NAD! 75 Vibrolux Reverb, and a question

flatcat90

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Just want to first say thank you for the threads about this amp, there's a lot of interesting opinions and good information, and I really appreciate you all for sharing a lot of knowledge.

I stumbled on a 75 Vibrolux Reverb in my local Music-Go-Round a few weeks back and really liked it. It is I guess what you could call "Player's Grade" - it's in pretty good condition, but it's had some work done, has new speakers, and needs a little bit of work on a couple things. I thought the price was reasonable ($1600) - I mean, a new SRRI is over 2k, and honestly, the other amps I have been looking at over the past few years - Carrs, Tone Kings (God I loved the Sky King), even Vintage Sound amps - are heading towards 3k. I play guitar for fun (I'm actually a bass player, mostly), and am not young any more, so I just can't justify the close to $3000 for something like a Super Bee or anything with 6L6s. So I was kind-of ... wow that this amp was going for this amount.

Here it is:



When it arrived here (I am living in Bangkok), one of the transformers was hanging down from the chassis. I took the chassis out and found that it had been ripped free of the screw, so I basically just ... straightened it out and screwed it back on there:



The reverb is buzzy. The tremolo/vibrato also seems anemic; it's not that awesome throbby trem I expect, I have to turn the intensity knob nearly to 10 for it to be noticeable, so I think something isn't quite right there. And that's my question: since this is my first Fender amp, is that how they are? Or do these indicate little problems?

I have not been able to find a tech here in Bangkok to look it over. I've watched a bunch of YouTube vids, and have started reading some books. I've refrained from buying a soldering kit to this point, but I think if it's going to get fixed, I need to fix it myself. No experience. Oh, it was last serviced in 2001, including a cap replacement (I took the doghouse cover off, they're all Sprague Atoms in there and it was signed by the tech in Somerville who did it).

Speakers are Celestion G10 60Ws with the gold and black label made in the UK, I think they're ceramic? Not sure.

Oh, also: I feel like I hit a little bit of a jackpot with the tubes that came with it:

V1 12ax7 = Preamp normal channel - Sovtek 12AX7
V2 12ax7 = Preamp vibrato channel - Sovtek 12AX7
V3 12at7 = Reverb send - ElectroHarmonix (made in Russia) 12AT7
V4 12ax7 = 1/2 Reverb recovery and 1/2 gain stage for vibrato channel - 7025 Sovtek 12AX7
V5 12ax7 = Vibrato - 7025 Sovtek 12AX7
V6 12at7 = Phase inverter - JAN Phillips EGC 12AT7
V7 6L6 = Power tube #1 - General Electric 6L6GC
V8 6L6 = Power tube #2 - General Electric 6L6GC
V9 GZ34 = Rectifier tube - Raytheon 504GB

Kind-of amazing that it made it all the way from Massachusetts to Bangkok in one piece. Hooray for the U.S. Postal Service. :)

Sounds awesome. I don't ever remember seeing a VR in the wild. This is the first one I've ever played and ... again, wow. I used to play in a blues band and the guitar player played a 335 through a Super, and I think that was one of the best sounds I ever heard. I'm pretty excited to try my 335 through this amp. And I'm definitely looking forward to cranking it up in the apartment when my wife is out. :D
 

Vibroluxer

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I'm partial so congratulations! My favorite amp.

If you have the means, changing out the Sovtek for NOS or ANOS tubes in V1 and V2.

Enjoy that monster!!
 

Dacious

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I had a 78 - reverb should be lush, deep and silent for buzz or hum. Trem should be deep and smooth on 5/5. It sounds like a mini twin up to breakup level on about 6.

I can see an original white Mallory bypass electro on your V5 trem tube which will be well past useby. That could be your buzzy trem and weak vibrato cause. Or the tube could just be bad. I'd suggest trying to swap V4 and V1, or V5 and V1 - V1 is your normal channel preamp. V3 the reverb 12AT7 send is driven hard - it's worth getting a good NOS tube in that position. Or a Shuguang 12AT7. You need something tough as nails there. EH preamp tubes are ok but not especially rugged.
 
Last edited:

corliss1

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My favorite Fender amp :D

It's completely normal for the board to be warped - nearly all the vintage Fender boards are. No concern there.

If it was serviced in 2001, it's due for another service now as that's 21 years. What does a service entail? Swapping out all the electrolytic capacitors, cleaning controls and jacks, making sure the power cord is wired correctly, and just a general going over.

If there's no one in your area, that makes it trickier. You absolutely need a multimeter to ensure there is no voltage in the amp before you start working on it.

The trem and reverb issue could be solved by swapping tubes, or it could be the amp will need more attention. It's possible (likely) it got dropped in shipped and that's what caused the transformer to rip loose.

If you're going to try and DIY this, please read up on amp safety before you start. The good news is that vintage Fender is the easiest type of amp to work on ever - all the components and solder points are right there in front of you.

Let us know how it goes!
 

zhyla

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Without eyeballing a schematic, I think these have bias vary trem and that can vary in intensity depending on bias. You can reduce the trem limiting resistor to increase the trem intensity.

Cool amp. I agree, I think that’s a very fair price for that kind of amp.
 

flatcat90

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So some interesting findings, now that it's up and running. One is that I listened closely and was hearing the 'tik tik tik' from the amp, regardless of whether trem was engaged.

The other, somewhat more puzzling, is that the trem circuit and reverb are both available on channel 1 as well as channel 2. I thought channel 1 was like a dry channel?

If someone changed the circuit, why would you do that? EQ seems the same, if anything Ch 1 seems louder when set to the same level as Ch 2.

Looks like I get to learn how to read a schematic and read a board. :D

I really appreciate the thoughts on this. I've been to @robrob 's site and have watched a bunch of videos from Psionic Audio. I also bought the Fender book by Jeffrey Falla on How To Hot Rod Your Fender Amp. It's all new to me, but as I said, I've watched a bunch of videos. Famous last words. :D
 

Vibroluxer

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My favorite Fender amp :D

It's completely normal for the board to be warped - nearly all the vintage Fender boards are. No concern there.

If it was serviced in 2001, it's due for another service now as that's 21 years. What does a service entail? Swapping out all the electrolytic capacitors, cleaning controls and jacks, making sure the power cord is wired correctly, and just a general going over.

If there's no one in your area, that makes it trickier. You absolutely need a multimeter to ensure there is no voltage in the amp before you start working on it.

The trem and reverb issue could be solved by swapping tubes, or it could be the amp will need more attention. It's possible (likely) it got dropped in shipped and that's what caused the transformer to rip loose.

If you're going to try and DIY this, please read up on amp safety before you start. The good news is that vintage Fender is the easiest type of amp to work on ever - all the components and solder points are right there in front of you.

Let us know how it goes!

This can't be stated strongly enough. There are lethal voltages inside that guy and your life is worth more than the purchase price.
 

daperl0000

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I had to post. I have a '73 that is completely stock. I'm the second owner and I've had it since the early '80's. I opened it for the first time about a year and a half ago. As you can see from the filter caps it needs plenty of love. One day. What's interesting is the tube sticker is mislabeled. It says it has 6V6's instead of 6L6's. Strange.
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Dacious

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I had to post. I have a '73 that is completely stock. I'm the second owner and I've had it since the early '80's. I opened it for the first time about a year and a half ago. As you can see from the filter caps it needs plenty of love. One day. What's interesting is the tube sticker is mislabeled. It says it has 6V6's instead of 6L6's. Strange. View attachment 1038505 View attachment 1038506 View attachment 1038507 View attachment 1038508 View attachment 1038509 View attachment 1038510 View attachment 1038511
I would definitely not run that amp again until all the filter caps are changed - I'd also do all the small electros including the bias bypass (remember it's pos to ground!).

If you think it sounds good now, it'll sound incredible - you will probably need to tweak your eq settings, it's suddenly going to sound very bright. It's probably got a Deluxe Reverb tube chart. Happened all the time at Fender. The cabs are similar size.
 

daperl0000

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I would definitely not run that amp again until all the filter caps are changed - I'd also do all the small electros including the bias bypass (remember it's pos to ground!).

If you think it sounds good now, it'll sound incredible - you will probably need to tweak your eq settings, it's suddenly going to sound very bright. It's probably got a Deluxe Reverb tube chart. Happened all the time at Fender. The cabs are similar size.
Yeah, I'm not gonna turn it on again till I fix it. It'll be fun, but I've got too many projects going on at the moment.
 

Dacious

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Joined
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Posts
10,834
Location
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So some interesting findings, now that it's up and running. One is that I listened closely and was hearing the 'tik tik tik' from the amp, regardless of whether trem was engaged.

The other, somewhat more puzzling, is that the trem circuit and reverb are both available on channel 1 as well as channel 2. I thought channel 1 was like a dry channel?

If someone changed the circuit, why would you do that? EQ seems the same, if anything Ch 1 seems louder when set to the same level as Ch 2.

Looks like I get to learn how to read a schematic and read a board. :D

I really appreciate the thoughts on this. I've been to @robrob 's site and have watched a bunch of videos from Psionic Audio. I also bought the Fender book by Jeffrey Falla on How To Hot Rod Your Fender Amp. It's all new to me, but as I said, I've watched a bunch of videos. Famous last words. :D
Do you have the footswitch? If that makes the tik tik disappear when you turn it off then the teen circuit is the issue. If you're hearing 'tiss-tiss-tiss' it's a sign the bypass cap or tube or both are cactus

It's very easy to add trem and reverb to both channels, only a couple of wires resoldered. Why you'd want to? I don't know. You have two channels that sound the same.


Theres a very good mod you can do to split the shared cathode resistor - you can then modify the V1 preamp values, handful of resistors, to Brown Deluxe values which will 'Marshall it up' nicely - I did this to mine. You got a great blackface channel that's slightly stronger, and a brown Normal channel. Really adds a little Bluesbreaker/Bassman sort of tone with a bit more preamp distortion. Easily reversed.
 

Paul G.

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Rhode Island
Without eyeballing a schematic, I think these have bias vary trem and that can vary in intensity depending on bias. You can reduce the trem limiting resistor to increase the trem intensity.

Cool amp. I agree, I think that’s a very fair price for that kind of amp.
Not bias vary trem on the Vibrolux Reverb.
So some interesting findings, now that it's up and running. One is that I listened closely and was hearing the 'tik tik tik' from the amp, regardless of whether trem was engaged.

The other, somewhat more puzzling, is that the trem circuit and reverb are both available on channel 1 as well as channel 2. I thought channel 1 was like a dry channel?

If someone changed the circuit, why would you do that? EQ seems the same, if anything Ch 1 seems louder when set to the same level as Ch 2.

Looks like I get to learn how to read a schematic and read a board. :D

I really appreciate the thoughts on this. I've been to @robrob 's site and have watched a bunch of videos from Psionic Audio. I also bought the Fender book by Jeffrey Falla on How To Hot Rod Your Fender Amp. It's all new to me, but as I said, I've watched a bunch of videos. Famous last words. :D
1. The ticking noise is common. It is usually caused by the lead dress. Moving wires with a chopstick may fix it. If not adding a .022uf capacitor either across the 10Meg buffer resistor, or from the 10Meg (the end at the "roach" end) to ground will fix it. Look up on the web, you'll find instructions.

2. Trem/reverb on both channels is a common modification. I did it for a friend once at his request. He plays a Gibson and a Strat and wanted to set up each channel so he could swap between them without having to change anything. I don't like the mod myself, but that's the reason it's done, I guess.

Good luck, I hope you find a good tech. If you end up having to do it yourself, take your time and learn as much as you can, expect to make mistakes. The reason I do my own tech work is because I had some bad expreriences with "professional" technicians and spent the time and effort to learn. I'm not a genius, but once you understand how amps work, one can be fairly effective. Just make sure you learn all the safety stuff first.
 




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