Deluxe Reverb Build

[aussie52]

Hi all,

I've pretty much received everything I need to begin building my deluxe reverb clone. And before I've even started I've got a few questions for those of you who have done such a build before, or have some pics of the inside of your BF/SF DR chassis:



I can't identify which holes are for mounting the fibreboard. There are two that line up to the fibreboard, but that leaves 1 unaccounted for. Would anyone be able to mark up that pic with red circles or similar to indicate where & how their board mounts?

Below is the image of the fibreboard - likewise would anyone be able to markup which holes are used for mounting?



And finally (for the moment) the below pic is the cap fibreboard & backing board. I'm unsure where to mount this board in the chassis so I'm wondering can anyone point out where on the chassis this should mount to, and what holes in the fibreboard should be used for mounting?



Thanks in advance!

[zook]

Use the layout for a BF DR at http://www.ampwares.com/ffg/

The cap board goes on top of the chassis. You will need to get a cover for it that didn't come with your chassis. MOJO has them. I think Weber might too.

Winnie

[aussie52]

I've got a cap pan already so no problems there. When you say on top of the chassis I'm assuming you mean on the outside (i.e. next to all the transformers, valves, etc.)

Btw, that circuit layout doesn't detail the cap board nor the exact mounting locations.

[JohnnyCrash]

Originally Posted by aussie52

I've got a cap pan already so no problems there. When you say on top of the chassis I'm assuming you mean on the outside (i.e. next to all the transformers, valves, etc.)

Btw, that circuit layout doesn't detail the cap board nor the exact mounting locations.

It will show where the holes for routing wires underboard will be on the though.

The holes left over can then be assumed to be mounting holes. You can then lay the board in the chassis to see if these holes line up. If they do, chances are, they're mounting holes :)

[aussie52]

That's the thing I'm trying to get at tho - if you have a look at that chassis, you'll see that within the four mounting holes for the cap pan, there are no mounting holes for the cap board.

And that 1 remaining hole is hidden underneath the main fibreboard...

[PhatTele]

The filter cap housing (sometimes called "the doghouse") goes directly underneath the circuit board position (on the outside of the chassis of course). There should be 4 mounting holes to screw the cover down and at least a couple of large holes to run the leads through (in fact, I can see them in the picture). The classic layout for your filter caps will look something like what you find on the left hand side of the top of the following link:

http://www.el34world.com/charts/fenderservice7.htm

However, this is where pictures and knowing how to read the schematics for your circuit become important. Since you don't have an actual drawing (or an amp handy to look at??), make sure your terminal connections and lead connections match up to the AB763 schematic:

http://www.ampwares.com/ffg/schem/de...b763_schem.gif

Follow all of the [A] [b] [C], etc. connection points.

Unfortunately, the layout style drawings have gaps that you have to interpret. Meanwhile, the schematics show everything, but not the practical way to hook everything up. I highly recommend getting somebody to let you look inside one (even a larger Super, Twin, Vibrolux, etc.) just to get a feel for where the filtering leads generally go. A Deluxe is very close to these other amps in design. You can get a lot of milage out of looking at one of these other amps for a reference.

ps - If the mounting holes aren't there for the fiber board, you're going to have to drill them. I've built dozens of amps (kits, from scratch, whatever). I've had to drill holes in ALL of the chassis for some reason or another. None of the kits I've come across have been totally "bolt up."

[aussie52]

Cheers PhatTele,

So I take it from looking at that cap photo on el34world that the cap board will probably have two screws mounting it down - and I'm guessing the right holes will be firstly the one that can be seen between the two positive "rails" (at the bottom of the left cap board pic), and underneath the ground "rail" on at the top right of the pic (between the last & 2nd capacitors)... That leaves the three largest holes on the board to pass filtered voltage supplies & the ground thru - and they overlap holes in the chassis.

Does anyone use standoffs on their DR builds? I know that the backing board means they're not needed for insulation, but I'd rather not sandwich wires & leads that are running underneath main fibreboard when I bolt it all to the chassis..

[JohnnyCrash]

Originally Posted by aussie52

Cheers PhatTele,

So I take it from looking at that cap photo on el34world that the cap board will probably have two screws mounting it down - and I'm guessing the right holes will be firstly the one that can be seen between the two positive "rails" (at the bottom of the left cap board pic), and underneath the ground "rail" on at the top right of the pic (between the last & 2nd capacitors)... That leaves the three largest holes on the board to pass filtered voltage supplies & the ground thru - and they overlap holes in the chassis.

Does anyone use standoffs on their DR builds? I know that the backing board means they're not needed for insulation, but I'd rather not sandwich wires & leads that are running underneath main fibreboard when I bolt it all to the chassis..

I always use standoffs, but I get clausterphobic in general (maybe thats why I'm in a three piece now! HAHA)... I guess it all comes down to personal preference.

[aussie52]

That's good enough for me - I'll only need a few mm of seperation...

[PhatTele]

Fender did not use standoffs in their amps. The leads come up from the larger holes (use rubber grommets to protect the wire) and were snaked underneath the metal leads coming out of the front/back of the caps. Other leads run next to (snuggled up against) the caps bodies to get to the holes. In most cases (especially the larger amps which used the 70uF or 100uF caps with the 220K resisters), they even ran bare wire between the top and bottom sheets.

Depending on the caps you're using, there's really not a lot of room to work with underneath that cover. If you're using the big blue Spague Atoms, you'll probably want to go the original Fender route. If you've got smaller IC, Illinois, other smaller dimension caps, you might have more room for the standoffs.

[aussie52]

Yeah I agree - under the cover it wouldnt be possible - the cap board barely fits as is, so I'll have to run the standard route. But as for the fibreboard I'll be using standoffs... pity the closest place to buy them is an hour away from my house!!

[zook]

Originally Posted by aussie52

Yeah I agree - under the cover it wouldnt be possible - the cap board barely fits as is, so I'll have to run the standard route. But as for the fibreboard I'll be using standoffs... pity the closest place to buy them is an hour away from my house!!

If you really want to use standoffs, Get some nylon spacers at your local hardware store. get slightly longer sheet metal screws to mount them.

Winnie

[Larry Rodgers]

I see 2 0f the holes for the board on your chassis.That means 1 (in the middle) is left out .It takes 3 screws to mount the board.The boards usually dont come punched for mounting .The cap pan also is avail from CE Dist.

[aussie52]

Right,

I've gone and placed the board on 8 x 10mm spacers and done away with the backing board. I'm in the process of trimming the cap backing board and drilling the mounting holes for the cap board in the chassis. Actually, on that topic, I think I need to enlarge the wire holes in the cap board as they don't quite match up with those in the chassis...

As suggested I downloaded (and printed A3 size) the schematic & layout. As with the cap board, it doesn't show what's happening with the wiring of the transformers. The power & output are easy to track thru the layout, as is hte choke, but I'd like to know what's the go with the Reverb transformer.

Firstly, does the B+ voltage come from a wire that goes from the transformer thru the side of the cap pan and to the capacitors, or does it do a lap thru the chassis?

Secondly, where does the secondary winding get grounded? Should I run a ground wire up to the 3-terminal ground strip inside the chassis? (not so much asking for opinion as opposed to how it is in the original fenders...)

Cheers!

PS While I'm at it, how many of you use a ground bus strategy for the pots (i.e. running a ground bus back to the ground lug instead of just grounding on the body of the pots...?)

[PhatTele]

I generally follow Doug Hoffman's advice on a lot of this stuff:

http://www.el34world.com/charts/grounds.htm

Also, scope out his "Library of Information"

http://www.el34world.com/schematics.htm

He also runs a great technical bulletin board and parts shop:

http://www.el34world.com/Forum/yabb2/YaBB.pl

http://www.hoffmanamps.com/

[jjmantele]

Originally Posted by aussie52

Right,

I've gone and placed the board on 8 x 10mm spacers and done away with the backing board............................................. ............

Isn't that a flexible "fiber" board? I would think it would sag over time. Not having the backer board could allow solder to drip thru the eyelets too, No?

I think they make the "hard" (phenolic?) boards with the pre-pressed protruding solder lug thingies on them for common amps?

[aussie52]

Yeah the board is a bit flexible, but there are 8 spacers (4 down each side) that should prevent it from sagging.

As for the solder, it doesn't drip once solidified.

[aussie52]

Has anyone had to do the 2 x 100ohm artificial heater ground with their deluxe reverb builds?? I'm well on the way in the build, but noticed that my power transformer has no centre tap for the heater 6.3VAC...

[aussie52]

Oh yeah, one more thing.. how the hell do you get those ancient reverb RCA plugs onto the braided cable?? I know it's going to be something simple that will make me look stupid...

[aussie52]

Alrighty folks I've almost finished - The chassis is all wired up. I powered it on for the first time this evening and found a the B voltage to be up at 500V - not too worrying since its completely unloaded (no valves in the amp yet).

Then not long ago I plugged the speaker in and thought i'd see if everything else is OK. As soon as I turned it on I hear a hum through the speaker (every single pot was turned to zero) and a pop or two (the pops werent loud).

Obviously this is a very VERY broad problem to ask questions about.. but I have 1 lead: When I installed the output transformer the secondary polarity seems reversed to that of the original fender schematic, so I installed the secondary in "reverse" i.e. green & black wires swapped - what I assume is correct to fender schematic.

Anyways, looking at the Weber 6A20 schematic which is more or less a DR, I saw a note "If loud oscillation occurs reverse brown and blue wires" - these wires are the primary winding of the output transformer. So what I'm wondering is could it be that I have actually installed the secondary backwards?

Has anyone had this problem? I would try it out now for myself, but its after 1AM so probably time for getting sleep as opposed to playing around with 500 Volts...

[JohnnyCrash]

Did you have any normal sound in addition to the slight noise/pops? How did you know the OT was reversed polarity? Noise (hum/hiss) and popping is not a symptom of this.

Oscillation you will recognize the second you flip on the standby... there will be LOUD squealing - even with the volume rolled off.

If its not a LOUD squeal, but more a hum with no guitar sounds coming through - I'd bet your either:
1. Missing a ground (you forgot to ground something).
OR
2. Something is accidentally grounding out (a wire/component may be touching the chassis or a ground lug).

IF IT SOUNDS LIKE A NORMAL AMP, EXCEPT FOR THE HUM/HISS/POPS TRY:

1. I'd check all solders and make sure they're all shiney and not dull gray.

2. I'd check your RCA/Reverb section. Make sure its grounded well.

3. Try a few different 12AX7's in the first slot.

Otherwise... is the amp getting any guitar sounds through it at all?

We need a little more info on what the problem is.

[Texsunburst59]

Here's a pic of the guts of the '65 Blonde BF Deluxe Repro my amp guy built for me.

[aussie52]

Right, I have a bit more info..

The amp did squeal when I turned it on and let it warm up - the bias was pretty high. I adjusted the bias down and found that you can't get anywhere near the 15-20mA range where I'd like to set it. To stop the squealing I have it set at about 5mA!!!!

I think that low bias could be the cause of the next problem: There is a guitar signal but on loud notes (particularly bass) the note breaks up (not good distortion more like breaks into a crackle).

Also the tremolo does not appear to work... Oh boy, looks like a long week of troubleshooting!!

[aussie52]

Well, problem solved.. Turns out the output transformers' secondary was wired in reverse. Once that was corrected there was no squeal - set the bias at approx. 19mA and it sounds AWESOME. Unfortunately there's a considerably harder problem to solve now and that is the hum - it still has a reasonable amount of hum (at power line freq's). Also, I managed to dribble solder down one of the legs of a 9-pine tube socket, which prevented the reverb 12AT7 from being inserted so I can't get reverb until thats changed...

Oh yeh, and on the tremolo.. I realised no footswitch = no tremolo :)

[Telenator]

The hum can sometimes be solved by carefully re-dressing the wires. Also, try plugging the amp into several outlets to be certain it's not a bad ground or line problem with the electricity.

[aussie52]

I think you're right. Looking at Texsunburst59's pics above, he has twisted wires going to the pots - mine are all parallel.. Is there a rule as to which wires should be twisted (if indeed that is a way to go)? At the moment everything is running in parallel to the pots...

[goteleonthemt'n]

Also on the hum tip: You earlier asked about the 2x100 resisters to make an artificial center tap on the heater wiring. Did you get that figured out? That should help with the hum.

The following is from memory, so confirm elsewhere or proceed carefully:

You basically solder a 100 ohm resister to somewhere on each side of the heater output, and ground the other ends. A common trick is to just solder them to the heater pins of one tube (e.g., pins 9 and 4/5 on a preamp tube), and solder the other ends to a wire to ground. Or, even better, you can raise the artificial ground a bit in voltage, which can help with the noise even more, by "grounding" them not to absolute 0V ground, but rather to one of the cathode pins of the tube socket you're using. These will will be several volts above ground. The whole thing just fits on the socket of one of the tubes, by stretching the bodies of the resisters directly across the necessary pins.

Does this make sense?

[zook]

Originally Posted by goteleonthemt'n

Also on the hum tip: You earlier asked about the 2x100 resisters to make an artificial center tap on the heater wiring. Did you get that figured out? That should help with the hum.

The following is from memory, so confirm elsewhere or proceed carefully:

You basically solder a 100 ohm resister to somewhere on each side of the heater output, and ground the other ends. A common trick is to just solder them to the heater pins of one tube (e.g., pins 9 and 4/5 on a preamp tube), and solder the other ends to a wire to ground. Or, even better, you can raise the artificial ground a bit in voltage, which can help with the noise even more, by "grounding" them not to absolute 0V ground, but rather to one of the cathode pins of the tube socket you're using. These will will be several volts above ground. The whole thing just fits on the socket of one of the tubes, by stretching the bodies of the resisters directly across the necessary pins.

Does this make sense?

The best and most often used place to do this is the pilot light socket. Attach one end of each resistor to the wire terminals (one to each side) and the other ends to ground.

Winnie

[aussie52]

Yep did that. Off the back of the pilot light I used 2 x 100ohm resistors and grounded the centre "tap" to one of the power transformer mounting bolts.

I made an intersting discovery with the noise tonight:

The preamp pots (i.e. bass/treble) don't have any effect on the hum when the volume is off which leads me to think that the hum isn't necessarily dependent on the layout of my preamp/pot wiring. Buut, turn the reverb knob up and the hum gets waay louder. Remember that I've got no 12AT7 reverb driver in nor the reverb tank.. I think it might pay to get a new tube socket in as soon as possible and connect up the reverb tank and see if that makes a difference...

[aussie52]

The reverb 12AT7 socket got replaced today & the cabinet is drilled ready to take the chassis, but I still haven't got this noise problem sussed. I checked the filter cap connections (particularly ground) as recommended by my local amp tech. I am yet to twist the preamp wires.

I also tried the amp without a few of the preamp tubes in:

With no phase inverter, got no signal at all.
With no reverb 12AX7, still had hum.
With no "normal" 12AX7 (i.e. furthest from the rectifier), there was slightly less hum.
With no "vibrato" 12AX7 (next in line), there was hum.

What I'm a little sus of is that with either of the 1st or 2nd preamp tubes pulled, i couldnt get any guitar signal thru the amp at all. From the looks of the schematic, each tube works for a single channel (independently)...?

Guess who's confused!

[aussie52]

Do you builders ever twist the leads to/from your transformers? (in particular the output transformer)

[jjmantele]

Twisting heater leads and HV leads from the power trans is normal. Twisting the 2 plate leads on the OPT should be ok but they are normally not near preamp tubes/leads and have only DC on them at idle. DC does not induce noise in nearby components. I don't think they are likely to cause "noise/hum" problems. Perhaps oscillation if near a preamp lead but the root cause of hum.

Where is the CT of the OPT attached?

[aussie52]

The CT is attached to one of the eyelets on the very end of the fibreboard - the same one that the standby switch & choke are connected to (as per the AB763 layout).

Good news however: HUM IS GONE... I originally had all of the preamp cathode resistor & cap pairs grounded to a common point on the board, and then a wire going from that point back to the PT mounting bolt. I removed those grounds and instead grounded each cap/resistor pair on the ground bus wire attached to the back of all of the pots.

Now I'm down to the last problem - the reverb makes a massive squeal when you turn it up.. I was thinking of just taking it to an amp tech, but I think I'm too close to the finish line!!

Despite having no reverb I gigged with it yesterday tho. Sounds great!

[jjmantele]

I meant to ask where the CT of the HV on the power tranny was thinking you might have a ground loop. Sounds like you had a loop elsewhere and it's fixed.

I'd try some other tubes for the reverb as a 1st step. And double check the wiring. Test it with no footswitch. A footswitch for the reverb needs to be shielded. Does it squeal if you unplug a reverb pan cable?

[aussie52]

Not sure if it squeals if i unplug a cable... haven't been able to check lately (busy). To answer your question about the PT CT, it's grounded on the PT mounting bolt where all the other stuff is grounded to.

[JohnnyCrash]

Squealing Reverb... hmm...


1st try a new Reverb tube.
2nd check the pot wiring (good solid connections?).
3rd check to make sure everything in the Reverb circuit that is supposed to be grounded, is ground (also check your RCA reverb jacks).

You are now the "tech," so don't waste your money on taking it to one... besides, you'll learn more and it'll be cheaper - just start eliminating things Sherlock Holmes style :)

[aussie52]

Originally Posted by JohnnyCrash

Squealing Reverb... hmm...

You are now the "tech"

HAHAHAHAHA you are spot on Mr. Crash. I think me wanting to take it to an amp tech is more a reflection of being at the end of a week of debugging and getting the $hits with the amp. Now that I've got the noise sorted and I've gigged / practiced with it, I've found some extra patience!!

[aussie52]

Well folks it's been a long while since I've posted anything about this build so...

It turns out that the squealing reverb was due to bad reverb cabling - i measured it and it was shorting. So there's some new cable in there now but it's not the "vintage reverb cabling".. i'll probably do that at some point down the track. Apart from that the amp works a treat and hasn't missed a beat. I've left the thing biased at around 23mA @ 450V (or was it 460...?? will need to check).

Anyways, here's the finished product:

[JohnnyCrash]

Very nice!

[Big Lug]

Ace!