hellslinger
Well-known member
Hi Guys, just going to put it out there that I'm interested in getting an ethernet card for an SE/30 if anyone has one.
I recently recapped an SE/30 and got the right sound channel working. Something to keep in mind is that I didn't have enough 47uF caps to recap the entire board, so the problems I describe later might be a result of remaining bad caps. I have already cleaned the local radio shack out of these caps, so there's no more to be had until my ebay shipment arrives.
The left channel was still out, though, so I checked all the pins on the sound chips to see if the appropriate signal was getting to them. Everything appeared to be OK except for the Left Channel Sony Snd chip. It's getting power and PWM signal from the ASC chip, but isn't producing any analog signal on the SND pin. I checked to make sure this pin wasn't shorted.
I think that if a CMOS part has died, the power supply of the circuit is suspect. It is possible that this chip was damaged due to static while connecting headphones. I decided to continue anyway.
I have a dead SE/30 Motherboard due to corrosion of the RTC battery. Fortunately there was no corrosion near these sound chips, so I was able to desolder and remove these through-hole chips with some considerable effort. Using tinning flux and a soldering gun, I was able to get most of the solder off the pins for removal, but it still needed a bit of prying and heat. The tinning flux worked, but boy is it messy. I bought a solder sucker and cleaner flux from ebay as a result of the work.
I soldered a DIP socket to the good board so that I could try all 3 Sony chips (2 from bad motherboard). I also wanted to be able to verify that the old chip was actually bad.
I messed up by severing the trace connecting pin 3 of the internal speaker op amp (TLO71) on the negative input terminal. I patched this trace easily with some wire-wrap wire.
So here's where it gets interesting. The old Sony chip was bad. The two chips from the bad board work -- but not exactly right. When the machine is booted the sound works perfectly with both channels. I checked full volume range to see if there was distortion and there isn't. However, the boot chime is distorted, like it is overdriven and clipping. This happens on reboot or power off just the same.
The older damaged board has a slightly different layout than the good one, theres a few surface mount parts in slighty different spots. The good board has a socketed 68030RC and the bad board has it soldered in.
Accordingly, the Sony sound chips have slightly different numbers on them between the board revisions. The resistor values in the sound circuit on the good board are a bit different than the schematic. R1 and R2 appear to be 150 ohms on this board and are supposed to be 50 in the schematic.
Could it be the Sony Snd chips are a different revision between these boards?
I recently recapped an SE/30 and got the right sound channel working. Something to keep in mind is that I didn't have enough 47uF caps to recap the entire board, so the problems I describe later might be a result of remaining bad caps. I have already cleaned the local radio shack out of these caps, so there's no more to be had until my ebay shipment arrives.
The left channel was still out, though, so I checked all the pins on the sound chips to see if the appropriate signal was getting to them. Everything appeared to be OK except for the Left Channel Sony Snd chip. It's getting power and PWM signal from the ASC chip, but isn't producing any analog signal on the SND pin. I checked to make sure this pin wasn't shorted.
I think that if a CMOS part has died, the power supply of the circuit is suspect. It is possible that this chip was damaged due to static while connecting headphones. I decided to continue anyway.
I have a dead SE/30 Motherboard due to corrosion of the RTC battery. Fortunately there was no corrosion near these sound chips, so I was able to desolder and remove these through-hole chips with some considerable effort. Using tinning flux and a soldering gun, I was able to get most of the solder off the pins for removal, but it still needed a bit of prying and heat. The tinning flux worked, but boy is it messy. I bought a solder sucker and cleaner flux from ebay as a result of the work.
I soldered a DIP socket to the good board so that I could try all 3 Sony chips (2 from bad motherboard). I also wanted to be able to verify that the old chip was actually bad.
I messed up by severing the trace connecting pin 3 of the internal speaker op amp (TLO71) on the negative input terminal. I patched this trace easily with some wire-wrap wire.
So here's where it gets interesting. The old Sony chip was bad. The two chips from the bad board work -- but not exactly right. When the machine is booted the sound works perfectly with both channels. I checked full volume range to see if there was distortion and there isn't. However, the boot chime is distorted, like it is overdriven and clipping. This happens on reboot or power off just the same.
The older damaged board has a slightly different layout than the good one, theres a few surface mount parts in slighty different spots. The good board has a socketed 68030RC and the bad board has it soldered in.
Accordingly, the Sony sound chips have slightly different numbers on them between the board revisions. The resistor values in the sound circuit on the good board are a bit different than the schematic. R1 and R2 appear to be 150 ohms on this board and are supposed to be 50 in the schematic.
Could it be the Sony Snd chips are a different revision between these boards?
