Low cd audio, kinda?

[MNKyDeth]

Ok, so I went through the audio repair/fix thread that is stickied and read every post. But I feel I still need to ask before jumping the gun on what I think is wrong.

I have a PCE Duo here that has perfect Hucard audio. The audio in Ys 3 is also perfect once I get to the beggining town and the people are talking.

However, the intro and music cd's are barely audible. I can hear it barely with the volume maxed out.

If I put headphones into the headphone jack all of the audio is perfect.

I have swapped out all of the 4558 op-amps on the top side of the board with new ones. I have more coming from mouser so I can do the back side. Continuity tests along the A/V din port and following the traces back seem to be ok.

So, I plan on swapping the couple of op-amps out on the bottom of the board just to make sure those are not causing the issue.

Where else should I look? Since the audio issue is only effecting the Din port I assume I would have had a bad trace someplace. I have cleaned the heck out of this area as well with a toothbrush and rubbing alcohol and then q-tips before I even recapped it. I don't have a dishwasher so....


Edit:
The voltage to the IC506 op-amp is the proper values. Actually the voltage seems to be the proper values to all the op-amps. I compared each op-amp to a 100% working system to verify.

[Keith Courage]

There is probably a bad trace or via hole somewhere. These two caps circled in Red are typically the ones that deal with CD audio. Check there first to make sure they are getting the correct voltage and that their grounds are good as well. I believe the 22uf gets 7.5V and the 47uf gets 5v.


If those are both good then start checking for other bad traces closest to the 22UF cap near the Din port op amp. Circled in blue. Usually you can hold the board up to a light and see some via holes that are filled in with old cap goop. I like to fix these by using a cut off cap leg through them and solder on each side and bending it over to the corresponding pad where the connection was weak or lost.

[MNKyDeth]

This was a very hard trace to track down for me. Basically after swapping out the 4558 op amps on the bottom of the board I knew they were all good at this point. And, at this point the voltage's for the op amp located at IC521 were all over the place. With the old op amp the voltages read normal for some reason, or at least within range of a working board.

I followed the positive trace to that amp back to Cap C322. At this cap it read the normal voltage but at the hole that goes through the PCB right next to L303 the voltage dropped. The contact in the hole looked clean and I couldn't find any broken trace along this line with my magnifying glass's and loop. So I soldered a wire from the cap positive directly to the IC521 op-amp input voltage and voila. All sound in cd-rom and hucard games working correctly.

I do appreciate the input Keith. Those areas are actually where I focused most of my attention and even replaced IC505 and IC502 on this board because I couldn't track it down. I replaced the 7805's just in case and even most of the NPN's on the top and bottom of the board because of this.

Really, this board is practically new except of course the original Hu chips and other major chips on the board.

[Keith Courage]

 yeah, sometimes the bad Vias show no signs that can be seen with the human eye as to if they are bad or not. That is why a multi-meter is your friend. Glad you got it figured out.