[amandarae]

I checked and triple checked the parts, grounding, etc.  The LED flashes upon turn-on but that's it.   I cannot measure any output on the oscilloscope per Jim's picture on the manual!  

I have been troubleshooting for two days to no avail!

Are there test points that I can measure to check?  I replaced Q1, Q2, U3, U2, and U1 and still cannot get any output.

Any ideas will be greatly appreciated!

Abe

[hagtech]

Track down backwards through power supply.  Start at the dc power jack and work your way in.  Let me know what dc voltages you have on each chip.

Does the LED flash once or continuously?  Are all ICs installed with pin 1 in the right corner?

jh

[amandarae]

Jim,

The LED flashes continuosly(but changes in frequency then cycles) and yes, the IC's are installed with pin 1 on square trace( as pin 1 on the left).

Here are some measurements that I made.

From DC jack: 15.35V

Ramp gen:  pin2=6.42V  pin3=8.55V  pin1=4.92V

Base of Q2 (from schematic)= 6.45V

Source at R22,23,24,25=13.03V

Noise Source:  pin 7=7.24V

SSineWave Gen:  pin9 = 7.8V, pin2=5.24V,pin3=6.45V

Modulator (MC1496): pin6&12= 13.62V   pin10&8=0.169V pin1=4.86V G+=4.0V  G-=4.0V

Output Amp(LM386)   For both:  pin5=7.17V

All values are DC voltages!
Thanks

[hagtech]

Thanks amandarae!

Most of those signals have large ac voltage swings on them, so are quite difficult to get an accurate reading.  However, the problem showed itself.  Pins 8 and 10 of the MC1496 should bias at the 9V from the opamp U3B (which was pulled down a bit to 7V).  You measured something close to a short to ground.

I don't think the chip is bad, most likely C14 is in backwards.  Ok, maybe the chip is bad, no way both pins 8 and 10 should be exactly the same if C14 shorted.  I'd guess 0.6V difference.  

I think you got most of it working, the LED indicates the ramp and sinewave generator are probably working.

jh

[amandarae]

Finally!  My FryKleaner is working .  

As per your suggestion, I found two things:

1.  C14 does not charge up and always measures 0.15V!  
2.  The Chip is bad!  Luckily, I ordered 2 from Jameco so I have a spare.

I first replace the cap.....
Then I replaced the 1496 chip............   Voila!!!


Thanks Jim for your support!