Leslie 147RV

[SandersAudio]

So I have a Leslie 147RV that was missing the back panels when I bought it - which sadly means I lost the serial number and apparently the reverb unit. I bought it about 15 years ago and replaced the upper and lower speakers, the upper rotors and belts. Everything else seems to be working fine except the reverb of course.

I'm not even sure the reverb speaker itself works, but I have some questions about this Leslie.

The reverb amp is missing the fuse - what kind does it take?

As you can see from the pictures, the power cord for the reverb amp is very short - why wouldn't they make it long enough to reach the main amp?

I know there's a specific replacement spring reverb unit for the speaker which I'll probably get if I decide to get the reverb working. Would a spring reverb from a Vox AC30 work in the meantime for testing purposes? The one I have is missing one of the 3 springs but works.

Is there a way to control the volume of the reverb?

I bought oil from Tonewheel General and oiled the upper rotors and tried to oil the lower baffle rod, but I can't seem to get close enough to it, even when removing the speaker and metal rod that holds the baffle in place. It's making some friction noise when running on tremolo and I'm sure it just needs oiled.

Is there a way to remove the baffle to gain access to and oil the bottom part of the rod/axle?

Thanks,
Chris

[David Anderson]

You do not oil the bearings on the lower drum axle. They use sealed ball-bearings that are replaceable. Noise can be from the bearings or some other cause, like missing grommets around the axle ends, a missing spacing washer under the rum, or a loose scrim cloth, if present.

The reverb amp takes the type of fuse described on the front of the amp, which is easily visible in the photo you posted. It should be a 3AG fuse (3AG = general size and shape), which is the standard in pretty much all older gear.

[Jyvoipabo]

Good evening,

The reverb is controlled by a simple volume control. It is not possible to remote control it.

On the vintage AC30s the reverb was piezo. I assume you are talking about newer models using the accutronics 4AB2AIB tank or =.
All the details of the codification are here :
https://organforum.com/forums/forum/...verb-tank-help

Because input impedance = 8 ohm, i think, that should work fine.

If you haven't already done so, consider checking your crossover.

JP

[SandersAudio]

You do not oil the bearings on the lower drum axle. They use sealed ball-bearings that are replaceable. Noise can be from the bearings or some other cause, like missing grommets around the axle ends, a missing spacing washer under the rum, or a loose scrim cloth, if present.

Interesting - is there an easy way to remove the drum? Can you get to it from underneath?

The drum has never had a scrim cloth and has sounded fine when recorded. Would there be any significant benefit to adding one?

The reverb amp takes the type of fuse described on the front of the amp, which is easily visible in the photo you posted. It should be a 3AG fuse (3AG = general size and shape), which is the standard in pretty much all older gear.

Wow - that's embarrassing. Didn't even see that - sorry!

The reverb is controlled by a simple volume control. It is not possible to remote control it.

Ok, thanks. I guess I could wire an on/off switch for it and attach it to the back of the cabinet. Or just use a power strip to plug the reverb amp into. I just hate the thought of that nice reverb amp sitting there and never getting used!

[David Anderson]

Power cycling a tube amp (turning it off and on frequently) is a very bad idea. It causes a lot of wear and tear on an amp.

If you need remote control over reverb, you want to interrupt the signal, as in switching between the speaker load and an appropriate load resistor.

The better solution is to use a Trek II spring reverb unit, which sounds better than this early speaker-driven reverb ever did.

[SandersAudio]

Oh, ok - good to know. I probably won't bother then as I'm only using this in a studio and can add reverb later anyway. I guess that's why the fuse was removed - so the amp doesn't power up.

[SandersAudio]

Just saw this from 2014 user sfp1954: "The first step is usually to replace all the .1 600V caps in the amplifier. They are supposed to be blocking/absorbing the pop."

I'll try this to see if it helps.

[David Anderson]

This only involves pop getting into the audio when switching speeds.

[SandersAudio]

Yes, that's the pop I'm hearing now since I just installed the EIS-147B relay. Thanks!!

[David Anderson]

As far as I know, when installing the EIS relay (and I have installed a few), you remove the two arc-suppressing capacitors on the original relay contacts. Replacing the audio path 0.1uF capacitors should have no effect on reducing pop, so that's probably a waste of time.

One thing that can affect switching pop in 147 amps is poor wire dress. All the AC wires should be "dressed" as far as possible into the corner of the amp chassis away from the audio circuits. In some cases, it was not even done very well at the factory. Sloppy motor wiring will result in pops.

[SandersAudio]

Ok, thanks again - I'll give that a try.

[Sweet Pete]

The reverb amp takes the type of fuse described on the front of the amp, which is easily visible in the photo you posted. It should be a 3AG fuse (3AG = general size and shape), which is the standard in pretty much all older gear.

David raises a good point in that,3AG is NOT the fuse amp rating,but the type/shape of fuse.
Power consumption on 147 is 190 Watts @ 2.1 Amperes 147RV is 250 Watts @ 2.7 Amperes,all 8's expression matted.Below 3 amps.

Reverb amp chassis takes a 3/4 Amp 125V Slo-Blo. 3AG types available in fast blo or ceramic etc,you want Slo-Blo.
Listed in the service manual as part FZ2 /029884.
147 amp has a 1.5 Amp 125V Slo-Blo listed in the same as part FZ1/021766.
Higher rated fuses not recommended unless you want to burn up more than a fuse.
Pay attention to the type of 3AG.
Haven't looked at the under hood safety fuse recently.
Could that be a 3AG as well?

[Jyvoipabo]

Ok, thanks. I guess I could wire an on/off switch for it and attach it to the back of the cabinet. Or just use a power strip to plug the reverb amp into. I just hate the thought of that nice reverb amp sitting there and never getting used!

After removind the transistor input stage, this amp is a very good amp.
It is not very well in its place in the Leslie because on stage, the reverb you can adjust are often in the mixer.

If you are a little handyman you can think of using it elsewhere.
Exemple : Treble amplifier of a Leslie 760. I did it. and the result is fantastic.

JP