Airline GIM-9131A knowledge/repair question

[btah]

No, don't take it wrong. Not doubting you. As we have already seen my knowledge of how electronics works is lacking. Actually worse than I thought when we started...

To ground the jack, as you say, I would run a jumper from the chassis to the bar the jack tip touches when it is inserted, right?

[The Dude]

Yes

[btah]

By the way, the deep buzz was not present when I started this adventure. It is something that has been introduced by me somehow.

[The Dude]

Well, maybe after the jack problem is corrected, there's still some other buzz. Saying that, with the wrong jacks installed, it will buzz if volumes are turned up with no guitar attached. There's no getting around it. So, I don't think you caused all of the buzz............, unless you installed those jacks.

[btah]

No, I didn't install the jacks. However, I just found out something interesting. I was checking resistance between the jack connection that has the resistor. One the channel 2 jacks I noticed the resistance was .220 with the scale set at 2M. I then checked the channel 1 jacks and it was infinite resistance. I started tracing the path to ground because it only has a few components. The resistor hooked up to the jack. The other end goes into a bank of connections which then has a resistor coming off the connection to another lug on the bank of connections. The connection is direct to the chassis. I then wiggled the bank of connections around and I noticed the resistance between the jack bar and the chassis then went to .220. The deep buzz is now gone. Seems like I have a bad connection there.

[The Dude]

Yes, you could. It's not a huge deal if you just turn the volume down when not in use. If it was me, though, I'd want it right and silent. Sometimes, even with the volume down, you can get a bit of extra noise if the unused input is not grounded.

[btah]

So now I am down to some low buzz with a pulsing to it and it isn't affected by the volume control and the reverb. I don't think the reverb is doing anything at all to the sound. You have suggested before that I pull the reverb tank, which I will do tomorrow. Anything I should start looking at as far as that is concerned?

[btah]

I also just noticed, concerning the low buzz/pulse that still exists, if I put my hand about 1 inch above the 12ax7 or 6v6 tubes, the buzz/pulse cuts down by about 50%. I am not touching anything, just have my hand about an inch away from where the wires connect to the tube socket.

[g1]

Is the chassis in the cabinet? Sometimes there is shielding in the cab that will cut the hum when it is reassembled.

[The Dude]

+1 to that ^^^^^^.
And, not to sound like a broken record, but............those input tube grids not being "grounded" , albeit through a resistor (because of the jacks) will pick up noise.

[btah]

The chassis is not in the cabinet. I will put it back in there tomorrow evening and see what happens.

Is there an easy way to check the reverb tank? Not sure what to expect when I take it off...

[The Dude]

1) Look for broken springs. You'll see them laying in there if they are broken.
2) You'll see two wires going to each jack from the transducers. Check them for continuity.
3) That outta do it.

[btah]

I am thinking the reverb might actually be working. I guess I don't really know what reverb is "supposed" to sound like. Is it supposed to just introduce an echo like sound. It is very subtle. With reverb turn all the way up should it be incredibly noticeable?

[btah]

Adding a video that has the sound of the reverb (and the buzz I still have left). Hopefully this will work and you can let me know if the reverb sounds like it is doing what it is supposed to.
https://youtu.be/svEPCQ-sG6A

[btah]

I happened to have a buddy over today that plays guitar. He listened to the reverb and told me it is doing what it should be doing.
So, I think I am down to trying to get rid of some buzz. I know The Dude has said a few times that the jacks should really be different types. I am curious if there is a way to either point the issue to the jacks or something else. Can I temporarily ground each of the jacks to eliminate the jacks being the issue? If so, I am not sure which connection on the jack I would need to ground to the chassis.