T 524 Project: foldback, busamps, extra pedals, Leslie 122 connection

[Joakim Bergstrom]

Dear enthusiasts, I would be thankful for some input with regard to various issues I need to have clarified in order to be able to continue my project.

1. Pro and cons re. one and two octaves lower manual foldback. The organ vill have bass roll off filters removed etc and be connected to a Leslie 122 but I d like to keep the internal loudspeaker setup together with an on off switch so it can be used on low volyme without the Leslie.
2. Regarding the busamps, Carsten M. suggests replacing the C240, 236 etc capacitors while Kon Zississ suggests leaving them in place and soldering some additional bi polar capacitors in parallell instead. Do the different solutions lead to different sound or is it just two different techniques to achieve the same effect?
3. I am curious to know how complicated it would be to add more pedals to the organ, like I see on Brendon Wright's impressive rig. Would the manual foldback affect the pedals in any way? I have one extra T 500 I can use for donor parts.
4. When trying to disconnect the tape recorder in order to remove it - i have a hum (green wire -strong hum, black wire -a bit hum (maybe just needs to be grounded, other wires no affection). Despite the fact that several others in the forum tell the wires could be cut and isolated.
5. Does it matter what Hfe value should be used for the PNP type - BC557 transistors to replace the NPN transistors on the percussion board (Carsten M's mod)
6. I understand that it is possible controlling the Leslie speed with DC voltage of approx 50 Volts in a separate cord between a control on the organ and the speaker amp instead of the original solution of mixing the VDC with the signal cables between the organ and the Leslie. Does anyone know from where (on the organ or on the Leslie) it could be most convenient to tap the necessary voltage required for this circuit? Does it mean that I can use a ground cable between the Leslie (which is supposed to have a balanced connection with the organ) and the organ's chassis and use the ground as a negative for the circuit for the motor speed control and then use a simple on off button on the organ to open/close the circuit? I understand that I will have to hook up the positive VDC cable to the cable connected to the tremolo/chorus relay in the Leslie amp.
7. I read here about several ways to tap the signal from the organ to an external Leslie, e.g. directly from the internal loudspeakers, from the existing tone cabinet socket, from the organ's preamp or from the headphones outlet. Which would be the best location considering I d like to retain the organ's reverb and expression pedal functioning and minimise hum?
8. Despite having changed all electrolytes in the organ, disconnected the Rythm III unit, the lamp transformer, checked for bad grounds and disconnected the transformer on the vibrato amp, the organ still produces more hum than acceptable. Any ideas what to do next?

[Brendon Wright]

Hi Joakim!
1. The cons of folding back the LM by two octaves is that you can't solo in the higher octaves.
The pro for the same is that you can get the low notes found on a full console, in fact an extra half octave though it tends to get muddy down that low.

3. The extra pedals aren't as good as they look, I've actually removed them since, in order to have the swell pedal in the proper, accessible place.
The extra pedal tones came from the lower manual and I used pedals from an LSI organ which only had one contact each, meaning I could only have one lot of tones, not 8 and 16 together.

The rest of the questions I can't remember the answers to right at the moment. Will have to think!
I think the speakers are the best place to tap the signal for the leslie, but your hookup kit will need to include a load resistor.
The preamp will be too weak and it won't include swell and reverb. The existing leslie plug passes through a crossover which removes the bass.
The existing headphone socket passes through a filter to drop the volume. Any of those can be bypassed very easily, too.

The T is fraught with hum, the one thing which worked for me was rebuilding the pwer supply using a toroidal transformer and encasing it all in steel. Worked wonders!
Unfortunately not long after that the T developed other faults and I put it away for a rainy day.

I'm about to donate my M100 and 122 to a friend's home studio, so the T is going to get worked on again, after all these years, for better or for worse.

[Joakim Bergstrom]

Thanks Brendon! I'll start doing the one octave manual foldback today and I ll probably take the signal from the existing tone cabinet outlet but remove the filter which I assume is one of the caps located between the internal speakers. I intend to do a chop later on so a new power transformer is a good idea anyway. Since I have both the pedals and the circuit boards from the other T I am tempted to try add them but It would be interesting to hear if it was complicated to integrate the electrics into the organ. From your photos It looks like your T still has the lower sides/frame but they form one unit with the pedals which can be detached from the upper part or?

[Joakim Bergstrom]

Now that the organ is functioning and starts to sound better and better I feel it's worthwhile to defoam it before it' becomes too late. By reading other threads I learnt that there are instructions on how to do it and if anyone would be willing to share them with me I would be thankful. I m worried about loosing the different metal covers and plates in the wrong order and damage these fine cables.

[Brendon Wright]

HI Joakim,
The lower sides of my organ bolt to the box containing the pedals, at the top of it is a brace which bolts on to keep stability.
The plug-in wire harness developed faults which mean I've currently lost the pedals. It's quite difficult to make a really robust system using the T, with all it's fine wires!
I'll have to find some old threads which have written instructions with photographs on how to get into the manual wire loom. They were all a long time ago and the forum's shifted platforms a number of times. I'll see what I can come up with.

[Brendon Wright]

this will help a little bit...

[Brendon Wright]

This post will help a little too, though the photobucket watermark maes the pic harder to decipher:

[kziss]

Hi Joakim.

2. Regarding the busamps, Carsten M. suggests replacing the C240, 236 etc capacitors while Kon Zississ suggests leaving them in place and soldering some additional bi polar capacitors in parallell instead. Do the different solutions lead to different sound or is it just two different techniques to achieve the same effect?

With the bass boost modification on the buss amps, there is no need to remove the original capacitors, you can simply solder the new, higher uf value bipolar capacitors on the underside of the circuit board directly in parallel with the existing capacitors. The higher uf values of the new capacitors will allow the fuller low frequency response to be produced.

7. I read here about several ways to tap the signal from the organ to an external Leslie, e.g. directly from the internal loudspeakers, from the existing tone cabinet socket, from the organ's preamp or from the headphones outlet. Which would be the best location considering I d like to retain the organ's reverb and expression pedal functioning and minimise hum?

The headphone socket is a very suitable source for a line out signal and this will include the reverb signal as well as the expression pedal function.
However there is the C432 1 uf treble cut capacitor which is activated when a phono plug is inserted into the headphone socket, but it is very easy to remove this C432 treble cut capacitor.

On the T-series organs the C432 1 uf treble cut capacitor is mounted on the smaller terminal strip which is mounted higher up near the 12 inch speakers. The wires from this smaller terminal strip go to the headphone socket.

On the XTP organ, the C432 1 uf treble cut grounding capacitor is located in the floor base section next to the inductor and capacitor crossover for the stationary speaker cabinet and the rotary speaker cabinet. The C432 1uf capacitor and the crossover are to the left of the middle pedestal when looking from the front side of the organ.

I also recommend removing the C430 2 uf capacitor which is wired in parallel with the large cylindrical shaped L430 8 milli Henry inductor coil.

The C430 2 uf capacitor sends the high treble frequencies to the stationary 12 inch speakers whilst the internal Leslie unit is in use, and this results in an unpleasant sounding mixture of the treble frequencies diluted through both the internal Leslie rotor and the 12 inch stationary speakers.
The Leslie effect sounds much better and more natural when all the treble frequencies are sent to the internal Leslie unit without any treble frequencies being heard through the 12 inch stationary speakers.

Removing the C430 2 uf capacitor will only allow the bass and the midrange frequencies to be heard through the 12 inch stationary speakers.

On the T-series organs the C430 and the L430 inductor are both mounted on the larger terminal strip which is mounted between the two 12 inch speakers. The C430 2 uf capacitor is the large white rectangular shaped capacitor with rounded edges which if I remember correctly, it is mounted on the underside of the terminal strip.

All the best.
Kon.

[enor]

There's really no need to de-foam a T-series organ, or any model with overhanging keys. Yes there is a foam seal in those manuals, but it's smaller and placed differently than in the B3/C3/A100; so even if the foam does get sticky and starts to dissolve, there's really no way it can make its way onto the resistance wires. The bad process all takes place in a harmless location.

[Hans S. H.]

Thats a relief for me, as I think my L-100p still has its foam under the manuals.

[kziss]

There's really no need to de-foam a T-series organ, or any model with overhanging keys. Yes there is a foam seal in those manuals, but it's smaller and placed differently than in the B3/C3/A100; so even if the foam does get sticky and starts to dissolve, there's really no way it can make its way onto the resistance wires. The bad process all takes place in a harmless location.

Hi Enor.
There were a few foam damaged resistance wires in my1968 L-142 organ, and there were a few foam induced green stains on the cloth covered resistance wires in my 1963 L-102 organ .

Even though the foam strip in the spinet organ manuals is half the thickness of the foam strip in the manuals of the post 1963 A100 series, B3, C3, D-150 series and RT3 console organs, the foam in the spinet organ manuals can still be very destructive, especially if the self adhesive strip holding the foam on the metal panel has dried up and come loose, or if the foam itself has become brittle and broken off and fallen on to the manual resistance wires. In this case the foam is just as destructive as the foam in the console organ manuals.

This all means that it is highly advisable that the foam is removed from all organ models including all the spinet organs.

Unlike the console organ manuals whose short wiring harness set up necessitates the manuals to be unsoldered and taken out of the organ in order to be de-foamed, the spinet organs have a very long wiring harness which means that the manuals do not need to unsoldered and taken out of the organ, instead the spinet manuals can be unbolted and then opened up whilst still being on the organ so therefore defoaming the spinet organ manuals is much less tedious and time consuming.

All the best.
Kon.

[Joakim Bergstrom]

I will try to describe what I believe is the amount and location of the gooey foam so that people can decide for themseles:
Since I anyway needed to delete the piece of sheet metal forming the end wall of the metal box protecting the fine enamel wires in order safely cut it to make the wires reach for my lower manual foldback mod, I took a peek into the box, now open in the short end. The end walls themselves have the gooey foam on the whole inside and can be cleaned easily - I could just tear the adhesive away from the metal - but there is small strip of foam on the inside wall against which the edge of the plastic holding the enamel wires is up against. If falling off, the crumbs will fall down and mostly through those pretty large holes in the plastic but it could be possible that crumbs would find its way horistontally on the plastic surface, around those holes and onto the wires when the organ is moved. I guess the recommendation should still be to get rid of the foam especially considering that it seems fairly easy on the T series but if not done, I would believe that the damage would be much more limited than on other models.

[Joakim Bergstrom]

here are the pics:

[Joakim Bergstrom]

[Joakim Bergstrom]

Sorry for my premature opinion earlier.. I do not have the experience to tell how much damage this strip of foam can make. I will try to defoam my lower manual as it is halfway opened anyway. And thanks for all good advices and links :-)