OK, I could blame it on the sudden run of summer weather... or the chores around the house... or the high temps in the garage. But the unvarnished truth is I've been slacking-off on the M3 over the last week or two. Yeah, all those things above are factors, but it's time to put the nose to the grindstone on this project.
So, this weekend is moving weekend - I'm going to move the organ into my basement. It will be easier to work on down there, not to mention cooler, too. The garage is getting quite warm these days (into the 90's). I got a combination power cord grommet and stress-relief plug from my friend Joe (thanks Joe!) that will go in, along with the new fuse holder and a 1/8" mono jack for my line out. I'm going with 1/8" rather than the more standard 1/4" because there is limited room on the amp chassis to add a jack.
I may also be buying a used Peavey KB-60 keyboard amp from Daddy's Junky Music. It should be in at the local store in a few days. If it looks and works good, it will be a better amplifier solution than the Carvin bass combo I'm currently using. The Peavey has a 12" woofer and a horn tweeter and features 2 separate input channels, and a headphone output for silent practice.
So we'll see how this all goes and hopefully I'll have a lot of news to share here on babyb3 after the weekend!
Wednesday, May 26, 2010
Wednesday, May 19, 2010
Bringing Back Baby - Links Edition
It's been a busy week here... not much time to work on the Baby.
Here's a few Hammond/Hammond-related links I've found interesting:
"Hammond M3 vs. B3" - A YouTube overview of the similarities and differences between the M3 and the B3... unfortunately they guy uses a Nord Electro for the "B3" but it's still a good overview.
"Hammond M3 with Wah and Boss RT-20" - If you can't afford a real Leslie, the Boss RT-20 simulator isn't half-bad!
"The Ventilator" - A fantastic Leslie simulator pedal made in Germany... gets rave reviews (and costs $500 too)... still cheaper than a new 122A ($3200)!! Company website here.
"John Lord's Hammond Sound" - Deep Purple organist John Lord talks about how he got his signature overdriven, over-the-top sound.
That's it for now, enjoy! And I will get back into the organ this weekend, I promise!
Here's a few Hammond/Hammond-related links I've found interesting:
"Hammond M3 vs. B3" - A YouTube overview of the similarities and differences between the M3 and the B3... unfortunately they guy uses a Nord Electro for the "B3" but it's still a good overview.
"Hammond M3 with Wah and Boss RT-20" - If you can't afford a real Leslie, the Boss RT-20 simulator isn't half-bad!
"The Ventilator" - A fantastic Leslie simulator pedal made in Germany... gets rave reviews (and costs $500 too)... still cheaper than a new 122A ($3200)!! Company website here.
"John Lord's Hammond Sound" - Deep Purple organist John Lord talks about how he got his signature overdriven, over-the-top sound.
That's it for now, enjoy! And I will get back into the organ this weekend, I promise!
Thursday, May 13, 2010
Amplifier Progress Update
As I mentioned, a new batch of tubes arrived this past Monday, from Electron Tube Enterprises in Maine. ETE is owned and operated by Dick Bergeron, whom I worked with for a few years about 12 years ago. Dick sells NOS (New, Old-Stock) and used vacuum tubes at very reasonable prices. I picked up enough tubes to finish repopulating the amplifier with it's full complement of tubes.
Box of tubes, waiting to be installed
The AO-29 amplifier, with all tubes installed
Tuesday night I put the new tubes into the amp and gave it go. The good news is that the percussion and bass pedals are working! The bad news: there is now some rushing and crackle-y noises in the audio output from the amp. It seems to be worse when the organ is cold, and mostly goes away once the amp is warmed-up. So more work there to chase down the source of the noise. I have also found that the lowest pitch drawbar for the lower manual is somewhat intermittent and touchy. Probably some dirty contacts.
The percussion feature is pretty cool. The addition of percussion makes this a "3" level model, just like it's big sister the B3. Percussion in this case has nothing to do with rhythm - its an extra amplifier stage that adds some harmonic content to the beginning of a note that is played, giving it some extra "pop" or percussive sound. Here's a pretty lame video of me playing around on the organ with and without percussion... remember, I can't actually play keyboard yet so be kind 8):
Box of tubes, waiting to be installed
The AO-29 amplifier, with all tubes installed
Tuesday night I put the new tubes into the amp and gave it go. The good news is that the percussion and bass pedals are working! The bad news: there is now some rushing and crackle-y noises in the audio output from the amp. It seems to be worse when the organ is cold, and mostly goes away once the amp is warmed-up. So more work there to chase down the source of the noise. I have also found that the lowest pitch drawbar for the lower manual is somewhat intermittent and touchy. Probably some dirty contacts.
The percussion feature is pretty cool. The addition of percussion makes this a "3" level model, just like it's big sister the B3. Percussion in this case has nothing to do with rhythm - its an extra amplifier stage that adds some harmonic content to the beginning of a note that is played, giving it some extra "pop" or percussive sound. Here's a pretty lame video of me playing around on the organ with and without percussion... remember, I can't actually play keyboard yet so be kind 8):
BabyB3, Late Night Edition
Well it's been a busy week so far... didn't do the "safety" work on the amp this weekend because it was just too damn cold in the garage (snowed a good part of the day on Sunday). Late night at band practice tonight... so no time to do a decent post tonight (it's now 12:22AM as I write this...).
The quick update: more tubes arrived Monday in the mail, so more progress made on Tuesday! Look for a full update tomorrow night. Might have a lead on a strain relief/grommet for the power cord, too.
The quick update: more tubes arrived Monday in the mail, so more progress made on Tuesday! Look for a full update tomorrow night. Might have a lead on a strain relief/grommet for the power cord, too.
Friday, May 7, 2010
Safety, Safety, Safety....
While I'm waiting for another batch of tubes to arrive for the amp, I think I will address a couple electrical safety concerns this weekend. Take a look at this picture, do you see any problems?
OK, well first someone before me installed a 3-wire electrical cord and made a nice solid ground contact to the chassis with the green wire. That's great! But - there's no grommet or strain relief in the hole in the chassis where the power cord enters. The sharp edge of the chassis could eventually cut into the power cord. Also there's no strain relief, nothing to prevent a sharp pull on the cord from damaging the wires where they connect to the solder tabs in the chassis. So I'm going to try to find a grommet to fit the hole, and figure out some way to provide some strain relief.
One more safety item - there is no provision for fusing in the power supply. If something shorts, the only protection is the mains circuit breaker - 20A in the case of my house! That's a lot of current. So I'm going to install a fuse holder next to the line cord inlet in the chassis, with a 3 amp or so fuse installed.
OK, well first someone before me installed a 3-wire electrical cord and made a nice solid ground contact to the chassis with the green wire. That's great! But - there's no grommet or strain relief in the hole in the chassis where the power cord enters. The sharp edge of the chassis could eventually cut into the power cord. Also there's no strain relief, nothing to prevent a sharp pull on the cord from damaging the wires where they connect to the solder tabs in the chassis. So I'm going to try to find a grommet to fit the hole, and figure out some way to provide some strain relief.
One more safety item - there is no provision for fusing in the power supply. If something shorts, the only protection is the mains circuit breaker - 20A in the case of my house! That's a lot of current. So I'm going to install a fuse holder next to the line cord inlet in the chassis, with a 3 amp or so fuse installed.
Monday, May 3, 2010
Major Progress
I'm happy to report some major progress over the weekend with the M3!
First, I got the AO-29 amplifier ready for servicing by disconnecting the three wires on the left front of the chassis that supply 120V AC power to the motors in the tone generator. I didn't want the tone generator running while working on the amplifier. This also removed the "run" switch from the circuit, so I made my own on/off switch for the amplifier using a common household light switch, a plastic electrical work box, a switch plate cover, and a few feet of 2 wire lamp cord. These were all materials I had stored away in the workshop from other projects around the house. I hooked up one end of the lamp cord to the terminals on the light switch and the other to the "blue" and "black" wire terminals on the amp chassis. Now, I could turn the amp on and off right where is was working, rather than go around front to the "run" switch.
Next step was to remove the bolts holding the amp down to the cabinet, and I disconnected the linkage for the expression pedal. I also had to remove the green and black wires that go the the switch on the expression pedal. I was then able to lift the chassis up and rotate it 90 degrees onto it's side, with the underside facing me. A couple blocks of 2x4 wood help provide some slack for the rest of the wiring still connected to the amplifier:
I powered the amp up with no tubes, and checked the AC voltages coming out of the power transformer. Filament voltages looked good, and the secondary measured about 760V AC, which agreed nicely with the schematic (380V from winding to center-tap). I turned the power off and inserted the 5U4GB rectifier tube; turned AC back on and started to measure DC voltage points. First thing I noticed was all the B+ voltages were 80-90V higher than the schematic indicated (more on that later). Nothing smoked, and so I decided to go ahead and put the remaining tubes I had available. These 4 tubes were enough to get the manuals, vibrato, and intermediate preamplifier sections working.
I remeasured DC voltages and found them all still 80-90V high. I decided to press on anyway. I disconnected my home-made on/off switch and reconnected the power supply wires for the tone generator motors. Next, I tapped into the intermediate preamplifier with a 0.01uF disk ceramic capacitor at R40, between V4b and V3b (sorry, not the best picture):
The wire connected to the cap goes to a RCA phono plug, plugged into the line input on an old Carvin bass combo amp I own. The ground side of the wire goes to a screw on the AO-29 chassis. With this all set, I started up the M3, and turned on the bass amp. Pulling out a few drawbars, I turned up the input volume on the bass amp and hit a key on the organ....
SOUND! YooHoo!! After a bit more fiddling with levels and the disconnected expression pedal control, I got a pretty decent sound level coming out of the amp, with no sign of hum or other bad sounds. I was then able to verify that the vibrato was working perfectly for both manuals, and all but one key (the highest one on the lower manual) were working fine, too!
Here is a really bad video of my oldest soon noodling around on the organ - basically shot this to prove that it was now making some sounds 8-):
Remember those voltages that were too high? I posted a question about it to the "Hammond Zone" forum on YahooGroups and almost immediately got the answer that it was likely the missing power amplifier tubes that was responsible. Of course! Without the tubes drawing current, and with no regulation to speak of in these old tube amp power supplies, the DC voltage will rise much higher than with the power tubes in place.
Next step is to get some 6V6 power tubes, because the voltage without them is too close to the working limit of alot of the capacitors in this old amp. I will also pick-up tubes for the percussion and bass pedal sections of the amplifier at the same time and see if I can get the rest of the preamp working.
First, I got the AO-29 amplifier ready for servicing by disconnecting the three wires on the left front of the chassis that supply 120V AC power to the motors in the tone generator. I didn't want the tone generator running while working on the amplifier. This also removed the "run" switch from the circuit, so I made my own on/off switch for the amplifier using a common household light switch, a plastic electrical work box, a switch plate cover, and a few feet of 2 wire lamp cord. These were all materials I had stored away in the workshop from other projects around the house. I hooked up one end of the lamp cord to the terminals on the light switch and the other to the "blue" and "black" wire terminals on the amp chassis. Now, I could turn the amp on and off right where is was working, rather than go around front to the "run" switch.
Next step was to remove the bolts holding the amp down to the cabinet, and I disconnected the linkage for the expression pedal. I also had to remove the green and black wires that go the the switch on the expression pedal. I was then able to lift the chassis up and rotate it 90 degrees onto it's side, with the underside facing me. A couple blocks of 2x4 wood help provide some slack for the rest of the wiring still connected to the amplifier:
I powered the amp up with no tubes, and checked the AC voltages coming out of the power transformer. Filament voltages looked good, and the secondary measured about 760V AC, which agreed nicely with the schematic (380V from winding to center-tap). I turned the power off and inserted the 5U4GB rectifier tube; turned AC back on and started to measure DC voltage points. First thing I noticed was all the B+ voltages were 80-90V higher than the schematic indicated (more on that later). Nothing smoked, and so I decided to go ahead and put the remaining tubes I had available. These 4 tubes were enough to get the manuals, vibrato, and intermediate preamplifier sections working.
I remeasured DC voltages and found them all still 80-90V high. I decided to press on anyway. I disconnected my home-made on/off switch and reconnected the power supply wires for the tone generator motors. Next, I tapped into the intermediate preamplifier with a 0.01uF disk ceramic capacitor at R40, between V4b and V3b (sorry, not the best picture):
The wire connected to the cap goes to a RCA phono plug, plugged into the line input on an old Carvin bass combo amp I own. The ground side of the wire goes to a screw on the AO-29 chassis. With this all set, I started up the M3, and turned on the bass amp. Pulling out a few drawbars, I turned up the input volume on the bass amp and hit a key on the organ....
SOUND! YooHoo!! After a bit more fiddling with levels and the disconnected expression pedal control, I got a pretty decent sound level coming out of the amp, with no sign of hum or other bad sounds. I was then able to verify that the vibrato was working perfectly for both manuals, and all but one key (the highest one on the lower manual) were working fine, too!
Here is a really bad video of my oldest soon noodling around on the organ - basically shot this to prove that it was now making some sounds 8-):
Remember those voltages that were too high? I posted a question about it to the "Hammond Zone" forum on YahooGroups and almost immediately got the answer that it was likely the missing power amplifier tubes that was responsible. Of course! Without the tubes drawing current, and with no regulation to speak of in these old tube amp power supplies, the DC voltage will rise much higher than with the power tubes in place.
Next step is to get some 6V6 power tubes, because the voltage without them is too close to the working limit of alot of the capacitors in this old amp. I will also pick-up tubes for the percussion and bass pedal sections of the amplifier at the same time and see if I can get the rest of the preamp working.
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