[DSP-10] Problems Loading UHF3x35A.HEX

[Richard Miller]

Hello Mike: Yes I have checked and the modification was apparently done when I built it. R108 does in fact read 472. With regard to Lock recovery after the transition, the answer is no. Once the lock is lost, it take a complete reload of UHFA394.EXE and a reset of the DSP board to recover from this. There are also other issues, such as the one I mentioned about the intermittent A/D level. When I say intermittent, I don't mean the level is fluctuating, but instead is completely absent. I have also seen cases where I would leave the system sit for a half hour, when in a faulted state, and it miraculously recovers on its own with no intervention from me (i.e. poking or prodding the PCB's). Last night I rewired everything, I thought maybe I had an intermittent in the wiring harnesses. I have rewired everything inside the DSP enclosure, and the harness leading from the DSP harness to the DSP-10 main board. This too has left me with the same faults. With regards to frequency changes while in RX, I am able to navigate the entire 144 - 148 MHz span in large sections without a PLL lock warning. I think it may be time to look at replacing U104, and if that is not the issue, then the only thing left is something on the DSPx board.   73 Rich, AJ3G
 

      From: kd7ts <kd7ts at comcast.net>
 To: Bob Larkin <boblark at proaxis.com>; Rich Miller via DSP-10 <dsp-10 at mailman.qth.net> 
 Sent: Thursday, December 17, 2015 4:03 PM
 Subject: Re: [DSP-10] Problems Loading UHF3x35A.HEX
   
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

 
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