My Wurlitzer 950A Saga!!

[alandlees]

Hi All,

Some time ago I posted on here about various problems although minor with my 950.
Most have sorted themselves with use and I now have a very nice functioning organ, including the
leslie 700 I bought to plug into the already fitted 9 pin adaptor. However in what I am sure is a
familiar story to organists, one organ was not enough so I went and bought a little white and
gold 580 theatre model. I was in no way an expert when I bought the 950 but the little 580 has
made me realise that the 950 doesn't really sound like a wurlitzer... There is no reverb. I have now
realised that there is actually no leslie. To be precise there is but no sound comes from it.

Last night I had a look in the back and the leslie is rotating, responds to fast and slow but doesn't make
a sound. I couldn't see any broken wiring but I did wonder if the fitting of the external leslie would mean
the internal one being disconnected?

Or is it more likely that the external one was fitted because the internal one broke?

Any tips much appreciated!!


Alan

[Hamman]

Internal leslie amp not working? Internal leslie speaker completley blown?

[SubBase]

The 950 has a spring reverb with a fader control on the left key cheek. The yellow-button tuned percussions also have a two-level (long/short) sustain, but were you the one for whom those were dead? They are really worth having, I had to solder the PC board back together (it's right behind the rear grille cloth) from being almost broken in two.
I think my reverb has stopped working, however; it used to be discernible but now isn't.
The Leslie channel has its own amp, and I guess it's own pot on the expression pedal. (there are 4 pots) Of course there's the leslie switch on the rail, and the amp's fuse to check.
Casey

[alandlees]

Hi thanks for tips, no all my buttons etc work fine, i can get a reverb-ish type effect by selecting piano or harp with the tibias together. silly question guys, which is the leslie amp as i look into the back of the organ? tried following the wires but cant tell...

[Lucien Nunes]

There are four amp channels, two on each chassis. I am having a complete mental blank and can't recall which is where, IIRC the left hand chassis has the main channel (phono plug 1) and Leslie (plug 2) but this could be nonsense - perhaps someone could confirm? If you look at the speaker wiring where it enters the amps on the 3-pin Molex connectors at the top (remember it goes via the headphone socket) the Leslie channel is white, main channel green, presence channels orange and violet. All speaker grounds are black and they are commoned together at the tagstrip near the headphone socket so only appear at one of the amps. Perhaps your first check would be to see whether the white wire from the headphone socket to the internal Leslie drive unit has been interrupted by the added 9-pin adaptor.

As your Leslie channel is dead in some way, you won't get any reverb as the reverb spring tank output is injected back into the Leslie amp channel only, despite containing main channel sound too. Turn the reverb slider all the way down when tracing the signals as it can get confusing with other sources being mixed into the Leslie amp, and play only Tibia stops during testing as they are the main source for the Leslie. For the present purposes ignore the 'reverb-like' effect you hear from piano and harp voices, this is a sustain effect that does not rely on the acoustic spring tank.

Supposing that you have a genuine fault rather than just the speaker having been disconnected, a dead amp is most likely. The reverb output is mixed back in downstream of the swell pedals so it's reasonable to assume that the fault is past this point, i.e. in the power amp itself. We can cross this bridge when we reach it.

Lucien

Hey, wait, maybe I've misread this - does your external Leslie work?

[alandlees]

Thanks lucien great info as ever. I had a look at the external leslie kit connections. I'm not an expert at describing so bear with me.
You've got 2 big aluminium type finned chassis - both of these have a connector on top stamped speaker, my external leslie connector
Is wired into the speaker wires, on the left its a white wire going into a plug at the back of the unit and on the right an orange also a
Purple wire. If I pull these 2 plugs no sound at all comes from the organ.

Another strange thing though, there are 2 phono type sockets with a long wire soldered into the area of the
Headphone socket - I assume these are also an addition. I'm wondering if a previous owner has connected
All of this to bypass the broken internal leslie? I will try and get to the headphone socket area and report back!

[Lucien Nunes]

Do you have a multimeter and are you familiar enough with it to take resistance and voltage measurements with confidence? If so, start by pulling the speaker plug out of the top of the amplifier and measuring the resistance between the white and black wires, which should be the voice coil of the Leslie speaker. Post your reading. If it is open-circuit, there is a problem amongst the speaker wiring / headphone jack / modification area. If not, the amp is the next likely suspect.

To test the amp, remove the speaker plugs from the top of both amplifiers, switch on organ, measure for DC voltage between amplifier Leslie output and ground (socket contacts of the amplifier that would normally receive the black and white wires of the 3-pin plug) If over 0.5V the amp is faulty, don't continue with tests. If under 0.5V, connect a pair of wires to an ordinary domestic speaker and carefully, without allowing any wire strands to short anything, insert them into the Leslie output and ground sockets on the amp. *CAUTION* Do not allow these wires to go near the AC power wiring or the power switch connector (I think this is on the other amp though). Switch on organ, put on a variety of stops including Tibias and Ensemble stops e.g. Diapason, and open the swell pedal as you play. If no sound, Leslie amp is dead or not receiving signal. If sound produced, fault lies in speaker or wiring.

Move test speaker wire from Leslie output (socket for white wire pin) to Main channel output (socket for green wire pin) while leaving black in place. Play all stops as above. Sound should now be heard from the test speaker as this is monitoring the main channel amp. Now swap over the two phono plugs near the top of the chassis to feed Leslie signal through proven main amp channel. Play again - if you hear sound now, the Leslie amp is faulty as its signal is being successfully amplified by the main channel amp instead. If no sound, there is no Tibia signal reaching the phono plug.

To double check, move test speaker lead back to Leslie amp (socket for white wire pin) while phono plugs are still reversed. If sound heard, Leslie amp OK as it is successfully amplifying the main channel signal. If no sound, Leslie amp faulty.

Reconnect the speaker plugs and restore the two phono plugs to their original positions. Post all findings...

Lucien

[alandlees]

I will give all that a try... Interestingly I had a look last night to case out where I needed to test and
noticed a blown fuse in the leslie amp.. From memory it was F1. Could it be that simple?

Alan

[Lucien Nunes]

It might be, depends what killed the fuse. I can't recall which fuse is F1 but I am going to suppose it's one of the two on the amp output stage, 2A fast blow I believe. If someone was experimenting and shorted the speaker line to ground maybe they could have blown the fuse without damaging the amp. But realistically these normally fail when the amp output transistors fail, causing a catastrophic short between the power rails. Check the other one of the pair as that might have failed too.

If you don't want to do lengthy troubleshooting around the amp, you could just replace the fuses and test. In this case, before you switch the organ on, disconnect the speakers. This reduces the chance of drive unit damage if the output stage is shorted. If the fuse does not immediately blow, check as mentioned above for DC on the output socket, you should expect no more than maybe 100 mV if the amp is working. Check also for shorts between white and black speaker leads as mentioned above - IIRC it's an 8 ohm driver (maybe 16?) so you should see no at least 5 or 10 ohms DC resistance respectively. Any less and there is a short that probably caused the fuse to blow.

Personally I would check for obvious electrical signs of failed transistors before powering, and/or power up through a lamp limiter, but you might not want to go to this trouble rigging these up when it could just be that the fuse was blown by a simple overload on the amp output and all is well otherwise.

Lucien

[paulj0557]

Sorry to jump on this thread late. The Leslie and rhythm/bass & reverb are all associated with the long chassis mounted to the inner right side. There are two RCA inputs at the top of this amp that can easily get shorted due to an inferior jack. I replaced mine. Wurlitzer recommends changing all transistor components at once for each side of the two amps on this chassis. The second chassis is for non-tibia upper manual voices and lower manual non-tibia voices. There is no Leslie connection on my Wurlitzer 625t so I ran a -Y- adapter from the two channels on the big finned chassis I just described. My Leslie two channel amp plays Tibia and Bass/Rhythm and Solo voices associated with this amp. The organ's 2nd internal amp functions quite well to handle the organs 3rd channel voices (reed,string,horn- all of the non-tibia voices that the two channel amp does not amplify.

Yes, the reverb is part of the two channel amp.

I accidentally burned up both channels on my two channel amp so I simply ran the RCA's that feed this amp on the top to a nice TOA D-4 rack mount professional preamp. It is from here that I run the organs two channels to both a Marantz stereo amplifier that runs back to the organ and hooks in where the speakers used to hook into the organ's 2 channel amp. It is also from the TOA D-4 that I feed my Leslie 705 inputs direct. I need to get the transistors from Morelock's Wurlitzer Parts soon because I would like to restore the organ to it's original playing ability, but truthfully I like the extra control I get by running my system outside of the organ. Once you enter a mixer you can add reverb and EQ etc.. Here is a list of the prices for transistors for the amp. If you don't mind spending a little money Morelocks will rebuild it even. Too bad you don't live near Cleveland, someone is giving away a Wurlitzer 630. Anyway, here is Morelock's info- GREAT PEOPLE!

MORELOCKS WURLITZER PARTS
37A Main Street
Rienzi, MS 38865
(662) 462-7611
Fax Number:*
(662) 462-7611
email:
morelocksorgan@frontiernet.net
Web Address:*
http://mitatechs.org/morelock

2 Channel amplifier- transistor compliment for both sides & Whatever 1% resistors & diodes associated with it (if any)."power transistors that mount to the side of the heat" $3.00 except 507664-1 which cost $4.00 each [ be sure you contact Lucien about proper installation IF you even need any...double check your connectors first- Molex ( white plastic on top the amp) and RCA...put some DEOXIT on the connectors. Note too that the fuses can slip on the 2 channel amp so be sure they are secure.

# 142173 (4016be quad bilateral switch) $4.00 [ these go out often and never hurts to have a few spares. If you lose a footage or coupler then check these out for the problem circuit in question. There are several in the 625t and 950 etc.

Contact Jan Giradot here on the forum for a manual for your 950- they are genuine tech manuals in a binder. Mine even had tech notes written in it. Excellent mauals for about $10-$12 ea. plus a few to ship TOTALLY worth it.