Heathkit IG-18 problems

[Mickey]

G'day, I know this is probably not the correct department, but my Heathkit Audio Signal Generator model IG-18 has died on me. Was OK a week ago when doing some work on a 5W guitar amp but today when i switched it on - nothing.
The power supply is working but no oscillations, checked for oscillator signal with my CRO but to no avail.
Has any member had any experience with one of these units, maybe you could suggest where to start. Any help will be appreciated as I'm lost without this baby.

[nosaj]

Linked the build manual page 58 starts the troubleshooting section. Should be enough to get ya going. If not just ask.
nosaj

[Mickey]

Unit up and running again, the oscillator transistors had gone to heaven!
While on the bench I checked and found a number of resistors out of tolerance so these were replaced and now the unit is working as designed,
There is a little amount of ringing on a leading edge when oscillating in the 100Kcs range but not that important to me.
Thanks for the assistance.

[SoulFetish]

Unit up and running again, the oscillator transistors had gone to heaven!
While on the bench I checked and found a number of resistors out of tolerance so these were replaced and now the unit is working as designed,
There is a little amount of ringing on a leading edge when oscillating in the 100Kcs range but not that important to me.
Thanks for the assistance.

I love that machine. I bought one of the updated later versions, and modified and regulated the power supply, installed an Isolated BNC jack on the front panel for convenience, as well as built in a driver stage for the panel meter to remove the non-linear loading inherent in the original design.
I had a bit of a scare though, when I first powered it up at my shop, I smelled the dreaded odor of burning electronics and had to power off and set it aside til I could suss out what happened on my own time. Turns out, there was a Hair-line solder bridge on the project pcb +/- rails that caused a short and took out the 47Ω resistor in the power rail. Once I cleaned that up, everything worked as expected and I use it every day now

[g1]

I'll throw this in here in case someone has a similar problem. My IG-18 had an amplitude modulation, the output voltage was fluctuating up and down at a frequency of around 1Hz. You could see the output level meter moving like a metronome. Cleaning the internal trimpots solved the issue.

[Mickey]

And while you're at it, clean all the switches, that oscillating was always an issue especially if the unit hadn't been used for a while (a month or more) but they are a great unit especially for guitar amplifier repairs.