Hello Gents
Sorry to bother you again with yet a thread on biasing the S200 - but despite the guide found here on this site (ZenMod provided plenty of times) I'm still in doubt...
I've measure the temperature on the top of the heatsinks - around 58 Celcius on right channel, and 62 celcius on the left - thinks this is what classifies as "¤!#* hot" in the Pass Nomenclature?
I've measures voltage over the big 1 ohm emitter resistors - on startup (cold amp) the right channels stabelizes after about 10-20 seconds on appx 230mV, the left (hottest) on around 280mV.
Now - the document states that the initial voltage at startup should be 180mV when starting the adjustment - so am I correct that in order to bias the amp correctly I should:
1. Power on the cold amp, and carefully adjust the two potmeters so the voltage over the 1 ohm resistors reads appx 180mV
2. Put the lid back on
3. Wait xx minutes - check temperature - if less than 49 celcius, raise bias, if more, lower it?
I states that the amp will "lock" into biasvalue after a while and will become non-responsive to changes on the potentimeter - so - how long should I wait before adjusting?
BTW - this amp sounds great!!!
Best regards
Hans
Sorry to bother you again with yet a thread on biasing the S200 - but despite the guide found here on this site (ZenMod provided plenty of times) I'm still in doubt...
I've measure the temperature on the top of the heatsinks - around 58 Celcius on right channel, and 62 celcius on the left - thinks this is what classifies as "¤!#* hot" in the Pass Nomenclature?
I've measures voltage over the big 1 ohm emitter resistors - on startup (cold amp) the right channels stabelizes after about 10-20 seconds on appx 230mV, the left (hottest) on around 280mV.
Now - the document states that the initial voltage at startup should be 180mV when starting the adjustment - so am I correct that in order to bias the amp correctly I should:
1. Power on the cold amp, and carefully adjust the two potmeters so the voltage over the 1 ohm resistors reads appx 180mV
2. Put the lid back on
3. Wait xx minutes - check temperature - if less than 49 celcius, raise bias, if more, lower it?
I states that the amp will "lock" into biasvalue after a while and will become non-responsive to changes on the potentimeter - so - how long should I wait before adjusting?
BTW - this amp sounds great!!!
Best regards
Hans
values for cold amp are , for my logic , more of informative character, confirming expected behavior ....... being of secondary importance
in other words, Iq in temp.. equilibrium is of primary importance
besides that , first thing I can think of - if there are NTCs , check cold resistance of each , desoldering one leg from pcb
if there is 10% difference to written value , replace
in other words, Iq in temp.. equilibrium is of primary importance
besides that , first thing I can think of - if there are NTCs , check cold resistance of each , desoldering one leg from pcb
if there is 10% difference to written value , replace
Easy now, working on it.... 
It's a little tricky - first 20-30 seconds after power on, the amp needs to stabilize the bias, then I find you only have few minutes to adjust - after that, the bias pot kind of loses it's function, the voltagedrop over the resister does not really change much when you turn the pot after this. So - quick adjust, then power off, then reassemble amp, let it cook for 1-2 hours, then measure with my IR temp probe.
I'm down to 54 degrees on one side now, and 53 on the other, so getting close to the target 49 degrees - but I can only make one run on it each day (busy man, little kids, animals and wife to feed etc. ). I'm measuring in the top bolt hole on the back - inside one of the "feet" which is mounted on the back...
It's a little tricky - first 20-30 seconds after power on, the amp needs to stabilize the bias, then I find you only have few minutes to adjust - after that, the bias pot kind of loses it's function, the voltagedrop over the resister does not really change much when you turn the pot after this. So - quick adjust, then power off, then reassemble amp, let it cook for 1-2 hours, then measure with my IR temp probe.
I'm down to 54 degrees on one side now, and 53 on the other, so getting close to the target 49 degrees - but I can only make one run on it each day (busy man, little kids, animals and wife to feed etc.
). I'm measuring in the top bolt hole on the back - inside one of the "feet" which is mounted on the back...
Looks like I nailed it now - 49,2 degrees on one side and 48,7 on the other measured with IR thermometer in upper bolt hole on the back of the amp
Offset is stable 16 and 34 mV
Ended up with about 170mV and 160 mV as initial voltage drop over resistors - a little less than recommended.
Plays nice music
But now I have to turn on the electric heater in the listening room again
Thanks for your assistance!
Regards
Hans
Offset is stable 16 and 34 mV
Ended up with about 170mV and 160 mV as initial voltage drop over resistors - a little less than recommended.
Plays nice music
But now I have to turn on the electric heater in the listening room again
Thanks for your assistance!
Regards
Hans
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