Spring Reverb For Farfisa Organ

[sarakisof]

Hello everyone, i have a Farfisa Foyer spinet type tube organ, it is exactly same as Mini Deluxe I Compact plus tube amp with 2 speakers and spring reverb included. Found it at a flea for 20 bucks back then, had fully recapped and repaired and works like a champ so far
Moved to a new house recently and unfortunatelly its spring reverb unit was damaged during transporting. It seems not a huge damage, i couldnt manage to fix it though. As you may know, Farfisa used piezo spring reverbs, so its a bit pain in the ass try to repair it. I sent photos to some guys i talk with in an online organ group but they both replied that it is worthless to try to repair. For those who may know about piezo's (i don't) the damage is that, both two little edges (like cat's ears) from one cartridge were broken. They are used for attaching the cartridge in its base/place. So this cartridge and its spring got disengaged/"unhooked" and now the unit is like a mess. Managed to glue those little edges and placed the cartridge/spring with my hand but cannot mount it permanently in this little mounting. If anyone is curious or willing to help in this path i can discuss further and send pics indeed.

Anyway, after this, i am thinking of forgetting the original internal unit reverb idea and focus on an external diy spring reverb that will have other uses too.
I had already built a spring reverb in the past but it is dedicated mostly for drippy guitar effect with low input (B type) 8 oms. I read that those piezo's are mostly high input impedance.
I am looking for a long and like type F many ohms, or even one of those C/D/E types , but my purpose is to find a drive circuit that has a 100% dry signal , no eq, pots, bla bla  and just a mix pot that will be mixed with spring effect. Found this "Music Thing" project, for modulars etc.,could fit to my plans, but i dont know if it gives real dry signal cause i saw many functions. I dont want to change/affect Farfisa's original signal at all. Just keep it simple.

Is there any spring drive diy projects/schems/gerbers out there that can keep dry signal unaffected at all? (well, cables from their own can make an impedance difference, but thats tiny, i talk about harmonics/eq/sound affection-no many components at dry path trace).
Open to hear your suggestions, specially from those who use an external spring with their combo organs.

[thetragichero]

have a tube to drive/recover the reverb or are we looking for solid state? there's plenty of one tube reverb schematics out there. i used a 12dw7 (1. because it was in there and 2. the 12au7 half is better for driving) for my Hammond conversion and i am happy with the results. i mostly play overdriven and only like reverb on cleans

[Rob Strand]

'mac' from this group built a reverb using one of those ceramic disc elements as the receiver,

https://www.youtube.com/watch?v=aO-ozHPYAyY

https://www.diystompboxes.com/smfforum/index.php?topic=120207.80

There's a pic in the video but I couldn't find a pic in the thread.

There might have been another thread as well.

Perhaps you can use one of those to repair the your existing spring and attach it to the spring like mac did.

Here's what someone else has done,



Here's the thread but no pics come up,
https://www.soundonsound.com/forum/viewtopic.php?f=24&t=65065&p=590332&hilit=

[sarakisof]

thetragichero, i was thinking of a simple solid one that could not affect the character of dry signal. have many projects running and being in the middle of  a music project too so dont want to take many time. If it could be possible to fix the internal original unit i would go through.

Rob Strand, took some pics of the unit to see what the situation is now. Is it bad? The black cartridge at the bottom had its "legs" broken, i glued as you can see in the 3rd pic. How this works? When i attach the cartridge to its black mounting (2nd pic) by hold it there with my hands, reverb still doesnt work.
Firstly i have put of course this thin metal hook that is connected with springs (last pic) into the hole of cartridge. Does this mean to be connected somehow inside or just it can be hanged in this hole? Cannot find many infos about this kind of farfisa piezos.

[Rob Strand]

Is it bad? The black cartridge at the bottom had its "legs" broken, i glued as you can see in the 3rd pic. How this works? When i attach the cartridge to its black mounting (2nd pic) by hold it there with my hands, reverb still doesnt work.

I won't pretend I know what to do here but it might  be fixable.

I'll try to explain where I think the problem is.

I think the black broken part you have is the transmit/send transducer.   When you apply an electrical signal it moves the spring, it's kind of motor.    In order for the motor part to move the spring, the moving part of the motor must connect to the spring.   The larger black part in your second and third picture is the "motor".

In your last picture you can see a black sleeve over the wire.   That point supposed to be bonded to motor so that the motor can move the wire.   Currently it is detached so the motor isn't moving the wire.  It needs to be rebonded to the motor.

If you go here, there's some nice pics here about 80% the way down,
http://claviers.mezei.fr/dossiers/FarfisaFoyer.A53-124/FarfisaFoyer.A53-124.html

You can see how the wire hooks over the back of the black motor part, then the wire runs over it and there is a point where the wire is bonded to the motor.

Before you start you might be able to wire the *motor* part to an amplifier then tap on it to see that it's not damaged.  If you tap on the point where the wire and motor are bonded you should get a stronger signal (a tap sound) than tapping elsewhere.

Once you are certain it works perhaps see if you can get wire to hook over the back of the black motor part.   Then *as a test* put something between the wire and the motor, like a small piece of hard plastic or metal to mechanically connect the two.  Then see if you can get any signal.  Once you are sure  it is generally working and holding together put it together then once it's in place bond the motor and wire back together.

Oh,  when bonding the two be very careful not to bond the moving part of the motor to the black outer plastic part.  That will glue the motor in a fixed position and it will be very hard to undo that!

[Rob Strand]

Then *as a test* put something between the wire and the motor, like a small piece of hard plastic or metal to mechanically connect the two.

Just to be clear.  The idea of putting the thing there is to provide some down force onto the motor part *for the test*, a bit like a guitar bridge.     The intention is to remove that piece of stuff when you bond it *unless* you find you can't bond it without some thing between the wire and the motor.

Also you might find what I've said isn't 100% correct but I'm sure you will work out the finer points with the thing in front of you.

[sarakisof]

Rob you re my hero.  I found that guy's post on SOS in his blog with pics. If the solution you suggest fails i will go through this idea with piezo big disk and maybe talk with this guy. By the way this topic on SOS you sent the link is an excellent and very interesting conversation,  real pleasure to read 

About mezei organ site you gave the link above, this is Stephane from France, the guy i talk with and suggested me that it is maybe worthless to repair. Very good guy, he has helped me a lot we talk each other often. I was glad seeing you posted his excellent and informative site !

Rob, i will be away for the next two days for a live gig, so i dont have many time now, but i will read further all of your advice, will talk with Stephane too, and be back if have any questions. I will try first your solution see and if it fails will go with piezo disks and xperiment.
With first sight i generally got an idea of what you are saying, but i must read more carefully to find out. For example how should i make connections for this clever test you mention ...

Really thanks Rob 

[Rob Strand]

By the way this topic on SOS you sent the link is an excellent and very interesting conversation,  real pleasure to read

It's a very similar problem to yours and they discuss a lot of the options and limitations.

At the top of the thread I noticed a link to a schematic.  The way the schematic is drawn implies the three springs go to the receive side (not the transmit/send side, in my previous post I thought it was the send side.).  You might be able to check the wiring to see which side goes to the amplifier output and which side goes to the amplifier.   Anyway the main point is if that's the case you can use the existing organ amplifier to do the tap test.   *However* if the schematic doesn't represent reality, which is quite possible, a tap test using the existing amplifier will fail even if there's nothing wrong with the element!  In that case you will need to wire up the broken element to an amplifier.

About mezei organ site you gave the link above, this is Stephane from France, the guy i talk with and suggested me that it is maybe worthless to repair. Very good guy, he has helped me a lot we talk each other often. I was glad seeing you posted his excellent and informative site !

That site is full of beautiful pics.

Rob, i will be away for the next two days for a live gig, so i dont have many time now, but i will read further all of your advice, will talk with Stephane too, and be back if have any questions. I will try first your solution see and if it fails will go with piezo disks and xperiment.
With first sight i generally got an idea of what you are saying, but i must read more carefully to find out. For example how should i make connections for this clever test you mention ...

Really thanks Rob

No problem.  Sounds like a good plan.  A few tests and you will know where you stand I'm sure.
I'm in favour of fixing it.   It would be hard to find a Farfisa replacement.

[anotherjim]

Wow, that Mezei document is incredibly thorough. I had no idea the Farfisa ceramic reverb spring transducer was an ordinary record player type.
I also like the organs mechanical "Chorder" overlay device. The kind of thing that's being reinvented all the time for guitar.

The 1978 Farfisa organ I parted out had the same swell pedal Lamp/LDR block but by then the reverb had changed to a more standard Accutronics type.

[Rob Strand]

I had no idea the Farfisa ceramic reverb spring transducer was an ordinary record player type.

Someone in the SOS thread mentions an engineer from Farfisa said they used piezo transducers to get around the Hammond patents.

[PRR]

> the black broken part you have is the transmit/send transducer. 

Sure looks to me like a plain ordinary old ceramic phonograph cartridge!!

Which I see confirmed later in the thread.

I'm not clear if the cart is broke or the rigging from cart to springs. But it sure has to be fixable. Ceramic phono carts can still be found; in overwhelming variety of mechanical mounting but fairly similar guts and needles (the parts that matter). Some bent beer-can and glue should cobble it together.

[sarakisof]

Back in the base after my live gig. First of all, during trip return i googled and totally got how exactly phono "ceramic" carts work making use of piezo phenomenom, so i hope can now speak in a more safe way. It is unbeliavable from a reverb unit i thought "dead" how many useful things you can learn even if i finally dont manage to fix it.
To speak more accurately i attach a pic below with the inside mechanism of a ceramic. You know for sure, but just to be able to communicate as it is labeled.
According to pic, my yoke (that soft rubber plastic thing that stylus's cantilever sits on - in our rvrb example cantilever=hooked wire soldered to springs) is a bit bend. By bend i mean a little turned from one side (lets say from right) it isnt 100% straight if u see from horizontal/from above sight. You can get it straight with a bit pressure but feels like it will get warped position with time again.
Also, always  compared to the good white cartridge and mezei's one.  In the white, the yoke is "glued/stuck" with a "silicon like" adhesive material (marked red in the second pic). In my black "bad" cartridge it seems like the yoke has unbonded from this silicon adhesive. Imagine this material like a cylinder tube (like hot glue gun's sticks) that its end normally gets into the yoke and get bonded together. In my case this milky adhesive has a tiny crack and its end is some mm. away from it, they are not bonded.
3rd pic: white (good) cart. You can see adhesive material like in mezei's second pic.
4th pic: Black bad one. No adhesive bonded (ignore wire's position etc. as i said i try to keep all this wire/sleeve/cart combo with my hand  )

Rob, i did the tap test and i can hear a "crack/tap" sound, far less when i tap to the spring itself, more stong when i approach the "heart". The springs during test were loose though (like my first post's picture situation exactly), not tightened as it should be (as i cannot mount cartridge to its black metal mount).
I did test by keeping in place with my one hand the spring wire to cartridge's hole (wire and its round black sleeve sits on yoke) and with the other tapping.
Should i do this without spring wire at all? Just catridge?
So i assume it is the receive side as schem mentions.

I have many questions from your suggestions. This black round sleeve (over spring wire) is normally glued/bonded with yoke? Because according to mezei's site pics its like that (indeed seems like melted together lol) but in my "good" white cartridge seems like this black round sleeve just sits on yoke. I dont want to reassemble as i m scary of making things worse.
If so, you think i have only to bond somehow this black round sleeve to yoke, then just insert the hooked  springwire's end to cartridge's hole over it, mount all this to metal mounting and thats it?

PS. I havent fully understand yet if the spring hook wire gets attached or connected with cartridge and how.  Tell me if i am correct, i ve understand that the whole system functions vice versa piezoelectric phenomenom. So if in phono cart the stylus by its moving, vibrates and mechaneically moves the piezo element inside so that gives electrical signal which we get as audio in the end, here in reverb's example is vice versa (as we know piezoelectrism works also like that) so we give electrical signal to elements inside cart which makes the yoke moves so does the spring wire, so does the springs. This happens for send side. For receive side i guess we have a similar case with phono.  So my guess is that spring wire must simply gets attached mechanically to yoke and just put into this cart's hole over it, it does not make any electrical connection with anything inside cart that i can see right?

EDIT: Used a friend of mine (4 hands) and tightened up springs with wire sleeve cart combo as it should be (cause still cannot find a way to mount cart to its mounting) and did tap test again. Can hear clear n loud "splash" effect from spings when tap on them etc but receiver (black bad cart) cannot blend/mix this with notes so no effect produced. So i think my receiver cart is "dead", could bonding the yoke to the adhesive and then the black sleeve to yoke make the difference?
If not or hard to do, do you think i should go with another ceramic cart and adapt to my project or with a piezo disc like the guy in the SOS link? (asking that cause if you read carefully his project, the effect he created didnt produced that characteristic spring sound, as he says, it was that plus a "plate" kind of effect or smthng like that and he liked it, so speaking of creatin the original thing or as similar as possible maybe ceramic phono cart would be better don know)

http://mezzoauto.blogspot.com/2019/05/farfisa-compact.html

[j_flanders]

I had no idea the Farfisa ceramic reverb spring transducer was an ordinary record player type.

Someone in the SOS thread mentions an engineer from Farfisa said they used piezo transducers to get around the Hammond patents.

As did Vox:
http://www.voxshowroom.com/uk/misc/reverb_hood.html

It was clear that Hammond was not only ready to defend the patents for the Type 4 reverb system, but also would require a license fee from a manufacturer building a product that included their invention. While Leo Fender was willing to license the Hammond Type 4 reverb system, Tom Jennings, president of Jennings Musical Industries was not. Jennings sought to develop a spring reverb system for Vox amps that would alter the Type 4 design sufficiently to avoid prosecution from Hammond.

Maybe there's additional info to be found when searching Vox related reverbs (instead of Farfisa)?

[Rob Strand]

It is unbeliavable from a reverb unit i thought "dead" how many useful things you can learn even if i finally dont manage to fix it.

Indeed!   Please give me a day to catch up with you.

[sarakisof]

Please give me a day to catch up with you.

Wow thanks   talked with the guy from SOS thread, Adam, very kind and talkative person and decided to go with his idea using piezo disc. As we know piezo element of ceramic carts tends to worn out and decays with time.
I have a "last hope" though that my situation can be fixable as "there is still life in it", i mean this "splash" sound i can hear by tapping the springs is something. It means receiver cart to output works. I d like to give to the original cart a last chance so i am full of ears.
Do we know what this "like adhesive silicone material" thst bonds the yoke indide cart could be and how i could add it to fill the gap? Its in the 2nd pic of my previous post. My cart (with the "gap"/missing msterial is in 4th pic.

[Rob Strand]

decided to go with his idea using piezo disc

It's up to you you if you want to use the disk.

I have a "last hope" though that my situation can be fixable as "there is still life in it", i mean this "splash" sound i can hear by tapping the springs is something. It means receiver cart to output works. I d like to give to the original cart a last chance so i am full of ears.

You can only try.   You have nothing to lose.   Fix anything that looks broken using the information you have and see what happens.

You can get it straight with a bit pressure but feels like it will get warped position with time again.

If you look at your cartridge diagram (first pic) you can see the yoke and the yoke connecting to the ceramic elements.  You can also see them in the pics on this page [Click on the pics to get the larger pictures].
https://www.ebay.co.uk/itm/BSR-C1-Ceramic-Stereo-Phono-Cartridge-Replacement-BRAND-NEW-in-BOX-/222453570617

Also on you cartridge diagram (first pic) you can see the mounting block.  So I guess there's few things that could be broken (or not) which would cause the twisting
- the coupling yoke is damage or twisted.      Maybe fixable.
- one of the ceramic elements is broken   
- the mounting block has come loose.          Maybe fixable

Part that bonds to cartridge body should be the mounting block.   That should be the least critical part and would be easily glued back in place.    The yoke should only bond to the ceramic elements.

Do we know what this "like adhesive silicone material" thst bonds the yoke indide cart could be and how i could add it to fill the gap? Its in the 2nd pic of my previous post. My cart (with the "gap"/missing msterial is in 4th pic.

I don't know what that glue is.  I can't tell if it is soft like silicon or hard.   My guess is if it is kind of hard and could some sort of epoxy.    I lot of small things like that used clear/smokey glue which dried quite hard.

Another thing I'm not sure about is if the wire is bonded to the yoke, or  they just placed a (black) tube over wire to make it fatter then that pushes into the yoke just like a needle part of the cartridge.

You might be able to work out some of the details by looking at the good cartridge.

[sarakisof]

Thanks Rob, just a question before start to experiment with. Could those cheapo new ceramic carts (used on those Crosleys garbage tt's) do the job? https://ebay.to/2nH2Tfc
I wouldnt like to spend too much on that project 

[Rob Strand]

Thanks Rob, just a question before start to experiment with. Could those cheapo new ceramic carts (used on those Crosleys garbage tt's) do the job? https://ebay.to/2nH2Tfc
I wouldnt like to spend too much on that project 

I saw those as well.   They should work fine.   You might have to do a bit of work on the mounting and how the spring attaches to the yoke.  Copy the same L or R connection as the original - not sure how much difference that would make.

I was thinking about bonding the spring to the yoke.  One problem with that method is if the spring becomes detached all the spring force pulls on the yoke.  Whereas if it was jammed in there like the stylus it least it has an opportunity to come free.   Another scheme is the wire is allowed to slip lengthwise inside the small black tube, even if the tube was bonded to the yoke.   Anyway just thoughts.

[sarakisof]

Just for the record wire is not bonded to the yoke. Checked in the good cart and all parts wire-sleeve-yoke can move free.
Problem with bad cart was that yoke had deattached (it is not bonded too) from ceramic material, managed to attach it, but the prob is not there.
Did a test also with piezo disc. Still the same results. No effect mixed with signal but big "splash" when moving or tappin the springs. So the problem is not in the "bad cart" and i think when i solve it the "bad cart" will work fine (i get more nice rvrb effect with cart instead of piezo disc, Adam from SOS was right, piezo gives a more bassy dark echo/plate kind of fx, not that it is bad, but you it isnt that drippy splash).

So i must concentrate on this. I get splash but no fx signal out, any thoughts?
Might the other cart (that we supposrsd as "goid") is the bad one? But it seems mounted and working properly...
Rewire backwards or swap carts or put in to out and out to in maybe?
Somrwhere read also that not all those piezo discs work with DC. How could i know/test if mine works in DC?

[Rob Strand]

Just for the record wire is not bonded to the yoke. Checked in the good cart and all parts wire-sleeve-yoke can move free.

OK thanks.  Good to know it's done the right way.

Problem with bad cart was that yoke had deattached (it is not bonded too) from ceramic material, managed to attach it, but the prob is not there.

Did a test also with piezo disc. Still the same results. No effect mixed with signal but big "splash" when moving or tappin the springs. So the problem is not in the "bad cart" and i think when i solve it the "bad cart" will work fine (i get more nice rvrb effect with cart instead of piezo disc, Adam from SOS was right, piezo gives a more bassy dark echo/plate kind of fx, not that it is bad, but you it isnt that drippy splash).

I read that as the receive side is working.   If the receive side is very weak you might only hear strong "splashes".

So i must concentrate on this. I get splash but no fx signal out, any thoughts?
Might the other cart (that we supposrsd as "goid") is the bad one? But it seems mounted and working properly...
Rewire backwards or swap carts or put in to out and out to in maybe?

Yes that would be a good test.   You need to confirm the transmit side is working.  We are kind of assuming that is working but it might not be.  You could even try the "tap" test on drive side cartridge (ie. the one that looks OK) by re-wiring it to the preamp.

Was the organ fully working before it got damaged?   If it was, we shouldn't suspect the faults in the electronics.

If all is good the splashes should be more or less the same level when wired in either direction.

Somrwhere read also that not all those piezo discs work with DC. How could i know/test if mine works in DC?

I suspect high enough DC could hold them in a deflected state such that small AC signals would not longer cause further deflection.

I'm not sure what reverb circuit the Foyer actually has but most of the circuits I've seen have AC coupling to the elements.    You should be able to see DC across the cartridge with a multimeter.