Help with DE sound issue (TMNT)

[Spadge]

Hi, helping to renovate a TMNT for a friend. Had a disfunctioning sound card, got another one that is allegedly working fine and it exhibits the same sounds as the first one; hard to hear "scratchy" sound and music overlaid by a hum and high frequencies. It would appear grounded or something but the logic appears fine as such.

I've checked the speakers and also taken the pot out of the loop but still the same.

Can anyone help?

 

[Sgt GrizZ]

The 'hum and high frequencies' sound like the classic DE hum issue ..... which I think can affect non dmd DE games also.

Discussed recently on here

http://www.pinballinfo.com/communit...-de-sound-card-de-hum-cure.36572/#post-209030

And a lot on Pinside

https://pinside.com/pinball/forum/topic/data-east-speaker-noise-ideas-for-a-cure

Could be worth trying a few things suggested ?? - some people have had success eliminating the hum. I personally haven't

 

[Spadge]

Getting the loan of an xpin psu to try, will then get the mm out

 

[Spadge]

The hum totally masks the audio btw

 

[new forest pinball]

Hi spage,
You need to do the following...it will help improve things but not totally cure the problem.
The power ic's used on these sound pcbs are prone to a high thd percentage.
1. Replace all the capacitors on the pcb. (We used to do a kit, will check if we have any left if you like?)
2. Replace the crystal.
3. Check for clean earth .
4. Use an 8ohm subwoofer.( reduces the load on those naff power ic's)
5. Use high sensitivity backbox speakers (4 ohm is ok , make sure the sensitivity is at least 90/91db per watt metre.)
Hope this helps...the supply voltage on these machines is dirtier than an arabs sandal.....

 

[ianw]

Been drinking...... edited