Thank you Sir.
Do you mean I have to keep the value as 0.15uF but can increase the voltage?
As for the other two, these are PS but maybe PP will improve the sound as per material nature. How is your experience?
Keep capacitance values the same. Remember to check that the pin spacings on the caps you are interested in, are compatible with the PCB.
If its PS as in polystyrene, then changing to polypropylene is probably not worth the expense in time or money. You'd probably need to go to teflon but I don't think it will be a significant audible difference. In the end it's your judgement call.
Changing from a 10uF polyester input cap to a polypropylene input cap could be beneficial, but, the polypropylene one will likely be much larger and not easily fit.
Replacing old electrolytics with new ones in an old amp makes far more sense than debating over polystyrene vs polypropylene.
Tantalum caps are certainly prone to failure and should be replaced.
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Thank you for the clear advice.
I will give a chase to Russian military grade Teflon FT3 to tray against orange drop 0.1uF. But FT3 is BIG but the place is convinient to fit.
For the input MKT I already see the fitment issue against PP, looks like fiol has not chance to fit, but maybe metalized one...
PWR CAPS already replaced, gave a huge difference, now I am waiting for the IYXS bridge to arrive.
I will give a chase to Russian military grade Teflon FT3 to tray against orange drop 0.1uF. But FT3 is BIG but the place is convinient to fit.
For the input MKT I already see the fitment issue against PP, looks like fiol has not chance to fit, but maybe metalized one...
PWR CAPS already replaced, gave a huge difference, now I am waiting for the IYXS bridge to arrive.
One more question. the orange coin-type parts in parallel with the switcher and in the cable entrance, are they varieties or ceramic caps? I belive they should be varistors.
Question about Bias Threshold S-300.
Is Bias/DC Ofset measured at speaker outputs. Left bang running about 15 degrees hotter.
Could one channel be in class A and other in A/b ? Thank You for any help
Is Bias/DC Ofset measured at speaker outputs. Left bang running about 15 degrees hotter.
Could one channel be in class A and other in A/b ? Thank You for any help
DC offset is measured at the speaker terminals (provided the amp works OK) and should be near to zero although values of -/+100mv are no real problem in practice.
A high DC offset should cause any speaker protection to trip. In a non working amp you must measure before any such protection (relay).
Bias normally refers to a preset quiescent current that is flowing in the output stage and must be measured correctly, normally calculating the current with reference to some volt drop across a resistor in the output stage.
Small temperature differences mean little as the ventilation will not equal on each side of the amp.
A high DC offset should cause any speaker protection to trip. In a non working amp you must measure before any such protection (relay).
Bias normally refers to a preset quiescent current that is flowing in the output stage and must be measured correctly, normally calculating the current with reference to some volt drop across a resistor in the output stage.
Small temperature differences mean little as the ventilation will not equal on each side of the amp.
S300 is A/B by design.
You want temperatures at about 50 deg C on the tops of the sinks after an hour or
so, assuming 22 deg room temp. Much higher or lower calls for adjustment.
You want temperatures at about 50 deg C on the tops of the sinks after an hour or
so, assuming 22 deg room temp. Much higher or lower calls for adjustment.
The bias is about -.13 so guessing bias is not the issue. Left channel is running about 145 F to 155 Fat top center of heatsink, It has one generic part which is the optical coupler NTE 3041, I have not been able to locate an original but the channel has very clean signal at 1000 hz / 1.2 volt with 8 0hm load resistors. It is as though running in class A mode compared to the right channel . The gain of each channel is equal but right channel is somewhat cooler by about 30 degrees F. Any Idea's of where to look for an issue would be much appreciated. Everything test very close to equal in respect to other driver boards values. I do not want to return it to a friend until sure it will be stable. The turn on thump is negligible. My Plinius can bake potatoes in class A but have read the S series should not be that hot to the touch.
There is a pot on the channel which should adjust the bias. The current through
the output stage 1 ohm resistors needs to be monitored during adjustment, so that
you don't overdo it. Very gradual adjustment upward, waiting an hour between,
until you get the temperature up.
the output stage 1 ohm resistors needs to be monitored during adjustment, so that
you don't overdo it. Very gradual adjustment upward, waiting an hour between,
until you get the temperature up.
Thank you so much for your help. It turned out trim pot for the left channel was intermittent/oxidized and so replaced it and offset across emitter resistors fell in range after replacement and adjustment procedure. The temperature dropped within specs. All is well and thanks once again
After a years with Threshold s300, and s300II I finally mange to get nice Optical Bias model which I was catching for a long time, I got S200, with one of the channel showing DC offset 99 mV which is not good.
I still see Tantalum 0.15uF caps in place, which need to be relapsed, but I have only 0.1 uF film at home and to order a 0.15 is a long story (thanx to the COVID).
My question if I can replace 0.15 with 0.1 with no issue?
What are the other places to look in to fix the 99mV DC offset?
I also found 5 different types of well known small transistors: 2N5566, MPSA42, MPSA92, MPSU10, MPSU60, and one type unknown transistor on both channels.
Please, advice what could it be?
I still see Tantalum 0.15uF caps in place, which need to be relapsed, but I have only 0.1 uF film at home and to order a 0.15 is a long story (thanx to the COVID).
My question if I can replace 0.15 with 0.1 with no issue?
What are the other places to look in to fix the 99mV DC offset?
I also found 5 different types of well known small transistors: 2N5566, MPSA42, MPSA92, MPSU10, MPSU60, and one type unknown transistor on both channels.
Please, advice what could it be?
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you can put 2pcs of 100n
be creative, and it'll not look uglier
you can put second one on back of pcb
re-new all soldering points you find suspiciously looking
that's it for start
be creative, and it'll not look uglier
you can put second one on back of pcb
re-new all soldering points you find suspiciously looking
that's it for start
Deeply appreciate your advice!
But I have just a pair, another pair 100n I have at home is ceramic. Would be nice combination, right?
Got your idea on soldering points, I will pass through all of them.
Any thoughts on unknown transistor on the board aside the regular set?
you can search for S200 schematic, they're around, then compare
I wouldn't use ceramic cap there
anyway , 90mV is nothing to write home about, so just chill and wait to order proper ones
I wouldn't use ceramic cap there
anyway , 90mV is nothing to write home about, so just chill and wait to order proper ones
Zen Mod, checked all the s200 related topics, but no schematics for s200 other than thresholdadjustment file posted by you, but I found very useful topic with your advice on adjustment..., and here I have not enough English:
@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@
What is NTC?
I also got confused with info about two s200 modifications, one with two trimpots for bias and dc offset, but mine with just one for bias...
@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@
What is NTC?
I also got confused with info about two s200 modifications, one with two trimpots for bias and dc offset, but mine with just one for bias...
Zen Mod, sorry for delay with the answer, but the new thread dedicated to the s200 instead of the picture in the s300 thread.
Further to this topic of bias for these units, I just did 3 in a row. This is what I found:
As the Master (Mr.P) has stated above, put a mV meter across one the 1.0 ohm emitter resistors. I found 135mv to be a good reference, I averaged 45 degrees Celsius across the mid section of the heatsink. "Tweak" as you see fit.
Keep in mind there is a section of the main black fin assy that in not attached to the aluminum heat spreader plate, So the front couple inches nearest the faceplate will feel cooler than at the rear apron. Also, access to the horizontal style bias pots can be achieved by removing the sub-back panel, 8 screws.
One final thing as the Master said, this is not a quick procedure. Give it 2-3 hours, especially if you have to make multiple adjustments.
Much respect,
Tweakjunkie
www.tweakjunkie.ca
As the Master (Mr.P) has stated above, put a mV meter across one the 1.0 ohm emitter resistors. I found 135mv to be a good reference, I averaged 45 degrees Celsius across the mid section of the heatsink. "Tweak" as you see fit.
Keep in mind there is a section of the main black fin assy that in not attached to the aluminum heat spreader plate, So the front couple inches nearest the faceplate will feel cooler than at the rear apron. Also, access to the horizontal style bias pots can be achieved by removing the sub-back panel, 8 screws.
One final thing as the Master said, this is not a quick procedure. Give it 2-3 hours, especially if you have to make multiple adjustments.
Much respect,
Tweakjunkie
www.tweakjunkie.ca