I am going to measure each transistor pin relative to Audio GND, is 15VDC input sufficient to get a good reading? I have decoupled the boards from the chassis and if full voltage is used I fear the magic smoke and collateral damage...
In the likelyhood of a defective cap.bank how should I proceed With measuring them? Discharge rate/voltage rate vs time?
In the likelyhood of a defective cap.bank how should I proceed With measuring them? Discharge rate/voltage rate vs time?
One or more of your output transistors has failed. Remove them and test.
This is the paper ZenMod was talking about - https://www.passdiy.com/gallery/articles/matching-devices
This is the paper ZenMod was talking about - https://www.passdiy.com/gallery/articles/matching-devices
Ok, pulled out Q1-Q6
ZTX450/550 each measure around 550Mohm between base and emitter/connector. No reversed connection was detected.
SK170
Zero ohm measured between base and emitter/collector. Zero ohm measured with reversed probes.
J74
Around 650Mohm between base and emitter/collector. No reversed measurement detected.
Mosfets next.
ZTX450/550 each measure around 550Mohm between base and emitter/connector. No reversed connection was detected.
SK170
Zero ohm measured between base and emitter/collector. Zero ohm measured with reversed probes.
J74
Around 650Mohm between base and emitter/collector. No reversed measurement detected.
Mosfets next.
Just prior to summer I scrapped my troubled channel and built a new one, it appear to be solid now 
Its been biased to 0,625V, heat is quite manageable and it plays music. I remeasured bias after a continouos 6weeks of power-ON and bias still 0,625V (nom.) and offset = +1mV on one side and +4mV on the other.
I still have hum issues which are audible on my high-90's sensitivity system, I have reduced some of it but issue isnt cured entirely.
On a side-note : I got the chance to do a quick comparison of my F5 against a Pass X30.8. Both played very well indeed, with some audible differences. The X30.8 chassis was quite a bit warmer to the touch than my F5 - perhaps I can up my bias a little more...
Its been biased to 0,625V, heat is quite manageable and it plays music. I remeasured bias after a continouos 6weeks of power-ON and bias still 0,625V (nom.) and offset = +1mV on one side and +4mV on the other.I still have hum issues which are audible on my high-90's sensitivity system, I have reduced some of it but issue isnt cured entirely.
On a side-note : I got the chance to do a quick comparison of my F5 against a Pass X30.8. Both played very well indeed, with some audible differences. The X30.8 chassis was quite a bit warmer to the touch than my F5 - perhaps I can up my bias a little more...
I have them also at .625. I got nervous of overheating in June, when i got a clicking sound in the right speakers. It turned out to be the neighbour who is refurnishing his apartment. Some ground loop perhaps. It was gone the next day. The reason why I did not hear it in the left speaker was probably the autoformers. I use L-pads in the right that was making the sound.
Really? Higher bias? I don't dare to. I use the clone chassie and it is so hot that I can only hold on to the fins for 2 seconds.
Enlighten us in what was the differences? Is the F5 inferior to the X30.8? :O
Really? Higher bias? I don't dare to. I use the clone chassie and it is so hot that I can only hold on to the fins for 2 seconds.
Enlighten us in what was the differences? Is the F5 inferior to the X30.8? :O
Its stated that as long as the heat sinks do not exceed 55degC (25deg above ambient) one is within temp tolerances of the mosfets. Provided proper heat transfer between mosfets and sink obviously
I use a 4U/400mm chassis which I have never seen past 41degC with ambient around 18-19degC, to the touch it feel luke warm, not hot. I can touch the washer on the mosfets with two fingers for a couple seconds before I feel the need to remove them..
The XA30.8 was quite a bit warmer, but still not close to the "2sec OUCH-test" Warm? Yes, Toasty? No.
I will refrain from making any serious attempt to compare the two because I havent spent enough time with either on a known system or being very analytical about it. However the F5 was a little richer (audibly) in the bass range while the XA30.8 packed a more physical bass. Both were pleasing to my ears
Don't forget that the XA30.8 is a significantly larger amplifier, drawing close
to 2x the power of an F5.
Cheers,
Dennis
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