Wait until you see the lid!
Oh no, don't tell me you prepare a Kangaroo shaped ventilation cut out on the lid
Blown fuse
I recently went to listen to my preamp and found a dead left channel. I also hear a loud pop at turn on and noticed my amps protection circuitry had been activated. Upon inspection I found the positive rail fuse on the left channel was blown. I replaced the fuse which promptly blew upon power on. I found a negative 6 volts on the output. Further inspection revealed a wire clipping on the circuit board. This wire clipping came from my bench that is located next to my equipment rack. How it got thru the vent slots and into my preamp I will never know. I removed the clipping and the dc servo chip , replaced both rail fuses and powered it up. I was able to zero the offset and replaced the op amp. I now have zero volts on the affected channel and 3 mv on the right channel. The 3 mv has been there since day one. Is 3 mv acceptable or should I buy another op amp ? My fuses are T500 ma and the design calls for T350ma. The only place I can find these fuses is a lighting store on Amazon. Should I replace these fuses or will 500ma be ok ? The preamp is up and playing music quite nicely.
I recently went to listen to my preamp and found a dead left channel. I also hear a loud pop at turn on and noticed my amps protection circuitry had been activated. Upon inspection I found the positive rail fuse on the left channel was blown. I replaced the fuse which promptly blew upon power on. I found a negative 6 volts on the output. Further inspection revealed a wire clipping on the circuit board. This wire clipping came from my bench that is located next to my equipment rack. How it got thru the vent slots and into my preamp I will never know. I removed the clipping and the dc servo chip , replaced both rail fuses and powered it up. I was able to zero the offset and replaced the op amp. I now have zero volts on the affected channel and 3 mv on the right channel. The 3 mv has been there since day one. Is 3 mv acceptable or should I buy another op amp ? My fuses are T500 ma and the design calls for T350ma. The only place I can find these fuses is a lighting store on Amazon. Should I replace these fuses or will 500ma be ok ? The preamp is up and playing music quite nicely.
@ eslheadphone
Flying wire clippings are evil. Especially clipped pins from pcb parts can travel several meters and land anywhere. On some unlucky day they might end up in a computer or in a scope. T500mA fuses should do for now. Especially if running the output stage bias at 150mA.
The 3mV DC offset isn't harmful at all. Same type AD823 op-amp other samples usually do better, could differ less for your other channel, but no worries either.
You reminded me I want to test some OPA1656 or OPA2156 new generation CMOS op-amps in the DCG3 at a point to see if they respond well to the servo task and if they improve the sonics further or not.
I have a couple already on through hole interface boards. But better I don't get tempted borrowing the cheese from another mousetrap of mine before I have spares to torture or kill...
Flying wire clippings are evil. Especially clipped pins from pcb parts can travel several meters and land anywhere. On some unlucky day they might end up in a computer or in a scope. T500mA fuses should do for now. Especially if running the output stage bias at 150mA.
The 3mV DC offset isn't harmful at all. Same type AD823 op-amp other samples usually do better, could differ less for your other channel, but no worries either.
You reminded me I want to test some OPA1656 or OPA2156 new generation CMOS op-amps in the DCG3 at a point to see if they respond well to the servo task and if they improve the sonics further or not.
I have a couple already on through hole interface boards. But better I don't get tempted borrowing the cheese from another mousetrap of mine before I have spares to torture or kill...
Attachments
Salas I knew someone would give me grief over the wiring. Wide open on 100 dB horns, Ear against the horn, dead silent. Grounded this one different. First one had no headphone jack so both channel grounds came together at ground lifter. This one headphone jack ties grounds together, thought about running wire to ground lifter from there. But ran it for input rca Jacks which is tied to volume control, less wire involved. It worked, both preamps are the dead silent. Even got the right value pot in this one, got it from hifi collective As you suggested.
Well, the impedance is very low from DCG3's HP out and maybe the Stax interface has no electrical problem tapping from there also but I don't know the divider ratio it uses i.e. if its gonna be too quiet unless driven from SPKR outputs or even if it must be a floating output to avoid ground loop. Better find the manual for the Stax in HiFiengine or somewhere.