(Topic ID: 155782)

Doctor Who sound problem..


By Wariodolby

3 years ago



Topic Stats

  • 15 posts
  • 6 Pinsiders participating
  • Latest reply 3 years ago by Homepin
  • Topic is favorited by 1 Pinsider

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PickME.jpg
Power_supply_sngle_chnl_audio_(resized).jpg
wmsaudio_(resized).jpg
image_(resized).jpeg
image_(resized).jpeg

#1 3 years ago

Need help!

Doctor who sound has always worked but today not so much.

The sound is static/crackling noise.but all music and voices can be heard.

When in sound test mode the voices are clear but the music has the static/cracklings noise.

So is there a separate amp for music and voices ?

#2 3 years ago

Nope. Pre-DCS sound boards utilize only one amp.
There are four separate sound "lanes", three of which are unique and used.
If the problem occurred with all sounds, I'd suspect caps as documented in the Wiki.
--
Chris Hibler - CARGPB #31
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#3 3 years ago

Here's a video of the test mode.
When playing the game the static noise is constant.

#4 3 years ago

This is what I found !!
C47 split in half .

What is that ?

image_(resized).jpeg

image_(resized).jpeg

#5 3 years ago

Well spotted!!

That is a tantalum capacitor and it is in the audio output circuit. It is very likely your problem.

It is a filter on the negative supply voltage line with its mate on the positive line, C46? I would probably replace both.

It could be replaced with an electrolytic capacitor in this application if you have trouble finding a suitable tantalum replacement.

It will probably be listed in the parts list but it is a 1mfd probably at 35 volts?

wmsaudio_(resized).jpg

#6 3 years ago
Quoted from Homepin:

probably at 35 volts?

Yes, 35 Volts is a safe value as it works on 25volt.
Power_supply_sngle_chnl_audio_(resized).jpg

#7 3 years ago

I love it when a problem sticks up it's hand and says "Ohh Pick Me"

faz

PickME.jpg

#8 3 years ago

Yep. 1mfd tantalum. They usually fail a bit more spectacularly.
I see that one fail fairly often. Why? I don't know other than tantalums don't last forever.
Ed at GPE has the part.
--
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

#9 3 years ago

I have 1uf tantalum from radio shack.
Which way is positive and negative ?
Not sure how to install.

#10 3 years ago

Pretty sneaky problem there

#11 3 years ago
Quoted from Wariodolby:

I have 1uf tantalum from radio shack.
Which way is positive and negative ?
Not sure how to install.

Never mind the board is clearly marked + - and the long leg is the positive on the capacitor .

Wish me luck about to replace ...

#12 3 years ago

Did not fix the problem
Looks like I'm moving on to the caps.

#13 3 years ago

Tantalums "ARE" caps (capacitors) so I'm unsure which caps you are moving on to? There isn't much else in this circuit to go wrong.

Try measuring the voltages around the audio output IC first. Please don't start randomly replacing things, that doesn't always result in a fix but certainly can cause more damage.

#14 3 years ago

I moved onto to pinwiki part to change caps c36,c38 and c15.

I've changed them all now and nothing has changed for the worst or better.

As of right now I have no clue what to do next.
So my understanding is right now 2 of the 3 channels have static and fuzzy noise.
The voice channel still sounds great!
I have swapped the ribbon cable with a known working one and still no change.
Anymore help?

#15 3 years ago

Yes, stop doing random things - it won't help in most cases. Grab a meter and start measuring as that might give you a direction to head without replacing anything.

You can't "see" electrons but you can measure them!

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