Harmonilux Reverb AA964???

[Willabe]

Better Transformer Orientation?

Yes. It should be quieter that way.

Remember face the OT primary wires side towards the PT. OT secondary wires side towards the preamp. Just like you have it now in the pic.

Hey, where are the speaker jacks going?   

[Toxophilite]

Haha
They were going to go on the same side as the transformers just above the power tubes. I was only going to use 2 of the taps (4 and 8) and have a line out as well
Bad placement? i have a similar deal on my AB763 one channel deluxes I built and it seemed to work okay


I could also put one between the power tube sockets (on the back edge) and one between the power tube socket and the PI tube)
I have a few options


I really should've offset my tube sockets a 1/4" or so to have a little room


I'm probably going to put my footswitch jacks, and maybe even my line out on the faceplate

[sluckey]

What are the dimensions of that chassis?

[Toxophilite]

20.5 long  5" wide by 2.5" deep

[Toxophilite]

Well because I'm totally crazy ( and because that side of the amp was mostly aluminium faceplate and steel with long holes in it)
I shifted the preamp tubes 3/8" in one direction and the power tubes and rectifier 1/4" in the other os now I have about 3/4" more between the PI and power tubes (about 2" clear space so I can mount a couple of speaker jacks front to back between them.
My new aluminium plate looks better than the old one anyway.
Onward

[Willabe]

Well because I'm totally crazy

No, not crazy, just didn't think the layout through. We've all done that.

I shifted the preamp tubes 3/8" in one direction and the power tubes and rectifier 1/4" in the other os now I have about 3/4" more between the PI and power tubes (about 2" clear space so I can mount a couple of speaker jacks front to back between them.
My new aluminium plate looks better than the old one anyway.

Good deal. 

But it could/would be better to mount the speaker jacks on the same plain as the tubes.
 

[Toxophilite]

I mounted the speaker jacks on the same edge (the 'bottom' edge) the tubes are mounted on. that's why I moved the sockets...i believe that's what you mean right?

[Willabe]

Yes.   

[sluckey]

I urge you to rip your board to 2.5" wide and plan your layout accordingly. This may avoid a struggle when putting the board in that 5" wide chassis.

[Toxophilite]

I have a couple choices on hand
The original cone boards 2 - 7.5" x 2" = 15" x 2"
and some turret boards from a baldwin organ preamp
one of which is 2.5" x 13"
with a couple of 5" ones
all of which would need more turrets!


I might check out the local electronics store too


what do you think


preamp
reverb
harmonic vibrato
PI
POwer amp


or
Preamp
harmonic vibrato
reverb
PI
power amp


Either way there'll be a little going back and forth

[Toxophilite]

No answers on the layout question??


okay what about this one
On a 30-40 watt amp is a standby necessary?? good idea??
THanks

[shooter]

standby necessary

I've only used 1 standby and from all I've read, unless you're gonna leave it unused, *cooking* for long periods of time there probably isn't any earth shaking benefit.

[Willabe]

On a 30-40 watt amp is a standby necessary?? good idea??

I always used my stand by switch at gigs. All the guys did. When the boss/band hit the stage, your ready to go at the flip of a switch. Doesn't look good to be standing there waiting for the tubes to warm up, the band leader/boss won't tolerate it, dollar waiting on a dime and the bar owner won't like it either, if he/she's used to pro bands.   

There's 2 views on having a stand by to prevent cathode (K) stripping. That's where applying the B+ dcv to the tubes plate before the K is warmed up fully by the heater cause the K coating to boil and the coating flakes off, shortening the tubes life, prematurely killing it.

Some say this only happens with B+ dcv's at 1K and above, power triodes and transmitting tubes.

And rectifier tubes that have indirectly heated K's (GZ34/5AR4, 5V4) are slow turn on and are easier on the tubes. But you still have to wait for them to warm up fully before you can play.   

[Toxophilite]

OKay, apologies if I'm being a PITA
This is my third and final desperate time at asking this question


I have my chassis mostly mounted up, heaters and power supply wired so I was going to start filling up my board
I did the preamp and now I have to make a decision
This amp is a bit of an experiment
I have the preamp feeding into the harmonic vibrato and then coming out of vibrato into the reverb and the last 12AX7 stage prior to the PI. This could change if things start interacting poorly with each other


Classic Fender layout is:


Preamp
Reverb
tremelo(harmonic vibrato)
PI
Power amp


My schematic would suggest that I reverse the positions of the reverb and tremelo(Harmonic Vibrato)
like this:


Preamp
Harmonic Vibrato
Reveb
PI
Power Amp


As I've only built one reverb amp, I'm just a little nervous that the reverb circuit won't like being closer to the PI , power amp and the TRansformers down at that end.


Also if the harmonic vibrato circuit doesn't work out, (for whatever reason) I can always go to a bias vary which would be easier to implement if I used the traditional layout




Any ideas? Concerns? Things I should consider?? Recommendations??

[DummyLoad]

typically layout follows signal path. if necessary, redraw your schematic should you need clarification to determine signal flow.

sometimes, subsystems have to cross one another, so use discretion on what would introduce the least amount of noise/hum/feedback components. e.g. what layout keeps the signal path the shortest overall and keep the most sensitive subsystems away from noise sources such as power transformers, high current power supply rails, other signal sources, and power amps. 

--pete

[Willabe]

+1 on what DL just wrote. 

Classic Fender layout is:

Preamp
Reverb
tremelo(harmonic vibrato)
PI
Power amp

No it's not. Leo never built an amp with harmonic vibrato and reverb. Leo changed from the harmonic vibrato (4 1/2 triodes) to bias trem (2 triodes) when he added verb to his amps.

As I've only built one reverb amp, I'm just a little nervous that the reverb circuit won't like being closer to the PI,  power amp and the TRansformers down at that end.

This is the thing that your going to have find out for yourself. I don't think I would be to worried about putting the verb recovery tube close to the PI. And I would also try the harmonic vibrato before the verb like you are.

The weakest signal in this build will be coming back out of the verb tank to the grid of the verb recovery triodes grid. Less than the amps input signal from a guitar. Watch that carefully how/where you put that.

But this is where good layout and lead dress skills come in. And the right decoupling in the B+ power supply including it's grounding, which you found out about when you added verb to a build.

[Toxophilite]

Okey Dokey
Onwards!


Just for the record
I know Fender never had an amp with Harmonic Vibrato and reverb
and I'm aware of the signal path, I just have limited experience regarding design in general


Thanks very much!

[Toxophilite]

another orientation/layout question if I may regarding the reverb driver transformer and associated jacks


Here's a picture of the chassis with a similar sized reverb transformer on it..this is not the actual transformer though it does play one on TV (it's actually a reverb driver from a garnet unit but it's 600ohm pri and 1.7 ohm sec.)


I have it laid out above the reverb circuit tubes on an angle similiar to the way fender has it laid out.
to the left of it is a hole which I plan to put a grommet in and run the transformer leads through and then to the left of that I will put the two RCAs jacks for the tank.(one of which is shown with green tape)


To the right of the transformer will be the 1/4" jacks for the reverb and vibrato footswitches


Okay??


The other shots show the heaters, faceplate. and most of the pots installed and AC power supply and PT wired up(Waiting on my 1st exciting Hoffman order, It's making it's way from Florida over to Texas I hope it doesn't hit every state! )
The Boards are mostly stuffed, just have to do the bias circuit and maybe the first filter right on the end
mounted them to check placement etc, might still do a little adjusting to straighten them out


One other question...one of my boards has a burnt spot!! I was testing it with my meter and couldn't get any continuity anywhere on it, totally open, but still I think it's not the best idea that I went right through the burnt area...we'll see. Might have to move everything and cut out a section if it becomes a problem. Admittedly I'm kind of impetuous

As you can see I had to mark the boards with marker indicating which sides the tubes would be on as this build is backwards to the conventional fender layout. Very confusing at first!

;note the extra speaker jack hole , moved to accommodate the heater wires...this is a hallmark of my layout 'style'

[Toxophilite]

NO takers on my reverb tranny layour question?


One update is my electrical technician brother says the burnt circuit board likely won't be a problem
I'm curious what others think

[sluckey]

NO takers on my reverb tranny layour question?

Mount the RT so the green and black wires can solder directly to a RCA jack. Hopefully the blue wire will reach the driver tube socket and the red will reach the board.

[Toxophilite]

Thanks!

[Toxophilite]

Hey Sluckey
You said a few posts back

• "Fender used a 47Ω rather than a 100Ω resistor in the NFB divider for 8Ω speakers. The 100Ω like you have was used for 2Ω and 4Ω speaker configurations."

Does this apply if you're using the 8 ohm tap of a multitap OT ?(apologies if this is a really dumb question)

[Willabe]

No.

Let's say you have an OT with a 2, 4, 8 ohm taps. If you hook up the -FB loop to the 8 ohm tap, it will always only see that taps voltage. It doesn't care what the tap is hooked up to the speakers.   

[sluckey]

If you connect your feedback circuit to the 8Ω tap, use a 47Ω resistor like Fender did. Doesn't matter which tap your speaker is connected to.

This is not a critical issue. I have a 100Ω resistor in my TDR. It uses an 8Ω tap. I realized the mistake long after building the amp and plan to correct it if I ever open the amp up again. It's been 9 years now. 

[Toxophilite]

Well I got my amp wired up and fired up


I haven't received my trem pots but I did a bojang with a 2M pot for the speed and a couple of 4.7M resistors for the intensity to try it out (the pots will probably arrive in the next day or so)


Right now the amp is kind of noisy (the bojang trem control) hanging out the side can't help and various other bits to adjust


And I can't seem to get the bass control to work properly (have to check that out more)


However it currently passes signal (not huge amounts as there is almost NO bass) and in my experience that's a big part of the volume


The Harmonic vibrato is working though I think I need to tweak the voltages via the dropping resistors
The reverb works too but is currently a little quiet


All the other plate voltages seem to be in the ballpark so that's good


Obviously much trouble shooting and finishing up needs to be done but so far something has been accomplished!

[Toxophilite]

ooops had the 10k mid accidntally swapped with the 250K bass
better, bottom end is there
but the amp is too quiet
time to start going over things
Build amp, then fix it! 

[Willabe]

but the amp is too quiet

Can you define that a little better?

[Toxophilite]

Okay. compared to me Ab763 deluxes I would say it's significantly quieter, doesn't seem to start breaking up till around 9 on the volume dial, this with bass almost cranked mids at around 3-4 and same with treble
The deluxe (in my apartment) would be nervous making loud and starting to break up at around 4.5 on the volume

[sluckey]

You know the drill. We need voltages for all tube pins (even if the pin reads zero) and all power supply nodes. And repost your final schematic.

[Toxophilite]

here are some voltages:
they're all for the most part LOW!



V1 pre      V2 vibrato    V3 vibrato     V4 reverb(12AT7)  V5 Reverb12ax    V6 PI 12aT    V7 6L6
1- 147       1 - 118       1 - 272           1 +6 - 385           1 - 158               1 - 158          plate - 393
2 -            2 -              2 -                  2                        2                        2                   input grid - -40
3 - 1.2      3 - 1.18       3+8 - 2.48      3+8 9.04             3+8 - 1.22          3 +8 - 67       cathode - 25ma
6 - 148     6  - 158     6 - 269                                 4 - 148              6 - 152
7              7                               
8 - 1.14     8 - 1.22

I changed the schematic except I forgot to change the fact that currently(haha) I'm using a 5U4Gb rectifier as I hadn't made a plug in unit yet
annd as you can see I perhaps unnecessarily added another filtering stage for the reverb and put in a 2watt 1K resitor prior to the preamp...I'm not sure if that's totally unnecessary and or perhaps harmful..it seemed to make sense somehow

I had used an old bumblebee cap in the reverb recovery stage because I forgot to pick up a .003...tuned out it was LEAKY! surprise, so I popped in a new .0047 and it solved the problem with the voltage on the preamp stage of V5 (the voltage was really LOW! 96vdc)


The reverb is going whoppa whoppa whoppa through the speaker


THe tremelo works
the amp is quiet

[Toxophilite]

oh a little adendum. I just tried it with an SS recfier (I borrowed one from another amp that's just using 2 diodes) and most of my voltages jumped up around 20-30 vdc (except for the pre which just came up around 10-15)


the bias current came up to 36 ma and the amp is waaay louder


It makes some big pops on the power and standby (I added the standby for kicks) as well it was making quite a pop when I plugged the guitar cable in.


Still some stuff to check


Annoyingly my hoffmans order came while I was off doing elections training so I have to wait till tomorrow..no doubt some duty to pay!

[Toxophilite]

Did some checking of solder joints and I have all the voltages pretty close, pre a little lowish at 156, power amp, Demonic vibrato which sound great though I only have it 1/2 intensity


the  amp is pretty quiet (noise-wise) plenty loud (volume wise)


The reverb however makes a very scary fast oscillating low(sub low) like noise through the speaker(the sort of think that's REALLY LOUd and sounds like it's going to pop your speakers!).so I currently have it disconnected.
Any ideas on that, maybe it doesn't like the tremelo?
I'm going to go over the circuit

[Toxophilite]

How horribly embarrassing. I'd forgotten to attach a ground wire to the 100K reverb pot!..hmm I wonder why it made that scary noise??
Ah well
Seems to all work pretty good though I might swap out the .22 decoupling pot coming out of the vibrato for something a little bigger and see if I can squeeze a little more bottom out of this unit, That and a bright switch.
Then maybe rearrange some grounds a little


So I'm confused about one(well many) grounding things
I was under the impression that it's best to ground things at ground for the B+ node they are using
But some fothese diagrams show everything but the power amp(and maybe the PI) grounded with the preamp at the input jack
1/2 my reverb and all of the harmonic vibrato use B+ point B(same as the power tubes) so my inclination was to ground it at that point...but then I have wires running everywhere!
which is supposed to be bad

[sluckey]

and all of the harmonic vibrato use B+ point B(same as the power tubes) so my inclination was to ground it at that point...

Well, point B feeds into the vibrato circuit, but V4 and V5 each have their own B+ node. So ground those circuits where their filter caps are grounded, NOT WHERE NODE B CAP IS GROUNDED.

[Toxophilite]

Thanks
I have a little terminal strip beside the vibrato circuit on the board containing the filters and the dropping resistors for that circuit.
i guess this begs the question, where do I ground that node to. I'm assuming the preamp ground bus?
I have two main points right now, a small terminal strip on a PT lug with the center tap, earth ground and power amp, I'm thinking the PI should be there too?
and a bus bar on the preamp vibrato board that grounds to the input jack


The reverb doesn't have any filters but it uses the power tube B+ 12at7 and the preamp B+ 12AX7
It confuses me!

[sluckey]

i guess this begs the question, where do I ground that node to. I'm assuming the preamp ground bus?

We're talking about two filter caps (two nodes), one for the oscillator and one for the modulator. Where are those caps grounded now? I would probably have both grounded with the preamp grounds.

The reverb doesn't have any filters but it uses the power tube B+ 12at7 and the preamp B+ 12AX7
It confuses me!

Ground the driver with the power amp ground. Ground the recovery with the preamp ground.

And remember, all grounds must have zero ohms resistance with the PT high voltage center tap.

[Toxophilite]

Cool! I appreciate that .time to start shortening some wires!
Got my bright switch installed and Now for the lineout and footswitch jacks which I know I should've done beforehand but I was putting off making the decision till I had a better idea of the topography. THis is my relative lack of experience/layout showing.
Besides how else am I going to drive a drill bit through my wiring and shower the inside of my chassis with metal shavings??

[Toxophilite]

I have a couple of cabinets kicking around that it might be good to utilize, or I can start anew (I have a sheet of 1/2" baltic birch(the good stuff)
-The one on the left was originally mounting 2 12s and the converted sherwood S-1000 amp. It's a little deep and a little wide, but I could cut it down front to back pretty easily and side to side with a bit of patience. I would also lengthen the faceplate cutout. It's Baltic Birch


-The one on the right I banged together from an antique armoire my building manager demolished (grrr), though the finish is beat, the ply is really good quality with many plys(like baltic birch) It has a birds-eye maple veneer on the outside and a mahogany veneer on the inside. It currently is mounting my JBL D130 and could be made to fit the harmonilux or visa versa(I would have to bend /cut off0 the original horizontal mounting tabs on the amp chassis).
A vertical mount cutout could be made in the cabinet easily and I would swap the handle to the long side.


They both sound really nice.
I have a 15 and some very usable 12's


Any opinions? I like both and generally don't want anything to be larger than it needs to be (25 years of using a super reverb)

[Toxophilite]

Sorry bumping this back to the amp, I got too ahead of myself


I have a weird problem
My preamp voltages seem to keep getting lower
for a bit I had them at a decent level 160-170 and now they are different every time i fire up the amp and get lower as  it sits there on..like water dripping from a bucket. this morning they were at 98??  I spent some time reheating and checking all the power rail connections and grounds and it seemed to go up to 140 and then slowly start sinkink.
THis is affecting the recovery and preamp stage of the reverb(same B+ node) and maybe the PI to a lesser degree, but not the Power amp B+ node. I've been checking the point that the B+ feeds into the PI and preamp and that seems good


In 10 min of playing with a meter on pin 1 ov V1 it went from 155 vdc to 99 and was still going down


I have a hole in my bucket!

Any other ideas about what to check?

[shooter]

and then slowly start sinkink.

guesses would be you have a slowly dyeing cap or tube.

[Toxophilite]

I swapped out the PI reverb recovery and preamp tube , same deal
Tried  taking out the preamp tube and testing at the reverb recovery 12ax7
B+  on reverb recovery tube still dropping
Took out the reverb recovery tube and tested at the Pi 12at7
And it was still dropping
Al the caps are new. I'm going to pick up a couple more filter supply caps and decoupling caps and swap a few things out(I planned to do the power amp decoupling caps anyway)


Any other ideas. I can watch the meter dropping by tenths of a volt , goes down pretty quickly

[sluckey]

My first bet is on a filter cap. The one farthest up stream (ie, closest to rectifier) that is dropping volts is most likely.

Second bet is look for something hot that should not be hot. Then find out why it's hot.
 

[Toxophilite]

Once again the mighty seers have spoken and all is resolved...at least with that problem!


My 'extra' filter stage on the reverb recovery stage seemed to be the problem
I decided to clip out those filter caps, and the 1K resistor I had seperating it from the preamp stage and BOOM
I had 200 flipping steady volts on V1 and V5  and 199 on my PI !!!! yikes!!
and 420 on my 6L6s at 34 ma  -42 volts


Should I bother bringing those numbers down at all?


Maybe increasing the dropping resistance just before the PI or just after


That would certainly make for more voltage up stream at the Power amp giving the amp a little more juice


What say you? and Thanks very much!!


P.S Got my pots from Doug today (Thanks Doug, quick shipping!!) Holy auto-wah Batman what a sound with the vibrato!
I do get a little thump through the speaker at the highest intensity settings
Also it'd be nice if it went a liiiiittle slower
Any way to accomplish that?

[sluckey]

My revibe uses the same trem circuit. Look at the fast/slow switch.

     http://home.comcast.net/~seluckey/amps/revibe/revibe.pdf

[Toxophilite]

Cool
i'll give that a try I have a 4.7meg resistor that should be close enough and the appropriate pot and a little switch kicking around. So nice when others have laid the ground work


I might add another 2.2 or 4.7 K to the first dropping resistor as I was trying it with some different power tubes and after or maybe 2.2 to both 10K resistors
I'm trying an older pair of 6L6s and I seem to be getting 422 on the plates of teh power tubes...245 on the phase inverter and around 225 on V1 and V5..amp sounds good though. I popped a 12ax7 in the phase inverter spot and it seems to brighten it up a bit, just goofin' around.


from reading people claim the brownface amps are midway between a tweed and a Blackface amp
Less scooped and bright than Bf but more hifi than a tweed. I've never really compared them

I wonder if this is in part a result of the vibrato circuit as I need to push the bass and treble more on this amp than I do the deluxe to achieve a similar sound, also the bright switch is quite a bit less effective (in a good way) than my deluxe builds(which don't have the bright cap)

How hard would it be to add a presence control to this hybrid circuit?

[sluckey]

i'll give that a try I have a 4.7meg resistor that should be close enough and the appropriate pot and a little switch kicking around. So nice when others have laid the ground work

I meant ONLY look at the switch. It's putting a .01 cap in parallel with the original .01 cap. That slows the oscillator down. You can use a switch like I did or you can simply change the original .01 cap to a .02.

All that other stuff is not important toward changing the speed. You may also be interested in the LED since it gives a little eye candy. Red or yellow work best.

[sluckey]

How hard would it be to add a presence control to this hybrid circuit?

Very easy. Just change a couple resistors in the NFB circuit and add a pot/cap. Copy the 5F6A presence/NFB circuit.

[Toxophilite]

ooh that is easy and easy to try with alligator clips to see if I like it before commiting to it(drilling holes)



Is there a way to adjust the vibrato, mine seems to whoop whoop around 7 on the intensity dial and sooner if the speed is turned up higher

[Toxophilite]

Wow that bassman 5F6A presence control has way more effect than the concert 6G-12 one!
i tried both and I really enjoy the tactile sound..with a space echo in front it sure accentuates the hiss though
I guess if I find the max volume of the control a bit much I could just drop the value of the NFB resistor..i think
I'm going to try it tomorrow when I can play it more at volume

[Toxophilite]

a couple questions if i may:


- I was going to install my line out (see schematic)
Would it be okay to mount it on the faceplate between the white reverb knob and the pilot light?
I'd have to run a line over the board from the speaker output
Too potentially noisy? I just know when it's all boxed up it's be harder to get at the tube side as it's going to have a back panel ala a tweed amp




- Harmonic Vibrato whoop whoop after about 7 on the dial (sooner when you turn up the speed) anything I might adjust? idears? (don't know if this is the problem but my voltage on the 2nd 12AX7 in this circuit is about 35 volts too low, 285 rather than 320)


excuse my kooky lead dress..it really is a very quiet amp, even dimed (with no guitar, my giutars have single coils...they're always noisy)


Also a picture of my scary looking SS rectifier, perfectly safe but it should dissuade the unwary