Twin Reverb Buzzing Issues

[Paul-McShartney]

I was wondering if you guys can help me isolate the noise issue with my 65' Twin Reverb Reissue.


Things I've noticed with nothing plugged in the amp:
-buzz gets louder as I turn up vibrato channel volume, and lesser so when I turn up the normal channel
-buzz gets significantly louder and in higher pitch (think 120hz?) when I turn up the reverb knob
-buzz goes away when unplugging v6 so I'm sure its a reverb related issue or that plus something else in the preamp


Things that didn't change the buzz at all:
-Swapping V1 with V2
-Swapping V3 with V6
-Swapping V4 with V5
-Removing V2
-Removing V3



I haven't tried unplugging the reverb yet but I checked to see if the rca plugs were tightly in and they were. Thinking its both a grounding issue with the reverb tank and maybe a resistor on one of the tube sockets in the Vibrato channel?

If you guys can help me with this id greatly appreciate it, need to record with it soon but really don't want to pay for an amp tech at the moment

 

[Lowerleftcoast]

I checked to see if the rca plugs were tightly in and they were.

These can cause problems. Clean the connections, and try different cables.

Does pulling V4 stop the buzz?

Depending on the buzz, it could be a bad filter cap.

Are you knowledgeable enough to not get zapped working with high voltage?

 

[Paul-McShartney]

Thanks for the reply.

I'll try using contact cleaners on the inputs and clean the plugs as well.

I just tried pulling v4 and it killed the noise of the vibrato channel (and reverb noise is gone too of course). Normal channel has a slight bit of buzz that gets worse as I turn it up and goes completely silent at 10 (don't know what that happens).

I've never worked inside an amp myself but have watched plenty of videos and know how to successfully drain filter caps. I also have a friend who works on this stuff who I might ask to help me.

 

[schmee]

I was wondering if you guys can help me isolate the noise issue with my 65' Twin Reverb Reissue.
Things I've noticed with nothing plugged in the amp:
-buzz gets louder as I turn up vibrato channel volume, and lesser so when I turn up the normal channel
-buzz gets significantly louder and in higher pitch (think 120hz?) when I turn up the reverb knob
-buzz goes away when unplugging v6 so I'm sure its a reverb related issue or that plus something else in the preamp
Things that didn't change the buzz at all:
-Swapping V1 with V2
-Swapping V3 with V6
-Swapping V4 with V5
-Removing V2
-Removing V3
I haven't tried unplugging the reverb yet but I checked to see if the rca plugs were tightly in and they were. Thinking its both a grounding issue with the reverb tank and maybe a resistor on one of the tube sockets in the Vibrato channel?
If you guys can help me with this id greatly appreciate it, need to record with it soon but really don't want to pay for an amp tech at the moment

It can be the reverb cables. I had one amp that drove me crazy, I started to remove one of those cables and it went silent then loud again. I had to clean the cables and jacks, especially the old corroded outside of the amp jack.
But it could be many things. I'd start there and also try pulling both reverb cables and see if it goes away.

 

[Paul-McShartney]

So the noise is the same when plugging v4 back in while unplugging the rca cables. I dont have contact cleaner at my house at the moment but my buddy has some and so I'll clean the jacks and plugs a bit later. But I guess this means it's not the cable?

Also, it's probably not the tube right? I swapped v4 and v5 and the same amount of noise is there

 

[Lowerleftcoast]

Normal channel has a slight bit of buzz that gets worse as I turn it up and goes completely silent at 10 (don't know what that happens).

WAG... bad filter cap.

Does it sound reminiscent of this 120Hz hum around 1:15 in this video? It doesn't have to sound exactly the same.

 

[Paul-McShartney]

So the reverb seems to be making that hum when increasing the reverb knob. When turning that all the way down, and turning up either normal or vibrato volume, the hum seems to be lower (guessing 60hz).

here's a vid of the issue (you can tell the normal channel, while having some hum, is still significantly lower than the vibrato channel):

 

[Paul-McShartney]

Btw I got the amp new in 2015, can filter caps really go bad that fast? thought it was closer to the 20 year mark, though I have used this amp a lot

 

[Lowerleftcoast]

can filter caps really go bad that fast?

Parts are parts and capacitors can and do go bad.

It is just a guess but my guess is still a filter cap. They may or may not show visual signs of bulging or spewing. IDK how easy it is to have a look under the cap pan on a Twin RI.

 

[Lowerleftcoast]

Try swapping the power tubes around. Actually, try it with just the two outer tubes removed and then with just the two inner tubes removed.

There is no danger to test it like this. It might rule out a power tube problem.

 

[Paul-McShartney]

For sure, I'll look into the filter caps then.

Also, wouldn't the fact that removing v6 removed all the noise mean that it's not a power amp issue? You obviously know more than I do but I figured that was a big hint towards the issue.

 

[Lowerleftcoast]

wouldn't the fact that removing v6 removed all the noise mean that it's not a power amp issue?

Yep.