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hot box!

Posted: Sat Dec 12, 2015 9:50 am
by ocoughi
Greetings dubbers!
long time i didn't post here.... happy to see that when talking about fisher reverb on the web, Interruptor remains THE reference website to get info abouts this unit!

Anyway, by "hot box" i mean 2 things: hot because it's a really good unit with splendid sound , both dry and reverberated signal are relly good! mine is quite silent, dry is really clean, revrb has little humm/hiss but really on the back...
and hot because the chassis , after 3 hours of use, is getting really really super hot!!! i use a converter 220 to 120 (not 110 but 120!)before the unit and the selenium rectifier is the original one (rated at 250v if i'm not wrong). all parts and tubes are originals, i'm planning to recap it, change the rectifier for a 400v 8a as suggested by Dr Zee. and also make some mods, but i wanted to test it before....

is this temperature normal? hotter than my soundcraft CPU! and i can tell ya this soundcraft cpu is really hot when used several hours!

another question concerning the power transformer, in the future i want to change the 110 original one for a 220v.... but i'm questionning myself about secondary part of the power transformer (power and intensity)... i saw two interesting transformers, first one is the fender 6g15 reverb unit transformer rated at 250vac/25mA & 6,3vac/1A at secondary and second one is a Carnhill toroid rated at 240vac/30ma & 6,3vac/1A.
both are around 50$...
any suggestions? is 240 or 250 too much? around 200 would be better? i'm little confused with this part...

Posted: Sat Dec 12, 2015 2:16 pm
by ocoughi
few measures later….
at the output of my converter 220 to 120VAC, i have 140VAC.
at the output of the secondary of the fisher i have 305Vac and 11vac…
at the output of the rectifier i have 330 Vdc! instead of 290vdc!
now i know why it gets hot!!!!
mesure taken without any tubes installed…..
that's a little bit upper than the values of Dr " K10 boss" Zee schematics….

Posted: Sat Dec 12, 2015 11:42 pm
by interruptor
mine gets hot as well. i also have it powered from a converter (230V to 110V). i can't comment on the internals though as i never tried to do any modifications. i'm just happy with it's sound as it is. in my case it was the fourth spring reverb that i bought and it's by far the best!
daniel / interruptor

Posted: Sun Dec 13, 2015 4:39 pm
by ocoughi
Yo daniel! i must admit that the way it is, she's also the best sounding spring reverb i have...and i have also 4 good ones... but as an upgrade and modifie addict i need to put my fingers into it... it's my first tube project so i'm reading and learning lots of tings about this technologie those past days....
i want to put the fisher ina 2U rack, tank included, and also in the same rack a passive highpass filter. to get all this the less noisy as i can, i have to move all the transformers outside on the back of the rack and think about a serious grounding plan.
concerning the power transformer, i compared the fisher with all the fender 6g15 originals and clones like weber ones, and also the Mod "the wave" tube reverb kit... basically it's "around" the same technologie, some variations in the tubes used but same range of power consumption... so i think any PT made for those kind of verb will fit well the fisher. there is some "MOJO", "TrIODES","Hammonds", "Valvepower", "Edcor" and a bunch of chinese stuff...(personaly i'll choose first the made in UK and US ones...)

Posted: Sun Dec 13, 2015 8:28 pm
by interruptor
i decided to keep the tank as a separate unit after i found out that it picks up far more noise in certain positions. you might overcome this by using a shielded metal enclosure. also you can change the length of the reverb time by changing the orientation. you get a longer reverb tail when the strings are in a vertical postition.

Posted: Sun Dec 13, 2015 10:52 pm
by ocoughi
seperated tank is the best solution but i want to use the fisher in live so i need to pack in in only one box....(it was designed for car audio so it should not be a problem to bring this in da truck for live dubbing...)
aloso about tank orientation etc...i ve modded some tanks! i have changed the springs...type 9 have 3 series of two springs for a total of 3 diferent lengths a shorter one, medium and a longer , type 4 have 2 series a shorter and a long one...swaping those springs, short x2 or else change the sound... i've also took some springs from unlabeled short spring tanks from farfisa and other organs, the diameter of the springs is bigger than accutronic assembly 2 of these springs to reach the length of the accutronics and the sound is super boingy!! my prefered combination is a short accu spring with one of those unbranded springs, both inna type 4.... :-)

Posted: Thu Dec 24, 2015 1:30 pm
by ocoughi
this thing is a real big mess to recap!!!! no space!! :eek: also all the internal wires are pseudo-shielded...those going to the rca's, control cable and selector... i'm going to change this...wondering if i de-solder ALL the unit and start from the beginning.... considering that all the plate resistors needs to be changed also...hmmmm...i think that's the only way...
back to work now and happy christmas time to all...(especially to all the sufferers around the world...innocent killed, wars, migration, poverty, homeless...if santa claus exists, i hope he'll choose the right place for his presents....some needs more than others...)

Posted: Thu Dec 24, 2015 8:26 pm
by interruptor
good luck with your soldering work..
and happy x-mas to you! :champagne:

Posted: Sat Jan 09, 2016 12:07 am
by ocoughi
the toy is finished! sounds incredible, all noises has deasepeared, incredibly quiet! no more need of a preamp before the more 220 to 110 converter... it's perfect! there is an overall gain pot at the input, a reverb drive pot, reverb level pot and dry level pot...
i put some pictures on my facebook here: ... 509&type=3
the best reverb i have and i've heard...
(ps: nuff THX to Dr Zee for the output B to input convertion idea! big deal!)