PAPA'S KOAN ....... was Papa's Surprise

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as some of you already know for preceding story : ...... I'm blessed with Papa's Suprise ...... ( where is that "notworthy" smiley when you need it ..... ;) ) .

there is rest of story .
I'm certainly one of not many , having opportunity to dismantle FW chassis in pieces ; as Papa likes AR2 , he didn't put usual Donut and caps in it , probably counting on fact that Vladimir will bring it all the way on his shoulder ( not having enough trust in Air baggage departments ) ......
anyway - little jewel box is even without these few parts heavy enough ...

so - to have Papa's Surprise Amp in working condition I had to do few things :

.... install new Donut ; what I already had on my shelf is just right (to squeeze in ) size - 4x18Vac/800VA ; according to that - decision to use 2 Graetzs per channel is logical , same as dedicated filter bank per channel .
so - 2x18Vac windings , two bricks , 4x 33mF/25 Panas , along with 2x 0R1 in CRC ; all that per channel
I didn't want to make new holes in bottom plate , so nice Cu plate is cut and bent , to serve as donut and bricks holder . I also made new filter pcb ( wisely sprayed in black ) , while Papa's original one , along with two finest original FW Chinese Porcelain 35A bricks will end in some less demanding project ( maybe some HP amp ) .

power wiring is made from finest quality cut-in-dust LS cable , produced by local factory

Donut squeezed in sandwich (top & bottom ) of soft rubber ; my usual praxis for all toroids ; you can rotate it few degrees and move about 5mm side wise , but it's secured completely

so - few pics for start ( I'm lazy bstrd , so random order is my native state)


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Official Court Jester
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Papa sez :rofl: that pcbs are from early pre-production ; meaning that pcb itself is right as schematic posted in first post in famous F4 thread ; later and final iteration have few changes - mainly with goal to save and secure tiny fragile input Jfets from excessive input signal which , in case of amplitude greater than actual F4 working voltage , will burn them in silent puff :rofl:

I had dilemma few days - leave it as is , counting on fact that I don't need much of input amplitude for my spks ...... or to tweak pcb a little and make it according to final schematic ; naah ....... as Papa sez in one e-mail - " I though that you will put something else in that case " , decision was made - I'll leave present as is , but I must play with it a little ; so - every butcher detail you'll see on pics is made as change to that schm .

electrolytics are my fave - Elna 470uF/35V/125C :rofl: , maybe because I have few kilos of them ;
bypasses on two Elnas in power filtering are 100n/some-film-who-really-care-which-type ; bypasses on two signal carrying Elnas are 10n MKC - polycarbonats

one funny thing is - major-trouble issue for Vladimir , and also major-laughing issue for me - fact that front plate was badly scratched in transport (probably bubble-wrap slipped and back side of zip in Samsonite made those scratches ) ,exactly where Papa's Surprise sticker is put , on pics in linked post above ;
I had instantly cunning plan ( I'm pretty often in Baldrick mode) to send front plate in capable hands of local Metal Guru - Leonardo ( nick on Baby Diya) ;
said and later managed - Leo cleaned existing elox , brushed , made new elox and Fugly! new logo .
possible similarity with existing FW logo is pure coincidence , of course , and your's Mighty ZM is responsible for that coincidence :rofl:

I know that my fave Dutchie Jaccovitty is dumb as Dutchie Whale , so here is link to wikipedia - meaning of Koan ..... for his eyes and education only :clown: : K?an - Wikipedia, the free encyclopedia

why "Koan" ?

just because Papa's crumbs , thrown in ZM's direction , are usually 3 times stiffer than his usual PassDiyA crumbs ...... :clown:
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as I said - I'm lazy bstrd ......

so - 'nuff typing ; now random pics


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tip :

if you want to save surface around screw holes from damage , use plastic washers ;

if you don't have plastic washers handy - DIY them - from roentgen foils :rofl:

all you need are ( what's proper word) - hole making tool and scissors .

funny - I have full box of these foils in A3 format, scavenged from local health center ...... they're good for many things in electronic :clown:
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Dumb as a Dutch Whale. Now I will have to remember that phrase.

but remember that that phrase is reserved for my Dutchie Whale , as expression of love ; but don't tell him that - he's spoiled too much already :rofl:

How does it sound?

exactly as proper F4 ;)
usual FW job - honest amp , no bigger than life ; I can't ask for more

I wish I could afford all that copper to use for brackets and such.

try at junkyards ; that piece is surplus (sort of ) from little local factory
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