4700 mFD vs 12000 mFD capacitor in System 7 sound board

[getg...@gmail.com]

Hello,

I was rebuilding my System 7 sound board and replacing all the old
capacitors.

The schematics call for a 12000 mFD capacitor, but the original
installed is a 4700mFD in the lower left corner.

Would it hurt to replace with this capacitor with the 12000 or is my
schematics wrong?

THanks,

-Rob

[keith]

No it won't hurt. This is a full wave rectified filter cap.

keith

[AL]

Rob,

Caps usually do 1 of 3 things in life:
[1] Power Supply Filters
[2] Noise elimination
[3] Determine circuit timing

The key points in replacement are operating voltage and (in the case of
electrolytics) polarity. The Capacity is actually tertiary. A cap of
that size would typically be used for Power supply stability. OK GANG
YOU CAN START LIGHTING THE TORCHES.

As long as you can find a 12000ufd cap of equal or greater voltage
value, and comparable size, it'll be fine.

Yup, that's one opinion, I'm sure there's others out there.

AL
www.PinMonkeys.com

[seymour...@excite.com]

I don't see any 120000 on my laser cue system 7 sound board schematic -
I do see a 4700 though. It's in the lower right corner though and the
biggest one, C27. Looking over the materials list really quick I don't
see any caps over 4700 on the whole board.

[keith]

schematic shows 12000.

http://www.pinrepair.com/sys37/s67snd.pdf

k

[seymour...@excite.com]

AL wrote:
> Rob,
>
> Caps usually do 1 of 3 things in life:
> [1] Power Supply Filters
> [2] Noise elimination
> [3] Determine circuit timing
>
> The key points in replacement are operating voltage and (in the case of
> electrolytics) polarity. The Capacity is actually tertiary. A cap of
> that size would typically be used for Power supply stability. OK GANG
> YOU CAN START LIGHTING THE TORCHES.
>
> As long as you can find a 12000ufd cap of equal or greater voltage
> value, and comparable size, it'll be fine.
>
> Yup, that's one opinion, I'm sure there's others out there.
>

If the circuit in question actually called for a 12000 I'd agree. But
sounds like his schematics are wrong. You're practically tripling the
capacitance there - something about shocking the bridge rectifier??

[Frank-Rainer Grahl]

The first revisions had the 12K mounted. It was later replaced with the smaller
one. I didn't notice any difference using either one so go with what's available.
Until Ed had them remade the 12K was NLA. Still pricy compared to the 4.7K so I
wouldn't bother for this board.

Regards
Frank-Rainer Grahl

-----------------------------------------------
www.pinballz.net - The #1 pinball forum for me

[AL]

Thanks for the schematics Keith.

The cap is the filter for the 12 V unregulated bus and the source for
the 5 volt regulator. The 12 Volt unregulated bus isn't ripple
sensitive and those 7805 regulators will cover up a multitude of
voltage variances. So I'll bet Williams realized this and subbed in the
4700ufd to save a few bucks. And going back to what I mentioned before:

As long as you can find a 12000ufd cap of equal or greater voltage
value, and comparable size, it'll be fine.

...and don't worry about your rectifier getting shocked, it works
around electricity all day.
8-)

AL
www.PinMonkeys.com
Ask your doctor if capacitor substitution is right for you.

[getg...@gmail.com]

THanks for all the replies.
I ordered a sound board rebuild kit, and it came with the 12000mFD cap,
instead of the 4700 mFD. The board looks like it will fit either the
4700 or 12000.

I will go ahead and put the 12000 in. The old 4700 looked pretty
fried!

Thanks again to all.

-Rob

[Chad Tower]

seymour...@excite.com wrote:

> If the circuit in question actually called for a 12000 I'd agree. But
> sounds like his schematics are wrong. You're practically tripling the
> capacitance there - something about shocking the bridge rectifier??

You can't shock a bridge rectifier. Those things have seen it all by
now.

[GPE]

I may be a bit late on this conversation, but...

"keith" <kdo...@sbcglobal.net> wrote in message
news:1152738729.3...@m79g2000cwm.googlegroups.com...

True. The schematics were used to create the kit for the System 6 & 7
boards. I have seen boards with the smaller caps but didn't know if these
were original or somebody already plopped in a smaller cap. Like somebody
else said - Williams probably reduced the value in a cost cutting endevour.
Seeing as this cap is used in the low voltage filter cap area - it will be
fine to use the 12000uF cap.

For as light loaded as this supply is -- the 4700uF and MD200 bridge
rectifier will be just fine... as will the 12000uF cap and the MD200 bridge
rectifier.

--
Ed Krzycki
Great Plains Electronics
www.GreatPlainsElectronics.com