ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi,
I am trying to repair a MX4000, type 8720. It is completely dead, no red led and no picture. After reading a lot of other posts in this forum and others, I changed the following components, hoping it would fix the problem:
C32, C130, C61, C137, C31, C29, C132, C82, C100, C44, C120, C121, C131, C134, C46, C48, C53, C52, D82, TR33.
The TV is still dead, no red led or picture. I measured voltage on some capacitors (probably should have started with this), when the TV was plugged in and power button pressed to on position (no red led, nothing happens when pressing TV on remote):
C29: 3,64 V (should be 5V I think)
C31: 0 (should be -5V I think)
C44: 0,25 V
C48: 0 V
C52: 0 V
C120: 0
C9: ~315 V
Since C9 gives ~300V, I assumed the main power works and perhaps some TRs had failed. I desoldered and measured the following TRs, which all seems to measure ok with my multimeter (my multimeter have a diod setting and it shows 700-800 mV between base-emitter)
TR1, TR2, TR10, TR11 (PNP I think), TR12
I also desoldered D34 and D36, which seems to be ok, ~0,4 V (?). I measured D35 in circuit, and it also seems to be ok.
Visually, the power supply PCB seems ok, I can not see any dry joints, all components looks nice. I received the TV for free, and do not know what has happened with it before I got it.
Does anyone know what I should check next? Would be fun to get the TV working again.
Best regards