I thought I'd drop a message here to see what people think about running SSHV2 at around 350Vout & about 60mA working current for a PX25 output stage?
From reading through this thread, I get the feeling it's up at the higher end of what's safely achievable.
I also intend to run SSHV2 for the pre-amp stage (2 stage IT coupled SET amp) but at 130Vout & 6.5mA I'm not too worried about that.
From reading through this thread, I get the feeling it's up at the higher end of what's safely achievable.
I also intend to run SSHV2 for the pre-amp stage (2 stage IT coupled SET amp) but at 130Vout & 6.5mA I'm not too worried about that.
Output stages have high peak to idle ratio in music so to cover that an also high CCS limit is asked to be set for. There is a 100-120mA set ceiling usually here anyway (depending on DN2540 sample IDSS). Burning much current difference (Pk-idle) on the shunt Mosfet at 350V for most of the time is a big thermal issue. Calculate your output stage's case and see about waste and sinking ability.
Thanks Salas
Extreme case on output stage would be a current swing of about 30mA, so quite a lot on top of the 60mA idle. Might be manageable though; heatsinks for Q3 will need to dissipate 10.5W (350 x 30mA). Should be possible, but depends on actual build and heat being generated by other components.
I will bear in mind design and thermal considerations given here and elsewhere in the thread but probably give it a go after experimenting with pure passive and then SSHV2 at a lower bias point (300V, 45mA) before attempting the 350V, 60mA configuration.
Just thinking of safe design limits and out of curiosity, what happens if the output stage (or any stage for that matter) asks for more current than the CCS has available to provide?
Extreme case on output stage would be a current swing of about 30mA, so quite a lot on top of the 60mA idle. Might be manageable though; heatsinks for Q3 will need to dissipate 10.5W (350 x 30mA). Should be possible, but depends on actual build and heat being generated by other components.
I will bear in mind design and thermal considerations given here and elsewhere in the thread but probably give it a go after experimenting with pure passive and then SSHV2 at a lower bias point (300V, 45mA) before attempting the 350V, 60mA configuration.
Just thinking of safe design limits and out of curiosity, what happens if the output stage (or any stage for that matter) asks for more current than the CCS has available to provide?
It simply limits the current at set value and the output voltage goes lower when more current is demanded. Its acting like a bench supply in CC protection mode*. That will lead the audio amp to compress the signal peaks. For the reg itself to remain fed for max contained peaks you should also allow it at least 5mA margin on top of those.
*CV CC example video
https://www.youtube.com/watch?v=Z0zRkfVpU6c
Ok time for ask for help :. I bought 2 complet sshv2 from tea-bag put the elements in and output 0.3V led is not on. Q1 heatsink get extreamely hot. But on positive site...i can set up current over 100mA (1V+ on test points). Thow i need only 60mA (40mA for the load).
I check zener,bjt,mosfet,led,jfet...all ok. For jfet i measured 3.34 and 3.28mA of Idss
When regulator is not connected i can measure resistance between emitter and collector on Q5 form like 100-400ohm.
Tryed to put C on input...No effekt.
My load is 5k
Im running out of ideas. The only thing that i can think of is mybe due to floating power supply. And slite chance if i dont know how to measure jfet (2sk117gr).
I do have scope... If you tell me what to look at...your regulator is verry specially. Thank you for the help.
I check zener,bjt,mosfet,led,jfet...all ok. For jfet i measured 3.34 and 3.28mA of Idss
When regulator is not connected i can measure resistance between emitter and collector on Q5 form like 100-400ohm.
Tryed to put C on input...No effekt.
My load is 5k
Im running out of ideas. The only thing that i can think of is mybe due to floating power supply. And slite chance if i dont know how to measure jfet (2sk117gr).
I do have scope... If you tell me what to look at...your regulator is verry specially. Thank you for the help.
I hope i did connect load correctly ... i resistor connected on external points and external points bridged on inner... off course negative and positive seperate...
I have quite big voltage drop on supply--- from 271V to 218V.
Zener was orientated as on picture from pcb..
My be you should tell me what kind of steps should take to test or in HV test or LV test.
I made pictures but i cant upload them here...
Q5 and Q4 those are little difficult to see..but text is looking to input side and physical shape is same as bottom picture (on pcb)
I have quite big voltage drop on supply--- from 271V to 218V.
Zener was orientated as on picture from pcb..
My be you should tell me what kind of steps should take to test or in HV test or LV test.
I made pictures but i cant upload them here...
Q5 and Q4 those are little difficult to see..but text is looking to input side and physical shape is same as bottom picture (on pcb)
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Your CCS works as you say. So no LV test needed for that. You must not be having current through the voltage reference resistors (R9,R10) in the way you describe the problem. That current normally comes from Q6. Which needs Q5's Vbe to operate so to have normal Vout and the LED on. Measure BE voltage of Q5. Must be 0.5-0.7V. Make sure that Q4 & Q5 have the correct orientation. Letters on them can be faint, and in the way their cases are made when not using a flashlight their front & back can be easily mistaken. If you want to do LV test and debug for Vout safely you must change R9,R10 to an order of magnitude lower values so to make the reg LV and work on it. Use LV Vin also then. 30-40V.
P.S.
Take out D3 also and put a 1A diode in its place. Schottky even better. Just in case D3 is broken but it does not show as burned.
P.S.
Take out D3 also and put a 1A diode in its place. Schottky even better. Just in case D3 is broken but it does not show as burned.
I done as you told me...nothing and 0.... D3 was changes to uf1007... I dont think there is problem in power supply ..i have 2x 100ohm and 2x C about 600uF.
In 2 weeks i will get New parts like bjt....
Btw i have some fake 117 ant they put out 17mA of Idss... Will they work if i will need them in future?
I find something interesting while checking resistors if they wore in right place. When i measure ccs resistors inside pcb...values wore offcourse incorect (cant make measurments inside pcb) but i get correct value in shunt part- is that normal?
Tomorrow i will check capacitors... I really dont know what to do. As for Q5 and Q4 in addition to writing Are 3 small circles facing input side. And in back is 1 circle facing C2. I looked on bartolas pictures how they Are turned ... As for connection load there was picture on these form ...you helped some guy from us..about page 340 ..ish
In 2 weeks i will get New parts like bjt....
Btw i have some fake 117 ant they put out 17mA of Idss... Will they work if i will need them in future?
I find something interesting while checking resistors if they wore in right place. When i measure ccs resistors inside pcb...values wore offcourse incorect (cant make measurments inside pcb) but i get correct value in shunt part- is that normal?
Tomorrow i will check capacitors... I really dont know what to do. As for Q5 and Q4 in addition to writing Are 3 small circles facing input side. And in back is 1 circle facing C2. I looked on bartolas pictures how they Are turned ... As for connection load there was picture on these form ...you helped some guy from us..about page 340 ..ish
Yes Q4and Are as you Said. I check 2 times led...for stupidity i will turn it incorect. Oh these led have Uf 1.6V will be ok if i put led with Uf1.7V?
Now i need to write administrator why i cant upload pictures. Are smd versjon of 2sk117 1:1 ? Because those Are in production if im not mistanken called something 0880... I forgot specific name.?
Now i need to write administrator why i cant upload pictures. Are smd versjon of 2sk117 1:1 ? Because those Are in production if im not mistanken called something 0880... I forgot specific name.?
Try to light the led up if your DMM can in diode mode or with a 9V battery briefly. Black probe to square pad. Red probe to round pad. If it does not light up that way its either backwards or burned. Any red Led will do.
*For attaching pictures go to advanced answer menu and manage attachments button
**2SK880GR but they will need an adapter mini board like the ones they sell on ebay etc
*For attaching pictures go to advanced answer menu and manage attachments button
**2SK880GR but they will need an adapter mini board like the ones they sell on ebay etc