Leslie 21h with 31h series 3 amp and field coil speaker - connecting a synth

[mpeets]

I would like to connect my old Korg synth to a Leslie 21h. I've been experimenting, but have no real background in this kind of electronics. Plugging the motors into a powered foot switch was simple enough, so I know the motors work. I've identified the power pins on the 31h amp connector and, wired them to AC. The tubes light up. What I don't know is whether the amp actually works or whether the old field coil speaker works. I clipped the audio output from the synth to what I believed were the proper audio connector pins on the amp, but all I get is a buzz. I'm guessing it needs a balanced signal, and I suppose I can probably get an unbalanced to balanced converter. Any advice on how to test the amp and speaker or how to connect these two disparate devices?

[David Anderson]

At this point in history, any tube amp from the 1950s, including Leslie 32H amps, needs to be properly serviced before being put back into service. If you don't know how to determine whether or not it's in proper working order, you need to take it to someone who can.

[mpeets]

So I buy a TWG 21H Series 3 Parts Kit (32H) but I have a problem. My 32H amp has a 3 section can cap (30/30/10 @450V); however, the purchased kit has a 4 section cap (30/30/30/10 @475V). The old cap has what looks like a part number of 850102, but I can't find that anywhere. Any suggestions?

[Wes]

I don't understand, what's the issue?

[DanielP]

I don't understand, what's the issue?

Best if you stuck with your SS 760 "Leslie" Wes, and let the pros handle this one.

My 32H amp has a 3 section can cap (30/30/10 @450V); however, the purchased kit has a 4 section cap (30/30/30/10 @475V).

I experienced the same thing with my 32h amp. You can use the 30-30-30-10 electrolytic cans but it will have to be oriented differently because the icons (square, triangle, etc.) on some of the old cans are different for those than the new. My old 32h amp had a 30-30-10 originally and the 10 had the triangle icon whereas on the new can the 10 is just a "-". So, just make sure you break off the correct ground lug so that the 10 goes in the right spot. That is what I did on mine and it works just fine.

David Anderson, the knowledgeable gentleman who commented earlier in this thread wrote about this also in an old thread with an alternative solution, hopefully he won't mind if I quote him:

All the 21H, 32H, 44W, and 46W amps originally had 30-30-10 @ 450V filter capacitors. You can use a 30-30-30-10 capacitor, but the 10uF section will be in the wrong place if you break off the usual ground lug. On the other hand, you can use CE Distribution's 30-30-30-30uF @ 475V capacitor, and avoid the problem. The extra 20uF of supply capacitance at the 6SN7 driver tube will have no negative effect. Also, because of the way the capacitor socket is wired, there will now be 60uF of capacitance connected directly to the output transformer, which is a good thing in terms of instantaneous current demand.

[Wes]

Wow, are you really treating me like crap because one of my Leslies is a solid state unit? I would think if you wanted to act like a jerk that you could at least start with an ad hominem attack.

Your explanation is appreciated but your attitude is not. The OP did not explain that he was having a fitment issue, I was trying to extract more information from him about the in the hopes of getting him some help or information. If I had known that your arrogant ass was available for help, I would not have bothered.

Can I assume you will be available to answer all model 30 and model 31 queries from now on?

Wes

[Silken Path]

Wes, I'm still looking for a cheap 760. You will be among my first choices to ask for help when I need it.

[DanielP]

Relax, Wes. No need to take yourself so seriously.

All the regulars on the forum here know I'm no pro, which is what could potentially lend the sentence in which I stated "let the pros handle this one" a humourous aspect for those individuals with the astuteness to recognize not just humour but particularly the humour in poking fun at one's self.

Said phenomenon of poking fun at one's self being a wonderful way to remind one not to take one's self too seriously, a characteristic which typically makes a person very boring to be around.

All this perhaps foolishly executed at the very grave and real risk of being wholly and misfortunately misinterpreted on a forum largely dealing with often meticulously particular, precise technical issues. Not to mention that many of these particular meticulous issues precise require maintenence on or around electronic devices potentially carrying very high and possibly life threatening voltages. (370V on a 32H, 420v on a 147…) No doubt a very serious business, not to be taken lightly. Believe me, I know, Wes.

That said, hopefully I'll be forgiven one day for any reckless and ruthless comments in the past directed towards other sensitive, thoughtful fellow human beings. And dually, if possible, for any scathing scorn hidden in seemingly innocent but clearly irreverent attitudes having to with the SS Leslie Pro Line series. And then with the great generosity and boundless expertise of the organ forum's extensive member list we can all proceed in a positive and fruitful manner.

In doing so, perhaps the OP will not only be able to properly orient his 30-30-30-10 electrolytic can and get his 32H amp up to spec, but also take care of any other issues which may be holding him back from realizing his maximum creative potential as a musical artist and human being on his current given gear.

"It's not what you play. It's not how you play. It's the fact that you're playing that counts."

Well said.

[mpeets]

The issue is the four section cap 4 section cap (30/30/30/10 @475V) doesn't fit into where the old 3 section can cap (30/30/10 @450V) was plugged in. I get it that the three section cap probably has not been available for decades, but if the new four section cap doesn't fit, what's the alternative? Can I somehow make the four section cap fit?

[Wes]

mpeets - did you understand DanielP's instructions?

I haven't seen a 31H amp, but my 51C has a socket for the capacitor that is "keyed" by having three holes to fit "four" ground tabs. When you cut one of the four tabs off the capacitor can, it is possible to insert it into the socket.

Make SURE you clip off the correct tab so that the 10uF section goes in the right spot. Do not assume the markings on the new and old capacitors are the same.

Wes

[picothinker]

Relax, Wes. No need to take yourself so seriously.<snip>

That said, hopefully I'll be forgiven one day for any reckless and ruthless comments in the past directed towards other sensitive, thoughtful fellow human beings. And dually, if possible, for any scathing scorn hidden in seemingly innocent but clearly irreverent attitudes having to with the SS Leslie Pro Line series. And then with the great generosity and boundless expertise of the organ forum's extensive member list we can all proceed in a positive and fruitful manner.

</snop>

DanielP, perhaps I read it on a bad night, but my first impression was: WTF? I quoted here lots of backpedaling, but Wes is one of our best and most experienced contributors, players and techs. It did seem reckless and ruthless.

[DanielP]

Mpeets, I'm not sure if you've gotten this taken care of yet. But in case you still aren't certain what needs to be done check this out. First, does your original 30-30-10 cap can look like this? (see photo).



If so, take a look at the values, see how the 10 mfd is indicated with a triangle icon? Now take a look at the new cap 30-30-30-20 can, (I'm assuming this is the same one you have?). See how the 10 mfd is indicated by a dash icon?



Here are both of them side by side, with the clipped tabs at the top. You can see that the icons do not match up, but that the cans are oriented so that both 10 mfd sections are in the same spot.



If these cap cans are the same ones you have then the tab you need to clip on your new can cap is going to be on the OUTER rim between the square and triangle icons, just like in the photo.

[DanielP]

mpeets, I know we've been more or less focusing on getting the can cap oriented in your amp, but keep in mind that if you want the amp to truly run properly there are other components in the amp which more than likely also will need attention.

You may just want to take the amp to someone who can get it all up to spec for you, preferably even someone who can check out the whole speaker and let you know exactly what it will take to get it in shape. With luck your driver and woofer are both working properly, if the motors haven't been cleaned and oiled you will want to do that. Recapping the crossover is always nice. 21Hs are awesome speakers and well worth it, they often do need some attention if they haven't been used for a lengthy period of time though.

Also, it sounds like you have some ideas on how you want to connect your Korg to the Leslie. Keep in mind that there are a couple preamps on the market which work with 6H (or 122) style Leslies. One is the Trek UC1A, another is made by a company called Speakeasy, and there is a quite rare model by Hamptone(?) I believe which occasionally come up for sale. These preamps will power your speaker, give you some tonal options and also a footswitch to control the rotors. None, however, are particularly cheap.

Depending on how you plan on running the speaker, you may want to do some research as the cost of first fixing up the speaker and then the cost of either purchasing a preamp vs. the cost and time of getting a working DIY way like you described in your first post of connecting your Korg to the Leslie. All of which may be more of a commitment than you initially anticipated. Just a heads up!