Harmonilux Reverb AA964???

[Toxophilite]

Could this work as an unholy pairing of good things??

[sluckey]

That's exactly the way I'd approach it.

[Toxophilite]

That's good enough for me!
Maybe next week buy the bits (have to wait for extra funds)
And give it a go

[Toxophilite]

I'm finally revisiting this potential build
I'm making a parts list and ooooeee there sure is a lot of components
I don't think there's a local source for a 4m ra pot or even a 3m ra pot (though I see Hoffmans has one)
Where the *&@$^$#($@$ does one get a 10m L pot????


I'm pretty curious to try this tremelo but I'm curious if those that have used it think it's worth it...I've only heard it on youtube videos and that's never a great example

[sluckey]

That circuit is the same as the vibrato circuit used in the revibe. Just use Hoffman's 3M and 10M pots. They work fine.

[Toxophilite]

Cool thanks
I didn't notice the 10m pots...maybe it's finally time top put in an order.

[Toxophilite]

I have a 7 henry choke off of a Baldwin 51 organ power amp chassis. The original amp used 2 6L6Gcs and a 5U4gb rectifier. the choke was hooked pretty well straight to the rectifier
I know vibrolux amps only want a 4 henry choke
Is over henry-ing okay?

[sluckey]

Yes, if it's up to the current.

[Toxophilite]

Cool
On the hammond site they have a vibrolux reverb choke the same as a deluxes 4L  50 ma
If I was to go with the larger one and say it had  a larger current rating, say closer to 90ma , is that a big deal?
Just seems like it can handle more but one doesn't have to use it's entire capabilities, yes?

[Willabe]

If you had a piece of 12ga wire rated for 20A, could you only run 5A through it and be fine?

Just seems like it can handle more but one doesn't have to use it's entire capabilities, yes?

Yes.

[shooter]

I'm lurking back here, looking at a data-sheet, your 90mA looks close, 80-118mA for your bias n B+, still fuzzy on henry, the bigger he is the better he filters? 

[Willabe]

I have a 7 henry choke off of a Baldwin 51 organ power amp chassis. The original amp used 2 6L6Gcs and a 5U4gb rectifier. the choke was hooked pretty well straight to the rectifier

[Toxophilite]

Thanks
I know some of this stuff is obvious and I have been reading on it bu it is nice to have those that are in the know confirm my thinking on some of these things and I appreciate that


I'm also debating on buying one from hammond simply because the hammond unit is a nice light small one and the Baldwin organ one is about the size and weight of a deluxe reverb OT!


Just to clarify I'm not using the the other Baldwin components(OT and PT) I'm using a Hammond M3 amp chassis and the PT that comes with it
I have a multiap vibrolux type OT ordered off Hammond a while back

[Willabe]

I'm also debating on buying one from hammond simply because the hammond unit is a nice light small one and the Baldwin organ one is about the size and weight of a deluxe reverb OT!

That's the thing with salvaging sometimes. If you have room on the chassis, use it. 

[Toxophilite]

Getting going here
I was panning on using this Hammond M3 chassis and PT
Originally i was going to use the tube sockets where they are but I though a tweed bassman sort of socket and transformer orientation might work well and enable me to build a tweed type cab which I find pleasing looking.


-As you can see all down the 'new' tube socket edge there's a series of long oblong cutouts. so I could mount a long plate down that side(probably Aluminium) drill holes, and mount the sockets there. (I have new ones..yay!)


-leave the PT where it is and put the rest os the transformers and maybe caps(maybe can cap , maybe cab barn maybe inside, still deciding) on the same side I would also be covering most of that side with a aluminium plate ( have extra aluminum kicking around)


-Use the mostly blank edge for all the controls which will be facing up


Seems sensible to me. I was curious if the different transformer orientation would mess with my reverb pan, but this will be a taller cabinet (I'm probably going to use my JBL D130 in it)


Any other pitfalls I'm not seeing?

[Willabe]

You forgot to post a pic of the chassis.

[Toxophilite]

Crap! and I took such nice ones


Tonight then when  I get home
It's a hammond AO-29 chassis I think, From a Hammond M3 I have removed Everything except the PT
Here's a stock photo of the unit I have , mentally remove EVERYTHING except the PT  
The tubes would be mounted where the brown terminal strip is now (there's several long oblongs of space behind it)


Another question, besides space considerations and price is there any advantage to using a cap barn arrangement with individual caps over using a multi section can cap?
I'm thinking a cap barn might have less B+ leads running hither and thither

[Toxophilite]

here's the photos that go with the post...2 posts ago

[Willabe]

Ummm, I think you have room for that salvaged choke. 

[Toxophilite]

yes but, yes but...my other questions!

[Toxophilite]

No takers on the use of this chassis in a tweed orientation??
 seems perfectly possible to me
I was just wondering if anyone noticed any glaring problems with the idea

[Toxophilite]

So I've been slaving over a proper schematic for this amp
and here it is
I wonder if a couple people could check it out for me

Right now everything is off a AA964 Vibrolux Reverb except:
- the Harmonic Vibrato Circuit(apparently I have Ham-onic Vibrato...which could be tasty)
- the Hoffman bias steal
- Line out
- SS rectifier (might've been overkill with the 4 diodes)

My main point of concern is where the signal comes out of the Harmonic vibrato into the next stage
I'm not sure if I have that right

[sluckey]

Here are a few things I see on the schematic...

• Wipers of bass, treble, and speed pots must be connected to something.
• Some of the tube pin numbers are written backwards.
• 1Ω resistors on output tubes must be grounded.
• 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.
• 220K connected to V3-1 should be connected to V3-2. It's usually mounted directly on the reverb return (or footswitch) phono jack.
• V3A cathode resistor should be 1500Ω. You would use 820Ω only if V3A and V3B share a common cathode resistor like the original Fender circuit.

My main point of concern is where the signal comes out of the Harmonic vibrato into the next stage

I'd try it like that but be prepared to experiment once it's built if you're not happy with it. You may also want to experiment with where you pick off the reverb input signal. Another possible option would be the bottom side of the 3.3M/10pF. I'd design the board layout with these two points in mind.

An AO-29 PT will support a tube rectifier if you prefer. 4 diodes is fine too if you need a higher B+.

[Toxophilite]

Thanks for looking at it!


-the wipers on the schematics I was copying slash diagonally through the resistor part and Jschem doesn't have that symbol
I will see if I can edit the symbol a bit.
- I was flipping the tube symbols around to make it easier to copy the original schmetaic layouts and forgot to NOT flip the symbols. might fix that too
- OOOps have fixed the ground on the power tube cathodes now, forgot to do it
- Would 47K be best on the NFB divider if I have a multitap OT ? I plan- to (at least initially) use my JBL D130 so it's 8 ohms
But if I can hunt down a couple of nice 10s I might go that way too
- I thought the schematic had it going to ground? I was using the AA964 vibrolux schematic
- the aa964 has a 2200 ohm resistor on V2 and the 820 on V3A, I'll look at other circuits, maybe it's a silverface thing??


I was wondering how the harmonic vibrato would react to an extra gain stage after it, reading on the 6G12 concert seemed to suggest it didn't have piles of preamp gain


I appreciate the suggestions regarding moving things around a bit
I'm curious how it'll turn out


I have some 5U4Gbs but I think I want a little more B= or at least that was the idea. I'll probably make a plug in unit to keep my options open


A question. I have an extra dark green wire tap on my PT. It goes to a 'pedal cut' pot and produces about 27 VAC when the Pt primaries are getting 120VAC
I wonder if it could be of any use. otherwise I'll just cap it off

[sluckey]

Would 47K be best on the NFB divider if I have a multitap OT ? I plan- to (at least initially) use my JBL D130 so it's 8 ohms

It's 47 ohms, not 47K. Fender used 47Ω whenever the NFB was connected to an 8Ω speaker tap. 100Ω was used if NFB is connected to a 2Ω or 4Ω speaker tap.

I thought the schematic had it going to ground? I was using the AA964 vibrolux schematic

Are you talking about the 220K resistor I mentioned? If so, yes, one end connects to ground. But the other end connects to pin 2, not pin 1, just like the AA964 schematic shows.

the aa964 has a 2200 ohm resistor on V2 and the 820 on V3A, I'll look at other circuits, maybe it's a silverface thing??

It's not a silverface thing. It's all about sharing cathode resistors. Look again at your schematic. True, there is a 820Ω resistor on the cathode of V3A. But V3A cathode is also connected to V3B cathode, so you have two cathodes sharing the same 820Ω resistor. If you want to use the 820 you should remove the 1500Ω/22µF from pin 8 and connect pins 3 and 8 together. If you don't want to share a single 820Ω cathode resistor, you should change it to 1500Ω.

A question. I have an extra dark green wire tap on my PT. It goes to a 'pedal cut' pot and produces about 27 VAC when the Pt primaries are getting 120VAC. I wonder if it could be of any use. otherwise I'll just cap it off

Not enough voltage to use as a bias tap for 6L6s, so just cap it off. This reminds me though. Since you don't have a 50VAC tap on that PT, you'll need to feed the bias circuit from the HT winding. This means you will need to change that 470Ω/3W to 100K/1W (like you would see on a Princeton Reverb).

[Willabe]

In your drawing the bias is wrong. It should not be connected to the B+ D node and the junction of the .1 cap/1K5 grid stopper for the 2nd power tube.

[Toxophilite]

ooops!


-Sorry the 47K comment was a oops in my noggin..couldn't sleep last night, yes 47 ohms


- and also yes i hooked up that 220K to the wrong spot I checked it again and fixed it, thanks!


- Ans yes again, you are so right I forgot I replaced the 'E' point on V3b as it confused me


Is it fine to share the cathode on V3 as was done originally ?(saves on space and components?


- Good call on the bias, my deluxes have the 100K there ala the princeton, but i switched to to the Hoffman Ab763 setup when I did this schematic, I'll switch it back




Thanks Willabe for noticing that (re the bias), I was moving whole sections around and I think the program attched taht line to those two points. It shouldn't have been attached and I fixed it


A bit better now?

[sluckey]

Is it fine to share the cathode on V3 as was done originally ?(saves on space and components?

I bet you know the answer to that! 

[Toxophilite]

Right duhh
If it was done originally it was probably fine

[Toxophilite]

I've ordered my first bits from Hoffmans!
Gonna start installing tube sockets etc tomorrow!
yeeha

[Willabe]

You would have to test this for your self, but some say, that separating V1a from V1b, or any other 2 gain stages with a shared K R/bypass cap, gives more touch/dynamic feel.   

   

[Toxophilite]

Well I was just testing the PT on this hammond(It's a replacement PT obviously the original got cooked and the new ones leads are soldered in.
Unloaded with a 5U4gb in the rectifier socket and measuring across a 22 Uf cap between pin 8 of the recitifier and the centertap (as Sluckey suggested many many mons ago)


I get about 500VDC
I wonder what that translates to when load down by a couple of 6L6Gcs 4 12ax7s and a 2  12at7s?


Anyone have a rough estimate??

[Toxophilite]

On my deluxe with a tube rectifier, plugged straight into the wall, unloaded I have 455vdc measured at point A
With the tubes in that drops to 425  and then 416 after the choke
The dluxe has 2 6v6s 212AT7s and 3 12AX7s
total drop from unloaded, measured at point B is about 40 VDC
Probably more with 6L6GCs and another 12AX7


Oh and I checked the accuracy of my variac scale and it's a little off
When I'm actually putting out 120vdc into the Hammond AO-29 PT I actually get 475 unloaded and this with a 5U4Gb or a SS rectifier. So i should probably hopefully end up nicely in the vibrolux range once it's loaded down with all those tubes!

[sluckey]

Anyone have a rough estimate??

Unless someone is familiar with that particular PT a rough estimate is just a wild ass guess. If you have a 5000Ω 50W resistor you can put a 100mA load on the power supply. This won't actually be a 100mA load because the voltage will drop, but it will be enough load to get some kind of idea.

[octal]

I just glanced quickly at this thread and didn't see any one else mention it (maybe I overlooked it?)  but I notice that you aren't using the split plate resistor on the final triode stage before the harmonic vibrato.  On the 6G12, the plate resistor is a divider with 100K / 6.8K.  Without that, you're going to have WAY more gain before the vib circuit, maybe to the point of overdriving it.

hope that helps

Nathan

[sluckey]

On the 6G12, the plate resistor is a divider with 100K / 6.8K.

Good catch!

[Toxophilite]

Cool, Thanks!
Will the lowered gain affect the reverb circuit do you think?

[sluckey]

You could continue to pick off the reverb input signal just as your schematic shows but relocate the input for the vibrato to the junction of the voltage divider.

Or, and I like this better, move the reverb input to the bottom side of that 3.3M/10pF just as Fender did. The added effect will be that now the vibrato signal will pass thru the reverb. Hopefully that would be a good thing?

[Toxophilite]

Like this then?

[sluckey]

Yes. That's how I'd try it first. I'd also plan the layout such that if I needed to move the reverb input I could easily do so.

[Toxophilite]

I like the idea of a presence control, maybe try that instead of the 120pf bright switch arrangement. could I just steal the whole setup from the concert circuit? or would the different PI make it not as effective?

[sluckey]

Why not just build the 6G12 and add on the reverb?

[Toxophilite]

Well I'd thought of that but


I'm not sure if my Pt will supply a high enough voltage to the 6L6GCs
The 6G12 has 456 on the plates of the 6L6Gcs


I'm thinking I might end up more in the neighbourhood of 415 and it might be even lower with the higher negative bias voltage required , not sure if this matters other than just getting less power out of the amp


Also I dont' have experience with these amps too and I'm curious how different they sound from a AB763 type of circuit which is more of a know quantity for me

I'm game though, from what I hear the concert is a less gainy amp which tends to break up less..but that is just hearsay really

[Toxophilite]

So I initially imagined my layout would be:


preamp
reverb
harmonic tremelo
phase inverter
power amp


but I'm thinking it would be good to swap the order of the reverb and vibrato



preamp
harmonic vibrato
Reverb
phase inverter
Power amp


Will it cause a problem with the reverb tranny to be close to the PI and power amp?? , my chassis is pretty long
And can anyone forsee a problem using this chassis in a tweed sort of configuration?

[Toxophilite]

well on my way to plugging all the holes in the chassis, I love pop rivets, I've replaced many a mercedes floor with organ sheet metal, seam filler and pop rivets!

[Toxophilite]

Tube sockets in, full speed ahead
OT and choke next
This one is going to be a southpaw!

[Toxophilite]

a choke, a fancy multitap hammond OT and a power jack, reverb transformer is in the mail still

[Willabe]

1 thing, your PT is a lay down, so you could have all 3 pieces of iron on a different plane.

PT is shielded and has a copper band, very good, OT is shielded, very good too.

With respect to each other, orientation/position of PT is good, orientation/position of OT is good, just turn the choke 90degs. Then all 3 have their cor's on a different plain from each other, quieter. 

Edit; Or leave the choke as is and turn the OT 90degs, OT primary side facing towards the PT.
 
 

 

[PRR]

> I love pop rivets

My experience is that the popped-off heads eventually rattle inside the rivets. You may someday want to go in with some goo to damp that.

[Toxophilite]

Better Transformer Orientation?