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SteveA
diyAudio Member

Join Date: Dec 2001
Location: St Paul, MN
Quote:
 Originally Posted by AndrewT If the bulb briefly glows and then goes out, that tells you the start up surge drew enough current for long enough to warm up the filament to dull red. It then tells you the current after that surge was too low to maintain that dull red glow and confirms the running current is now quite low. The circuit/equipment attached to the other end of the transformer is not going to blow up. There is simply too little power available to cause serious damage. The DMM readings were changing ! Do you know how to set the DMM to get a reading from it?
I am not sure what happened yesterday. Today I read 40V between the CT and reach rail so, with the exception that I should be reading 35V everything seems okay. Any reason why I should see 40V instead of the 35V (I do have a second identical transformer I can measure for a comparison)?

Thanks Andrew, your help is much appreciated.
Steve

currentflow
diyAudio Member

Join Date: Apr 2008
Quote:
 Originally Posted by SteveA I am not sure what happened yesterday. Today I read 40V between the CT and reach rail so, with the exception that I should be reading 35V everything seems okay. Any reason why I should see 40V instead of the 35V (I do have a second identical transformer I can measure for a comparison)? Thanks Andrew, your help is much appreciated. Steve
Hi,

From your earlier post, Y236752 was the transformer part code I believe you mentioned. From the data sheet, these have a quoted regulation of 6% (typical) which is determined by the formula:

Reg% = (VN - VL) / VL * 100
where VN is the no-load voltage and VL is the full-load voltage (=35V)

Rearranging, VN = 35+(35 x 0.06) = 37.1V. This assumes that your mains voltage matches the manufacturer's quoted primary voltage. In essence, 40V measured off-load isn't anything to be concerned about.
__________________
Regards,
currentflow

SteveA
diyAudio Member

Join Date: Dec 2001
Location: St Paul, MN
Quote:
 Originally Posted by currentflow Hi, From your earlier post, Y236752 was the transformer part code I believe you mentioned. From the data sheet, these have a quoted regulation of 6% (typical) which is determined by the formula: Reg% = (VN - VL) / VL * 100 where VN is the no-load voltage and VL is the full-load voltage (=35V) Rearranging, VN = 35+(35 x 0.06) = 37.1V. This assumes that your mains voltage matches the manufacturer's quoted primary voltage. In essence, 40V measured off-load isn't anything to be concerned about.
Thanks currentflow,
So then the +/-52.3 V I read at FC3 and FC1, respectively, is also nothing to be concerned about (vs +/-49V) correct?

currentflow
diyAudio Member

Join Date: Apr 2008
Quote:
 Originally Posted by SteveA Thanks currentflow, So then the +/-52.3 V I read at FC3 and FC1, respectively, is also nothing to be concerned about (vs +/-49V) correct?
Could you provide a link to the schematic you are using please?
__________________
Regards,
currentflow

SteveA
diyAudio Member

Join Date: Dec 2001
Location: St Paul, MN
Quote:
 Originally Posted by currentflow Could you provide a link to the schematic you are using please?
It's AAK's design with the PSU on the board as well. See post #53 of this thread for amp schematic and post #114 for PSU schematic.

currentflow
diyAudio Member

Join Date: Apr 2008
Quote:
 Originally Posted by SteveA It's AAK's design with the PSU on the board as well. See post #53 of this thread for amp schematic and post #114 for PSU schematic.
Your off-load measured voltage of 52.3V DC is fine and will reduce when the amplifier is delivering higher power levels into a load. This is a perfectly normal characteristic of unregulated power supplies.
__________________
Regards,
currentflow

 27th May 2012, 02:18 PM #497 SteveA   diyAudio Member   Join Date: Dec 2001 Location: St Paul, MN I bought 6 (and rec'd 12) of the version 1.3 amp quite some time ago. I have now returned to the project having completed all the boards(except for output transistors on 4) I have tested the 8 boards which are complete (complete with dim bulb tester). The bad news is 3 failed the smoke test. The somewhat better news is that the other 5 all passed the smoke test (all 8 board display the correct rail voltages of +/- 52.3 V which is inline with noload conditions for a 35-0-35 transformer I'm using). Testing the 5 boards with the 100R safety resister inplace I measured voltage drops accross this resistor ranging from 1.4V tp 1.7V. The assembly manual for version 1.4 indicates this drop should be 2.5-3.5V. Should the voltage drop for version 1.3 be the same or, if not, what should it be (and do I have an issue with the 5 smoke free boards)? Thanks, SteveA
 16th June 2014, 12:28 PM #498 cucicu   diyAudio Member   Join Date: Oct 2011 Location: Italy pcb file Hi guys! I'm now trying to build symasym 5.3 version and I was looking for pcb files...I lik the AAK ones, hey are you in? can you send that files for fidocad or eagle software?? thanks a lot bye
 26th August 2014, 08:04 PM #499 mrsavage   diyAudio Member     Join Date: Nov 2011 Location: Columbus, Ohio PCB files, etc.
 27th August 2014, 08:08 AM #500 touchdown   diyAudio Member   Join Date: Mar 2006 Location: Vicenza In case anyone is interested, I have a stereo pair of Symasym 5.3 boards from original group buy and I could also provide a pair of AAK ver. 1.3 boards, unused by one of my friends. Nicola/touchdown

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