Can someone please tell me how to fix the power supply on a Threshold S/500 STASIS Power Amplifier? I have some schematics, but they're general overviews for several later designs. I need the specific technical information on this particular model. Hopefully, someone can tell me the voltage, tolerance, and bias.
Attachments
Can you be a little more specific as to what's wrong? Honestly, it's unlikely that the power supply itself has died, unless you've got an old cap that's given up the ghost. There's not much else to screw up. There's a power transformer, bridge diode, and caps for each channel. Nothing fancy.
I've got two S-500s and have done a little of this and that over time. It's been a while, but I seem to recall that the S-500 rails are around +70 or 75V. The bias is set, not so much by voltage, as by the temperature of the heat sinks.
You'll need to specify what it is you're seeking the tolerance of.
Grey
I've got two S-500s and have done a little of this and that over time. It's been a while, but I seem to recall that the S-500 rails are around +70 or 75V. The bias is set, not so much by voltage, as by the temperature of the heat sinks.
You'll need to specify what it is you're seeking the tolerance of.
Grey
Threshold S/500
I've got to get it back out to look. Another person looked at it and told me that was the problem. If you still have yours are able to take a picture of the inside for me . The area where the AC line comes in has had some serious physical damage. A small PCB (approx. 40mm x 80mm) has places where wires were and some missing components. I'll try to get to it ASAP. Thanks a lot for your help. It was sooner than expected.
I've got to get it back out to look. Another person looked at it and told me that was the problem. If you still have yours are able to take a picture of the inside for me . The area where the AC line comes in has had some serious physical damage. A small PCB (approx. 40mm x 80mm) has places where wires were and some missing components. I'll try to get to it ASAP. Thanks a lot for your help. It was sooner than expected.
hello,
good evening to all of you,
I am newbie of this forum and would like to ask something about my amp (threshold S500 II )bought used a few months ago. I bought it to drive my Apos Centaur. But result was a little disappointing: very good bass and dynamics, large front soundstage but reduced trasparence and little definition and airiness. So, I would like to replace the old capacitors in main power supply with fresh ones ( bypassed with Jantzen HighEnd Z-Superior Cap 0,47 uF - 800V).
I wanted to know if instead of the originals from 29000uF could I put 4 from 47000uF or if this could cause problems with the bridge for the increasing current, and therefore it is better to stop with only 33000uF.
I have also inspected the 5 fuses (to renew them with the magic liquid of Van der Hul) and I discovered that the previous owner had them all replaced with SLOW fuses instead of fast. I changed them with those of the original type ... but the sound is much worse: low lighter and confused, small dynamic, aggressive medium-high. The amplifier has more than 20 years (though it seems, even within, upon leaving the factory) and who knows how long have those kind of fuse. None of you has done the same change on your Threshold? Which are the really risks ?
Many thanks
Alessandro
good evening to all of you,
I am newbie of this forum and would like to ask something about my amp (threshold S500 II )bought used a few months ago. I bought it to drive my Apos Centaur. But result was a little disappointing: very good bass and dynamics, large front soundstage but reduced trasparence and little definition and airiness. So, I would like to replace the old capacitors in main power supply with fresh ones ( bypassed with Jantzen HighEnd Z-Superior Cap 0,47 uF - 800V).
I wanted to know if instead of the originals from 29000uF could I put 4 from 47000uF or if this could cause problems with the bridge for the increasing current, and therefore it is better to stop with only 33000uF.
I have also inspected the 5 fuses (to renew them with the magic liquid of Van der Hul) and I discovered that the previous owner had them all replaced with SLOW fuses instead of fast. I changed them with those of the original type ... but the sound is much worse: low lighter and confused, small dynamic, aggressive medium-high. The amplifier has more than 20 years (though it seems, even within, upon leaving the factory) and who knows how long have those kind of fuse. None of you has done the same change on your Threshold? Which are the really risks ?
Many thanks
Alessandro
I concur with your conclusions. Have one of the smaller brothers in a cupboard somewhere. Seriously doubt that power supply improvements will help the transparency enough. Maybe from a wet blanket to an almost dry blanket
But on the bright side so many other designs will fit the case and the heatsinks. If you are increasing the capacitance a new discrete rectifier may help the sound a little bit more, especially using nice Schottky diodes.
Fuses generally suck soundwise but if you really must have them why not give the new ones a chance to break in? And maybe try a few different makes.
Thanks for the quick response!
I'm asking because I have a S/500 since a few days.
The first thing I did was the "hands on heatsinks test".
I have different results on the both sides Left/Right.
Let's say 10 sec left - 5 sec right.
I haven't measured the voltages values already, will do this tomorrow.
So I wonder should I adjust both sides to the 5 sec version?
Kind regards,
Gerhard
I'm asking because I have a S/500 since a few days.
The first thing I did was the "hands on heatsinks test".
I have different results on the both sides Left/Right.
Let's say 10 sec left - 5 sec right.
I haven't measured the voltages values already, will do this tomorrow.
So I wonder should I adjust both sides to the 5 sec version?
Kind regards,
Gerhard
I replaced the blue singleturn Bourns pot (5K) with a Spectrol multiturn one to control the bias somewhat better. I can now reach the pot from the top.
When the amp is cold remove the top cover an backplate. Remove one of the rialfuses (negative one is always advised) and attach the leads of a MM (with the highest Amperesetting) firmly to the poles of the empty fuseholder. Rearrange the leads in such a manner that you can put the topcover on again. Block the exposed back as much as you can but you must still be able to reach the biaspot, The final biassetting should be reached with the amp closed that's why. Put a temperaturerod in one of the screwholes at the back to measure the temp. Now power up the amp and watch the biascurrent go up very quickly (that's intended to get a stable temperature more quickly) and when the amp is warmed up it will decline gradually to a stable value. This should be reached within two hours max. For a S/500 a value of 1.25 Amps biascurrent and a temperature of 50 degrees Celcius is nice. You'll have 50 Watts of Class A peak power per channel.
Turn the biaspot very gentle with small increments otherwhise you will overshoot!
I performed this procedure several times with my S/1000 Series II and I have them stable at 2 amps bias and 50 degrees Celcius.
Good luck!
When the amp is cold remove the top cover an backplate. Remove one of the rialfuses (negative one is always advised) and attach the leads of a MM (with the highest Amperesetting) firmly to the poles of the empty fuseholder. Rearrange the leads in such a manner that you can put the topcover on again. Block the exposed back as much as you can but you must still be able to reach the biaspot, The final biassetting should be reached with the amp closed that's why. Put a temperaturerod in one of the screwholes at the back to measure the temp. Now power up the amp and watch the biascurrent go up very quickly (that's intended to get a stable temperature more quickly) and when the amp is warmed up it will decline gradually to a stable value. This should be reached within two hours max. For a S/500 a value of 1.25 Amps biascurrent and a temperature of 50 degrees Celcius is nice. You'll have 50 Watts of Class A peak power per channel.
Turn the biaspot very gentle with small increments otherwhise you will overshoot!
I performed this procedure several times with my S/1000 Series II and I have them stable at 2 amps bias and 50 degrees Celcius.
Good luck!
Bias on S500
Hi, Did adjusting the bias to 100mV across the 1 Ohm resistor on the emitter side get you to the correct temp?
Hi, Did adjusting the bias to 100mV across the 1 Ohm resistor on the emitter side get you to the correct temp?
Bias adjustment on the S500 - need help
Any way you can take some pictures of the procedure you do it the next time and post - not sure where the rail fuse is nor the pot..
Any way you can take some pictures of the procedure you do it the next time and post - not sure where the rail fuse is nor the pot..
Just got a clean S/500 optical bias amp, The sound is wonderful however there are 3 problems with it that some of you Guru's can help Me with: First off the LED light went out so I replaced it and the 68ohm resistor which was a little toasted with a 2watt metal oxide however the new resistor burnt up in 5 seconds, any suggestions? Secondly there is a lot of Static noise from the amp at the speakers wandering if new PS caps would be the cure? And lastly the ubiquitous turn on THUMP that I have seen mentioned on the site but never addressed as to the CURE! Please help! Thanks
68 ohms is an unlikely value for a LED current limiter. You want a couple mA,
so find out what voltage is driving that circuit, subtract a couple volts for
the LED drop, and figure out what resistor you need.
Static noise is usually a bad connection somewhere, although heard claims
that it's old capacitors, something I have not seen personally.
so find out what voltage is driving that circuit, subtract a couple volts for
the LED drop, and figure out what resistor you need.
Static noise is usually a bad connection somewhere, although heard claims
that it's old capacitors, something I have not seen personally.
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