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FDP Forum / Amp Mods, Repairs, and Projects / Converting Deluxe Reverb to Vibroverb

rockman627

New York

Mar 21st, 2017 01:25 PM   Edit   Profile   Print Topic   Search Topic

I bought a Deluxe Reverb built by Mike Marsh of marshamps.com before he moved to Florida. Mike's DR is heavily modified with a self/fixed bias switch, bias probes, a Marshall-style normal channel, and other things.I used it a lot for 8 years and it died on me Jan 2016. It powers on and the tubes are good, but no sound. I said, "I'll use my Fender Concert and fix the DR later", which of course never happened.
I just recently discovered Rob Robinette's page and if I understand this page correctly (https://robrobinette.com/AB763_Model_Differences.htm), I can rebuild a standard AB763 DR (no mods), change the power transformer and output transformer to accommodate 6L6 GC tubes and I would have pretty close to a Vibroverb with a 12" speaker. This would be great for me because sometimes the 22 watts would get drowned out, and now I would have close to 40 watts, and a 1-12" DR would be easier to lug than a 4-10" Concert, and eventually I will get a neodymium speaker.
Is my thinking correct? Furthermore, will the new transformers fit it a DR chassis?

RDR
Contributing Member
********

I tried to think

but nothing happened!
Mar 21st, 2017 09:00 PM   Edit   Profile   Print Topic   Search Topic

A learned gent here described his method for this. I can't recall the name, someone here will reveal it shortly. He also increased the filter capacitance and converted to a Weber Copper Cap rectifier with no sag IIRC.

pdf64

UK

Mar 23rd, 2017 02:31 AM   Edit   Profile   Print Topic   Search Topic

I think that the big square chassis hole for the PT may need to be made a bit bigger, and new holes drilling for the fasteners for the PT and perhaps OT.
But it's all quite 'doable'.
To maximise output, a Bassman/SR size OT can be squeezed in; bigger iron using thicker wire and interleaved windings gives more of everything, if that's your goal, though some of the sweetness of the little VR size OT is lost.

Bear mind that the existing PT may be able to cope with 6L6, so check with Marsh about that.
It may be that fitting a sag-free silicon rectifier, 6L6 and a re-bias will get you where you need to be.

Alternatively / additionally, a more efficient speaker could get you there for way less $$$; have you tried a Celestion G12H, Jensen C12K or other heavy magnet, 100dB/watt speakers?

(This message was last edited by pdf64 at 06:16 AM, Mar 23rd, 2017)

Hammond101
Contributing Member
**********

So. Cal. USA

Mar 23rd, 2017 05:58 PM   Edit   Profile   Print Topic   Search Topic

My 1-12, 2 6L6 build is pretty much as you describe. A Deluxe Reverb size cab and chassis with a Vibrolux PT(yes the hole must be bigger) and a multi tap OT for extension cab options. 4 or 8 ohms using the polarity switch as the control.

I used a DR board, left the filters as they were (same a Vibrolux) and melted it together. I'm running a Weber copper cap with no sag.

The little sucker screams.

rockman627

New York

Mar 24th, 2017 10:53 AM   Edit   Profile   Print Topic   Search Topic

agghhh, I gotta figure out how to widen the transformer hole? oh well, I hope one of my handyman friends can help. Thanks to all.

JJuran
Contributing Member
******

Boston Area

Mar 24th, 2017 02:15 PM   Edit   Profile   Print Topic   Search Topic

Chances are that amp chassis is 16ga Galvanneal. Not as hard to work with as other steel alloys. So you can do it without esoteric metal fab tools. But you do need good tools, time, and patience.

The bigger challenge will be to enlarge the xfmr hole without damaging anything inside or outside of the chassis. Depending on how you cut the galvaneal, you may need to remove some things. For example, rectifier tube socket, power tube sockets, AC line, choke, anything your cutting tool might bump into while enlarging the hole. You'll need to survey.

You'll need to re-drill all 4 pwr xfmr mounting holes. Do that before you cut. Most pwr xfmrs come with a drawing that has dimensions for hole size and mounting hole dimensions. Follow that and mark the chassis accordingly.

You want to cut from the "outside" of the chassis - that is - flip the chassis over and cut from the bottom side where the xformers and tube sockets are. Don't try to manage a power tool from "inside" of the chassis. So mark your cut lines on the exterior surface of the chassis, not the inside.

Once you mark the cutting lines, a good, accurate, and manageable jig-saw with a good metal-cutting blade will do the trick. Use a good one that you can vary the cutting speed with and keep it slow. Don't use the "orbital" type unless you want a fight you can't win. Whatever saw you use, make sure you have a can of Marvel Mystery oil or 3M oil that you can put on the blade every few seconds as it cuts. That blade can become quite brittle and break from the heat. The oil will keep it cool enough to finish the job.

If you're going with a bigger output transformer, you'll need to re-drill at least one of the mounting holes for that. Keep the o/t lamination "perpendicular" to the p/t lamination. They're already that way so just don't re-orient the o/t while replacing it.

Good luck!

Hammond101
Contributing Member
**********

So. Cal. USA

Mar 24th, 2017 02:43 PM   Edit   Profile   Print Topic   Search Topic

It isn't a big jump from a Deluxe PT to a Vibrolux PT size wise. I drilled the mounting holes, marked my cuts and my Dremel did the rest. A "nibbling" tool also works well.

The trannies mount the same way so it was pretty easy.

Another way to go is to use a generic vertical mount transformer so you have mounting legs like on your OT but four of them. Just choose a PT with the correct voltages and taps and your in business. You may also be able to use an actual Vibrolux PT flipped up-right and use "L" brackets on the mounting screws to secure it without enlarging the cutout. This may require turning the OT 90 degrees to keep the thing guiet, "Perpendicular" as above.

Just thinking out loud here.

You'll have to pay mind to speaker clearance but that shouldn't be an issue with a DR 1-12 cab.



Mars Hall

USA NW Indiana

Telefunkin'
Mar 24th, 2017 04:46 PM   Edit   Profile   Print Topic   Search Topic

As others have stated, there are less invasive ways to get a little more out of your DR. JJ makes the 6V6S, reviews have called it a 6L6 in a 6V6 package, with more headroom and tone like a 6L6. That along with the Weber Copper Cap, might get you in the tone zone you seek.

JJ 6V6S

(This message was last edited by Mars Hall at 09:33 PM, Mar 24th, 2017)

stratcowboy
Contributing Member
**********
*

USA/Taos, NM

Mar 24th, 2017 06:15 PM   Edit   Profile   Print Topic   Search Topic

"...less evasive ways..."

I believe you mean less **invasive**. Correct?

Mars Hall

USA NW Indiana

Telefunkin'
Mar 24th, 2017 07:32 PM   Edit   Profile   Print Topic   Search Topic

stratcowboy, yes. I'm usually better than that with my grammar. Lol

rockman627

New York

Mar 25th, 2017 12:22 PM   Edit   Profile   Print Topic   Search Topic

wow, thanks for the info! This is such a great forum.

Peegoo
Contributing Member
**********
**********
******

The spotlight

looks like a prison break
Mar 26th, 2017 10:07 AM   Edit   Profile   Print Topic   Search Topic

One of the rules in the amp world is it's generally a bad idea to convert an amp into something else unless it's just to satisfy your curiosity. Swapping tubes or a speaker can make a big difference in the tone and response. But gutting an amp to make it into something else is usually not the best approach.

Getting a certain vibe from an amp circuit that it wasn't originally designed to do is not necessarily a cost-saving approach.

If it's a Vibroverb you want, sell the amp and get a Vibroverb.

JJuran
Contributing Member
******

Boston Area

Mar 26th, 2017 11:58 AM   Edit   Profile   Print Topic   Search Topic

Hmmm - I overlooked the original post ... if the OP is seeking "Vibroverb" then we need some clarification. Which one? The brown-face 63 with the normal and bright channel or the '64 black-face with the 15" speaker ???

If you want to re-use the AB-763 circuit in the Deluxe, I assume it's toward the black-face vibroverb with the 15" speaker... That one needs a PT and OT similar to black face super reverb ...

The brown face vibroverb is 6g16 not ab-763 and differs in many areas ... I have one of these and it is my favorite amp (at the moment).

willie

Too Near Atlanta GA

Amp Tech Emeritus
Mar 26th, 2017 12:52 PM   Edit   Profile   Print Topic   Search Topic

++++ and then some on what Peegoo said...it is a major "no no", if not a sacrilege to butcher a vintage tube amp or change it from one type of amp to another....however, the amp in question is a Marsh amp build which is essentially a deluxe reverb clone...and I see no big issue with doing a major mod to that amp. Just be sure you are sure you want to do this versus simply selling the Marsh Deluxe Reverb clone and buy the amp that you really want...always makes sense to me but that's just me....

willie

JJuran
Contributing Member
******

Boston Area

Mar 26th, 2017 03:27 PM   Edit   Profile   Print Topic   Search Topic

With all due respect to Willie and Peegoo, the OP can't sell a broken clone amp.

He can spend what it takes to fix the amp (say $150-$175 for a new o/t worst case). Best case he gets $600 for it after he fixes it.

After that, he's looking at $1500 outlay for a black-face vibro-verb (used if he can find one) and it won't have the "Marshall-style" tone stack in the normal channel or a 12" speaker. He seems to like these aspects of the amp.

In this case, it makes sense to mod the amp for the new transformers, tubes, and some filter caps and a few resistors. I believe he'll get what he's after.

willie

Too Near Atlanta GA

Amp Tech Emeritus
Mar 26th, 2017 08:50 PM   Edit   Profile   Print Topic   Search Topic

Hmmmm....a Hammond OT (1750H) for the Deluxe Reverb style amps run about $40.00...Resale on a Marsh, or even a Weber or Mojotone style clone of this type is easily $750 and up assuming it's a good build in good condx...Ive built and sold a few in my time. :)

That said, no intention to dissuade the OP, just a comment based on experience...and for sure, there is no harm and no foul for modding up a clone style amp if you have want to take the chance of the mod being less than successful and maybe losing any value that the original product had in it. Might be an interesting project though... ;)

willie

rockman627

New York

Mar 27th, 2017 03:33 PM   Edit   Profile   Print Topic   Search Topic

The DR I bought from Marsh was originally a DRRI that was probably his first project; I say that because it is a little messy in there. It is also heavily modified. When it died, I couldn't just look at a standard schematic and start troubleshooting. But I had success rebuilding an inherited 6G12A Fender Concert, and when I read from Rob Robinette's website that the AB763 circuit was pretty much the same for all models that used it, I figured a Super Reverb is about 40 watts, so I'll build an plain AB763 circuit board, and use transformers appropriate for 6L6 GC's. Then I found out the Vibroverb used an 8ohm output transformer. So my project is to get a Vibroverb into a DR cab, partly for the convenience of such an item at the places I play, and partly because I really like building this stuff. As I did with the Concert, I would use a turret board (I find them very convenient) and 1 watt resistors. If I get that to work, then I may put back some of the mods. But re-building is the way I want to go. Lots of thanks for all your input.

D Rogue
Contributing Member
**********

Hollister, CA

Is it supposed to make that sound?
Jun 7th, 2017 03:54 PM   Edit   Profile   Print Topic   Search Topic

I believe the "learned gent" RDR was referring to is Fritz_D_Cat. Do a search on his name, using the Any Date option under the search dates drop down and you'll find lots of good stuff. I also recall the 6L6 with the copper cap discussion, but couldn't find it. However, I did include a link I got from the search that was a pretty cool read. Also, if you look in his profile he has some good stuff, including a pic of a DRRI with a larger OT and copper cap rectifier. Good luck!

Fritz's Formula for One Mean Sounding DRRI

ejm

usa

Jun 8th, 2017 09:02 AM   Edit   Profile   Print Topic   Search Topic

I admit that I didn't read every post in detail here.

Amp mods: What has always scared me about these is that you don't know if the mods were done by someone who really knows what they're doing. Therefore, buying/selling used can be a different ball game. Being a buyer can be a little more risky. I would think that a stock DRRI would be easier to sell than a modded one.

As was said, if you want to do it because you can, or if it's a learning experience, go ahead. But know the downsides going in.

Guitar mods are easy by comparison. Pickups and electronics are cheap and not dangerous. It's easy to see what has been done. Investigating amps takes a little more effort.

I may have missed it, but why not shop around for a kit and build what you want? Assuming the kit designers know what they are doing, that takes away that element of risk.


rfrakes331K
Contributing Member
*******

IL USA

RonHalen Jokingly He Says
Jun 16th, 2017 02:07 PM   Edit   Profile   Print Topic   Search Topic

Peegoo, I have to agree , but a VA is loud. I have often wanted a 65 lower power Vibrolux Reverb. I have been looking for years for such a beast. And it most likely wouldn't sound like a Vibrolux!

FDP Forum / Amp Mods, Repairs, and Projects / Converting Deluxe Reverb to Vibroverb




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