Wurlitzer 4140 effects loop

[MelodyShaker]

Ok guys and gals. I'm new here, signed up to pick your brains a bit. So I just took ownership of my grandparents 1965 ( so I'm told) wurlitzer 4140 organ. I know little to nothing about organs as I've been a lifelong guitar player. However the organ intrigues me. I'd like to be able to casually play it. It's needs a good cleaning on the inside and the spinning spectratone speaker is jammed. But I'll deal with all that. What I would really like to know about is adding an effects loop. So I can overdrive it an such and make cool spaceship sounds lol. I would like it to end up so that I have two 1/4 inch jacks somewhere in the front of the organ preferably beside the volume pedal. One jack being a send the other being a return. So if I wanted no effects bedal connected I could just run a six inch jumper chord between the two so I could get the origional organ sound or use my guitar pedals in the loop for the crazy ****. I know the loop would go after the signal from the keys and before the internal amp. What wires do I cut lol?. Any help would be greatly appreciated

[toodles]

I strongly suggest you not try to use overdrive on this organ--organ amps and speakers are not designed to withstand this--the distortion will blow the output drivers on the amp and probably damage the tweeters in the organ.

[MelodyShaker]

How so. I'm not boosting the input signal hitting the amp. I'm just gunna make it clip before it gets there.

[toodles]

You are actually boosting the signal, especially in the high frequencies.

When a signal is clipped, it creates lots of harmonics increasing the power demanded of the amplifier, and lots of that power is in higher harmonics. Amps for organs are like those for stereo systems--they are not intended for 100% continuous full voltage, which clipping tends to cause. Likewise, tweeters for organs are not rated for super high power.

If you are lucky, you'll just blow a fuse. If not, you can blow the output driver transistors (if it is a transistor amp); in either case before the amp blows the tweeter(s) can fry.

If the amp is a tube model you'll have better luck, as tubes clip softly, reducing the high frequency content (the tubes saturate more slowly than transistors).

By the way, clipping on an organ sounds horrible--it causes lots of intermodulation distortion which sounds really ugly. The intermodulation distortion also causes an increase in power demands sometimes at very low frequencies.

The rule of thumb in loudspeaker design has always been to never use high fidelity speakers in musical instrument systems (mostly meaning guitar) because the musical instruments can damage the speakers--for the reasons above.

[MelodyShaker]

I appreciate your insight. And I apologize if I sounded slight in my reply before. I just find this confusing cause I've seen videos of guys using the exact leslie assembly out of my organ hooked to a guitar amp for recording purposes. I'm not looking to go play with boston here. Just dick around in my spare room at a sensible volume. I've seen lots of vids of guys running effects pedals into old Hammonds and stuff and it sounded great. Should I instead be inquiring on how to hook up an external speaker jack?

[tucsondave]

IF you look at the amplifier you will see an RCA plug. That is the audio input to the amplifier. You could use that point to connect your FX using the proper cables and adapters without any cutting or soldering. The signal at that point is before the expression pedal.

td

[MelodyShaker]

When you say expression pedal. Do you mean the volume pedal on the organ? Or do you mean I would run that rca into my effects then back into the amp?

[tucsondave]

Yes, volume pedal. I mentioned that so you would know the signal into the FX would be a constant level.

The RCA plug would go to your FX then the FX would connect to the RCA jack on the amplifier.

td

[MelodyShaker]

Thanks man. That's all I wanted to know. On a side note. Do you know a good source of parts for that organ. I believe all the contacts just need a good cleaning. But some of its functions aren't working and upon hitting some of the keys the notes are scratchy or intermittent and I don't beleven I'm getting sound from the spectratone speakers

[tucsondave]

Use Caig Deoxit D5 spray on the key contacts and tab switches.
Parts from : http://mitatechs.org/morelock

td

[MelodyShaker]

Thanks for all the help

[MelodyShaker]

Use Caig Deoxit D5 spray on the key contacts and tab switches.
Parts from : http://mitatechs.org/morelock

td

So what's your take on me doing this to the organ? Will I **** up the internals like the other guy said I would

[tucsondave]

If you won't be using it as an organ but more of an experiment then does it matter if you blow it up? Also the output transistors are fused giving you some protection. I do agree that playing clipped audio at high levels will cause problems but you say you will keep the volume down. You are dealing with 1965 technology in a system designed for the living room, not a power head that goes to 11.

td

[MelodyShaker]

If you won't be using it as an organ but more of an experiment then does it matter if you blow it up? Also the output transistors are fused giving you some protection. I do agree that playing clipped audio at high levels will cause problems but you say you will keep the volume down. You are dealing with 1965 technology in a system designed for the living room, not a power head that goes to 11.

td

It was my great grandfather's organ so I don't wanna trash it. Can the output transistors be replaced if I do **** em up. Or are they a bespoke thing?

[toodles]

Wurlitzer didn't use custom transistors, but the specific parts might now be obsolete.