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QCX 40m no #BPF tone #bpf

Scott
 

After build, no BPF tone and no effect from trimmer cap. Meter is 09 and plenty of bars; triple checked all solder joints with loupe, no bridges, no threads.

All wound Ls and T1 good continuity; R59 good and no shorts to ground; faint 700hz tone on xmit w/ant, but no receive; lcd display is good; all IC’s pins good continuity to board.

R35 when touched with fingertip generates feedback! —AF gain pot seems OK along with headphone jack output. Also all pins on microcontroller good connection with board.

I’m a Novice technician, had a great time with the build—this problem has gotten me into the schematic and learning more, but would like some sage guidance on what to do/check next. I don’t have an O scope, only multimeter.

Thanks in advance,
Scott
73 KA6HPH

Scott
 

UPDATE: Upon closer inspection of T1, I found the secondary windings wound opposite direction from the primary. I was able to de-solder, rewind the three, and re-solder everything. Quite a pain. The only difference now is that the trimmer cap is responsive -- but still no BPF tone, and no any audio coming out.
Would really appreciate some help.

Alan G4ZFQ
 

UPDATE: Upon closer inspection of T1, I found the secondary windings wound opposite direction from the primary. I was able to de-solder, rewind the three, and re-solder everything. Quite a pain. The only difference now is that the trimmer cap is responsive -- but still no BPF tone, and no any audio coming out.
Would really appreciate some help.
Scott,

The first thing is to do the voltage readings around the ICs, section 6.4 of the manual.
report the values of any that are wrong.

73 Alan G4ZFQ

Scott
 

Alan,

Input is 12.67v

I found the following:

C43,44,45,46....all a constant 2.6v; no subtle differences
IC6, pins 1-3 all 2.74v; pin5-7 also 2.74v; pin 4 is 0; pin 8 12.19v
IC7 is similar..pin 1-3 and 5-7 are 2.71v; 4 is 0; 8 is 12.19v
IC8 pin 1,2 is .973v; pin 3 is .1v; pin4 is 0; pin 5, 6 and 7 are 2.7v; pin 8 is 12.19v
IC9 pin 6,7 are 1.247v
IC10 pin 1-3 are 6.11v; 5,6 are 6.07v; pin 7 is 6.11v

LCD (works fine), but...
pin 4 is .086v....no 4.92v as the guide states...red flag??
pin 7-10 are all around 4.85v...way too high. 

Thank you Sir,
73, 
Scott

John
 

I had a short at Q7 because of the solder blob needed for the pot.
I only had a real faint tone.

John
KG5WJQ

Alan G4ZFQ
 

C43,44,45,46....all a constant 2.6v; no subtle differences
IC6, pins 1-3 all 2.74v; pin5-7 also 2.74v; pin 4 is 0; pin 8 12.19v
IC7 is similar..pin 1-3 and 5-7 are 2.71v; 4 is 0; 8 is 12.19v
IC8 pin 1,2 is .973v; pin 3 is .1v; pin4 is 0; pin 5, 6 and 7 are 2.7v; pin 8 is 12.19v
IC9 pin 6,7 are 1.247v
IC10 pin 1-3 are 6.11v; 5,6 are 6.07v; pin 7 is 6.11v
LCD (works fine), but...
Scott'

pin 4 is .086v....no 4.92v as the guide states...red flag??
Let's start here. Pin 4 is shared with the Si5351, if that is not controlled then it will not work. [LCD pin 4 marked LCD RS, goes to processor pin 27 also marked SDA, - Si5351 control.]
The schematic shows that it should be fed 5V through R3.
So check 5V on that, make sure there is no short to ground anywhere.

pin 7-10 are all around 4.85v...way too high.
No sure, but they are not connected..

73 Alan G4ZFQ

Alan G4ZFQ
 

The schematic shows that it should be fed 5V through R3 > So check 5V on that, make sure there is no short to ground anywhere.
Actually there should be about 3.3V on R3. I remember Hans saying something about this, It's a not quite correct method according to the data sheets.
5V must be fed from the processor, still look for a short to ground.

73 Alan G4ZFQ

Scott
 

Thanks John. I checked Q7...looks good. Also I've routed the pot off-board using the small connections on the side of the PC. I appreciate the reply. Scott.

Scott
 

Alan, here's what I found:

Processor pin 23 has the same as LCD pin 4 -- .085v
R3 has 3.44v

The only strange continuity with ground I could find was IC8 pin 3.

Many thanks,
Scott.

Scott
 

Looks like C16 and/or R31 would be next check?

Scott
 

C16 and R31 both good. No shorts to gnd.