[DSP-10] PLL locking and voltages at L21

[Chris]

Hi Mike


> Just some general observations of the circuit around Q4 and U6. Q4 runs 
> from the 5 volt regulator, U13. There should not be any voltage higher 
> than 4.8 to 5 volts in that area. The tuning voltage to the varactor comes 
> from U6 which runs from the 10 volt regulator.  This tuning voltage is 
> appled across L20 and might be anything between  some very small voltage, 
> near zero, to almost the full 10 volts.

Q4 has been turned and is ruuning OK at 5v

pin 6 uf U6 is running at 9.1v so this seems OK

> It seems likely L20 is where you are seeing 9.1 volts, which, if true, is 
> nothing extraordinary. And... if this is the case, it means the PLL (U7) 
> wants to run the frequency down as it thinks the frequency it is comparing 
> against, on Fin (pin 4 of U7), is lower than where Q4 is oscillating. 
> Tuning C69 through it's range might be useful if it happens that 
> everything else is working. Adding more C lowers the oscillator freq. It 
> might require some change to the toroid inductor to get this right. It is 
> also possible that U7 is not being programmed with the correct data and 
> the frequency in the U7 registers is just nuts.
>
I had a look with the serial Diag progrm last night to see if the serial 
port was OK and this seems to have problems, the voltages this is supposed 
to give to alternate pins to see if it is running does not work correctly 
and maybe this is why U7 does not seem right. When i load the software UHF3 
with the ezkit lite then run the UHFA i get these messages after 2 sets of 
bleeping


Power10[]=627B:0004
prrdat[]=62fc:0004
dnorm[]=63fe:0004
It_dnorm[]=6500:0004
It_pwrdat[]=6581:0004
pd16[]=6602:0004
cwmbuf[]=6683:0004

Downloading DSP pointers...
table address = 0d82, Getting pointers...

Error in obtaining dsp_ptr[37 [validity check).
 Read 0 00 (1234 56 proper)
Filter design will not be available.
hit enter to continue


> A frequency counter can be very useful here to confirm oscillation and 
> frequency. I don't recall what frequency this comes up on, but I think the 
> tune up procedure covers this.

Ill try and borrow one today, but everyone in GM will have the classic 
hangover from the bells HI or ill remove my radio from the car

> Do you have the screen displaying on the computer ? Does the clock in the 
> lower left corner update ? We don't care if the time is correct, for now, 
> we just need to know that it updates. The ability to change the displayed 
> frequency on the screen demonstrates some functionality of the serial 
> communications between the display and the EZKIT.

The clock in the corner is updating and i am able to change frequency on 
screen


> Do you have the EZKIT or the KDSPX ? There is an error in the KDSPX wiring 
> depending on how old your diagrams are, but I don't think it affects this 
> symptom.

I have the EZKIT


> Just got your last message as I was about to send this....
>
> All of the above applies... could the voltage requlator U13 be installed 
> backwards ?? Where is this voltage coming from ?? As I recall the sillk 
> screen for both of the PLL  regulators is incorrect. Might be... Check 
> U103 as well !!

U13 and U103 have been turned, and U101 and 102 have been inserted correctly


> 73 Mike KD7TS
>

Thanks for the reply and Happy New Year to all on the list

73 Chris


> Cut from ...http://www.proaxis.com/~boblark/dsp10.htm
>
> Important! - The silk-screen legend is backwards for the 78L05 regulators, 
> U13 and U103. The flat sides of both TO-92 packages should be towards the 
> top of the board. There is no problem in installing the parts, of course. 
> The sketch of the package included with the board is correct. Thanks to 
> KD7TS for catching this. (Added 26 Oct 99)
>
>
>
>
>
>
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