Calling tube amp gurus

[GibsonSGgirl]

OK guys, I have a 1968 Fender Deluxe Reverb amp. It's never given me any problems...until now. It has the original footswitch with it that controls the reverb and tremelo/vibrato. While the reverb has always worked fine, and so has the tremelo, for that matter, I can't get the tremelo to work. I was playing my Strat tonight and tried the tremelo, nothing.

I think what happened was I left the tremelo on via the footswitch, ie I didn't turn it off, so while the control knobs for it were set at 0 on the amp, it was still on, lurking in the background.

I've been told not to leave the tremelo on when you're not using it. I don't know why that is. I normally am good about turning it off via the switch on the footswitch and then turn the knobs on my amp for that function to 0.

Anyway, there's always been a background tapping noise of the vibrato when it was on, which I thought was normal. Now, the guitar sounds the same whether it's on or not, and there's no noise after about 5 on the speed knob. When I turned it up to 10, there was a loud background tapping noise, and quite a bit of hum/buzz, which I attributed to the reverb being on.

On the lower vibrato speed and intensity settings, the guitar sounded distorted, but not in a good way. It sounded like when one of my pedals' battery is dying--it'll distort the guitar but it doesn't sound the way a distortion pedal or overdrive on the amp sounds. Also bear in mind that the volume of the channel I was using was between 1 and 2. I wasn't blasting anything out.

I am planning to take it tomorrow to my local Sam Ash to see what they can tell me about it. As it's a vintage amp, I am expecting a hefty bill.

I checked the connections from the foot pedal to the back of the amp, they seemed fine, no frayed wires or loose connections. I then unplugged it and untangled the rather long cord, plugged it back in, no change.

I don't know if there's a short somewhere, or if something needs to be replaced. Maybe I need a new foot switch/pedal?

And I hope at least some of what I've written makes sense. It's hard to describe unless you hear it.

Thanks in advance guys!
http://forums.pelicanparts.com/support/smileys/wavey.gif

I contacted the guy that sold it to me, who checked with his amp guy who said that it sounds like I need a new capacitor. I've also been told it could be a bad preamp tube, or dirty pots.

[JubileeMan 2555]

First check the V5 preamp tube. It drives the trem. If it was left on the whole time, it could have gone bad.

Thats the only help I can give since I never use trem. But I'm actually pretty sure its the tube.

[guitarsnguns04]

the preamp tube is the 12au7 i beleive ..I would use an ohm meter and check out the switch to the end connection of the amp. good place to start

[GibsonSGgirl]

Thanks guys! I'm real new to this, and don't know a lot about my amp, but am eager to learn.

[dbx]

You could also try pressing the tremolo footswitch a few times. I sometimes have this kind of issue with the footswitch on my Vibrolux. It "hangs up" and won't kick in either the reverb or tremolo (vibtrato) but a solid click usually gets the contacts to connect properly...the distorted reverb sound is a different issue but I would agree that it might be tube related...the DR is nice amp...

[GibsonSGgirl]

Thanks DBX. I have tried that already, and I know the reverb is working. The tremelo sounded better the last time I tried it, but that was a few days ago, so I might try it again tonight, just to see.

I've been told I should have the amp biased and as I have no idea if it is or not, I figure I'll get it checked to make sure everything's supposed to be working as it should.

Great sig, dbx, by the way!

[dbx]

How old are the tubes in your amp? I know there are other NC forumites probably in your area that can give you a recommendation on a solid amp tech nearby...being that it's a '68 (does it have the aluminum frame around the grill?) I would be very careful who I entrusted to work on it...

(I had spent some time in Dallas recently and was listening to The Doors "The WASP (Texas Radio and the Big Beat)", the line caught my moment, and it ended up in my sig...)

[fullerplast]

Anyway, there's always been a background tapping noise of the vibrato when it was on, which I thought was normal. Now, the guitar sounds the same whether it's on or not, and there's no noise after about 5 on the speed knob. When I turned it up to 10, there was a loud background tapping noise, and quite a bit of hum/buzz, which I attributed to the reverb being on.

On the lower vibrato speed and intensity settings, the guitar sounded distorted, but not in a good way. It sounded like when one of my pedals' battery is dying--it'll distort the guitar but it doesn't sound the way a distortion pedal or overdrive on the amp sounds. Also bear in mind that the volume of the channel I was using was between 1 and 2. I wasn't blasting anything out.

I am planning to take it tomorrow to my local Sam Ash to see what they can tell me about it. As it's a vintage amp, I am expecting a hefty bill.

I checked the connections from the foot pedal to the back of the amp, they seemed fine, no frayed wires or loose connections. I then unplugged it and untangled the rather long cord, plugged it back in, no change.

I don't know if there's a short somewhere, or if something needs to be replaced. Maybe I need a new foot switch/pedal?
I contacted the guy that sold it to me, who checked with his amp guy who said that it sounds like I need a new capacitor. I've also been told it could be a bad preamp tube, or dirty pots.

Good description and detail! First thing to check is the vibrato tube, that's the second one to the right of the power tubes; it's a 12AX7. Odds are good that's the problem. If you don't have a spare, borrow V1 from Channel 1 (first 12AX7 all the way on the right).

Second thing to check is your switch. All the switch does is connect the center of the jack to ground. You can do the same thing with a homemade shorting plug, or just a paper clip. With that jack shorted, the vibrato should be active all the time, controlled by the speed and intensity knobs. Ticking is pretty normal on a DR and hard to eliminate completely.

If that doesn't do it, it's possibly a bad opto-resistor in the trem circuit. Pretty easy to determine and pretty easy to fix but you will want help if you haven't done amp work before. (High voltage warnings apply as soon as you pull the chassis).

Worst case (the opto-resistor) you should be fixed up for $50 or so.

[GibsonSGgirl]

How old are the tubes in your amp? I know there are other NC forumites probably in your area that can give you a recommendation on a solid amp tech nearby...being that it's a '68 (does it have the aluminum frame around the grill?) I would be very careful who I entrusted to work on it...



Hey,

yes it does have the aluminum trim around the grille. I was assured when I bought it that it was a '68, at least that's what it was advertised on gbase as...

I agree about who works on it. I've been told to try a few guys that are really well known and really good, but they're located in Cary and Harrisburg, and I can't drive all that way out there just to have my amp looked at, so I'm taking it either tomorrow or Friday to Steve Stoeckel, who was the guy Guitar Center recommended to me.

Edited to add: I don't know how old the tubes are in the amp. I'll get in touch with the guy I bought it from and see if he remembers (this was 4 years ago)

[GuitarsFromMars]

GibsonSGgirl-if it's not the V5 tube,it is probably the 'roach'-the optocoupler device in the amp it's a little photovoltaic gadget that runs the tremolo/vibrato in the amp.usually to replace the tube(even with NOS) and the roach,we should not be talking more than 100 bucks...

[aeolian]

If the switch has gone bad you can try reversing which plug is in which jack on the back of the amp. This will put the tremolo on the reverb footswitch. If it comes back, you can temporariliy leave the one for the reverb unplugged. There reverb will work whether there is a switch or not. The tremolo needs to have a switch in there. Then try switching out the tube. As Fullerplast suggested, swipe the one from the first slot on the right (looking in the back of the amp, which is V1, V2 being the next one over, and so on). If neither of these work, you have to get it to a tech as either the optocoupler thingy is dead or some other component has gone away. In any event, poking around inside the amp is not something for the uninitiated. Biasing is something related to the output tubes. If you replace them, the amp should have the bias reset. Transition BF/SF Deluxe Reverbs use a blinking optocoupler to create the tremolo. There are older Fenders that vary the bias to get tremolo but you don't have one. Don't let some shop sell you things you don't need.

[GibsonSGgirl]

Well go figure. Tonight I tried the trem again, and it worked fine. But now the reverb is acting up. It was buzzing like it was working, only I was not hearing any reverb effect. So I switched the leads from the foot switch to see if that made a difference, and the buzz got really loud, but it did sound like the reverb was trying to work.

Also, something else I noticed, the volume and background hum is significantly different depending on which input (1 or 2) I plugged the guitar into. The input 1 sounded a lot louder, with a lot of background noise (not buzzing like reverb, but humming like it's being powered) and the same thing between the two channels in the 'Normal' area.

I don't know what's going on really.

I did look @ the tubes, and the big ones are Electro Harmonix, and the smaller ones are a mix of RCA and Phillips ECG (or EGC). Some of them look kinda old, but as I said before, I don't know how old they are.

[JubileeMan 2555]

Alright, heres some help:

First of all, the number 1 input will be louder than the number 2 input because the amp is designed so that there is less input allowed to pass in the 2nd one. This, I believe, has to do with the history of those old fenders of having a bass guitar used WITH the guitar.... but the bass would be in number 2.

Noise, buzzing, obnoxious noises are 90% of the time due to tubes acting up. The last 10 percent is caps and other misc. hard to find reasons. But tubes are probably the issue most of the time...

... I still think your amp is gonna need some T.L.C. in the tube department. It sounds like you've got some decent tubes in there, but because of your "issues" I'd recommend you spend a little cash and buy replacement tubes for all the preamp tubes (small ones). I don't want you to actually replace all of them, I just want you to have them so you can find which tubes are causing issues. By replacing them one by one you can find the culprit.

In a deluxe reverb, there should be 6 "small" tubes... 4 x 12ax7s and 2 x 12at7s. They should be marked which is which. If they don't there should also be a little white "tube chart" attached to the inside of your amps cab...somewhere on the sides. Find cheap replacements online and give it a try. We're not looking for tone here, just a good running amp. Once you get them all situated, come back and we'll start talking tone improvements;)

Hope this helps.

[brad347]

Buy ONE 12AX7 and one 12AT7. Then go "down the line."

Please do not throw away any of those old stock tubes. It's possible your tube sockets just need to be clean and/or re-tensioned.

[dbx]

I did look @ the tubes, and the big ones are Electro Harmonix, and the smaller ones are a mix of RCA and Phillips ECG (or EGC). Some of them look kinda old, but as I said before, I don't know how old they are.

:eek: ....like brad347 said, those old RCA and Phillips tubes are sought after and can be quite nice especially with the older Fender amps (do a search on NOS tubes.) Seems like someone along the way took some time to setup the preamp tubes well. I'd be more suspicious of the Electro Harmonix 6V6 power tubes for creating noise. I've had several go bad recently that have had very little time in...At the time you bought it did the prior owner say how long the Electro Harmonix tubes had been played? How much time have you put in on them since and at what levels?

[GibsonSGgirl]

Hey guys,

thanks! My amp did not have a tube chart when I bought it. I don't koow what happened to it, but it's not there.

As for the tubes, if I'm happy with the tone, why should I change anything? And don't worry, I have no plans to throw anything away!

[JubileeMan 2555]

Hey guys,

thanks! My amp did not have a tube chart when I bought it. I don't koow what happened to it, but it's not there.

As for the tubes, if I'm happy with the tone, why should I change anything? And don't worry, I have no plans to throw anything away!

You are not changing tubes to make the tone better, you'll be switching out tubes to find which one(s) are bad and making noise. Believe me, once you replace a tube thats making noise, it will more than likly make the amp sound better overall anyways.

..But its up to you.