[DSP-10] Problems Loading UHF3x35A.HEX

[Bob Larkin]

When changing T/R, the U107, U108 shift registers need to be changed. 
To save wires, this same serial string also programs the U104 126 MHz 
PLL.  So, U104 gets rewritten with every T/R change, even if the 
frequency didn't change.

Bob

On 12/17/2015 01:03 PM, kd7ts wrote:
> 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
>
>
>
>