Magnetron, no signal past R2?

[Pauleo1214]

I built the magnetron and there is no audio at all upon firing it up. The rate led works in conjunction with the controls. All the voltages in the ic chips were good.

I swapped chips to check for bad ones, no dice. So I decided to use an audio probe. Pin 1 of R2 had a modulated signal but pin 2 didn't. Correct me if I am wrong but the signal should be going through R2, right?

 

[chris.knudson]

Check the values of R1 & R2 - yes you should have signal on pin 2 of R2.

Try reflowing R1 -- it looks a little light on the solder.

 

[Pauleo1214]

Check the values of R1 & R2 - yes you should have signal on pin 2 of R2.

Try reflowing R1 -- it looks a little light on the solder.

R2 is correct but R1 is reading 0.001 on my meter so this could be a bad resistor. I'll replace it and see what happens.

 

[Pauleo1214]

R2 is correct but R1 is reading 0.001 on my meter so this could be a bad resistor. I'll replace it and see what happens.

R1 is the correct value. Replaced it with another 1M resistor that I measured to verify it read the value. Still comes up with the same reading of 0.001M at R1. I reflowed solder at all the joints and still no signal at joint 2 of R2.

 

[Erik S]

Could be a sneaky solder-bridge somewhere dumping your signal to ground maybe? You could try continuity testing between your signal path and a ground point to check.

 

[Coda]

Triple check the one pot that is naked…

 

[Robert]

IC1.1 is an inverting gain stage, it's normal to have no signal on pin 2.

Do you have signal on pin 1 of IC1?

 

[Pauleo1214]

IC1.1 is an inverting gain stage, it's normal to have no signal on pin 2.

Do you have signal on pin 1 of IC1?

Yes, I do.

Are you referring to pin 2 of IC1 or pin 2 of R2?

 

[Robert]

Yes, I do.

Are you referring to pin 2 of IC1 or pin 2 of R2?

Pin 2 of IC1 is directly connected to pin 2 of R2 so they're the same point.

If you have signal on pin 1 of IC1 you can move forward into the circuit, the input is working properly.

 

[Pauleo1214]

Triple check the one pot that is naked…

A100K pot is properly connected. All unsoldered lugs have continuity to the solder pads.

Pin 2 of IC1 is directly connected to pin 2 of R2 so they're the same point.

If you have signal on pin 1 of IC1 you can move forward into the circuit, the input is working properly.

Copy that. Will continue after I solder on two new B100K pots that just broke from me bending them back and forth...damn metal fatigue.