Farfisa FR-40

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Racing
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Farfisa FR-40

Post by Racing » Sat Apr 25, 2015 3:06 am

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No. Farfisa didn´t just make organs. They indeed made a toober or two too. Albeit intended for organ use this was,at the time,a sort of portable PA unit.
´N see...it carries a few peculiaritys,designwise.

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It´s a 212 combo..running EL-34´s. However,for some reason the Italians opted to run an EZ-81 tube rectifier. As to why? U guys tell me. But..we´ll get to that.

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Amp is in real nice nick,even the "condom" is still there.

Anyways. Seller told me that it hummed. A lot...but worked. IOW to someone like me...all good.


http://iloapp.elegic.com/data/_gallery/ ... height=966

(Schematic)

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Right. So that there was what touched down. Not knowing what to expect really a few things struck me... First up,this is a REAL compact build seing it´s a fullgrown 212 combo! What´s more,real light! We´re talking less then 20kg here.

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Reeeeeeeight. Point to point. For real. This then the powerstage unit of it. Yup. Per rather commoin setup this unit uses a powerstage/PSU chassis and then a separate preamp ditto.

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It hummed. Hm. Ok. Someone had replaced the e-lytes previously and as it turns out the reason for the hum was that the e-lyte for the phaseinverter had been installed to the wrong solderlug.
That handled the amp was as silent as we could ask of it.

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In turn the preamp box.

As a whole..make no mistake. A Farfisa FR-40 is a high quality build. Thought through and well executed. A few points where they struck out,of course,but as a general whole this is a rather neat amp.
What´s more,as you can clearly see,full of high quality components like "mustard caps" and what have you not.

But it does ONE thing. Clean.
See..this is where that EZ-81 comes into play. With a maximum of ~100mA ontap that basically tells that the EZ will run out of steam before the amp does,and indeed.
40? No. Once and for all...we´re talking perhaps 20 watts or so. As to why the Italians made this rather complex amp and then decided to "strangle" it with an EZ-81..well beats the F outta me at least.

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Yep. Look at the schematic. That there is an AC-151 germanium transistor. Used as a recoverystage for the reverb. Funky idea..

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Reverbtank is bolted to the baffle,on a separate piece of wood. In turn the powertubes asf are protected by that piece of sheetmetal in the pic. The knob is to lock the reverb unit down when in transit.

That said...cleanup time. As charming a true PtP setup can be they SURE are messy and what´s more..were going to reset the entire thing anyways so...

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That there is what was left of the stocker.

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E-lytes got installed to a board and glued down. Drop resistors installed to the same board.

Point is..that EZ. I fired her up having handled that there with the poorly installed e-lyte with a pair of "bias measuring resistors" installed,and the whole thing dialed in at approx 360VDC@45mA. Seing the mere size of that powertransformer..that was a damn joke,and indeed i had approx 360VAC inbound on the EZ. So yeah..it was running on its knees..

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The thing needed fuses and what have you not,and what´s more...tagboard time-mainly to clean the whole thing up.

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Seing B+ and so forth it turned out that bias voltage,PT carries separate taps for that,was way to low. No WAY i was gonna get the voltage needed to control this thing with the ideas i had i mind.
Well. Voltage doubler time. See..them taps ALSO runs rectified heaters for two of the preamp tubes AND the voltage needed for the AC-151 transistor.
A voltage doubler setup tho handled the whole thing flying colours. Got me 66VDC raw...which is ample enough.

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Apart from fuses...a PPIMV pot. Knowing all to well that this amp would end up putting out WAY more then a feeble 20 watts..a PPIMV was called for to be able to control it.

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The powerstage taking form. Output jacks..right. Altho not visable in the schem it turned out the output transformer carried taps for 4/8/16 Ohms. Neat! That far board in turn..bias control. Breaker got swapped in accordance with Swedish law,Ie; for breaker that cuts neutral and phase both.

FWIW. I these days more often then not end up using them generic "Vox boards". That way i can set the components out of amp and in turn wire the whole thing up flying lead,which shows as you get to install the thing. Especially with an amp like this. Rather small cmpt and..crowded all said n done. Thus..them Vox boards truly bring order and logic to it all.

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Belt n suspenders. Most likely not needed really,but seing the proximity between the PPIMV pot and the fuseholders..yeah well. Better safe then sorry.

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The biasboard. No. Your eyes ain´t foolin´ ya. Them zener diodes right there. Correct. They´re to drop voltage for the g2 points of the powertubes. In this case 25 volts worth. Yes. For a purpose,we can get into that eventually.

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All said n done that powerstage unit started to get cramped a bit. I played around a while with the idea to install the reverb trafo on the outside but...got it to fit within after all.
See..the powerstage unit apart from sporting the EL-34´s,the rectifier and phaseinverter tube also sports the ECL-86 reverbdriver.

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Preamp was cleaned out in the same manner the powerstage was.

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´N got populated in the same manner too. Yep. That there a tubedriven loop..correct. It is Tubetowns tube loop and...well,it works. As i see no reason to reinventing the wheel i´ve opted to use existing designs as far as that. Fabbing a tubedriven loop..to what avail?
Tubetowns loopS tho..the silicon powered one works very well. This tubedriven one...i´m a bit hesitant of still. Ergo i´ve ordered a few dittos from Riot Devices,and i´m going to evaluate these as well.

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Them are cut down Vox boards. IOW..that preamp box isn´t the biggest thing around and true enough the thing got cramped for space soon enough.

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Idea of mine here was to "build" gainstages ontop of each other and by the use of relays simple add or detract gainstages at will. Yep..that there to the top left is an EF-86. Correct. Lately i´ve come to use EF-86´s a LOT,mainly as they provide greater bandwith as well as attitude vs common ECC-83´s. Fantastic "solo tubes" if you wish.

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Seing that space is limited to say the least i opted to build this thing in "floors". Ie;i went 3D. Each board caters to a given task/tube and hence it got built up with sort of a module thinking. This also brings that when service is eventually needed the tech in case basically needs to pinpoint WHERE..and just remove that singular board.

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Reeeeeeight..i believe the picture says it all. That funky looking steel thing at the top is a pushbutton setup for tone that the amp carries stock. I opted to make that thing work together with the use of the EF-86,and indeed..it works rather well.
The tonecontrol is a James Network and this mainly due to the span of such a setup. For some reason most guitaramps to not sport James setups..which is a pity IMO. Once you as a designer get a hold of how it works it is VERY versatile. By simly replacing a few components you can alter the job it does in a monumental manner.

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Yup. Up n running. As much as i can appreciate that it might be a handful to take in..it works like this... Basic setup= two gainstages. By activating one relay you add an EF-86 ontop for all in all three gainstages. Where the "dual" setup is to cater to cleans..or at least thereabout...the EF ontop will truly push the thing into orbit. Old school rocknroll style,just with added articulation.
Then..
Deactivate the first relay and activate the second and...you get 4 gainstages. Now we´re into hardrock/metal territory,and it shows. Reverb and tremolo still inctact,and lemme tell ya...playing Bark at the moon with tremolo engaged is...different..
In turn..activate that first relay again and we´re talking 5 gainstages. HELLO!!! This is where we add solo capacity to that metal setup.

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The tremolo components got installed to a board as well,and indeed to tremolo works REAL well. However..as i reset the entire thing i now needed to make it all happen as far as the reverb. The truth of the matter was that that single AC-151 transistor simply didn´t deliver what i asked. So...something needed to be done.

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Indeed. In all haste another board was populated to cater to this as i had a triode left over. Presto...nicely resounding reverb.

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Now..that is one SERIOUSLY stuffed preamp!! I´ll tell ya that much!

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High quality build. The stock speakers are early Jensen C12R´s. Doesn´t sound all that bad to be honest.

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Here we go. A set of caster were installed too.

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Final product. Still rather stock looking...but carries quite the punch. As i reset the rectifier to common diodes indeed voltage jumped as did capacity. Bigtime. All said n done i had ~460VDC@32mA.
Can you say an easy 50 watts?
Why Farfisa at one time opted to set it up as they did..i guess i´ll never know.

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ziess
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Re: Farfisa FR-40

Post by ziess » Sat Apr 25, 2015 3:23 am

I am totally in awe of your rebuilds! Looks like you got a nice haul of Telefunkens from that amp too.

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Re: Farfisa FR-40

Post by sookwinder » Sat Apr 25, 2015 5:09 am

Wow ! just wow !

As I read this I feel like a small child listening to grown ups talk in depth about some subject that I know almost nothing about.

and it is still exciting to read !
relaxing alternative to doing actual work ...

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Re: Farfisa FR-40

Post by noisepunk » Sat Apr 25, 2015 4:42 pm

Well, hell, now I want one.
They tried to give me advice, down at the record shop. I said "Sit down boys, this may come as a SHOCK. But alls I listen to, it's all freedom rock."

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Re: Farfisa FR-40

Post by Racing » Sun Apr 26, 2015 3:31 am

Thanx gentlemen!

Rest assured,more builds coming up.

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goldwax
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Re: Farfisa FR-40

Post by goldwax » Thu Apr 30, 2015 7:00 pm

What does she sound like? Post a clip?

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Racing
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Re: Farfisa FR-40

Post by Racing » Fri May 01, 2015 4:50 am

Coming up.
Haven´t recorded anything with it as of yet.

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Re: Farfisa FR-40

Post by stringmaster » Fri May 01, 2015 12:44 pm

Wow, very unique and cool!

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Re: Farfisa FR-40

Post by jimboyogi » Sun May 17, 2015 4:29 am

Racing, this is flat out amazing. Both the electrical and the physical re-invention of this amp - wow!

I was wondering about how you are configuring your EF-86. Are you setting it up Vox style, with high gain (~200!), or changing circuit values for lower gain?

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Re: Farfisa FR-40

Post by OffYourFace » Sun May 17, 2015 10:52 am

Dude, you are the man! That's incredible.
synth tech at www.rosensound.com

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Re: Farfisa FR-40

Post by 46346 » Mon May 25, 2015 5:06 pm

i've been keeping this page open on my laptop all week!

i like the original design of this amp, and really like your modular approach to your own circuit.

really curious how the relayed gain stages are gonna play out.

i've been enjoying two EF86-driven amps lately. being in europe, you probably have a healthy stash, but let us know if you have a favorite source or type for non-microphonic EF86's.


cheers!
Dream Apes, ACME, Malcolm Mooney, Cat Museum, Cooling Time

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repoman
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Re: Farfisa FR-40

Post by repoman » Wed May 27, 2015 1:49 pm

Amazing work.

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Racing
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Re: Farfisa FR-40

Post by Racing » Tue Sep 01, 2015 5:43 pm

Thanx guys.
Sorry for the long abscence. Have had a couple of BnE´s at the shop that just about put me out of business.

Anyways.
For a cheap EF-86 source. Look into the russian offerings. Don´t recall their number at the top of my head but that should be easy enough to google.

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Re: Farfisa FR-40

Post by Langwich » Tue Sep 01, 2015 7:59 pm

Wtf . . . this crazy!

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Re: Farfisa FR-40

Post by 46346 » Wed Sep 02, 2015 12:44 am

wow, Racing, sorry to hear about the trouble with crooks. some of your stuff is pretty rare and some is downright unique. let us know if you are looking to recover anything recognizable.

-eric
Dream Apes, ACME, Malcolm Mooney, Cat Museum, Cooling Time

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