McIntosh MS300 Music server motherboard caps

[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

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?

[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....

[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

Ugggg, obsolete and n/a

[Cohibaman]

Re: Music server motherboard caps

Pair of FMS6418

[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

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'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

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

[stj]

Re: Music server motherboard caps

lazy bastard, use a meter & your eyes!
it shouldnt take more than a few min's to trace it to the source.

[Cohibaman]

Re: Music server motherboard caps

Unfortunately I dont have a schematic for the board, which would really come in handy.

[stj]

Re: Music server motherboard caps

trace the signal back from the connector and see what it passes through.

[Cohibaman]

Re: Music server motherboard caps

If (some of) the capacitors are in parallel, no matter what tool you use the results will be incorrect. Those capacitors in parallel will show as a single capacitor so the capacitance and esr will be incorrect.

Not saying the capacitors are bad, just that some of them may be. You'd have to disconnect a lead from the circuit to measure a capacitor properly unless you're absolutely sure there's no other capacitor in parallel with the capacitor you test.

Agreed, but all values were right where they should be so I'm taking a small leap of faith.

[mariushm]

Re: Music server motherboard caps

If (some of) the capacitors are in parallel, no matter what tool you use the results will be incorrect. Those capacitors in parallel will show as a single capacitor so the capacitance and esr will be incorrect.

Not saying the capacitors are bad, just that some of them may be. You'd have to disconnect a lead from the circuit to measure a capacitor properly unless you're absolutely sure there's no other capacitor in parallel with the capacitor you test.

[Cohibaman]

Re: Music server motherboard caps

Good news & bad news

Good news:

• I was surprised that I was able to test the 9 caps in question while in circuit - they all checked out ok
• I don't have to replace them avoiding potential to brick the motherboard

Bad news:

• Now I don't know what's causing the Component Video output problem.

[stj]

Re: Music server motherboard caps

i usually try to use smd tantalums when replacing those micro-can bastards.
i have large stocks from scap pcb's.

[selldoor]

Re: Music server motherboard caps

I dont know maybe even a bit over the top maybe FK would do - wait for someone else to chime in. One thing is to check the size of the base and position of the tabs carefully - that may limit your choice -in the through hole panasonics they dont do all sizes in all series.

[Cohibaman]

Re: Music server motherboard caps

Sorry I just meant it looks sad or worried and caught my imagination I have been looking for an avatar for some time. It is 10uf 16v but is probably fine. Main downfall of caps is heat so generally speaking ones on power supplies are first to go bad especially the ones near or under heatsinks. Main board ones are usually less stressed and in cooler positions

Ahhh gotcha. I thought it was somehow failing and I just couldn't see it.

Completely agree, heat is a worthy adversary of many components, especially caps, and the main reason I swapped out the PS caps with 105°C Panasonic FR series.

So...the motherboard smd caps, I'm definitely replacing the 220uF's and the 470uF's in the video circuits because the component video output is dead and there's a little flicker on the S-video output. Are the Panasonic FP series the best choice or is there a better series I should use?

[selldoor]

Re: Music server motherboard caps

Sorry I just meant it looks sad or worried and caught my imagination I have been looking for an avatar for some time. It is 10uf 16v but is probably fine. Main downfall of caps is heat so generally speaking ones on power supplies are first to go bad especially the ones near or under heatsinks. Main board ones are usually less stressed and in cooler positions