jFF_Bulbo
Active Member
Hello AK'ers.
i've finished the recap & restoration of my 300dc. abnd some problems are present.
unit power on, relay clicks and it sound. DBT (100w lamp) shine i think so much.
when connected to 120v, powers on, relay engages, and soun is present, but..
-DC OFFSET is 20-30mv on lef channel.
-dc offset is 1.1v on right chanel. both channel has te "gain" knos at maximum.
well. the unit reaches 39°c in both heatsinks after 10 minuts. is this too hight temp?
-when i tried to adjus vumeters, right channel has a bad response.
-i measure the RMS volts in both channels with gain at maximum. i measure 11.44Vrms on left and only 6.00Vrms an right chanel. I put a 1khz vpp signal trought the rca imputs of the unit.
well. i recaped it including the main cap (cde 15000uF/100V)
i follow the Audiokarma transistor guide to substitute all the transistors in the unit, output are mj21195/96. all from digikeys/newark.
important. i did´nt find the 2SA789, neither their replacements (ztx957), i used 2SA1370 instead. bad idea?
well. finally. when set the inpout in "dc coupling" the relay protect teh unit when gain in right channel is about 1/4. left channel dont have this problem. in the other hand, wheb AC coupling is selected, both challes can reach the maximum gain....
than you in advance for yourt help.
i've finished the recap & restoration of my 300dc. abnd some problems are present.
unit power on, relay clicks and it sound. DBT (100w lamp) shine i think so much.
when connected to 120v, powers on, relay engages, and soun is present, but..
-DC OFFSET is 20-30mv on lef channel.
-dc offset is 1.1v on right chanel. both channel has te "gain" knos at maximum.
well. the unit reaches 39°c in both heatsinks after 10 minuts. is this too hight temp?
-when i tried to adjus vumeters, right channel has a bad response.
-i measure the RMS volts in both channels with gain at maximum. i measure 11.44Vrms on left and only 6.00Vrms an right chanel. I put a 1khz vpp signal trought the rca imputs of the unit.
well. i recaped it including the main cap (cde 15000uF/100V)
i follow the Audiokarma transistor guide to substitute all the transistors in the unit, output are mj21195/96. all from digikeys/newark.
important. i did´nt find the 2SA789, neither their replacements (ztx957), i used 2SA1370 instead. bad idea?
well. finally. when set the inpout in "dc coupling" the relay protect teh unit when gain in right channel is about 1/4. left channel dont have this problem. in the other hand, wheb AC coupling is selected, both challes can reach the maximum gain....
than you in advance for yourt help.
