Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on September 13, 2015, 01:34:44 pm
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Hi friends, yesterday at a Ham Fest I got a Leslie Tremolo Unit 656170
this isn't my unit, but is similar (tomorrow I'll make some photo)
(http://i.imgur.com/S19xVPZ.jpg)
(http://i.imgur.com/FvRIt0q.jpg)
The speaker is small (I think a 10" - tomorrow I'll measure it)
I remember Sluckey's and TIMBO's nice realizations
but I've also seen other kind of solution
http://www.youtube.com/watch?v=QxdrGlA_VkI# (http://www.youtube.com/watch?v=QxdrGlA_VkI#)
I don't think to an orizontal solution totally open as in the video, but to something like the Vox Gyrotone
(http://www.nmia.com/~vrbass/vibratone/Vox_Gyrotone-corner.jpg)
like this homebuild unit (that on the photo sits on an amp)
(http://www.nmia.com/~vrbass/vibratone/Bohlender_cab.jpg)
The question is .....
A vertical (like Fender) or an Horizontal (like Vox) solution ?
What do you think about ?
Many Thanks
Franco
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Hi K, I would think that mounting them vertical is the way to go. You'll be surprised the amount of sound that projects through the foam wheel. The unpowered box has a pretty good sound with out the wheel spinning and could be a secondary cab to your rig.
Both of my cabs had 10" speakers and are more than enough. :icon_biggrin:
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The actual unit you get 'may' dictate whether to mount vertically or horizontally. My unit with that small two motor drive assembly has to be mounted on a vertical baffle.
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Thank TIMBO and Steve
Tomorrow I'll post photo and further details, at the moment the drum is not well fixed to the shaft and if I put the speaker on the bottom and
the drum on the top, the drum crawl on the woodden base, this don't happen if the speaker is on the top side and the drum on the bottom
Ideally don't you think that with the drum in horizontal the sound will be better released into the environment ?
Franco
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I'll wait until I see a pic of your actual unit.
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Did the guy in the clip say that he used a FAN controller to vary the speed...
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Yes, he told (but I don't know if he used a lamp dimmer as speed controller)
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Here are the pictures of my unit
(http://i.imgur.com/d3oxZIe.jpg)
(http://i.imgur.com/7BGkBr3.jpg)
(http://i.imgur.com/hqG6AIN.jpg)
(http://i.imgur.com/VtD5zy1.jpg)
(http://i.imgur.com/zgHkpCW.jpg)
http://i.imgur.com/U2iZ6kf.jpg (http://i.imgur.com/U2iZ6kf.jpg)
http://i.imgur.com/AwB0Pe5.jpg (http://i.imgur.com/AwB0Pe5.jpg)
http://i.imgur.com/mBXZfw3.jpg (http://i.imgur.com/mBXZfw3.jpg)
http://i.imgur.com/tn1uu0W.jpg (http://i.imgur.com/tn1uu0W.jpg)
http://i.imgur.com/ShX2vxw.jpg (http://i.imgur.com/ShX2vxw.jpg)
http://i.imgur.com/TZg36hj.jpg (http://i.imgur.com/TZg36hj.jpg)
http://i.imgur.com/RxgCb4n.jpg (http://i.imgur.com/RxgCb4n.jpg)
http://i.imgur.com/FlLEgwC.jpg (http://i.imgur.com/FlLEgwC.jpg)
http://i.imgur.com/GIa7lNP.jpg (http://i.imgur.com/GIa7lNP.jpg)
http://i.imgur.com/LMbCIqo.jpg (http://i.imgur.com/LMbCIqo.jpg)
http://i.imgur.com/nmCWdYy.jpg (http://i.imgur.com/nmCWdYy.jpg)
http://i.imgur.com/WgNdUtJ.jpg (http://i.imgur.com/WgNdUtJ.jpg)
http://i.imgur.com/ZJQT5xX.jpg (http://i.imgur.com/ZJQT5xX.jpg)
The base is 47cm x 49cm
the drum is 37cm diameter, tall 16.5cm
the unit is 30cm tall
the window on the drum is 17cm on the top, 18cm at the base
the speaker diameter is 20cm (unfortutately no 10" a mere 8") and his thickness is 7.5cm
the speaker impedance (I measured) is 9.6ohm and the resistance is 7.9ohm
the hole for the speaker on the panel to the drum is 18cm
the pulley diameter is 14.5cm (a small piece of gum that acted as "suspension" and for traction was broken and I rebuild it)
The shaft is joined to the drum using 2 squared pieces of relatively soft gum
On the link you can see that the smaller motor has the shaft that can move axially
(I rhink when it is on, the shaft moves on the axis and engage the pulley that is fixed to the shaft or the bigger motor)
On the link you can see also the PCB with a pair of (may be) triac or transistor and a relays
the PCB is labeled ELKA F000640
Motors are for 234v use
Franco
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I think all the drums are the same size and they used the mounting bracket/speaker baffle cutout and just popped in different sized speakers, 8"/10"/12"?
This picture shows see the drums 'throat' opening so if you make the speaker baffle larger to use a bigger speaker
part of the speaker cone will fire into the bottom of the drum. But that's probably fine.
The drum bracket that could be made longer so you can put in a bigger speaker. :icon_biggrin:
http://i.imgur.com/ShX2vxw.jpg (http://i.imgur.com/ShX2vxw.jpg)
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OR did they use all the same size drums but use different sized mounting brackets and speaker cutouts?
The 'throat' of the baffle where the sound comes out is quite a bit smaller than the drums outside diameter.
Mine looks like yours K but no little black box.
Drum is ~14" outside diameter, ~7" baffle cutout, ~9" mounting bracket and had an 8" speaker.
My unit (and yours I believe) need to be mounted vertically with the motors on top (^north^) so the weight of the motors cause them to hang/swing down to tighten the pulleys belt.
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Timbo/Sluckey what size speaker came with yours? And are the speaker cutout/mounting bracket/drum size the same as mine?
Drum is ~14" outside diameter, ~7" baffle cutout, ~9" mounting bracket and had an 8" speaker.
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If I remember well Sluckey modified the diameter of the hole for the speaker giving to the bracket a way to be evenly attached
(http://home.comcast.net/~seluckey/amps/leslie/leslie_03.jpg)
My unit (and yours I believe) need to be mounted vertically with the motors on top (^north^) so the weight of the motors cause them to hang/swing down to tighten the pulleys belt.
I think for vertically you mean as in the Fender units, however the motors are mounted in a way that acting on a thumbscrew you can tighten the pulleys belt (see the image)
(http://i.imgur.com/zgHkpCW.jpg)
Franco
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On the link you can see that the smaller motor has the shaft that can move axially (I rhink when it is on, the shaft moves on the axis and engage the pulley that is fixed to the shaft or the bigger motor)
That's basically the same as the drive assembly I have. The small (slow speed) motor shaft does indeed thrust forward about 1/8" to engage a drive wheel mounted on the shaft of the large motor (back side). So the small motor actually turns the shaft of the large motor. When at rest, the shaft of the small motor does not contact the drive wheel. This mechanism does not work reliably when the baffle is in a horizontal plane, so your unit will need to be mounted vertically as in the Fender unit.
I would make it work as is before beginning to adapt for a cabinet or larger speaker. Here's what I did to be able to use a 12" speaker...
http://home.comcast.net/~seluckey/amps/leslie/leslie_03.jpg (http://home.comcast.net/~seluckey/amps/leslie/leslie_03.jpg)
http://home.comcast.net/~seluckey/amps/leslie/leslie_07.jpg (http://home.comcast.net/~seluckey/amps/leslie/leslie_07.jpg)
Drum is ~14" outside diameter, ~7" baffle cutout, ~9" mounting bracket and had an 8" speaker.
That's the same dimensions as mine. My cheese wheel uses a cheap tripod support rather than a wide bar support.
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K, is that your work shop? Looks well stocked! :icon_biggrin:
If I remember well Sluckey modified the diameter of the hole for the speaker giving to the bracket a way to be evenly attached.
Yes that works too. :icon_biggrin:
I think for vertically you mean as in the Fender units, however the motors are mounted in a way that acting on a thumbscrew you can tighten the pulleys belt (see the image)
(http://i.imgur.com/zgHkpCW.jpg)
Yes like in the picture you posted. I know there's an belt tension adjustment but I still think they want the motor unit to swing down other wise they would have mounted the motors so they were pinned/mounted solid to the baffle with no swing.
This mechanism does not work reliably when the baffle is in a horizontal plane, so your unit will need to be mounted vertically as in the Fender unit.
Ahh, good to know. :icon_biggrin:
That's the same dimensions as mine. My cheese wheel uses a cheap tripod support rather than a wide bar support.
Ok, lets see what Timbo has to say. :icon_biggrin:
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> say that he used a FAN controller to vary the speed...
I tried that with disastrous results.... on a half-horsepower attic-fan. If a good induction motor falls far below line speed, the current goes WAY up and the house fills with stinky smoke.
This machine has a very small fan motor. I just put in a 45 Watt duct-fan and it looks like that same motor. I have a couple portable electric heaters which probably use the same motor. It is "impedance protected", meaning you can jam your finger (stall the motor) and it does not quite get hot enough to burn. It is too weak for its physical size, it can't harm itself.
While this type (special shaded-pole) motor wants to run at line speed, you can drag it down. Here the load has huge air-drag. It may be a smooth disk but it is much larger than the fan this motor would pull. If you reduce or chop the line voltage, the motor will run slower; and with this drag, it fall-off fairly smooth.
My duct-fan was plenty of air and way too much noise. I put 25 Ohm and 75 Ohm resistors to give 90% and 75% blow and whirr. It turned OK with a few hundred Ohms but not enough air for my purpose; might give a good speed for mellow trem.
In testing I used a 250r 100W rheostat. But the ones I got from China for $13 were heavy junk, would not turn by hand. 50W would have been plenty (10W marginal) but the cost of good-quality many-Watt rheostats is discouraging. Also the speed/dial relation is not linear, all crowded-up in one end.
For testing, a variable autotransformer might be handy (and more linear), but again the price is daunting, I only mention it because some of you have it for bringing-up sick amplifiers (or sickening healthy amplifiers).
I'll tell you what you'd think might work and does NOT: several uFd of capacitor in series. The impedance seems about right. However the motor is just inductive enough that the cap+motor resonates. The motor runs faster with 4uFd series than it does straight! 140V from a 124V line! This may be a way to go faster, but I wonder how long.
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If I'm not wrong Roly at http://www.guitargear.net.au (http://www.guitargear.net.au) reported he used some impedances (originally to be used with fluoreschent lamps)
to lower the voltage supply of a motor used on a leslie unit, but I don't remember well this thing
Franco
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> impedances (originally to be used with fluorescent lamps)
Ah, that may work very well.
And I did not think of that when I hacked my duct-fan speed, even though I have several sick fluorescent fixtures in the junk pile.
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For testing, a variable autotransformer might be handy (and more linear),
I've read interviews on the Clapton 'Layla' sessions where 1 (or 2?) of the recording engineers and producers said they used a variac (variable autotransformer) to change speed on Clapton's little Fender Leslie. They said it worked well with no problems.
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I've just find the old post of Roly, here it is
http://www.guitargear.net.au/discussion/index.php?topic=31863.0 (http://www.guitargear.net.au/discussion/index.php?topic=31863.0)
Franco
p.s.: I forgot to replay, yes, that's my shop
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p.s.: I forgot to replay, yes, that's my shop
I was wondering about that. :dontknow:
Very nice looking work shop K! :icon_biggrin:
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This is my desktop with homemade drawer
(http://i.imgur.com/t19uOaf.jpg)
(http://i.imgur.com/nvcrREW.jpg)
(http://i.imgur.com/mkjBz4G.jpg)
but my shop is a never-ending story :icon_biggrin:
Franco
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:thumbsup:
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Congratulations! Bitten by the Leslie bug, once you get it up n running the only thing better might be two of em! I'm sure you'll find its easy to modify for larger spkr if you want, even just mounting 10" over 8" hole if need be. I can't say I'm too familiar with horiz. Mount, but Fender's Vibrotone way-with the 3 cutouts-(both sides, and top) along with front firing is really cool sounding, the way it 'sprays' in a circle sort of clock like, around the room...so nice! How about lazy Susan bottom to move side to side (L to R) while spinning...too crazy? Oh yeah, what about ceiling fan speed control? Or sewing machine. Heck, you could diy another from old ceiling fan. And get another speed or 2. I've always figured a decent sounding model could be made as an accessory-small, thin, like a box fan, set in front of your amp. Eh, running on...best wishes, and thumbs up on such a nice clean up workspace.