Heathkit IT-12 Signal Tracer Probe Noise

[Kennyg2209]

I wasn't sure where to post a question about this , but since it's a tube amp I'd post it here . Even though the amp is working fine .

I recently refurbished the signal tracer that I've had for a while . I changed all the caps and resistors that were out of spec . The amp itself is quiet . I had the cap going to the volume pot disconnected and from the volume pot on the amp is quiet . Just a very slight hiss at full volume . When I connect that coupling cap to the probe , I have noise. It's quiet turned down , but pretty noisy getting close to full volume . It's the same with the probe switch on audio or RF. I did clean that switch also. Do these probes pick up that much noise ? I do have about 20mv at 17,500 Hrz noise on my scope without its probe connected to anything . I turned everything off in my shop , but it's still there . When I connect the ground to the tip on the signal tracer probe, it is quiet . If it's the signal tracer probe, Is there a way to modify it to make it quiet ?
Any help would be appreciated . Thanks

KennyG

 

[s-petersen]

Can you check if the handle of the probe is grounded?

 

[Kennyg2209]

Can you check if the handle of the probe is grounded?

The metal tube was not grounded. I wasn't sure if it should be or not since the end where the ground comes out is plastic . Also, there is only a signal wire coming out of the switch to the tip. I thought of putting a short piece of coax there also.

Kennyg

 

[s-petersen]

In the schematic it shows the handle grounded if I read it correctly, and it would be the same as using coax to the tip, you could try to ground the handle and see if the noise goes away.

From the manual, the braid gets shoved between the black probe end and the barrel.

"Push the black probe end into the end of the probe body, making sure that the flat braid is between the probe body and the flat side of the probe end. Fasten the end with two small self tapping screws. "

 

[Kennyg2209]

In the schematic it shows the handle grounded if I read it correctly, and it would be the same as using coax to the tip, you could try to ground the handle and see if the noise goes away.

From the manual, the braid gets shoved between the black probe end and the barrel."Push the black probe end into the end of the probe body, making sure that the flat braid is between the probe body and the flat side of the probe end. Fasten the end with two small self tapping screws. "

Got It ! Thanks. I only have a schematic and manual text that I downloaded. It only shows the shield of the coax grounded. I'll try that. Whenever I took the probe apart, The coax pulled right out the bottom. Great, Thanks

Or actually it pushed up in the probe.

Kennyg

 

[s-petersen]

Assembly manual
https://www.google.com/url?sa=t&rct...kit/it12.pdf&usg=AOvVaw3CGvR2lObXrZSLm20EzL5J

 

[Kennyg2209]

Assembly manual
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=12&cad=rja&uact=8&ved=2ahUKEwif-72HxM7hAhVIjlkKHR_UCAcQFjALegQIBhAC&url=http://www.pascalchour.fr/ressources/heathkit/it12.pdf&usg=AOvVaw3CGvR2lObXrZSLm20EzL5J

Thanks Scott, you've been a big help. Thanks for the manual. Now that I look at it closer I noticed how the body of the probe is connected to the shield, dotted line . It's working much better now. Put a signal through the probe from my signal generator and I have a nice clean signal. Don't need much volume on the tracer. I can't wait to put it to use. I think the noise feature will be a great help in troubleshooting. It will make a great addition to my test equipment.

Thanks for everyones help and input. Much appreciated!

Kennyg

 

[s-petersen]

I am actually considering building one, as it's pretty simple, and needs no special inductors