RECTIFIER VOLTAGE PROBLEM on a JTM45 RI with HW board ?

electricskychurch · Post by **electricskychurch** » Fri Nov 17, 2006 9:23 pm

why is there a single 16uf on the board in the amp kit whereas it's not given with the PTP board kit (i didn't buy the chassis...) ?

electricskychurch · Post by **electricskychurch** » Fri Nov 17, 2006 9:25 pm

i took some pictures but can i upload them all here ?

electricskychurch · Post by **electricskychurch** » Fri Nov 17, 2006 10:24 pm

HERE IT IS

electricskychurch · Post by **electricskychurch** » Fri Nov 17, 2006 10:27 pm

i upload little by little as my internet wi fi i share with a guy at the studio is shit !

electricskychurch · Post by **electricskychurch** » Fri Nov 17, 2006 10:31 pm

some other picts

electricskychurch · Post by **electricskychurch** » Fri Nov 17, 2006 10:39 pm

some other wiring

electricskychurch · Post by **electricskychurch** » Fri Nov 17, 2006 10:53 pm

nice job you did on that amp you built Mr JTM100.
cleaner than mine i suppose though it's not that bad for the second amp i rebuild in 10 days (first was the 74' JMP 50w).

electricskychurch · Post by **electricskychurch** » Fri Nov 17, 2006 10:57 pm

the first took me 3 days but this one was mounted in 2 but it is not working.
it's been 3 more days i try to find why !
good learning but i'd like to understand precisely how the different AC and DC circulate in the amp and why.
any good book for someone very bad in mathematics ?

electricskychurch · Post by **electricskychurch** » Fri Nov 17, 2006 11:11 pm

i removed the preamp tubes as well and it seems i don't blow anymore fuses.
i remember i wrote i blew some main fuses even without power tubes in (but with preamp tubes in) , so i suppose there might be something wrong in the preamp circuit ; i will check.

Flames1950 · Post by **Flames1950** » Fri Nov 17, 2006 11:25 pm

I'm trying to get ideas in my head as to why the mains would blow when you turn the standby on, instead of blowing the HT fuse........that one surprises me.......

electricskychurch · Post by **electricskychurch** » Sat Nov 18, 2006 8:30 am

i didn't know i could have such problems with heyboer trannies !
i don't think drake or dagnall ever did that.

electricskychurch · Post by **electricskychurch** » Sat Nov 18, 2006 9:14 am

the main reason that comes to my mind why the main fuse would blow is a short somewhere (maybe on the preamp but it should have react before !!???) but i don't know where.
although it may be something else like overheating.

electricskychurch · Post by **electricskychurch** » Sat Nov 18, 2006 9:38 am

i made some continuity tests and the only i found positive were the 3.15 black and red heaters to ground and together as well between the OT secondary to impedance selector and spk, but i think all that is ok looking at a schematic, unless i'm wrong.

maybe there are some other infos before in the thread, i could have wrote that could help finding a solution

electricskychurch · Post by **electricskychurch** » Sat Nov 18, 2006 11:38 am

it seems the main fuse blows up even with all preamp and power tubes out , as soon as i switch the std by on.

electricskychurch · Post by **electricskychurch** » Sat Nov 18, 2006 2:35 pm

after i stole nearly all the fuses on my (many) marshall and hiwatt amps (cause they fit) i finaly started to think about the rectifier tube.
aspen pitman wrote in his book that the main symptoms for a bad rectifier are wether no sound at all even if it glows, or fuses popping when coming off standby into play, when everything else looks right ! !!

as i went through the circuit and comp many times without seeing any mistake, i took my old CT160 military AVO TESTER (UK), that would need a little service (but in france there are nearly nobody to work on old gears like testers, old amps, old synths....or for skyrocket prices, just wine cheese and frogs et les petites femmes de paris ...oooh lala ) and saw the rectifier was in poor shape !
the one that sent georges was testing good so i replaced it and it seeems to work now !! at least i haven't blown anymore fuses.
i will try it now...