I have a WPC 16917 sound board (Dirty Harry) and the sound is very "tinny" "tin can ish", and doesn't produce sound out of the lower cabinet speaker, only the head speakers.

I swapped boards with another machine (Johnny Mnemonic) and the problem follows the board. Any ideas? I replaced the TL084 chips with no change, and the TDA2030A chips had been previously replaced, at least 3 years ago. Any ideas? ChrisHibler

(This board gave/gives the "Sound Board Interface Error" , but the sound always worked perfectly)

#2 4 years ago

TOX

ChrisHibler

Chris' Pinball Repair

Chesterfield, MO

12y 120K 9,996 46

I'd start by diode testing both amps for comparison.
Red on center leg...black on pins 1, 2, 4, 5.
Compare between the two amps.
This is to diagnose lack of cabinet speaker sound.

Tinny sound...tough one. You've replaced the opamps.
The analog side is pretty simple.
The DSP does most of the work on the digital side and ships that to the AD1851 A-to-D converter serially. Since it's serial data, "missing bits" aren't a possibility like we might find with older 1408 DAC systems.

I tend to not suspect ceramic caps at all since their construction is so simple that they don't fail, practically, ever.

Bottom line...TDA2030s are still suspect. AD1851 is suspect. Prior work, not done by you, would be suspect. A recent board repair I did where someone else worked on it connected a trace to the center leg of the TDA2030 that shouldn't have been connected (on a WPC95 AV board).
--
Chris Hibler

#3 4 years ago

MAP

mack505

Pinside member

Lorton, VA

8y 47,300 162 15

Thanks for responding Chris. I replaced U27, again, continuity was good, still same issue. Is U28 suspect here also?

Screen Shot 2020-03-16 at 8.05.22 AM (resized).png

#4 4 years ago

MAP

mack505

Pinside member

Lorton, VA

8y 47,300 162 15

Quoted from ChrisHibler:
I'd start by diode testing both amps for comparison.
Red on center leg...black on pins 1, 2, 4, 5.
Compare between the two amps.
--
Chris Hibler

Will do this.

#5 4 years ago

BOB

bssbllr

In Memoriam

Frankfort, NY

10y 75,050 1,730 1

I know a good place for some hotdogs.

#6 4 years ago

MAP

mack505

Pinside member

Lorton, VA

8y 47,300 162 15

Bob Kane, shared this with me - will replace all the 1uf 65v caps and report back.
https://www.instagram.com/p/BW530ZlFfKB/?fbclid=IwAR3sDLUPNJ8t1FlfBJ14gXADe-D6zBSnYLfiFRNhnFY1N_BBQFYQnzTfPjs

#7 4 years ago

TOX

ChrisHibler

Chris' Pinball Repair

Chesterfield, MO

12y 120K 9,996 46

OP
Quoted from mack505:
Bob Kane, shared this with me - will replace all the 1uf 65v caps and report back.
https://www.instagram.com/p/BW530ZlFfKB/?fbclid=IwAR3sDLUPNJ8t1FlfBJ14gXADe-D6zBSnYLfiFRNhnFY1N_BBQFYQnzTfPjs

I read that a while ago too.
Those caps usually prevent all sound when they fail.
It will be interesting if the behavior you note can also be caused by those caps.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Reply

Wanna join the discussion? Please sign in to reply to this topic.

Hey there! Welcome to Pinside!

Donate to Pinside

Great to see you're enjoying Pinside! Did you know Pinside is able to run without any 3rd-party banners or ads, thanks to the support from our visitors? Please consider a donation to Pinside and get anext to your username to show for it! Or better yet, subscribe to Pinside+!

This page was printed from https://pinside.com/pinball/forum/topic/wpc-16917-sound-issue and we tried optimising it for printing. Some page elements may have been deliberately hidden.

Scan the QR code on the left to jump to the URL this document was printed from.