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Old 10th December 2005, 08:01 AM   #11
lgreen is offline lgreen  United States
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Quote:
Originally posted by AR2
Unfortunate. And I have 6 boards!!!
6 boards, lucky you! I am starting to think that it would have been easier to have 0 boards and hand-wire everything.
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Old 10th December 2005, 10:40 AM   #12
steenoe is offline steenoe  Denmark
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Lgreen, just a thought. Do you use singleended input? If yes, did you remember to connect the -IN to GND then? Otherwise it wont say anything!

Steen
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Old 10th December 2005, 11:28 AM   #13
dhole is offline dhole  United Kingdom
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Hi Guys

Yeah I got mine working just fine. Apart from the diode situation there are also some diodes on the rectifier board the wrong way round. again that is in the thread (" heatsinks for bosoz "I think)
Yeah I used Mikkels input selector board and volume control. Im just putting the finishing work to the case today.... Will post when complete.
regards
dave
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Old 10th December 2005, 08:05 PM   #14
lgreen is offline lgreen  United States
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Default working!

Ok, I got it working. Turns out my negative 6.5V power supply was not sufficiently negative to turn the transistors on.

todays changes

- changed the edgemost 3.6v zener diode in negative supplies from 3.6 to 9.1v, unloaded supply is now 10.1 V, loaded is 9.2 V. This is weird, I've got 2 zeners about 3 and 4 v each, plus a 9.1 zener and all i get is 10v out unloaded.

- added 39K 1/4W resistor (positive) and 2K (negative) to ground at output of power supplies to dissipate/load power supplies when power is turned off.

measurements-
- Positive CRC filter in operation drops 93.3V to 88.8 V.
- Positive regulator outputs 60.1V from 88.8 V, runs at +44 degrees C in free air.

Looks like its working for now anyway. got a few things to do but will post pictures.

FYI, the + rail just doesn't drop when you disconnect power, so I think its very important to have a bleed resistor somewhere on the + supply.
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Old 12th December 2005, 02:21 PM   #15
SteveA is offline SteveA  United States
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Default lgreen

What value caps did you use in your power supply (I also got 6 sets of boards)? I have a bunch of 1000uF/100v caps from both a simple BOSOZ and Aleph P1.7 projects left over. Do I gain anything by going to, eg, 4700uf?
Thanks,
SteveA
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Old 12th December 2005, 04:43 PM   #16
lgreen is offline lgreen  United States
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Default Re: lgreen

Quote:
Originally posted by SteveA
What value caps did you use in your power supply (I also got 6 sets of boards)? I have a bunch of 1000uF/100v caps from both a simple BOSOZ and Aleph P1.7 projects left over. Do I gain anything by going to, eg, 4700uf?
Thanks,
SteveA

I used CRC = 2200 - 47R - 2200 in for positive; CRC = 4700 - .5R - 4700 in the negative supply.

Here is a large hires picture of the power supply. Counting everything there are 8 regulated power supplies in there.

I have no idea why the boards are sized for 4700 uF capacitors but that's overkill. Then again, this design uses 5 MOSFETs per channel instead of the 2 in the original, so maybe you need more?? But think about the fact that the original supply was supposed to be for 2 channels, so by using separate boards for each channel you are effecively already doubling the capacitance.

Essentially, I'm not an expert on this but I'd feel ok with 1000 uF if I had dual mono boards (1 supply for 1 channel).

I listened to it for about 20 minutes late late last night-- is it me or is the gain on this less than with the bosoz?

Anyone know what the gain is?
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Old 13th December 2005, 04:26 PM   #17
SteveA is offline SteveA  United States
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Default transformer(s)

lgreen-
I neglected to ask what transformer(s) you used in the power supply? Do you have a recommendation?
Thanks,
SteveA
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Old 13th December 2005, 08:48 PM   #18
lgreen is offline lgreen  United States
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Default Re: transformer(s)

Quote:
Originally posted by SteveA
lgreen-
I neglected to ask what transformer(s) you used in the power supply? Do you have a recommendation?
Thanks,
SteveA
two different answers

I used a plitron 60-0-60 wired in parallel for each + rail and another transformer with multiple secondaries for the negative rails.

I don't recommend this, as 60-0-60 is a little too high for the voltages you need.

I cannot see why people dont start a stampeded to buy out all of these surplus transformers at Parts Express $29.68

quote:
Quote:
This multi-tap toroidal transformer is excellent for power amp building, and offers extra possibilities thanks to its multiple output voltages. 55V-0-55V 350VA output will run a power amplifier, 16.2V-0-16.2V output can be used for powering a pre-amp or EQ section, and 14V output can be used to power a cooling fan. Factory buyout - limited quantity!
Click the image to open in full size.

One transformer is sufficient for dual mono supplies. Its a no brainer.
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