Same with other IPS's ??
Is your bias "squirrly" with the 2mhz ?
I have my OPS's remachined and am running them now to test stability. I'll
attach one of my Kypton C's to compare with yours (I/V readings). I can run at either 40 or 66V rails , as well.
Edit .. what caps are at the kypton VAS (tan ones) ... they dont look like the 33p poly's I use
or silver mica's ???
OS
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Bias isn't bad. The oscillation isn't there with CFA-XH. It's lower frequency and voltage with Symasui. I haven't had a chance to experiment much yet.
Neither have I.
If anything , the cap multiplier would make things better.
I've actually listened to the "C" (at a quite high volume).
I also might have oscillation , but I can't tell - it sounds great.
OK , just put those 2.4k's and trimmer in the "C" (below 1).
.... 63V rails
(below 2) - are my exact part values. Vas is 7.7ma on R22 minus 68V/33K for
R25 = 2.06ma for the blue leds .... a 5.64ma vas I.
Never adjusted the R24 -50K trimmer... should be 25K as new.
I'll see if the servo has anything to do with operation ( not in yet).
How big (amplitude) is this oscillation ?
Edit - try running G2 direct to PS ground and don't return your load ground to the OPS (right
to the PS. You mean the symasui oscillates , too ?
OS
If anything , the cap multiplier would make things better.
I've actually listened to the "C" (at a quite high volume).
I also might have oscillation , but I can't tell - it sounds great.
OK , just put those 2.4k's and trimmer in the "C" (below 1).
.... 63V rails
(below 2) - are my exact part values. Vas is 7.7ma on R22 minus 68V/33K for
R25 = 2.06ma for the blue leds .... a 5.64ma vas I.
Never adjusted the R24 -50K trimmer... should be 25K as new.
I'll see if the servo has anything to do with operation ( not in yet).
How big (amplitude) is this oscillation ?
Edit - try running G2 direct to PS ground and don't return your load ground to the OPS (right
to the PS. You mean the symasui oscillates , too ?
OS
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Board error !!!
Added my servo - did not work.
Edit - servo "railed" and could only get offset down to 40mv.
R6 on PCB was marked "10K" , I just stuffed it as marked.
Should be 220R , the mirrors were "floating" with just a high Z
servo reference. Put the 220R in .... 2mv steady offset.
Don't know if this could cause oscillation , but it caused me some
"head scratching" 😕 .
Jeff , review my last posted schema - and double check everything !
Mine seems to be quite solid now , normally offset is also "squirrly"
with oscillation .
A very slow cycle between 1.8- 2.1mv - pretty steady. 🙂
Edit - with servo Z so high ... parasitic feedback through R8 from the
G1-G2 current returns could be an issue. R8 is a safety thing - it can actually be
removed. C9 could of been the only thing keeping this thing from
getting full blown FB though the grounds.
OS
Added my servo - did not work.
Edit - servo "railed" and could only get offset down to 40mv.
R6 on PCB was marked "10K" , I just stuffed it as marked.
Should be 220R , the mirrors were "floating" with just a high Z
servo reference. Put the 220R in .... 2mv steady offset.
Don't know if this could cause oscillation , but it caused me some
"head scratching" 😕 .
Jeff , review my last posted schema - and double check everything !
Mine seems to be quite solid now , normally offset is also "squirrly"
with oscillation .
A very slow cycle between 1.8- 2.1mv - pretty steady. 🙂
Edit - with servo Z so high ... parasitic feedback through R8 from the
G1-G2 current returns could be an issue. R8 is a safety thing - it can actually be
removed. C9 could of been the only thing keeping this thing from
getting full blown FB though the grounds.
OS
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I've been planning to test my KryptonC but have been struggling with a couple other amps. I'm glad you guys beat me to it. I will benefit from your trials. So glad you finally have a test circuit OS.
Blessings, Terry
Blessings, Terry
I did notice the ground was dirty but never got to running it directly to the star ground. I can't remember for sure but I think the oscillation was around 1.5V. The oscillation on Symasui was around 1 volt. These are the boards that were modified to make the servo settle faster. They didn't seem as stable after the changes.
I see changes to R6, R15, R16, R22, R23, R26 and R27. Did I miss anything? My servo seemed to be working as it was but I'll make all these changes anyway. That's a huge change on R6.
I've attached the schematic these were drawn from.
Attachments
Hi
I saw in a earlier post in this thread that Kypton C schematic where the "Feedback resistor" R15,R16" are 1Kohm and R14,R15 are 39ohm
for low distortion
Did anybody test that and is it safe and stable?
The VAS should be high @ 8ma because it is the main Re's I (R22/27) minus
the LED current that determines the actual VAS I.
I left mine on overnight (below) - still 527mv -R22 (7.75ma) - 2.3ma LED I.
Offset after cleaning flux from TL072 is .6mV.
I notice LED's pass more current as total VAS current increased with temp. , keeping
the VAS at a constant current. Cool to see this in real life.
This IPS is now 5.4ma VAS , Ill swap it with my wolverine - which is also a
solid 5.4ma .... to see if there is any change to the OPS.
PS - on this test amp (and my dedicated amps) Load returns all go directly
to the chassis star (or cap bank ground) , not the OPS G1.
I'm in the "trenches" with Y'all now .. huh ? 😀
Edit - that toroid fell off the end of the board and fell right on my big toe !! (in the trenches - pain for amps).
OS
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What should the voltage drop be across a blue LED? There seems to be a fairly wide range now. Maybe that's where some of my issues are starting.
Just broke off R8 on the PCB - offset is 0 ? wow !
Now , no path for any ground contamination to the mirrors.
No R8 , total current of R7/9 set the input pair I ... servo is
in total control now. If the servo failed (railed) , the OPS might
put out some hefty DC (but we have protection).
But , How often does a servo fail ?
OS
Now , no path for any ground contamination to the mirrors.
No R8 , total current of R7/9 set the input pair I ... servo is
in total control now. If the servo failed (railed) , the OPS might
put out some hefty DC (but we have protection).
But , How often does a servo fail ?
OS
I just measured my blues (ones you ordered-kingsbright). 2.67V Vf.
This stays quite steady , unless you subject to 0-40C temperature swings.
If they light up the same they should drop the same Vf. As they heat the Vf
should drop a little ... (2.5+ - 2.6) , and current through R25/33K should increase.
R25 Voltage went from 68- <70V as I closed the front door to let this IPS
get warmer.
On this and any of the 5-6ma VAS's ... you do not need any heatsink.
They still run cool , even when I was running in my toasty amp case.
I DID add a very small piece of flashing cut with scissors to all the IPS's ,
just in case.
This is fun 😎 . (when things work , that is).
Simulator shows 84mv offset with no servo - that's what I had (86mv)
and nanovolt offset without R8 - this is what I have now.
Simulator matches the real deal almost exactly !!
OS
I wouldn't bother swapping but I'd sure get some 1206 100nF/100V X7R SMD caps and solder them in parallel on the opposite side. I use them exclusively in all my PCB designs. They are cheaper than dirt too, less than 2c a piece.
I'm using those red wima .1uf's and those "no-name" blue's you sent me ...
I notice no issues ??? This would not cause oscillation ?
OS