[DSP-10] Lurker now needs help

[Don Jackson (AE5K)]

Hi everyone...

I've been lurking on this list for a very long time, trying to gain 
some tips and information.  I finally "got a round tuit" and put my 
DSP-10 together.  The incentive was our "Four States QRP" group had a 
builder's contest this past Saturday.  Finished up (construction at 
least) the DSP-10 and applied power to it early Friday evening.  Out 
of 74 entries, it won 1st place in the homebrew transceiver category 
and also the "best of show" ribbon.  Pictures on pages 1 and 3 of:
http://w0ch.com/fsqrp/feb03/feb03a.htm  (Beb, I'll send you some 
better pictures soon.)

Now, I'd really like to get my DSP-10 working good and am in the 
midst of the tune up and check out.  That's where I'd like some 
advice and help from some of you who have already done this.  I'm 
trying to make this a learning experience for myself and others.

First off, most of the voltages check out OK, but a couple do differ 
by what I am concerned is enough to indicate possibly a problem.  
>From the QST article voltage checks, the following are different:
R110 - should be 0.23, reads 1.7 vdc.
U105 pin 3 - should be 3.5, reads 2.5 vdc.
U106 pin 3 - should be 4.6, reads 3.8 vdc.
In addition, the following two read a little low:
U8 pin 3 - should be 2.8, reads 2.46 vdc.
U9 pin 3 - should be 3.6, reads 3.41 vdc.

My instrumentation consists of a Fluke 87 digital multimeter and a 
Tektronix TDS220 100 MHz scope.

I've checked out the two PLL oscillators, first by breaking the loop 
as suggested by KA7EXM, and then adjusting frequencies.  Doesn't seem 
to be a problem.  The 10 MHz. xtal osc. was padded down on frequency.

Besides the voltages being some off as mentioned above, I used my 
scope to check waveforms.  Maybe I'm worrying about something that is 
normal, but I'd like to get it right (and learn from the experience). 
The 126 MHz. waveforms on my 100 MHz scope look reasonable at U105 
and U106.  I didn't try to measure voltages due to scope limitation.

However, the 19 MHz waveform is another story...looks fine (close to 
sine wave) at the junction of C70/C71/C72.  Measures about 4.5 v p-p 
on scope.  On the other side of C72 at U8 pin 1 (input to MAR-6) it 
becomes distorted and is about 1.5 v p-p.  U8 pin 3 is about 5 v p-p 
and of course remains distorted.  U9 pin 1 reads 3.5 v p-p and U9 pin 
3 is about 1.4 v p-p, the same on the other side of the blocking cap 
C78 where the coax is connected.

My +10vdc supply is at 9.99vdc, while the 5vdc supply to the Q4 VCO 
shows 4.91 vdc and 3.64 vdc on either side of the R45 series 
resistor. (measurements all to ground)

For the other oscillator, Q101, R111 shows 4.94 vdc and 4.56 vdc at 
each end.  This tallies with the R110 voltage (which is high) 
indicating about 17 mA. of current flowing -- more than it should be 
by a factor of 7.

If you've followed this so far, I ask: are these measurements still 
in the ball park for proper operation, and should I be concerned with 
the distorted waveform of the 19 MHz signal as it goes to the TUF-1 
mixer?

Thanks for any help anyone might give.

73,
Don AE5K
(North Arkansas Ozarks)