General Forum

Re: power supply of mx3500 dead

jens m — Sat, 28 Apr 2007 15:46:11 GMT

hi neil!

sounds good! that would mean, the other faulty component activated the protection circuit in the powersupply?

i guess line output transistor means one of the transistors in the horizontal output circuit on pcb 10, perhaps tr5 or tr 8 (BU508)?

as you see, i´ve got the service manual... plus soldering skills and some experience in diy audioequipment...ok brought two capstandrives of vx vcrs back to life, but that´s it in the field of tv... so repairing the tv would be more like trial and error, especially, as i haven´t got a oscilloscope for checking the components. but i think, i´ll give it a try ( of course, i´m fully aware of the high voltages in the tv and i won´t do anything riscfull at all!!!)

tim jarman from beocentral guessed exactly the same as you did about line output stage, so as two experienced experts are of the same opinion, that´s definitly the right direction to go!

thanks a lot for your help!

jens

Re: power supply of mx3500 dead

nobby — Sat, 28 Apr 2007 13:49:08 GMT

ok, that suggests to me that the supply is fine ... but there is a dead component ... most likely the line output transistor that is shorted. do you have someone who can look into this for you?

Neil

Re: power supply of mx3500 dead

jens m — Sat, 28 Apr 2007 13:04:03 GMT

hi neil!

no , it´s absolutly dead, when you plug it in, no red light, no noise; the only thing you hear, is when put the plug out, something which sounds a bit like a quiet, declining whistle....

thanks for your input!

jens

Re: power supply of mx3500 dead

nobby — Sat, 28 Apr 2007 09:31:25 GMT

Can you hear it trying to start? ie. is there a very quiet whistle ... or is there no sound at all when you apply power to it?

Neil

power supply of mx3500 dead

jens m — Wed, 25 Apr 2007 01:14:16 GMT

hello all! once again my mx3500 is dead . first it started with with a deformation of the picture... the lines in the upper third of the picture were horizontially out of place, it looked like the picture was waveshaped, but this went away after two to three minutes and then everything was fine, after a while the deformation after switching the tv on became a bit worse, but always went away after minutes.... but the other day, when trying to switch on, the powersupply went dead, no red light at all, nothing.... it´s already my second mx3500 whose ps got dead, the first one had a bad solderjoint on the deflection-transformator, which took the ps to nirvana.... any tips, which part of the ps is the one, which could have failed failed? of course i already checked the main fuse, but it´s ok. meanwhile we got a used mx4000 as replacement, but the mx3500 still look great and i don´t want to throw them away.... thanks for your help and ideas!

greetings from munich

jens