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Beomaster 5500 won't turn on.

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CBAP
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CBAP posted on Tue, May 22 2012 5:53 PM

Hello all,

I've recently got a Beomaster 5500.  I can not get it to start.

I've swapped out all of the Caps and checked the traces and solder joints.

When I turn the unit on, I can hear both the relays fire.  The voltages on P14 check out but p15 voltages are not there.  That makes sense as the relayis engaged.  I've got 5 volts at thecpu.  Anyone have any pointers on where to look now?

I hooked up the front panel to an arduino to test the LED driver.  Works fine.

Thanks.

Carl

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Dillen
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Dillen replied on Tue, May 22 2012 6:31 PM

Do you have the red dot standby light ?

Martin

CBAP
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CBAP replied on Tue, May 22 2012 6:48 PM

No.

Thanks for the quick response.

Dillen
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Dillen replied on Tue, May 22 2012 8:18 PM

Did it work better before you started replacing caps ?
Which type of cap did you fit for C15 (the large one near the power supply board edge) and did you
connect the negative pin to the correct pad (of the three) ?

Have you checked the fuse inside the CPU casing, I seem to remember there is also a zener diode
that can sometimes short (in which case the fuse blows).

Martin

CBAP
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CBAP replied on Wed, May 23 2012 4:41 AM

C15 and the 2 big filter caps are the only  electrolytic caps that I didn't touch.

I didn't change any on the preamp or tuner board either.  Only the little ones on the power supply, and the ones on the cpu board and display panel.

No stand by light before or after.

Thanks again,

Carl

Beobuddy
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Check the on-board  soldered fuse on the cpu board.

CBAP
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CBAP replied on Wed, May 23 2012 7:27 AM

I've got continuity across that fuse.


Cheers and thanks,

Carl

Step1
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Step1 replied on Wed, May 23 2012 11:30 AM

Did you reconnect the cpu plugs in correctly? - I am sure they could be easily be swapped over couldn't they?

Olly

CBAP
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CBAP replied on Wed, May 23 2012 2:43 PM

You can't really swap those arround.

Is there a way to test the cpu?

As I said earlier, I know the front panel display chip is working as I can control the light from an arduino via the serial protocol.

But is there a way I can test the cpu board with an alternative power supply.

Also, do you need to have the tuner board wired up during testing?

Cheers,
Carl

tournedos
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No standby dot means that the processor is not running (unless there are other problems with the connectors or displays).

If you have an oscilloscope, check the ALE signal at the processor's (the big 8031 chip) pin 30. It should output a regular 5V square wave of around one megahertz. It it doesn't, the processor isn't running, which probably means a problem with the power supplies (did you confirm them all, not just the +5V?), the reset circuit or a damaged processor. Testing with an external power supply is a bit difficult, as the reset circuit depends on the 13V rail as well.

Everything else should work without the tuner board connected.

--mika

CBAP
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CBAP replied on Sat, May 26 2012 1:03 PM

Yup.

I've changed the 4700 cap on the power supply.

All voltages are clear and present, but no life from the cpu.  I even wired in a new 13v / 5v power supply.

I've ordered an identical cpu in the hopes that will revive it as mentioned in an early post in the archives.

Otherwise I plan to throw in a ATMEGA to control it.  Only problem with that plan is does anyone know what the IR protocols are for the Master Remote. 

IE what the 2 way commands are?  Is that documented in any of the service manuals?

It would be awesome to replace the cpu and reprogram so that I can control my linux media servers via the beomaster 5500 using the cool remote.

Will regut the remote if I have too and switch over to 2.4ghz radio if that is the case.  But hoping the new CPU might spark signs of life.

 

Cheers,

Carl

tournedos
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None of the remote protocols (not even 1-way) are documented publicly anywhere. The basic frame structure and data encoding is, but that doesn't get you anywhere without a working unit to spy on.

I was actually going to replace the CPU in my former BM5000 with an AVR, but eventually managed to find a spare processor before I got round to it.

Anyway, there's a good chance that a new processor will be enough. Their protection from the extrernal world coming in through the various Datalink interfaces leaves a bit to be desired, and they are sometimes damaged by careless usage, messing with the MCL connections with the power on, etc.

But before you do anything, recheck all components in the reset circuit. The processor will fail to start properly if that signal is goofed.

--mika

CBAP
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CBAP replied on Sat, May 26 2012 1:37 PM

What should I be looking for in the reset circuit?  A specific output?  I'm away from home at the moment so don't have my notes.

 

Is it a voltage or a signal?

 

Cheers,

Carl

tournedos
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It should come up to +5V along with the power supplies, then fall down to 0 a short while (some hundred millisecs?) later.

--mika

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