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Prog Rock Voltage test


joe camilli
 

Hans,

Step 8 testing and I am getting 4.5 volts on pin 18 with 12v input. Any suggestions

Joe N7QPP


Alan G4ZFQ
 

Step 8 testing and I am getting 4.5 volts on pin 18 with 12v input. Any suggestions
Joe,

Check IC2 voltages, and R1, R2 are correct and soldered well.
Then all joints and components up to Q3.
If nothing found the voltages on Q1-Q3 might give a clue.
Best test without the Synth board in.

73 Alan G4ZFQ


joe camilli
 

Synth board and IC1 are not installed for this testing.
Voltages:
  • IC2 1-3.94, 2-12.2, 3-5.21
  • Q1 1-4.95, 2-4.4, 3-5.24
  • Q2 1-5.21, 2-5.1, 3-0
  • Q3 1-5, 2-0, 3-5.21
R1


joe camilli
 

Synth board and IC1 are not installed for this testing.
Voltages:
  • IC2 1-3.94, 2-12.2, 3-5.21
  • Q1 1-4.95, 2-4.4, 3-5.24
  • Q2 1-5.21, 2-5.1, 3-0
  • Q3 1-5, 2-0, 3-5.21
R1 and R2 are correct


Alan G4ZFQ
 

On 20/09/2020 23:04, joe camilli wrote:
Synth board and IC1 are not installed for this testing.
Voltages:
* IC2 1-3.94, 2-12.2, 3-5.21 OK
* Q1 1-4.95, 2-4.4, 3-5.24
Q1 base should be about 4.1V
Q1 emitter should be about 3.4V

Presuming your reading 1 is the base then is R5 present and soldered well?

73 Alan G4ZFQ


joe camilli
 

R5 is present and shows 4.2 v


Alan G4ZFQ
 

R5 is present and shows 4.2 v
_._,_._,_
Check Q1-3 are the correct types. Note Q2 is PNP.
Measure voltage on them, preferably identifying B, C and E.
And voltage on R6.

73 Alan


joe camilli
 

R5=4.2
R6=0
Q1 B=4.17, E=4.38, C=4.9
Q2 B=4.9, E=5.21, C=0
Q3 B=0, E=4.35, C=5.21


Alan G4ZFQ
 

joe,

R5=4.2
R6=0
Q1 B=4.17, E=4.38, C=4.9
Q2 B=4.9, E=5.21, C=0
Q3 B=0, E=4.35, C=5.21
R6 is connected to the other 0V points. Check with an ohm meter to see if it is grounded by a whisker of solder or even a un-etched whisker of copper track.
If it is not near zero ohms but 4K7 then you will have to load the output of the regulator and re-check voltages.
A resistor of around 500 ohms to 2K ohms put between pins 3 and 18 of the synth socket will do this.

Alan


joe camilli
 

you'll have to excuse my frustration. How could I mess up such a simple circuit??

As best I can tell everything is installed as it should be.