Recapped Quadra 660AV no sound

[mitchW]

I just recapped an old Quadra 660AV. Before a recap, the machine was dead, no chime, no video, just fan inside PSU was working. Old caps were leaking slightly, but there were no traces eaten off. I replaced all of them with SMD Tantalums (11x 47uF 16V and 2x 10uF 16V). Now the Quadra boots like it should, also the video is spot on, but there is no sound, even no chime. I triple checked my soldering work if everything is correctly soldered, and it is. I noticed that when you play a sound, it sometimes crackles in a speaker for a half a second, like something tries to put some sound out. On external speakers, the situation is the same.

Also the SEBASTIAN IC gets quite hot (cannot hold a finger on for more than a second) after a minute or two. Could this be the problem?

Any suggestions?

 

[techknight]

its probably toast. any IC that gets this hot, that fast, is bad or overloaded. or the voltages are way off. 

 

[mitchW]

Yeah, so I guess that it must have been already toast and the recapping really didn't actually killed it. The hottest part isn't really this IC, but two SMD resistors right next to it (marked with 240) and also a nearby VRM.

Does anyone know what this Sebastian IC does? It is actually labeled a Bt9845AKPF chip.

EDIT: Found it: http://support.apple.com/kb/TA29779?viewlocale=en_US

Sebastian

Sebastian - A video color palette and video digital-to-analog converter (DAC). It accepts up to 64 bits of digital input, either as one 64-bit port or as two 32-bit ports. Lets one 32-bit port handle digital video while the other processes graphics using the same or different color lookup tables. Supports mixing video with still graphics, uses a convolution filter to minimize flicker in line-interlaced displays, and supports displays with clock speeds up to 100 MHz.

So it must be something else also wrong...

EDIT 2: Even more data on AV subsystem http://www.filibeto.org/unix/macos/lib/dev/documentation/Hardware/Developer_Notes/Peripherals/Macintosh_DAV_Interface.pdf

 

[techknight]

God only knows, In cases like these, this is where you need either another logic board, or a real electronics technician. 

 

[Elfen]

Go in with a lighted magnifying glass and look for solder splash. Clean up any you might find. And recheck your recapping job and make sure there are no shorted traces next to the cap. You may have to desolder and then resolder caps to do this to check for traces that goes under a cap.

Though not  Mac, I fixed a Raspberry Pi where someone got angry at it and stomped on it for some reason and crushed the USB and Ethernet Ports. Then he sold it on Ebay where I got it for $10. In soldering in a new dual USB Ports, There was too much solder on one of the pins and shorted another trace that is under the USB Port casing. The R-Pi I/O chip got hot, very hot and nether USB Port worked. Desoldering the USB Ports, removing it, cleaning the board and putting the Ports in place with less solder, the R-Pi now works great.

Good luck to you.

 

[trag]

Did you clean the board thoroughly at some point, preferably, after you'd removed the old capacitors and cleaned the old solder off of hte pads?   If you have not thoroughly cleaned the logic board, try that.  You may still have old capacitor goo, or flux on the logic board causing shorts or other nastiness.

 

[Macdrone]

Just FYI I just learned the Quadra 660 acts just like the 6100.

Hates no battery, needs a double tap to power on and wants system 7.5.

I just recapped the one I recieved. It's loading 7.5 now from floppy.

 

[mitchW]

Well, I will try to find some time and go through all my solder joints again. Now I have some tube radios to repair/recap . But I believe that the board is toast, since I remember powering it on when it wasn't recapped, and it also didn't chime, it just made a very quiet chirping sound.

@trag: Yes I have cleaned the board, probably more than three times. I use mild degreaser/soap detergent when cleaning, usually after recapping, but in this case I cleaned it also before recapping.

 

[Macdrone]

Well without a good battery the 660 does chirp a few times, that is why you must double tap the power supply. On off right back on.

 

[mitchW]

Does anybody has the close-up picture of the Quadra 660AV board near the CD-ROM audio connector and the Audio IC? I somehow managed to knock one SMD tantalum cap, while I was removing the sound IC...

 

[mitchW]

I figured out, how this cap was oriented, when I turned the computer on and measured the voltage on the cap's pads, and found out where is positive and negative. Sadly the sound still doesn't work, even after resoldering the audio IC and some nearby components. I believe that the sound IC must be dead.