[DSP-10] Continuing troubleshooting

[Don AE5K]

Hi again Mike,

I've done some measurements.  Referring to the part designations in the 
QST articles on following.  Input voltage hovers around 13.7 vdc.

When I started it cold this morning, got +3.6 dBm (2.31 mW) output. 
After about an hour, I checked again and it was down to -0.6 dBm (0.865 
mW).  At that time, the +10T line measured 11.8vdc (I'm pretty sure, 
although I may have made an error - see later), in transmit mode, with 
or without key down.

It has been powered up most of the last 4 hours now.

In tx mode, the +10T line is zero.

The +10T end of R4 (680 ohms) measured 10.8 vdc in tx mode, key up.
The junction of R4, L6, and C13 measured 0.96 vdc in tx mode, key up.
This appears to confirm most likely D1 PIN is OK and conducting.

The junction of L17, L16, C46 etc measured 10.8 vdc in tx mode, key up.
The other side of L16 measured the same.

Pin 3 of U4 reads 4.0 vdc in tx mode, key up.
Pin 3 of U5 reads 5.2 vdc in tx mode, key up.

I have not tried the r.f. probe yet.

Mike, or Bob, do you still have the files that produced the large 11x17" 
2 sheets of the schematic?  Or the file with the top layer markers, also 
on large sheet?  Or the Gerbers showing the traces? Any or all might 
come in handy since I can put them on my computer and enlarge the 
section I'm interested in.  My eyes are not what they were 10+ years ago 
when I built the DSP-10!

Next, I plan to search the original QST articles plus the various notes 
I have that supplements the articles for troubleshooting and voltage 
information.  Obviously, if anyone finds something wrong with the above 
measurements, let me know, but they all (except power out) look OK to me.

Observation: I have suspected for some time in this troubleshooting that 
cold/hot makes some difference.  The cold readings this morning and 
later readings sort of confirm this.  My intuition from many years of 
experience tell me it could be a capacitor as that would seem to account 
for all the weird observations...poor gain, temperature sensitivity, 
etc.  But I have not ruled out my error in original construction as 
opposed to a part/joint failure since I never measured output before 
this past month.

Onward!

Don AE5K

P.S. - yes I am using only one speaker, mono plug into the stereo jack.