General Forum

Re: Beovision MX3500 repair

nobby — Mon, 19 May 2008 04:44:02 GMT

how about the two capacitors that smooth the +-5V supply for the drive circuitry.

Re: Beovision MX3500 repair

Barney — Sun, 18 May 2008 09:35:47 GMT

yep, it's ok...hhmm

Re: Beovision MX3500 repair

nobby — Sun, 18 May 2008 08:31:42 GMT

Check to see if the large 2R7 resistor is still in tact ... this may have fused

Re: Beovision MX3500 repair

Barney — Sun, 18 May 2008 06:49:42 GMT

hi tournedos

I replaced both TR20 and TR33 (driver transistors), they both were short circuited... And i also used a BUT12AF instead of the BUT12F.

The stange thing is that nothing happens, the fuse doesnt blow and the TV makes no sound at all..

Need to get some other clamps, so i can measuere what happens.. but maybe I have overlooked something on the board

Re: Beovision MX3500 repair

tournedos — Sun, 18 May 2008 04:47:07 GMT

What I learned while fixing my MX6000 (thanks, guys!) is that when the BUT12 shorts, it can take some of its driver transistors with it (no wonder, they might receive the 300 or so volts from the suppy line for a moment until the fuse blows).

I used a BUT12AF. The only specs I can see differing from the A'less version is a slightly smaller CE saturation current (5 vs 6 amps), but the maximum voltage is larger (1000 vs 750 volts), so I guess it can actually take more punishment than the original BUT12F.

From what I understand, the powerfail system won't be doing anything until you have a working standby (because the CPU isn't even running due to lack of supply), so don't worry about it yet.

Re: Beovision MX3500 repair

Barney — Sun, 18 May 2008 02:17:24 GMT

I have tried to repair the power supply, and it seem ok, but the TV still don't power up. The red LED doesn't turn ON, and I can't hear anything...

Do you think the (PowerFailure) protection is activated?

Got any ideas? Could this indicate a problem or another module?

Re: Bevision MX3500 repair

Barney — Mon, 12 May 2008 13:25:36 GMT

It seems to be discontinued, but i have seen it on some dealers websites... but not local, so I think i'll go for the BUT76 or the BUT12AF, which i can get..

http://www.nxp.com/#/pip/pip=[pip=BUT12F_1]|pp=[v=d,t=pip,i=BUT12F_1,fi=,ps=0][0]

Nobby, have you seen this fault before?

I have found following defects:

- TR1 short circuit (power part)
- TR33, TR20 short circuit (control part)
- Gotta check if L5 is still connected.. near the black hole ;)

The rest seem ok, but im gonna replace some the CAPS

Re: Bevision MX3500 repair

nobby — Mon, 12 May 2008 12:07:35 GMT

I understood that this part was still available. Which sources have you checked?

Neil

Beovision MX3500 repair

Barney — Mon, 12 May 2008 11:41:12 GMT

Hey

Í'm trying to repair the powersupply in a MX3500.

I think the fault is caused by by the TR1. I'm having some trouble trying to find a replacement. Do any of you know any cross reference to the BUT12F transistor?

Update: Seems like BUT 76 is a good replacement, http://www.datasheetarchive.com/crossreference/BUT12F.html.

Below you can see some photos of the print. The inductor L5 has a black hole around one of the pins.

If you have some good advice on this fault, please let me know.