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Old 8th November 2012, 02:38 PM   #2341
AndrewT is offline AndrewT  Scotland
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Your max becomes ~2.7A
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Old 8th November 2012, 07:28 PM   #2342
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I just finished installing the new 2x15V transformer and measurements are only slightly different. Does that show that the lower current is because of the certain fets?
I also removed the extra cement resistors leaving only the 10R one, so that I re-evaluate from scratch the sound per stage.

The voltage at the filtered caps is now +-20,3V

Vin: 9,99V and 9,95V
CSS: 1,598V and 1,618V
Offset: 0,9mV and 1,6mV

And after 20 minutes

Vin: 9,97V and 9,92V
CCS: 1,593V and 1,610
Offset: 0,9mV and 1,7mV


Which brings it again to about 160mA almost like before
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Old 8th November 2012, 07:36 PM   #2343
Salas is offline Salas  Greece
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Shows that your CCS was plenty alright before also.
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Old 9th November 2012, 07:28 AM   #2344
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Is there a way to snap the rectifier diodes from the pcb and put them on a separate case with the transformer?
Or will I have to just use a separate pcb ?

Last edited by dimkasta; 9th November 2012 at 07:34 AM.
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Old 9th November 2012, 10:16 AM   #2345
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Quote:
Originally Posted by dimkasta View Post
Is there a way to snap the rectifier diodes from the pcb and put them on a separate case with the transformer?
Or will I have to just use a separate pcb ?
You can just put them in a seperate case with some sepate caps, then run the wiring to caps directly.
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Old 9th November 2012, 10:38 AM   #2346
Salas is offline Salas  Greece
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You can mount and sink/isolate them diodes in a separate case with the one pair 4700uF filter capacitors, then use AC power chord like thickness umbilical to the DCB1 empty caps pair pads to feed the remaining capacitors. Can use small value power resistors between bridge and capacitors pair at the PSU case for dropping about 1V. It will smooth the EMI from the heavy current charge cycle.
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Old 9th November 2012, 09:20 PM   #2347
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I increased the CCS current again.
CCS resistors are now ~2R85 (1x10R and 3x12R) and voltage accross them ~1,37V giving ~480mA.
Temperature on the plate after 3 hours is ~36C and on the Fets ~39C.
I think that anything more than that would result in more than the psycological barier of 50C in the closed case.
So to further increase the CCS current I would have to either reinforce the plate with some additional heatsinks, or use some kind of battery powered small fan to circulate some cold air in there. Maybe both.
Either way, I have to finish the case before going further. Unfortunately I am still waiting for my new circular saw...
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Old 9th November 2012, 10:20 PM   #2348
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Ok I got a little impatient, so....
Adding a 4th 12R in parallel (2,3R CSS res) gave ~1,33V and ~1,37V or ~580mA.
And a 5th one (1,93R) gave ~1,29V and 1,326V or ~670mA

I also changed the fuse to a 5A one. Oh and the light bulb checker gets a nice glow now (I measure stuff without it of course)

Unfortunately it' s late here and I am getting tired for more testing. I hope I can find some nice heatsinks tomorrow, and hopefully some 5R @10W resistors to avoid all the stacking...
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Old 9th November 2012, 10:30 PM   #2349
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And a small additional sound impression.
With the Mills 10R alone, the buffer was impressive. My system had an almost SET big-tube feeling.
Adding parallel 12Rs (unfortunately cheap ones) kept increasing the separation of sounds and width and depth of the stage. Unfortunately things got a bit more weak as well and lost that SET sensation, but it could be because of that freshly soldered chunk of cheap resistors.
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Old 12th November 2012, 08:58 PM   #2350
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I got some more resistors and heatsinks to further push the circuit

With 2 of the additional heatsinks placed like that on the plate and the CCS current at ~670mA, the temperature was ~36C on the plate and ~39C on the fets.

So it was time for the next step.
I replaced the 5 12R resistors with 5 5R9 ones pushing the resistance to 1,05R and the current to 1,180mA.

I am currently listening to it like that. The increase in separation, clarity, textures and sentiment was again quite big. What is worth noticing is that instruments especially wind and string ones sound more emotional without sounding sweeter or bigger. Same with voices. Unfortunately it s late again, so I will have to watch its temperature silently
But first impressions are again that It`s definetely worh the effort to push it to the upper limit...

Another issue that occured is that I started to get some minor vibration from the Hammond transformer (damn hammonds always do vibrate). So I will have to either move it outside the case, or put it on top of a big chunk of wenge to dampen it.
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