[DSP-10] Continuing troubleshooting

[kd7ts]

On Fri, 12 Apr 2013 13:45:16 -0700, Don AE5K <donj at ae5k.us> wrote:

> Mike, or Bob, do you still have the files that produced the large 11x17"  
> 2 sheets of the schematic?

No, I don't. only my copy of the original stuff that came with the board.

> 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.

Pin 1 of these parts should show a lower positive voltage. U4 pin 1,  
something less than 4.0 V, etc. Just shows the part is not shorted. A  
shorted part will always draw current, so having a voltage on pin 3  
doesn't necessarily mean it will amplify. However, if pin 1 is zero, the  
part is history. It's probably good though ...

Having receive work pretty much tells us the path between D1 and ~Q1  
(common to TX and RX) is OK. Differences are before L32, and after D1.

I think I would try some non conductive stick to push on things around  
U4,U5 and Q2. Especially C41 C43 and C45. Maybe even C50.I have heard  
tales of surface mount capacitors separating internally, but my problems  
were always poor soldering or just not soldering one end. Make sure your  
power meter doesn't get zapped if you get it put out power.

At the input end of things, the path for transmit audio is through U109:B,  
Q5/Q6 and IF switch U11:A and U11:C. These are out in the open near the  
crystal filter. U11 is another place where +10T is used, with voltage  
coming through R13 to pin 6 and 13.

GL

Mike KD7TS