Chip amp power supply- a beginners guide - Page 41 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 5th June 2009, 02:20 PM   #401
tent is offline tent  Germany
diyAudio Member
 
Join Date: May 2009
Genial!

I tried out to outwind a bit the trafo and disconnect those two couples of wires that where tied toghether and soldered at the end: and yes! Now I have dual secondaries.. both exiting with 12.8V (!!)
So now I'd need only to decide which two of the now 4 wires are to be connected toghether to form the center tap and I'd try it with one trafo alone.
The real incredible news is also this: I tried to carefully move a bit the windings and try to put them more "flat" and "parallel" I'd not know how to say, but this finally LET THE TOROID sound less noisy!!! Woa! Ok you can still hear the humm if you are close but really nothing compared to previousely!
The Lamp tester is still showing a dim light, but really dim (you can just see the filament is getting orange)... ?

well.. lot's of things to learn from toroids, really!

tent:wq
  Reply With Quote
Old 5th June 2009, 03:28 PM   #402
tent is offline tent  Germany
diyAudio Member
 
Join Date: May 2009
I'm now trying to do a center tap configuration but when I connect two wires of different secondaries toghether I can measure still 12.8Vac between that just realized center tap and each of the remaining two wires, but I'm not able to measure 24Vac if testing only those reamining two free wires (I read 0Vac). Any ideas? I tried to connect both possilble wires togheter, excluding the other two that would short everything..

tent:wq
  Reply With Quote
Old 5th June 2009, 04:54 PM   #403
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Connect each of the four secondary wires to separate terminals of an insulated terminal block.
Connect each of the mains (primary) wires to a separate insulated terminal block.
Connect a plug top to the mains terminal block.
Insert the transformer plug top into the outlet socket of your bulb tester.
Insert the plug top of the bulb tester into the mains outlet socket.
Switch on. The bulb should remain off. If it flashes or glows dimly there is something wrong with your transformer.
Test both transformers.
Do not use either until they pass this "bulb off" test.
__________________
regards Andrew T.
  Reply With Quote
Old 5th June 2009, 09:40 PM   #404
tent is offline tent  Germany
diyAudio Member
 
Join Date: May 2009
Quote:
Originally posted by AndrewT
Connect each of the four secondary wires to separate terminals of an insulated terminal block.
Connect each of the mains (primary) wires to a separate insulated terminal block.
Connect a plug top to the mains terminal block.
Insert the transformer plug top into the outlet socket of your bulb tester.
Insert the plug top of the bulb tester into the mains outlet socket.
Switch on. The bulb should remain off. If it flashes or glows dimly there is something wrong with your transformer.
Test both transformers.
Do not use either until they pass this "bulb off" test.

Hi again,
and sorry for this neverending story..
I tried EXACTLY as you proposed above and BOTH trafos (220Vac-2x12.5Vac, 200VA) let the 60W bulb on the tester illuminate the tungsten filament very dimmly (but they certainly do).
So now I wanted to be 100% sure I was not doining anything wrong and decided to temporarily remove another toroidal transformer from another device and test it the EXACTLY same way on my light bulb tester (this third other test trafo is a 220Vac-2x25Vac, 120VA): the result is infact that the bulb is not illuminating in any way (not even dimly), only at the first power on it did very shortly but then no red filament any more.
Re tested back both the other trafos and again a very very dim filament gets enlightened.. is it possible they both are somehow broken/shortcircuited?
I decided to test them also with my instrument tester using the "beep" position to see if there are shorts between the primary wires (both) and the secondary ones (four), so like 8 test, but no beep (the beep only if touching the two primaries at the same time or any of the secondaries between them, so I suppose all regular. I also read the resistence of the primary winding (something c.a. 10ohm) and the secondaries (c.a. 1.5ohm) but this maybe makes no sense.
Well, I think that anyway now, even if they are not noisy any more, they have a clear destiny: tomorrow I'll se for some new ones..

Thanks for all the support, all was probably because of those two guilty trafos, sorry for the annoyances, and thanks again. :\

tent:wq
  Reply With Quote
Old 6th June 2009, 12:42 PM   #405
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
is it possible these are 110/120Vac transformers?

A transformer draws increasing idle current (when no load is connected) as the mains voltage is increased.
At some elevated voltage (~140% of rated voltage) the idle current increases rapidly and thus heats the transformer excessively. Eventually at some very elevated voltage the transformer will fail. During this elevated supply voltage the transformer is also quite mechanically noisy.

Can you insert a 10r0 resistor into the primary feed? Careful it will be live.
Use the light bulb as your limiter and measure the current through the 10r0 resistor and the voltage across the transformer. From this some transformer expert can probably identify if the transformer is faulty or overvoltage or OK.
__________________
regards Andrew T.
  Reply With Quote
Old 7th June 2009, 12:01 AM   #406
tent is offline tent  Germany
diyAudio Member
 
Join Date: May 2009
Hi, I finally solved the trafo issue by buying two new ones: those are completely SILENT and DO NOT let the bulb tester glow in any way, so very good I'd say..
The two old trafos are 220V rated, only one primary made of two wires, but if there is no error it's so. Did not get if the suggested resistor would be to inserted in series or in parallel to the primaries to do that test, Andrew.

Kr,
tent:wq
  Reply With Quote
Old 7th June 2009, 02:40 PM   #407
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
put a 10r0 resistor in parallel and BANG

220Vac across 10r0 is about 220 * 220 /10 Watts ~5kW
__________________
regards Andrew T.
  Reply With Quote
Old 7th June 2009, 04:02 PM   #408
tent is offline tent  Germany
diyAudio Member
 
Join Date: May 2009
/oh, well, I see: you're totally right!!

So, a couple of updates on my current situation:

But now I'm working with the new trafos (no bulb light if I use them alone).

Later I connected also the PSU: is it normal that so it is very very very dimly lit? (with my 60W lamp you can notice it only during the night by turning off all the other lights..

Then the next step was to connect also the lm1875 amp and no big difference in the lamp (and I also measured the diff voltage on the outputs and now I get a more beautiful 14mVdc..).

When I finally put there an 4ohm loudspeaker the lamp gets a little bit lighter but still so little it is difficult to notice. Is this supposed to be still good?


Anyway now that all was running more silently I begun to notice also some small humm and hiss from the speakers, I'm still without case and particular earth grounding.. so I tried some different setups but no particular improvement was reached.
I must now also confess that the volume levels of those small LM1875 chips is really ridiculous..

So I then also begun to do an LM3886, but starting from the PSU (the carlosfm felipe based one) again as buyed from chipamp.com (see there the PCBs if needed).

Now I did a quick test using that PSU on my current LM1875 system and I noticed two more curious things:
1) there is absolutely NO noise on the loudspeakers now! (shoking dead silent!)
2) now the bulb test is completely not glowing when also only the PSU is connected, but glowing a little bit more (still very few, almost unnoticeable) when I connect also the LM1875 amp.. is it somehow an issue or allright?

So, next step is assembling also the LM3886 amp.. see you soon.

tent:wq

PS: small schematic to sum up my current findings with the lamp tester ->

Thoroid = NO LIGHT AT ALL

LM1875 psu = ALMOST NOT NOTICEABLE ORANGE FILAMENT
LM1875 psu+amp = THE SAME AS ABOVE
LM1875 psu+amp+speakers = ORANGE FILAMENT A BIT MORE NOTICEABLE
(diff. 14mVdc)

LM3886 psu = NO LIGHT AT ALL
LM3886 psu+LM1875 amp = ALMOST NOT NOTICEABLE ORANGE FILAMENT
LM3886 psu+LM1875 amp +speakers = THE SAME AS ABOVE
(diff. 107mVdc)
  Reply With Quote
Old 9th June 2009, 12:10 PM   #409
tent is offline tent  Germany
diyAudio Member
 
Join Date: May 2009
Hi,
and now I finished up also the two LM3886 based amps. Even better now! This amp really rocks! It rules!
Powerfull and clear, and most important really without hum and hisses!!
So updated situation:

Thoroids (two NEW 2x12V, 80VA) = NO LIGHT AT ALL

LM1875 psu = ALMOST NOT NOTICEABLE ORANGE FILAMENT
LM1875 psu+amp = ALMOST NOT NOTICEABLE ORANGE FILAMENT
LM1875 psu+amp+speakers = ORANGE FILAMENT A BIT MORE NOTICEABLE
(offset 14mVdc) so should I worry about the filament?

LM3886 psu = NO LIGHT AT ALL
LM3886 psu+LM1875 amp = ALMOST NOT NOTICEABLE ORANGE FILAMENT
LM3886 psu+LM1875 amp +speakers = ALMOST NOT NOTICEABLE ORANGE FILAMENT
(offset 107mVdc) maybe related to the fact that GN+ and GN- go to the same point on the amp?

Other thoroids (two other NEW 2x24V, 85VA) = NO LIGHT AT ALL
LM3886 psu+amp = NO LIGHT AT ALL
LM3886 psu+amp+speakers = NO LIGHT AT ALL
(offset 4mVdc !!) this sound great!

tent:wq
  Reply With Quote
Old 12th June 2009, 08:05 AM   #410
tent is offline tent  Germany
diyAudio Member
 
Join Date: May 2009
up?

tent:wq
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
A Beginners Guide to Enclosure Alterations Bork Multi-Way 7 12th January 2009 02:10 AM
beginners ecl82 power supply emil_86 Tubes / Valves 15 25th September 2004 05:20 AM


New To Site? Need Help?

All times are GMT. The time now is 04:23 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2