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WPC Audio Board (A-12738-50004) Rebuild Components

LAP

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LAP

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I have a WPC Audio Board (A-12738-50004) from a Getaway which I need to rebuild as after a couple minutes play I am getting bad distortion and some audio just cuts out.

 

After doing some research on which components are the likely culprits I decided that while I have the board out and soldering iron hot I would just do a full board refurb and replace all the parts which tend to go over time.

 

It took me about 3 hours to search various sites which stock all these components and then identify of the components (had to go with slightly higher voltages on a couple capacitors due to availability). I thought I would post the results here just in case any of you think the components I have selected are not correct plus this table might save someone else the 3 hours....

 

The total cost for the full kit works out to cost just under A$39 and just over A$34 without the LM1875 chip.

 

RS Online = ~A$39 (Free delivery but has some min order quantities)

Great Planes Electronics = ~A$27 + A$25 Delivery but is out of stock in a couple items

Mouser = ~A$43 (Free delivery if I ordered >A$50) but also is out of stock in a couple items

Digi-key = ~A$52 (Free delivery if I ordered >A$60) but also is out of stock in a couple items

Marco, PSPA & RTBB do not stock all the items and generally were a littler more expensive than the electronic component suppliers but by less than I would have expected.

 

Some of the components on RS Online have minimum quantities so I will be over ordering for what I need, if anyone else is interested in a 'kit' (with or without the LM1875 chip) PM me and I if I have spare I would be happy to post you a kit (post would cost about $8-10) otherwise RS does deliver for free and the links are in the table below....

 

[table=width: 900, class: grid, align:left]

[tr] [td]Designator[/td] [td]Part Number[/td] [td]Units[/td] [td]Description (Click on Link to RS Online Store for Component)[/td] [/tr]

[tr] [td]C24, C25 [/td] [td]5040-12729-00[/td] [td]2[/td] [td]Radial Capacitor 4,700uf 35V [/td] [/tr]

[tr] [td]C22 [/td] [td]5040-12750-00[/td] [td]1[/td] [td]Radial Capacitor 22uf 35v [/td] [/tr]

[tr] [td]C32, C35 [/td] [td]5040-11036-00[/td] [td]2[/td] [td]Radial Capacitor 47uf 16v [/td] [/tr]

[tr] [td]C15, C18, C34, C36, C38 [/td] [td]5040-09332-00[/td] [td]5[/td] [td]Axial Capacitor 47uf 25v [/td] [/tr]

[tr] [td]C3 [/td] [td]5040-08986-00[/td] [td]1[/td] [td]Axial Capacitor 100uf 25v [/td] [/tr]

[tr] [td]C20,21[/td] [td]5041-09243-00[/td] [td]2[/td] [td]Axial Tantalum Capacitor 10uf 10V +-10% Tolerance[/td] [/tr]

[tr] [td]C26, C27, C28, C29, C37, C46, C47, C48 *[/td] [td]5041-09031-00[/td] [td]8[/td] [td]Axial Tantalum Capacitor 1uf 35V +-10% Tolerance[/td] [/tr]

[tr] [td]C23 [/td] [td]5048-12036-00[/td] [td]1[/td] [td]Axial Ceramic Capacitor 0.22uf 10v[/td] [/tr]

[tr] [td]U1[/td] [td]5370-12728-00[/td] [td]1[/td] [td]Audio Amp - LM1875 [/td] [/tr]

 

 

 

[/table]

* Updated to include @Skybeaux suggestion to replace all 10 of the the tantalum capacitors...

 

Hope at the least this helps someone else out and saves them trawling through component sites.

 

Jason

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ocyen Veteran

ocyen

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Fantastic work Jason. I wanted to do this at some point but never had a sound board fail on me to warrant it!

 

You may find a lot of these components quite cheaply on eBay also. Might be worth looking into if delivery time is no issue.

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Autosteve Pinball Wizard

Autosteve

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Hey Jason , you really should be replacing all Ten of the tantalum capacitors......especially if they are the yellow ones.

 

Agreed, when they die they blow up with a bang. I had one die on a T2 and it scared the bee jesus out of me as I had my head real close when it decided it was at the end of it's life.:o

 

It turned out to be the only component that was at fault and once changed the board worked fine but I still went ahead and changed them all. One involves removing the LM-1875 because it is pretty much under the headsink.

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LAP Rising Star

LAP

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Hey Jason , you really should be replacing all Ten of the tantalum capacitors......especially if they are the yellow ones.

 

I updated the original post with your suggestion plus changed the component for the C26, C27, C28, C29, C37, C46, C47, C48 on RS Online to the 35V as it was cheaper and is the rating required in the manual.

 

Thanks

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LAP Rising Star

LAP

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You have got to love RS and their efficient free shipping... Ordered at 10:40am yesterday and was on my desk at work at 8:30am this morning.

 

 

1548113464909.thumb.jpeg.34e82944eb315db821406e73cecf217a.jpeg

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LAP Rising Star

LAP

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As you most of you know from the questions I post that I am still fairly new to fixing machines and certainly I am not a super tech... but what I lack in knowledge I make up in the conscientious way I bumble thought gathering information and with any luck fixing the issue, often with the help of AA, plus once resolved I try to be disciplined to document meticulously the information gathered to with any luck repay the forum by hopefully helping others...

 

In this vain as I have been working through refurbishing this WPC Audio Board I came across a couple things which were not obvious and took some research to get to the bottom of:

 

  • Neither the manual not the board indicates the polarity of for the Tantalum Capacitors (C20, 21, C26, C27, C28, C29, C37, C46, C47, C48) and if you get the polarity wrong they go POP!
  • The polarity on Tantalum Capacitors are often not marked on the components but their shape indicates each legs polarity.
  • Ceramic Capacitors, used in C23, are not polarized so you can put them in any way.

 

I spent some time working through the schematics and a multi-meter to workout and documented the polarity of how each of the the Tantalum Capacitors needs to be inserted into the board... Below are the schematics and the board layout from the manual where I have highlighted all the components being changed in the full refurb and I have added a + on the side of the Tantalum Capacitors (remember I am still fairly new at this so please do your own checks).

 

Audio_Board_TantalumCaps_Schematic.thumb.png.c60fccb1e39ad4a326027b0f677b0d24.png

 

Audio_Board_TantalumCaps_Polarity2.thumb.png.95a69b1ace6024687dcc660434f455af.png

 

1313776722_AxialTantalumCapacitorPolarity.png.10d6785147cdfe4312f256872eb9b9f3.png

 

 

With any luck this helps save others time... I will post the final pictures once all the components are soldered in and I have confirmed that none of the capacitors went POP!

 

 

Jason

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LAP Rising Star

LAP

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So all the components listed above replaced but the heat sink is still getting very hot and audio is still as bad as when I started..... learnt a lot but back to square one.

 

See the video below with the heat sink hot enough to boil a cup of tea!

 

[video=youtube_share;c0-Wcph5G0U]

 

Any suggestion welcome.

 

Jason

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LAP Rising Star

LAP

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WPC Audio Board (A-12738-50004) Rebuild Components

 

Send it and other boards to Ken and put new speakers in it!
Kurt...That would be the easy way out and I would learn very little... There is joy in the journey... And the destination might well end up at @Skybeaux in the end but I am going to give it a crack before then.

 

Jason

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LAP Rising Star

LAP

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I finally got the sound on the Getaway fixed.... In the end I am not 100% sure what was the exact issue as I replaced many components & connectors plus reflowed several header pins on the board but I have documented the board refurb and eventual fix which is now up on youtube in a playlist of 5 videos which can be in the full playlist by clicking on this ==>

or any of the 5 videos below.

 

Thanks to all those you added suggestions in the thread or via PM's along the way.

 

Again I am no expert and if I can fix this sort of issue (eventually) then anyone can and hopefully documenting the journey helps other.

 

[video=youtube_share;c0-Wcph5G0U]

1337100651_ScreenShot2019-03-02at2_17_58pm.thumb.jpg.d9b0a83bebd4f988d5a71ff267ded28d.jpg

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