Just Bought a Baldwin 200 watt Organ Amplifier at an Estate sale 25 dollars

[silat]

The entire cabinet with the speakers 2x 15 inch speakers as far as I can tell any suggestions on what I can build from it? Oh yeah all the tubes are Gone it had 4x 6l6 and 2x 5u4G. Nice buy for 25 dollars. I will post picks later.

[silat]

Here are some pics.

[silat]

SOME MORE PICS.

[sluckey]

I would be very tempted to just build a point to point 4 x 6L6 AB763 power amp right on that same chassis. Drill out that octal PI socket and put a 12AT7 in the hole. I'd even keep the dual rectifiers but probably switch to 5AR4s. Then you could build any separate preamps to just plug into that monster.

I did something similar with a Wurlitzer juke box amp back in '76. I had a standard AB763 reverb preamp and a AA864 Bassman preamp. And it fed a 2 x 15 cab. Your Baldwin really took me back to that old project!

Look forward to seeing what you do. Keep us posted.

[silat]

 Sluckey, that Ab763 sounds like a really good idea... I have not had one since the early 80's. Can anyone tell what year this thing is by looking at it? Do you think it is 60's??
 

[DummyLoad]

i don't  think your amp is 200w. more likely it is 100watt.

build a marshall 2203 or fender ab763 bandmaster?

--pete

[silat]

It says on the placard that it is, maybe not. A Marshall sounds nice but I am really thinking about the Ab763 blackface.

[shooter]

It says on the placard that it is

That's on the primary side of the PT - 60hz, 200W.  That's what your electric bill see's, not what your ears hear, although they will probably start to bleed at 100W 

[mresistor]

I have one of these, it was out of a Baldwin but mine only had two 6L6Gs in it.  I stripped the connectors on the input side and made a aluminum mount and built a Western Electric preamp using one octal 6SL7 on the input. Then I had to build a string of diodes to bring the HV down to livable levels on the PS input. I mounted up two strips inside and built the PS filtering in it. 
I am using Russian 6n3c power tubes in it. Octal PI.  It has a really sweet round and glassy sound to it. Takes pedals well, and really is a nice amp. The iron is huge, especially that choke. Its as big as the PT. I call it my 8 ball amp. I have a bare cabinet ready for it need to finish it this fall winter. I drilled out the side and mounted the pots like a Marshall amp. I have some thin wood for the faceplate. If you want to see pics just let me know.
You could cap off the extra two power tubes and do something similar. 100W is way too loud unless you're playing in large venues. Mine sort of resembles an Ampeg B15?  Would make a great bass amp.
I used a 5R4 rectifier for max voltage drop, but I suppose a 5U4 or 5V4 would work too.

[silat]

Please! I would love to see some gut shots of it... If you do not mind?

[eleventeen]

The best part is that you didn't have to dismember the rest of the organ (though you  would have gotten a ton of tubes, probably 12AU7s    in there.


I have the 2-6L6 version. There are four modestly irritating things about these amps. I report, you decide. 


1: The choke is simply enormous, talking about make your finished amp 8-10 lbs heavier. It's every bit as large as the OT as you can readily see.


2: The PT puts out VERY high volts, about 450-0-450 (that was measured no load, in my case) You may have to/want to take steps (eg; buy parts and invest time) to reduce your ultimate B+ voltage a solid 50-75 volts. (Could also be my line voltage, but same outcome) I would absolutely start by changing the power supply config to choke input if it isn't already. I can't recall what mine is/was. That just means moving a wire or two, it's nothing, but it will probably knock down your B+ by 20-25 volts which works in your favor.


3: The chassis is 3" tall instead of 2" tall.


4: The chassis is really long. It nearly demands a 200-watt Marshall-sized cabinet if your aim is to box it up.


All that said, if you have no plans to incorporate it into something you move around, zero problem other than the big B+ volts.

[mresistor]

http://i122.photobucket.com/albums/o250/privateacct/IMG_3931_zps4kyl2wfo.jpg


http://i122.photobucket.com/albums/o250/privateacct/IMG_3932_zpspnkhpfik.jpg



http://i122.photobucket.com/albums/o250/privateacct/IMG_3926_zpsjtyjmdho.jpg


http://i122.photobucket.com/albums/o250/privateacct/IMG_3930_zpshbfo1o7b.jpg


http://i122.photobucket.com/albums/o250/privateacct/IMG_3927_zpsnnxys73g.jpg


http://i122.photobucket.com/albums/o250/privateacct/IMG_3928_zpsmwwjzsuf.jpg


http://i122.photobucket.com/albums/o250/privateacct/IMG_3929_zpsslven5yh.jpg


http://i122.photobucket.com/albums/o250/privateacct/IMG_3925_zpsrrbg9mgs.jpg

[silat]

I Appreciate all the input I am not sure what i want to do. I thought wanted the AB763 but all the tubes and money going inot that one but it is one I want. Then you all coming with good ideas also. Money can be an issue. i may have to sit on it for a while. I wish Slukey had pictures of that AB763 he built. there is a lot of heavey iron in this thing but for me the bigger the better I will more than liekly not lug it around anywhere. I could put it on casters though too. I appreciate any all input on this thing.

[mresistor]

I move mine with a small wheel barrow   LOL

[sluckey]

I never took any pics of the amp back then but I did save my documents and later scanned them. Here's the pdf...

     http://home.comcast.net/~seluckey/amps/misc/76_Amp_Project.pdf

[eleventeen]

Well the best thing about old electronic junk is that it has the patience of a saint when it comes to waiting for you figure out what you're gonna do with it. It won't mod itself, it won't run away and join a rock band or anything like that.


With mine, after pondering those things I mentioned in my prior post, I pretty much just swiped the OT and the rest remains as found. You did good if you can use those speakers for something but at the end of the day, the OT was pretty much the most (and only) useful part.

[Toxophilite]

I've successfully cut down those types of cabinets before into more manageable, less fridge-like proportions
They ended up looking quite nice
Looks like a fun project.
You could probably save a few lbs on the build by putting in a normal twin reverb sized choke in lieu of that monster unit

[PRR]

> i don't  think your amp is 200w. more likely it is 100watt.

+1

As Shooter sez, 200W is what goes IN to the chassis. Tube amps from wall to speaker hardly make 50% efficiency; there's some loss just converting from DC to test-audio, there's AC-DC loss, and you have to power Heaters and little tubes.

I'd guess lower than 100W but IAC this is not a "small" amp.

I do not see any urgency to chisel and burn. This was a GOOD MUSICAL amplifier. Put the tubes in it and play some music through it.

The immediate "problem" is that it is designed to take input from an organ console, which is already several Volts. Your guitar is much weaker. You need a preamp. Steal the first two stages of nearly any non-toy guitar amp and add it before this amp.

[kagliostro]

+ 1 for what PRR say


Franco

[DummyLoad]

build a split chassis head or combo. similar to standel etc., and leave the lower intact. the higher B+ probably won't be an issue. mods would be to fuse it, add 3 wire AC for safety ground, and add 5 pin XLR for inter-chassis connection.


i had one that i bought for 100 bux back in 2011. the OT was bad, but i recovered the PT, 3 6L6, and a around a couple dozen sylvania chrome top 6SN7 tubes.


the PS is kind of funky (choke loaded CT) but from what i've read, these amps sound really good.


replace the caps (you need 600V parts) and it should serve you well. i reverse engineered the PS and stopped there when i discovered the OT was a boat anchor. PT schematic is attached, so at least you have somewhere to start.


--pete

[silat]

What is the reasoning behind the overkill on the two 5u4G rectifiers? That is very weird. Thank you Sluckey for letting me see your  Schems!  I still appreciate all that you all have shown me with this project. The only thing that scares me is the price on all the tubes.

[sluckey]

One 5U4 can supply sufficient current for a pair of hungry 6L6s. But a quad of 6L6s may demand more current than a single 5U4 can safely supply. So, just put two 5U4s in parallel. The original Dual Rectifier!     This idea soon became obsolete when 1 amp silicon rectifiers appeared.

[mresistor]

It would be nice to find a suitable choke that is smaller and lighter. But the Henries are unknown on mine. The schematic says 8W 30 Ohm. No henries rating. And wouldn't the resultant voltage drop be dependent on the henries rating?

[eleventeen]

"And wouldn't the resultant voltage drop be dependent on the henries rating?"


Yeah. But in a world of tubes with 10% voltage variation expected and normal, even without a 6-8% line voltage variation, it isn't anything to worry about.

[PRR]

> the PS is kind of funky

Yes, but it is a simple cap-input with added Pi-filtering.

The choke is in the groundy-side, but that works the same.

See attached re-draw.

Since this is cap-input, the choke value only sets the filtering, not the DC Volts.

(Even in a choke-input filter, there is a minimum choke for the load, and any larger value gives the same DC Volts.)

This cap-input design uses a rather small first cap. The DC Volts out really does depend on this cap's size. Using DL's numbers, from 430V to 600V as you go from 4uFd to "huge". If the original caps are *oil*, they are still fine, 430V is fine for 6L6 with *this* OT, keep them. If they are e-caps, they may be shot, use two 10uFd or 22uFd 350-450V in series for each one. (2*22u=11u will raise the voltage a bit, but guitar IS different from organ.)

[mresistor]

I may give a smaller choke a go then, because to reduce the weight of this chassis would be a very good thing. On mine, that choke is literally as big and heavy as the PT. On the OPs 4x power tube unit   it is not. OH BTW upon looking at my schematic for my Baldwin orgasonic, I think it says 8 henries.

[HotBluePlates]

If you replace it, I'll take the big ass choke off your hands... 

[mresistor]

HPB - I will certainly let you know if it becomes available.


If I were to go with say a 50ma, 75 ohm rated at 500volts, wouldn't this shift the frequency of the pi filter? I am supposing that the big choke inductance was selected to work with the 4uf capacitor in the filter. BTW that oil filled cap is not small by any means.

[HotBluePlates]

If I were to go with say a 50ma, 75 ohm rated at 500volts ...

50mA sounds small; the B+ current of the entire amp flows through that choke. If the amp is presently functioning, I'd suggest lifting one end of the choke and inserting an ammeter to measure actual in-use current.

If I were to go with say a 50ma, 75 ohm rated at 500volts, wouldn't this shift the frequency of the pi filter? I am supposing that the big choke inductance was selected to work with the 4uf capacitor in the filter.

The frequency is fixed at 120Hz but the rectified a.c. voltage. Remember this is in the power supply... That said, more or less inductance will give more or less filtering of 120Hz ripple, as the choke works in concert with the caps.

And yes, your Orgasonic schematic says "8H 30Ω" for the choke. Any less-huge modern choke up to 7-8H will have quite a bit more d.c. resistance (like 5 times more). So a smaller choke would also likely be a lower rated inductance, so less ripple filtering.

[DummyLoad]

if you're going to use the same PS, why do you need to mod it? if you want light weight use larger filters with a CRC filter then small(er) choke for screens and preamps.

--pete

[sluckey]

IMO those three pieces of iron should never be separated.

[HotBluePlates]

IMO those three pieces of iron should never be separated.

+1.

I, too, used to think I could rob bits & pieces of a chassis of old tube gear to re-purpose into something else. Once I learned more about how things work and the design tradeoffs which result in a complete, assembled item, I found that all the parts are selected to work well with each other.

Dummyload is right that you could raise the filter caps value and reduce choke inductance; that said, you should expect a rise in d.c. voltage when you make such a change.

[mresistor]

Its probably best to leave it like it is. And it sounds great, it's just really heavy. I have already gone to significant length to lower the HV on it, don't want it higher.
Thanks for the discussion. 

[eleventeen]

You know, I was thinking on this (the high B+) and it occurred to me that your chassis uses two 5U4 and mine (the 2 6L6 version) has but one 5U4.


One would think that with 2 qty 5U4 you would get two 60-volt voltage drops. Yet...I don't think this is true, each phase loses 60 or so volts but the net result is not -120 volts. What does your B+ measure...under load? Just for curiosity.

[silat]

It did not come with an Ac cord but when I get time I will Let you know. I have put it up unitl I get money for the parts. I may get everything next week sometime.

[DummyLoad]

this one gets you a 12AX7 for the driver instead of the 6SL7 like in yours...

any else notice the gap in the choke lams?   

--pete

[mresistor]

Looks some rest on the lams, maybe due to water damage.. 

[HotBluePlates]

One would think that with 2 qty 5U4 you would get two 60-volt voltage drops. Yet...I don't think this is true, each phase loses 60 or so volts but the net result is not -120 volts. What does your B+ measure...under load? Just for curiosity.

2x 5U4's, but they're in parallel, so that's have the diode drop. But then you have 2x the output tubes, so double current. Voltage drop for 4x 6L6/2x 5U4 should be very similar to 2x 6L6/1x 5U4.

[silat]

I been thinking about having to wirie up the preamp and all that it envolves, but I was wondering about the best way to go about it. Do you just make  a special plug or do you just wire it up like everything else?  I am not grasping Sluckey's schematic? As much detail as everyone can give me; from everyone would help. I do not want to mess this up. I want this to be a nice useful amp.

[mresistor]

just use a Fender preamp    common one from any PP Fender amp   and graft it onto your power amp      I mounted mine inside the chassis   but mine is Octal 


you want a 12AX7 preamp     

[mresistor]

for layout  look at the preamp section of a Fender amp layout  like in a  deluxe reverb ... for example

[sluckey]

I would tackle this as two projects. Project one is to fix the Baldwin amp as it is with no modifications. That Baldwin is just a power amp, like pages 2 and 3 of the pdf I linked. It expects a line level signal. It's probably a very good sound power amp too!

Project two is build a preamp. There's not enough room on the Baldwin to add a preamp so build a stand-alone preamp in a separate chassis. AB763 would be a good choice or if you want grit, build a Marshall style. Really, you have a lot more choices. You can borrow filament and B+ from the Baldwin or you can use a small PT just for the preamp. Use RCA phono cable/jacks or standard 1/4" phone cable/jacks to connect the preamp to the power amp.

Doing a split amplifier allows a lot of versatility. Build several different preamp chassis and plug 'n play.

[eleventeen]

Well, there are sort of three levels of decision making. Physical/Preamp Electronics/cable electronics


Are you going to build a cabinet, have the big momma on the bottom right-side up and the preamp and some controls on the top? in a separate chassis? [physical] Or are you going to build it all-in-one?


Want reverb or trem? Other than those selections, what style preamp? Do you expect to have to experiment around a tad with some component values in the preamp? (I would) Thus your first attempt at building the first gain stage (or stages) should not be an exercise in NASA-grade neatness....you want to kind of build up something that can be changed without excess pain; try it for a while and see if you like it. The easy answer is to throw in several terminal strips with too many terminals and start building your first, second, and third revision preamps circuits point-to-point.


Maybe take a look at how a Sunn 200S type amp is built. The early Sunns were flat out Dynaco MkIII amps with a preamp section built point-to-point on a couple of parallel terminal strips. That's exactly what I am suggesting. Sluckey has pix of the guts of one of these.



For a separate chassis type of arrangement, you need B+ and ground and two heater wires, total of four wires, and a shielded coax connection. This is assuming you just want to make the simplest configuration. Very easy would be to use one of the 5U4 sockets for the interconnect. I'd run the coax completely separately, into a shielded jack either 1/4" or RCA and away from the power transfer wires.

[mresistor]

Sluckey - why do you say there isn't enough room in the Baldwin chassis for a preamp. I did it. There is plenty of room IMHO. Well, that is for a single channel preamp. Actually I could have put a lot more preamp in mine as that whole space behind my preamp is empty.  Also , these chassis are 3 inches deep, just have to figure how to mount something in there.
BTW  that weber 6a20 I posted is AB763.

[sluckey]

Sluckey - why do you say there isn't enough room in the Baldwin chassis for a preamp.

I was thinking on a much more elaborate scheme with a couple channels, reverb, trem, etc. Of course there is room to add a single channel one tube preamp. I'm not crazy about having to put it by the OT.


I think it would still be a good idea to fix that amp as is before doing any mods to it.

[DummyLoad]

  > I'm not crazy about having to put it by the OT.

+1

build a separate section for preamp. leave the 6SL7 PI as is. get the amp working with new caps.

you could build a head with a 6" x 2.5" x 17" chassis for the preamp with reverb, depending on the complexity of the preamp. also, you could use a 5f6a or 5e3 chassis for the preamp and just plug all the unused holes.

--pete

[silat]

I am going with this one but I am not too sure about the split chassis and how to connect the two? Sorry I have never done one but I do not want to gut my Baldwin. I cannot picture it since I have done only single chassis.

[sluckey]

I am going with this one but I am not too sure about the split chassis and how to connect the two?

Divide and conquer... Step 1 should be fix the Baldwin.

[Toxophilite]

I know there's a lot of older amps that do this (I had a Gibson once )  but those fender excelsior amps use flexible electrical conduit to connect a separate tube pre and power amp. Seems like a practical and readily available option. Available in electrical supply places or hardware stores