Problems with Heathkit IG-18 (Modified) rebuild.

[SoulFetish]

I only see the pics in post #2, and the empty small xstr spots look to me to have the B in the center. Are they TO92 or are they round ones?

That one is part of the Schmidt trigger and was originally a small round metal case. The others in the sine wave portion were originally TO-98, which the 2N3417s are. The PNP substitutes im using, 2N3906s are TO-92

[SoulFetish]

I don't know. I think of the man hours I've already put into this thing. I wonder if I should have just rebuilt it to use the HP-339a circuit. I got a VCR2N jfet for the AGC just for this purpose.




But I hate to give up on it now.
I'd like to eliminate the switches as the problem. Can you guys suggest something I could put in place of the notch filter just to see if it oscillates or biases?

[g1]

Sorry, no suggestions for the notch filter.
But Q5 base is measuring pretty much a double diode drop from B+ ?

[SoulFetish]

Problem Solved!

Just bought an IG-5218 in mint condition for $52 off ebay.

The 5218 seems to be pretty much the same circuit as the IG-18. But the one I bought seems to use better parts and hardware.


]



Works great. Modified the power supply board to use a LM317 regulator, and removed the neon and installed an LED.

[g1]

Will you be able to use it to figure out what's wrong with the other one?