I got suckered into hauling home a neglected 1963 Wurlitzer 4100bw organ for my budding jazz pianist son. 7868 Power tubes were shot, but all the others (5BC3, 9x12AX7, 29x12FQ8, 4x6EU7) test good.
This particular organ uses tube oscillators and dividers, rather than reeds or tonewheels - thus the pile of 12FQ8s. From what I've seen, it's got a great mellow tone when it's in good shape.
To get started, I swapped in some marginal 7868s and replaced the shot 40uF reservoir cap, and I was able to get some very quiet sounds, which tells me the oscillators are all working (whew!) Scope shows the signal hitting the power tube grids is tiny, so next I'm going to work backward through the preamp to determine where the signal is getting lost. I'll replace the rest of the electrolytics along the way.
The motor for the Spectratone (a Leslie-esque spinning speaker) runs continuously, by design; I'm going to add a switch for that, because it adds a lot of noise that's not always necessary. It needs a new belt too, but that's neither here nor there.
Voltages are hot, as I would expect from something designed for 110V running on my 124-125V wall voltage. It's not egregious, though. Plate voltage is 410V vs. 395V on the schematic. Screens are 380V vs. 365V. Preamp supplies are 325V vs. 310V and 295V vs. 270V. Bias is running the other way, though, at -15V when it should be -17V. I'll probably put in an adjustment pot for that.
Not sure whether I want to replace the 7868s with 7591 and new sockets, or 6P41S and a lowered screen supply.
Has anybody else ever worked on these? Any advice? Known trouble spots?
This particular organ uses tube oscillators and dividers, rather than reeds or tonewheels - thus the pile of 12FQ8s. From what I've seen, it's got a great mellow tone when it's in good shape.
To get started, I swapped in some marginal 7868s and replaced the shot 40uF reservoir cap, and I was able to get some very quiet sounds, which tells me the oscillators are all working (whew!) Scope shows the signal hitting the power tube grids is tiny, so next I'm going to work backward through the preamp to determine where the signal is getting lost. I'll replace the rest of the electrolytics along the way.
The motor for the Spectratone (a Leslie-esque spinning speaker) runs continuously, by design; I'm going to add a switch for that, because it adds a lot of noise that's not always necessary. It needs a new belt too, but that's neither here nor there.
Voltages are hot, as I would expect from something designed for 110V running on my 124-125V wall voltage. It's not egregious, though. Plate voltage is 410V vs. 395V on the schematic. Screens are 380V vs. 365V. Preamp supplies are 325V vs. 310V and 295V vs. 270V. Bias is running the other way, though, at -15V when it should be -17V. I'll probably put in an adjustment pot for that.
Not sure whether I want to replace the 7868s with 7591 and new sockets, or 6P41S and a lowered screen supply.
Has anybody else ever worked on these? Any advice? Known trouble spots?
Ha! As I went to check the voltages in the preamp, I discovered a broken lead on a coupling cap. Ran an alligator clip jumper from it to the corresponding grid, and she roared to life! Woo hoo!
Nice, your organ is probably more portable than my Wurlitzer Model 25 at least.
Seems you got lucky and just need to sort out power tubes for it.
Seems you got lucky and just need to sort out power tubes for it.
I would keep the 7868's in there. Unlike previously you can buy newly manufactured tubes at a reasonable price from what I understand.
110V is pre-WWII.
117V was common in 1963.
395/410 is 0.963; times your 124.5V is 120V back when those voltages were measured.
This is only 4% different and all tubewerk is +/-10% at least.
Portable is ... relative. it's still >250lbs, and required a trailer and a friend to retrieve 😀. Not looking forward to getting it up the stairs once it's sorted.
It's certainly playable now, and the boy is over the moon about it. Still needs a few things, but nothing too hairy.
I'd not recommend that, 'cause I can't imagine at all that a Wurlitzer organ's sound gets anywhere next to the Hammond JS used to play, let alone his playing skills 😉.
Best regards!
Best regards!
Yeah, if I take him to the Chicken Shack, next thing he'll be demanding a Hammond!
There are actually a couple M3s and M100 units around here for peanuts, but they are WAY heavy. Maybe when I can recruit two more friends to help ...
There are actually a couple M3s and M100 units around here for peanuts, but they are WAY heavy. Maybe when I can recruit two more friends to help ...
My 1964 Wurli 4500 was full of really cheap electrolytic caps. White plastic ones, and black ones that were even worse. Made no sound at all until many of those were replaced. 4500 is a transistor model, of course. The 1955 vacuum tube Wurli at the church had all the ecaps replaced by a pro before I got there, but was motorboating occasionally when I first visited, probably because of all the dust in the amps. Rather than spend hours & hours cleaning every high voltage part of dust, we moved in a 1980 Allen with more than two sounds.
BTW if you are going to do this more than once, a couple of 2x4 sheets of UHMW plastic help skid these things around swiftly: McMaster-Carr
I push them over door sills with a 6' board to rock them on and a sheet of the stuff.
Up the stairs I wrap them with a car haul strap, then a rope loop on one end, then use a porta-pull to provide the motion. Anchor for the porta pull is a 8' pipe stuck through an upstairs door frame, with phone books on the ends to protect the sheetrock. Takes 1 helper to keep the organ from falling over while I provide the oomph to rise up. Takes an extra chain or strap to hold the organ halfway while you unwind the porta pull for another 10' lift.
More power to your son. I like recreating those old 50's 60's organ riffs that used to fill the breaks in the hits. I play some JS Bach, too, 24 pedals is all one needs to play his best stuff like Passacaglia & Fugue Cmin. That low C! riff. Can't play guitar, skin is too oily to grow calluses.
As far as Hammond sounds, those midi encoders are a coupla hundred. that plus a PC or laptop to run jorgan software, you can have any sound you want. Wurlis have silver key contacts, are worth the effort to extend the life by midi conversion. Watch the 200 v on the pedal contacts, needs padding down. Conn's by contrast, use flexible plastic for key contacts: a sudden death contact if there ever was one.
If you midify, the cheapest outboard amp is a mono Peavey MMA-xxxx usually for $50 to $60. Today on ebay there is a working mma-8150, 150 W, for $60 delivered in US. MMA-875T at 75 watts are usually about $50. Make sure you get the RCA jack or XLR connector input card, the screw terminal cards are insensitive for phone lines or something.
BTW if you are going to do this more than once, a couple of 2x4 sheets of UHMW plastic help skid these things around swiftly: McMaster-Carr
I push them over door sills with a 6' board to rock them on and a sheet of the stuff.
Up the stairs I wrap them with a car haul strap, then a rope loop on one end, then use a porta-pull to provide the motion. Anchor for the porta pull is a 8' pipe stuck through an upstairs door frame, with phone books on the ends to protect the sheetrock. Takes 1 helper to keep the organ from falling over while I provide the oomph to rise up. Takes an extra chain or strap to hold the organ halfway while you unwind the porta pull for another 10' lift.
More power to your son. I like recreating those old 50's 60's organ riffs that used to fill the breaks in the hits. I play some JS Bach, too, 24 pedals is all one needs to play his best stuff like Passacaglia & Fugue Cmin. That low C! riff. Can't play guitar, skin is too oily to grow calluses.
As far as Hammond sounds, those midi encoders are a coupla hundred. that plus a PC or laptop to run jorgan software, you can have any sound you want. Wurlis have silver key contacts, are worth the effort to extend the life by midi conversion. Watch the 200 v on the pedal contacts, needs padding down. Conn's by contrast, use flexible plastic for key contacts: a sudden death contact if there ever was one.
If you midify, the cheapest outboard amp is a mono Peavey MMA-xxxx usually for $50 to $60. Today on ebay there is a working mma-8150, 150 W, for $60 delivered in US. MMA-875T at 75 watts are usually about $50. Make sure you get the RCA jack or XLR connector input card, the screw terminal cards are insensitive for phone lines or something.
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I got a Hammond M3 for free in Denver last year. It just needed oiling.
I am fairly sure it weighs less than the Wurlitzer you have.
I think the later model M3s lost 50-100 pounds when they went to permanent magnet speaker and they lightened the tone wheel cover.
I am fairly sure it weighs less than the Wurlitzer you have.
I think the later model M3s lost 50-100 pounds when they went to permanent magnet speaker and they lightened the tone wheel cover.