McIntosh MS300 Music server motherboard caps

[Cohibaman]

Re: Music server motherboard caps

Nothing to do with lazy. I don't know enough about component video signal analysis. Care to help?

[stj]

Re: Music server motherboard caps

i'm not talking about that, simple tracing from the connector backwards with the meter set to ohm's / buzzer mode.

follow the track till it gets to something - then see if it's going into the "something"

[Cohibaman]

Re: Music server motherboard caps

I've already done that & yes, all components check out right up to the video driver. I thought you were talking about video signals.

Anyhow, some other forums have suggested that it may be caused by corrupted bios. The bios is proprietary so there's no way to reflash unless you're an authorized service center, which have all but vanished.

[stj]

Re: Music server motherboard caps

i doubt it's the bios,
what is the video chip that generates the component output?

[Cohibaman]

Re: Music server motherboard caps

Pair of FMS6418

[Cohibaman]

Re: Music server motherboard caps

Ugggg, obsolete and n/a

[stj]

Re: Music server motherboard caps

interesting chip.
so if you can, see if the inputs are present and if they are, see if the A/B switch line is working.

often with a chip like that you would only lose a single channel out of the 3.

[Cohibaman]

Re: Music server motherboard caps

I have no idea what a good signal looks like vs bad let alone how to set up the scope to read the unknown signal. I'm good at learning though....

[Cohibaman]

Re: Music server motherboard caps

I did Google a bit and presumably I should see something like 400-700mV DC at 10uS on the component out. The chip prob lower amplitude?

[stj]

Re: Music server motherboard caps

well put simply, if the AB line goes from high to low when you select modes,
thenit's good.
and if the 3 inputs on each channel look similar then they are probably o.k.

leading to the question - where does the signals for the fms6418 come from?

[Cohibaman]

Re: Music server motherboard caps

There's no mode select; the Composite (yellow RCA), S-Video, and Component run simultaneously so I can't do any selection or on/off except for power. But you gave me a good idea to look at the output pins.

[stj]

Re: Music server motherboard caps

in that case, it's just used as a fixed amplifier.
so scope the outputs and inputs.

here is a sheet wih some scope examples!

[Cohibaman]

Re: Music server motherboard caps

Yep, that's same sheet I looked at earlier. Thanks for the help.

[selldoor]

Re: Music server motherboard caps

Ugggg, obsolete and n/a

maybe here? though no sales/ no feedback and in china



http://www.dhgate.com/product/fms641...1-1|3932834874

http://www.dhgate.com/product/fms641...2-1|1133488698

http://www.dhgate.com/product/fms641...0-1|1133488698

different seller one part
http://www.dhgate.com/product/fms641...3-1|1133488698

also long deivery and post goes up per item ???????


Perhaps contact this seller in us and ask if will do 5 If its 16pin you need?

http://www.ebay.co.uk/itm/PN-FMS6418...item1c3a48ca2e

[stj]

Re: Music server motherboard caps

check the power is reaching the amps.
it's probably a seperate filtered supply.

[Cohibaman]

Re: Music server motherboard caps

On another note, this is the power supply before the recap. Notice C17 bulging? I installed mostly Panasonic FR and 3 Nichicons where necessary.

This runs 24/7/365 - any other recommended replacements or upgrades on the PSU?

[stj]

Re: Music server motherboard caps

get rid of the brown glue before it turns conductive.
did you replace all the caps including the small ones in the center area?

[Cohibaman]

Re: Music server motherboard caps

Tnx. Yep, I got rid of most of the glue and I changed all the electrolytics out.

[Cohibaman]

Re: Music server motherboard caps

BTW, another guy has one of these and thinks his has a bad L2. He says if he touches it, it intermittently works. I guess it could be a bad coil, but not likely. I'm fairly sure it's the blob of crap underneath it that went conductive - or even a cold solder joint.

Any reason to change out any of the non-electrolytics? What about the dual Schottky rectifiers or the TOP249Y Switcher? Do they get weak over time?

[stj]

Re: Music server motherboard caps

no, they work - or they dont.
and topswitches usually fail by exploding btw!