Twin Reverb 65 Reissue Hum Buzz

[dkerlz]

HI all.
There’s a hissing/hum noise when I turn on my Fender 65 twin reverb reissue. I’ve seen people very knowledgeable and helpful on here but I haven’t been able to find something that fixes my problem. I figured I’d give it a shot. I’ve attached the audio file of the hum I’m hearing

Let me run through my troubleshooting
Increase vibrato channel volume – gets louder
Increase Reverb – gets a lot louder
All other knobs – no effect
Remove V1: Still buzz
Remove V2: only buss when turn reverb knob
Remove V3: still buzz
Remove V4: very little buzz
Remove V5: still buzz
Remove V6: none/very little buzz
Remove tube V4 & V6: very little buzz
Replace V4: Still buzz
Replace V4& V6: still buzz
Replace V6:: still buzz (maybe louder)

Let me know any suggestions. Thanks
Voice 1.mp3

[Leo_Gnardo]

Some hiss we expect, it comes along with amplification especially tubes. Hum/buzz, there's a hum balance pot on RI Twins. It's hidden away on the bottom of the chassis, on the other side of the power transformer, and you'll need a small flat blade screwdriver to adjust it. Beware there's another screwdriver adjustable control down there, it's the bias, and you want to leave that alone. Possibly your owner's manual might direct you where to look, then adjust for minimum hum/buzz when your controls are in normal operating positions.

Sometimes you get a noisy tube or 2 as well, hum & buzz will continue though you have set the hum control for a minimum. In that case swapping in new tubes, replacing noisy ones can help.

Removing V6 is telling, it's the output drive tube. Hum/buzz dropped to zero with it removed, then the problem is definitely in the preamp department. V1, V2, V4 are all possibilities. Your note that removing V2 resulted in very little buzz makes it a prime suspect to me. The two triodes in V2 are the vibrato channels first and second stage preamps. Hum/buzz continues with vol turned down? I'd try swapping in replacements for V2 & find if any give you relief.

Tracking down noise sources this way can be frustrating because new tubes, although many promises and guarantees are made about them, can be just as noisy or worse than the ones you're replacing. It pays to mark the tubes you take out as well as the ones you try as replacements so you can keep track. Also work in a distraction-free zone.

[tubeswell]

Increase vibrato channel volume – gets louder

This is where to start. As Leo Gnardo says, 1st thing to try is swapping V2 for a fresh (or known good) tube. (If you don't have another one handy, you could try swapping in the V1 tube. This will tell you if its the tube or something else going on in the channel)

[dkerlz]

Some hiss we expect, it comes along with amplification especially tubes. Hum/buzz, there's a hum balance pot on RI Twins. It's hidden away on the bottom of the chassis, on the other side of the power transformer, and you'll need a small flat blade screwdriver to adjust it. Beware there's another screwdriver adjustable control down there, it's the bias, and you want to leave that alone. Possibly your owner's manual might direct you where to look, then adjust for minimum hum/buzz when your controls are in normal operating positions.

Sometimes you get a noisy tube or 2 as well, hum & buzz will continue though you have set the hum control for a minimum. In that case swapping in new tubes, replacing noisy ones can help.

Removing V6 is telling, it's the output drive tube. Hum/buzz dropped to zero with it removed, then the problem is definitely in the preamp department. V1, V2, V4 are all possibilities. Your note that removing V2 resulted in very little buzz makes it a prime suspect to me. The two triodes in V2 are the vibrato channels first and second stage preamps. Hum/buzz continues with vol turned down? I'd try swapping in replacements for V2 & find if any give you relief.

Tracking down noise sources this way can be frustrating because new tubes, although many promises and guarantees are made about them, can be just as noisy or worse than the ones you're replacing. It pays to mark the tubes you take out as well as the ones you try as replacements so you can keep track. Also work in a distraction-free zone.

Thanks for your great input. Some really good stuff.

I changed the V2 tube, adjusted the hum balance. It got rid of a lot of the hum. When all knobs are down their is just a little hissing. The hissing/humming now increases when raising the volume and treble. Also when i increase the tone/treble on guitar that also increases the hum a lot.

I suspect there is nothing more I can do myself without taking it to a tech when i have the funds. Thanks for your help.

[Leo_Gnardo]

Also when i increase the tone/treble on guitar that also increases the hum a lot.

Keep in mind the amp will amplify any noise that appears at its input jacks. Guitar pickups pick up magnetic fields from ALL sources, not just vibrating strings. Bring your pickups near the power transformer on your amp, you'll hear hum & buzz pick up a lot. Humbucking pickups reduce this effect quite a bit but do not eliminate it entirely. If you insist on using single coil pickups you'll always be fighting hum & buzz, shielding the guitar's pickup & control areas can reduce it somewhat. In many cases it's possible to hold the guitar in some direction that minimizes hum pickup relative to everything else in the room. In studios & on stages I've had to put tape marks on the floor so Johnny Guitar can line his neck up with it & minimize hum/buzz for those times it's necessary.

It's not only the amp's own PT but anything nearby that creates a time varying magnetic field, power supplies of all sorts are prime hum sources, computers, wall warts, neon lamps, flourescent lights, etc.

It also helps to use a good quality guitar cable. On rare occasion a customer will complain of an awful hum, and he's using a SPEAKER cable & they aren't shielded, pick up hum like crazy.

[dkerlz]

Keep in mind the amp will amplify any noise that appears at its input jacks. Guitar pickups pick up magnetic fields from ALL sources, not just vibrating strings. Bring your pickups near the power transformer on your amp, you'll hear hum & buzz pick up a lot. Humbucking pickups reduce this effect quite a bit but do not eliminate it entirely. If you insist on using single coil pickups you'll always be fighting hum & buzz, shielding the guitar's pickup & control areas can reduce it somewhat. In many cases it's possible to hold the guitar in some direction that minimizes hum pickup relative to everything else in the room. In studios & on stages I've had to put tape marks on the floor so Johnny Guitar can line his neck up with it & minimize hum/buzz for those times it's necessary.

It's not only the amp's own PT but anything nearby that creates a time varying magnetic field, power supplies of all sorts are prime hum sources, computers, wall warts, neon lamps, flourescent lights, etc.

It also helps to use a good quality guitar cable. On rare occasion a customer will complain of an awful hum, and he's using a SPEAKER cable & they aren't shielded, pick up hum like crazy.

To clarify I was testing the amplifier without anything connected. when increasing the treble (vibrato channel) the hum increased greatly.

Afterwards i plugged in my guitar and also noticed that when i reduced the tone /treble to 0 there was very little hum but when it would greatly increase hum.

[Leo_Gnardo]

To clarify I was testing the amplifier without anything connected. when increasing the treble (vibrato channel) the hum increased greatly.

Afterwards i plugged in my guitar and also noticed that when i reduced the tone /treble to 0 there was very little hum but when it would greatly increase hum.

There's supposed to be a shorting bar on the inputs #1 of Fender amps, to minimize noise pickup when no instrument is plugged in. Perhaps yours is broken? If there's less hum/buzz when you plug in your guitar and dial its volume all the way off, compared to having nothing plugged into the amp, a faulty input jack is indicated. These days the jacks are connected to a PC board, and it may be a solder connection that has broken loose. If the amp's otherwise working OK this isn't necessarily a deal killer, just keep your amp volume control down all the way until you plug in your guitar. If it is too bothersome then get help from a pro. Let us know where you are, maybe there's a MEFster near you that can help out.*

*I hope you won't misinterpret as drumming up business for our MEF members. Of course you can bring your amp to anyone you like, no problem. We had a spot of trouble with another fellow who was seeking help a couple weeks ago, he started to get into a huff about it although a willing MEFster was available across town, that's why I'm mentioning this.

[dkerlz]

I'm starting to believe there is probably more than 1 problem with the amp.
I will try to take a look at any loose solders but I expect anything beyond this will require a pro. Right now it's not urgent or too bothersome as I hardly play. But down the line i will need to take it in. I'm located in Mississauga/Toronto, Ontario. Any MEF member is welcome to contact me.