470).
Some combinations of U107 and U104 have been found to have the data line
at U104 switching too early. These are cascaded shift registers and the
timing is quite close. The R108 resistor change slows down the data line
going to U104, making the timing less critical."

Unfortunately this is probably covered by the shielded box, and not likely visible. It would be good to confirm this value.

I would not suspect the ADSP-2185 to be causing the symptoms you mention. You describe what happens when going from receive to transmit as losing lock. If nothing else is done, is lock restored when returning to receive  from transmit ?

As I recall from previous discussions of lock indications, when the DSP10 is initialized, both PLL are programmed. After initialization only the 126 MHZ is reprogrammed and smaller steps are done by the third LO which is in software. Going into transmit, or returning to receive involves the same data path and registers. You can simulate this, after a fashion, by using direct entry of the frequency. Open the direct frequency box by ALT 9, backspace over the displayed frequency and type in a different frequency. Make the change fairly large, like a MHz or so, then close the box. Does the PLL indicate lock on the new frequency ? Don't change the transmit receive, this only adds confusion. Only change in receive. We are doing this to see if the data path is good or not so a few iterations would be good.

Mike KD7TS