Webster 88-24 amp? Possible conversion to Ampeg R12R?

[1blueheron]

I am trying to gather any info possible on this particular amp.  It currently resides in a Allen S12S organ.  I go pick the thing up tonight.  I have plugged it in and everything lights.  It passes tone and it does not seem to be humming or hissing to any great extent.   It has a compliment of over 30 Tung-Sol 6SN7 tubes apart from the amplifier itself.  Some massive power supplies and transformers. Lots of neat parts and goodies.

I can't find any information on this amp on the Web.

I am interested in rebuilding it as a Guitar amp for my son or perhaps trading it parting it out to get what I need to build a guitar amp for him.  I am assuming I will have to create a preamp for it.

 

[Platefire]

Webster/Chicago use to make a lot of Reel to Reel recorders and audio amps. I would guess that they must of made the audio amp for this organ manufacturer. The second picture has the makings of a good all octal tube guitar amp. I can't tell what the tubes are by looking but my best guess would be V1=6SC7, V2=6SJ7 Phase Inverter, v3 & 4 0ne old coke bottle 6L6 and a more modern 6L6GC and V5=5Y3 Rectifier. The others pixs I can't tell??? Power supplies for the other tubes? Platefire

[1blueheron]

Platefire,

Thank you for the response.

Just finished pulling the amp and transformers out, cleaning them up and doing inventory.  Here is what I have been able to log:

Amplifier
Tube design is 1- 5U4G (rectifier?), 1- 6J5, 1- 6SL7GT (preamp?), 2- 6L6G (power?) of which one is the original Coke bottle style and the other appears to be a newer 6L6GB.  Some oil from the leslie rotating peaker shaft appears to have dripped in that location and probably caused premature failure, thus it was replaced.  All tubes are RCA/USA most stamped 5-52

The large transformer has the number 13115 on the underside of the chassis.  The small aluminum cased transformer looks like it has 14898 stamped on it but is hard to read.

Other than needing the power cord replaced, the amplifier appears to be in excellent working condition.  We turned it on and played the organ for about 20 min.  It was very quiet.  No signs of bad caps or leaking voltage based on a listening.

It has a volume control, speaker outputs for 4, 8, 15 ohm speakers and an input jack that resembles an old style screw on unbalance microphone input.  There is a strange plug on it that says 1-low, 2-center, 3 high.  Not sure what that is?  It has a 2A fuse.  SN# is 28323 Type 88-24  and it says 117V,  104 watts.  Webster Electric Co. Racine, WI

Miscellaneous chassis #1 transformers...

Airdesign P-60602
Airdesign C-50254   

These are mounted on a chassis with a strange blue finned device (not sure what it is).  The outputs form this chassis are labelled as #1-14V, #2 GRD.  It has a 3A fuse.  Guessing this is the for the heaters on the bank of 42- 6SN7 tubes?

Miscellaneous chassis #2 Transformers...


Airdesign 20815 / 366544
Airdesign P-60602
Airdesign P or F (cant tell for sure) 90049-1

outputs on this chassis are labelled as #1-switch, #2 GND, #3 switch, #4 B-,  and 6.0V FIL.  It has a 5A fuse.  It has 110V outlets into which the other chassis were plugged in.


I don't want to get ahead of myself here.
?'s:

1. Do you think this amp will make a good guitar amp with these tubes?
2. What is the estimated output with this configuration? 
3. Does this amp need a pre-amp for guitar use or can we just connect to the input jack and use the built in volume control?
4. With proper bias adjustment I'm assuming we could swap the mismatched 6L6 tubes with matched pairs of EL34 or 6v6?
5. Do you know anything about the other transformers I mentioned?
6. Is there anything I should avoid doing that might mess this up?

I have lots of parts around and some additional tubes should I need to put together a pre-amp.  12AX7, 12AU7, 6SN7 etc.

The organ has also provided me with hordes of vintage caps, wire, and turret boards.  The leslie speaker is way cool and it works so I plan to build a cabinet just for it and put it to use.

I will try to post up some pics of everything tomorrow.  Kinda excited about this project.

[1blueheron]

Here are some more pics of the Webster Electric Type 88-24 after I pulled it out of the organ and cleaned it up a bit, the socket below the one labeled as a 6L6 is the second 6L6 which was replaced with a 6L6GB.  The print on the chassis is a bit difficult to read in the picture:

[1blueheron]

Here are some pics of the other chassis, Can anyone tell me what the big blue object is on chassis1?  A resistor with heat dissappator maybe?

[1blueheron]

Here is a picture of some of the bonus parts:

[1blueheron]

And then there is the "gyrophonic speaker system" that works, just needs a new belt and proper cleaning and lubrication:

[sluckey]

Here are some pics of the other chassis, Can anyone tell me what the big blue object is on chassis1?  A resistor with heat dissappator maybe?

selenium rectifier

[1blueheron]

Here are some pics of the other chassis, Can anyone tell me what the big blue object is on chassis1?  A resistor with heat dissipator maybe?

selenium rectifier

Thanks Sluckey!  I am learning!

[Platefire]

On your Weber amp, some of the first steps would be to making a guitar input and tone stack to your Existing Phase inverter(6SL7). Not to familiar with the 6J7 but from what I see is a single gain stage triode. You really need a two gain stage preamp tube for your new guitar input and to drive a tone stack. I would call the back of your amp the side with the speaker terminals and the power cord and fuse holder. You have the whole front of your amp chassis that is clear of stuff that could become your front face plate where the input jack, volume, tone, power switch and pilot light in which you would have to add in. Just giving you an idea of how I would approach converting it to a guitar amp--you choose. Do you know how to read a schematic? and was there a schematic of the amp attached to the organ??? having that schematic would be a help in planning your conversion but not totally necessary. Early Fender amps used Octal preamps and phase inverters before moving to the the latter 9 pin 12ax tubes. One of those early Fender Octal schematics might be a a good example to build your input jack to first gain stage and tone stack prior to phase inverter. Use could use your existing 6J7 socket and rewire it for a twin triode pre-amp tube.

So my recommendations would be to build input and tone stack up to the phase inverter and leave the phase inverter and power amp as is. You could always change that latter if need be.
that way you could see what you got as a guitar amp and tweak from there. Just throwing out some ideas. Platefire

[1blueheron]

On your Weber amp, some of the first steps would be to making a guitar input and tone stack to your Existing Phase inverter(6SL7). Not to familiar with the 6J7 but from what I see is a single gain stage triode. You really need a two gain stage preamp tube for your new guitar input and to drive a tone stack. I would call the back of your amp the side with the speaker terminals and the power cord and fuse holder. You have the whole front of your amp chassis that is clear of stuff that could become your front face plate where the input jack, volume, tone, power switch and pilot light in which you would have to add in. Just giving you an idea of how I would approach converting it to a guitar amp--you choose. Do you know how to read a schematic? and was there a schematic of the amp attached to the organ??? having that schematic would be a help in planning your conversion but not totally necessary. Early Fender amps used Octal preamps and phase inverters before moving to the the latter 9 pin 12ax tubes. One of those early Fender Octal schematics might be a a good example to build your input jack to first gain stage and tone stack prior to phase inverter. Use could use your existing 6J7 socket and rewire it for a twin triode pre-amp tube.

So my recommendations would be to build input and tone stack up to the phase inverter and leave the phase inverter and power amp as is. You could always change that latter if need be.
that way you could see what you got as a guitar amp and tweak from there. Just throwing out some ideas. Platefire

Platefire, that makes a lot of sense.  There was no schematic for the amp.  I have emailed Allen Organ to see if they can send me one if they have it.  If not I might try the tedious task of creating one by tracing it out by hand.   I am not a schematic reading wizard but i know basic component symbols and line diagrams.  Getting values on all the resistors will be a bit of drudgery but my son kinda digs decoding that type stuff so maybe he will do it. 

As for the 2 stage pre-amp, I have been doing some reading since you posted.  It seems like I might be able to replace the 6J5 single triode with a 6SN7 as the twin triode as you mention?  I don't know.  Lot's of reading but no practical and useful knowledge when it comes to things tubey

I ran across a couple things that might be applicable?  A Trainwreck topology with 6SN7's for the tone stack?  A 1956 Knight with 6SN7's?   

Or maybe 2- 6SN7's with 4 cascaded triodes? 

There seems to be some concerns about microphonics on octal preamps.  Because of this and the weight of this unit I am thinking it would be best to build it as a head rather than a combo. 

If I need to go to 12AX7 or such I can but I like the sound of the octals and think it would be nice to do something a little different If I can make it work.

[Platefire]

Your on the right track. Good research and studying the subject helps a bunch.

We mostly all use ExpressSCH software to draw our schematics on this forum. It is a free download and it works great. It also makes everybody's schematic accessible and interchangeable. With a little practice, it's pretty easy to build a schematic. This is a GIF copy of a schematic I did on that program to give you an idea what the finished product looks like. Also here is a link to a Download of the program.https://expresssch.apponic.com/

[sluckey]

I converted a Rock-Ola juke box amp to a guitar amp. Uses 6SN7, 6SN7, 2 x 6L6, and 5U4. I kept the PI and Power Amp and just converted the preamp to a Fender AB763 circuit. This would work well in your amp.

     http://sluckeyamps.com/rocky/rocky.htm   (schematic at bottom of page)

Or, many of the old Ampegs would work well too. Here's one I built in an old radio chassis...

     http://sluckeyamps.com/RCA/RCA.htm   (schematic at bottom of page)

[1blueheron]

Thanks guys for all the help so far.  Got email back from Allen Organs today.  They want 50.00 + S&H for a technical info packet on the organ.  No guarantee schematic is in it and no parts available outside authorized dealer.  So I went schematic hunting and think I found something really close.  It is a Webster 85 - 25.  Guessing they just took this amp and tweeked it for the Allen application.  It uses all the same tubes but leaves out the 6J5.

It is as follows:
  V1= 6LS7GT AF Amp
V2 = 6L6 Power output
V3= 6L6 Power output
V4 = 5U4G Rectifier. 

It shows a portion of a tube providing phase inversion but it does not define which tube it is and my Schematic reading ability is primitive. 

It appears the 1/2/3 input (low, center, High) is to control input impedance.   It says "teletalk connect jumpers 1&3, 50ohm impedance connect 1&2 and for 500ohm impedance omit jumper between 1&2.


I am going to download the program you linked to and I will draw it up in there and share.

[1blueheron]

So I am beginning to trace out the amp wiring.  So far here is the tube sequence:

Input ==> volume Potentiometer ==> V1

V1 = 6J5
V2 = 6SL7GT
V3 = 6L6G
V4 = 6L6G
V5 = 5U4G

[PRR]

.

[1blueheron]

Thank you PRR!

I have been pouring over schematics since last night.  I think I am coming up with a plan, of course I really don't have a clue how to go about some of this.  I think I would like to keep the amp intact as is until I have at least had a chance to see what it sounds like.   


I have some additional chassis and I am thinking I can build several different modular pre-amp sections that I can change out and experiment with by just plugging them in.  There are 11 of these 3 tube chassis and 1 with 6 tubes, all octal.  Each one connects via an octal base/plug.  Each one has a turret style panel for caps/resistors and there are 6 pots on each one.

From what I have been able to gather, I should be able to make 1 with a very simple pre-amp section to front end the amp using a 6SN7 in cascode as shown in the following schematic I found.  Does this look correct?

[PRR]

I don't think a cascode is either simple or really valuable; there are other opinions. Obviously if you are making many alternate preamps, a cascode should be on the short-list.

Does the amp need a preamp? The 85-25 clearly does, because it does not have enough gain. But your 88-24 has that extra pentode, which could be way more gain, though there should be a volume/gain control after the first stage.

Assuming the 88-24 "is" the 85-24 plus another stage, it should not take long to spot the differences and document them.

That thing with the 5 doughnuts *may* be a very nice trem/phase effect. Don't cut it up willy-nilly.

[bmccowan]

I would recommend that you seriously consider the projects that Sluckey recommended. His schematics are very clear and accurate. And he is super helpful. His projects have helped me figure out several of mine, and both amps he mentioned are on my build list (which is way too long.) And I also suggest that you do not shy away from using octal preamp tubes. I'm a cantankerous old guy who believes the tube industry switched to those annoying little 12v tubes to save $ on materials - all industries do that, so why not tubes. I enjoy the sound of octals and my arthritic fingers and old eyes enjoy wiring up the larger sockets.
BTW, I think I have that model Webster in my stash. I'm on travels right now, so cannot check the model #. To my mind they are well made, have good transformers, and good sockets - all the building blocks. When I get back, I might move it up to the bench and start a project.

[1blueheron]

PRR,

The more I look at it, the more I think you are right, I think I already have a preamp stage of some sort in that 6J5.  Is there something specific to look for as far as pin out, etc. that I could look at and tell how the 6J5 was functioning?  My tube physics are still a bit infantile.  I plan to get the new power cord on it tonight if time allows.  After that I think I will connect to a speaker,  give it an input signal and see what happens...   I am attaching 3 pics with pinouts denoted in red (pretty small you will have to open pictures), maybe someone can tell if it has a preamp stage from this?

The thing with the 5 doughnuts, as best as I can find out is a tone generator. I believe the "doughnuts" are inductors?  I believe the inductors and capacitors worked as a filtering network to create the different harmonics needed for each note and all the stops.  One of the doughnuts was labelled as A#.   Although I have disassembled 1 of them, there are still 10 of them that look almost identical to that one.

Bmccowan,

By all means I plan to stick with the all octal setup.  Would love to know if you have the same amp in your stash.  From all the docs I have been able to find on Allen Organs, they seemed to have had a penchant for only using high end stuff of the day. 

As a note to the pictures/labels below, the "V#" designation  I have assigned is just how I view them and not based on anything other than distance from the input.  Not sure if this is right as far as sequence goes.

[1blueheron]

I installed a new power cord and connected a guitar directly to the input connection on the amp.  It produced some amplification but not it was very low gain.  So either there is something that needs to be changed to correct input impedance or there is no preamp stage.

In looking at schematics and taking into consideration the recommendations of Sluckey to consider an ampeg design, I have found that the Ampeg R12R in its early forms and in the Heritage series used 2- 7SN7's, 2- 7SL7's, 2-6L6's.  The only real diffference in tube compliment is the 5AU4 Vs. 5AR4 which if I understand correctly is a minimal difference. 

I like the sound of the Reverberocket and I am considering using the chassis and useable components to make a reverberocket clone. I feel like this might be easier than trying to build a preamp and then trying to tweak the existing amp that I do not have a legitamate schematic for to share and lack the knowledge to do on my own.  Would this be a mistake? 

[shooter]

Would this be a mistake?

there are no mistakes here, just learning opportunities 
try jacking in and mp3 player, or something with a line out capability,  ~~ 1vac.
that will help you know the parts you wanna re-use work before you build something with bad parts.  If you really "catch the bug", the circuit is pretty easy to create a working schematic from.  You can just print out a PI and 2 pp power tubes from any amp, even use PRR's example, then start at the input and follow wires, note what's different, till you have a schematic.

[PRR]

> it was very low gain.

The 3-pin socket next to the input connector seems to do something to the supply voltage of the first tube. It *could* be a remote volume control. Some tracing and voltage-checks here would tell more.

[1blueheron]

PRR,  I suspect you may be on to something there.  The organ foot volume control pedal would be a "remote volume control"  and I suspect that's where the 3 pin connector was wired to.  I will need to check that out.  Don't have access to it for the next couple days while traveling but will trace out as soon as I get home. 

Shooter,

If PRR's suggestion doesn't solve the mystery, I will try connecting something with higher output and see what happens.

[1blueheron]

> it was very low gain.

The 3-pin socket next to the input connector seems to do something to the supply voltage of the first tube. It *could* be a remote volume control. Some tracing and voltage-checks here would tell more.

PRR,

You were exactly right.  The 3 prong plug was connected to the remote volume control on the foot pedal.  I cut it loose, resoldered the wires, plugged it in and it works!   It's still not exactly loud.  With both volume controls turned all the way up it is just comfortable to listen to.  Very clean.

I guess now it's time to build a guitar input stage/preamp.

Looking at Sluckey's RCA/RCA schematic and might start with , build on a separate chassis,  see what happens and go from there.

[1blueheron]

Think I have enough to begin laying something out.  Going to start a new thread on the build.

[bmccowan]

Hi Blue Heron,
I am back from travels and checked out my Webster. The number is different - 34517 type 212-23648. But, it looks identical inside and out and has the same tube and transformer compliment. So who knows how Webster assigned #s. I never tried hard to chase down a schematic because it would not be that useful to me as I would not be retaining this as an organ amplifier. When I get around to it, I would rewire the 1st preamp socket for either a dual triode (6SL7 or 6SC7) or a pentode (6SJ7) perhaps and include a simple V&T tone stack. Or even just go with a vol control, tweaking the component values for the tone I like, and controlling further from the guitar.
I would be likely to loosely follow a Fender 5C5 Pro schematic or a Valco schematic from the late 40s early 50s. Myself, I would not try to make a simple design complex, as simple tweed era amps have some of the coolest tones ever, and the Webster has all the trappings of an early tweed era amp.
I may start that amp next after finishing my current project. If I do, I would welcome sharing notes with you.

[1blueheron]

Hi Blue Heron,
I am back from travels and checked out my Webster. The number is different - 34517 type 212-23648. But, it looks identical inside and out and has the same tube and transformer compliment. So who knows how Webster assigned #s. I never tried hard to chase down a schematic because it would not be that useful to me as I would not be retaining this as an organ amplifier. When I get around to it, I would rewire the 1st preamp socket for either a dual triode (6SL7 or 6SC7) or a pentode (6SJ7) perhaps and include a simple V&T tone stack. Or even just go with a vol control, tweaking the component values for the tone I like, and controlling further from the guitar.
I would be likely to loosely follow a Fender 5C5 Pro schematic or a Valco schematic from the late 40s early 50s. Myself, I would not try to make a simple design complex, as simple tweed era amps have some of the coolest tones ever, and the Webster has all the trappings of an early tweed era amp.
I may start that amp next after finishing my current project. If I do, I would welcome sharing notes with you.

Thanks for responding.  I Googled that model number and you are right, it looks identical.  I have traced the amp out and have pretty much finished a schematic for it.  Would be happy to share/compare notes.

[bmccowan]

Great - please post your schematic when done and I'll compare it against what I have. I am now thinking about a plan for mine - scouring through a bunch of old Valco schematics, but a Bassman 5B6 is tempting too. Somewhere I read that George Fullerton said that was the best amp they ever built. Simple schematic like the Webster.

[bmccowan]

Or maybe I'd lean toward the Octal version of the Valco Supro Supreme. Check out this:
http://truevintageguitar.com/inventory/1951-valco-supro-supreme-510-1b-circuit/
I think I have an old Valco Gretsch with that circuit that is waiting in the wings. I bought it on ebay several years ago with the seller stating, "works great." It did not work at all and I removed the chassis back plate and found a dead mouse and most of the wires chewed away. Amazing how those mice can get through a taped carton undetected!

[1blueheron]

Yes, I have faced the mouse plague before.  This chassis is amazingly clean.

From what I have been able to read up on the Allen/Webster organ amps, Allen was very particular and used only the best parts available at the time.  I am pretty pumped up about doing something with this.

In case you didn't spot it,  most of the conversation on this has shifted to this thread https://el34world.com/Forum/index.php?topic=23736.0

Sluckey is assisting me with getting a clean schematic drawn and then coming up with a guitar preamp/tone stack to go with it.  We are looking at swapping out the 6J5 with a twin triode.

You will find the drawings there.  If you have anything to share, I would love to see it, especially if you have any info on the make of the transformers.

[bmccowan]

Thanks - I did see the other thread but did not go deep enough to realize it was the Webster project. I was thrown off by the chickens! From what I have seen, Sluckey is the right guy to be helping. I will certainly jump in in I have anything useful from my own experience.