Sabine Graphi-Q Holy Shorts, Batman!

[jazzie366]

So my dad has had this Sabine Graphi-Q for years and could never repair it as it's way above his head. Well, I went into it and found two things, the DIGITAL power in rail for the MC3310-KS chips was being dragged from 2.0V to 1.5V. The ANALOG power in rail was being dragged from 5.0V to 0.3V(!). So the chips are shorted. How do I know? Both of them go up to 300 degrees Fahrenheit, after I let them cook for awhile. Plus the inductors on the power rails have melted, not in a way that they're bad, they just have their plastic casings deformed. Still perfectly functional.

High res zoomable pictures attached. There are 4 components that are circled in one. Red was the 263 degree chips that eventually go to 300. The others are some MC33078 low noise dual op amps. They go up to about 180-190 ish. What I'm wondering is if all 4 chips have gone bad, should I replace them all or should I be looking further? I can't make heads or tails of anything because no schematic and double sided PCB that I think has multiple layers due to the microprocessor/DSP.

Let me know what you think.

[stj]

Re: Sabine Graphi-Q Holy Shorts, Batman!

desolder them and see if the voltages are still being dragged down.

[jazzie366]

Re: Sabine Graphi-Q Holy Shorts, Batman!

desolder them and see if the voltages are still being dragged down.

Removed them just now. Thing powers on, except C24 has gone up in smoke. No idea the value at all. Lit up red hot and then went out as the output relays click on. I checked the cap on the other chip for the one that fried, C31, and it measured 5uF. So probably something in the region of 6.3v 4.7uF.

Not sure where to go from here other than replace that cap with a 4.7uF cap and put a new set of chips in.

Edit: The Dual op amps still are getting up to 180 degrees. So I assume they are shorted as well. However they are much smaller so that would explain it powering on.

Also, C31 & 24 are both on the analog power in.

[stj]

Re: Sabine Graphi-Q Holy Shorts, Batman!

did it get spiked in the past by a bad psu or nearby lightning??

[jazzie366]

Re: Sabine Graphi-Q Holy Shorts, Batman!

did it get spiked in the past by a bad psu or nearby lightning??

Nope. It was in service years ago and stopped working. My dad is an audio engineer and was using it in his studio. Literally the thing quit while it was being used, Sabine wanted 500$ just to look at it without repair. Fuck that.

A bunch of chips have failed short and one capacitor has as well, all on the analog power rail. Very weird, going to replace all of them and see if that fixes it. If so, it'll be a nice piece of kit to have working again.

Also, the power that goes into ALL of his sensitive electronics is filtered by a Monster Power Pro 2500, so there's no chance of any surges hitting the equipment. But there was no surge when the failure occured, it just quit all at once.

[stj]

Re: Sabine Graphi-Q Holy Shorts, Batman!

you may want to look at the psu for leaky diodes or bad caps incase it caused it.

[jazzie366]

Re: Sabine Graphi-Q Holy Shorts, Batman!

you may want to look at the psu for leaky diodes or bad caps incase it caused it.

Update: There was a confession to why it failed. It was sandwiched between two power amps, pure class A, audiophile grade with tubes inside. It was subjected to the 180F heat of both for days on end.

Also, removing the two 3300's made all the chips in the area stop getting hot. HOWEVER, another problem has arisen. The PSU voltage is too low, the regulator is only putting out 4.5V, when the chips need a minimum of 4.75 to turn on, go figure. Well, I'm going to replace the voltage regulator, as there's not much else in it's way to stop it from powering everything, considering the output of it was put through two filter coils, and then a single 4.7uF 6.3V ceramic cap, as the chips are rated to draw under 1mA under normal operation. So considering these chips were dissipating so much heat it caused the heatsink temp of the regulator to get to 180 degrees, I can happily say that it's likely fucked. New regulator on the way, will check surrounding components, maybe the vref is fucked but I'll see.

[Th3_uN1Qu3]

Re: Sabine Graphi-Q Holy Shorts, Batman!

Yes, replace the regulator, it is most likely damaged. Should work fine then.