G1176 2x24V transformer sourcing

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Joined
Sep 14, 2005
Messages
17
Location
Würzburg, Germany
Hello everyone!

I´m in the process of sourcing parts for my 1167 clone, but neither Farnell, nor Conrad or Reichelt are offering 230V(Pri)-2x24V toroids. Can I just use a 2x25V toroid (the 7824 regulates the voltage anyway, does he?) instead? Thanks for your input, and have a nice weekend!

Michael
 
[quote author="RogerFoote"][quote author="moamps"]The 1176's power supply is 30V.
A transformer with 2*25V secondary is fine, but 2*22V is too low.[/quote]

Not true... If you measurea 22 V secondary, you will see that it puts out around 26.75 volts. Now, if you move up 5VA, your circuit will never drop that voltage below 25V. Even if it does drop to 25V, the raw DC will be 36VDC. More than enough for the regulators to do their job.[/quote]

Are you sure? (second time)
Wrong presumptions:
All transformers (different manufacturer and different power) have 20% regulation.
Rectification/buffering of 25VAC gives 36VDC. Do some math, please.
 
[quote author="RogerFoote"]
Anyway, the math would be 26.75 X 1.44 = 38.25
and 25 X 1.44 = 36[/quote]
You didn't count in diode's voltage drop.
Coefficient (Vpeak/Vrms)=1.41, not 1.44.

For instance the Amveco that I got for my 1176 was a TE62075, a 35VA unit rated at 22V@ 1.59A.
On the bench, with one secondary loaded at 1A, it puts out 27VAC RMS.
With both secondaries loaded at 1A, it puts out 25VAC RMS. (Measurements taken with Fluke 87III True RMS Meter)

The transformer isn't 35VA or you have serious problem with your DVM or the power grid.
 
[quote author="RogerFoote"]
The transformer IS 35VA, look it up, it's in digikey : TE62075[/quote]

This transformer is rated 44V/0.8A (from datasheet).
How did you get 2*25V at 1A? It's 50W, isn't?

I am not sure what you are getting at...

Your math is better now. Also, after your suggestion one can buy (here in Europe for example) a 22V transformer with only the 5% regulation which will fail if the power grid voltage isn't nominal or if it is slightly distorted.
 
Hey guys,

All I can find is a 2x24 @ 48VA. I know this is overkill but the extra availability of current won't hurt anything, correct?
 
hi william,
the 48VA rating will not hurt anything, though it is way overkill for a single channel G1176. the only problem you might run into is noise radiating from the transformer. if you're using a toroidal then you're better off, but hook it up and take a listen and don't mount the thing until you've tested for noise.
move the position (and orientation) of the transformer in the case if it is radiating noise and see if that helps. you could also move the pcb and keep the in/out connectors as far away from the AC power input as possible.
keep as much space as possible between transformer/AC inlet section and your pcb, but i don't think there will be a problem.
hope this helps.
-grant
 
I first ordered a single primary/secondary 24v transformer and it would only read 16 v where it was supposed to read 30 volts. then i was told to get the te62045 2/22 @500ma and i hooked it up but when testing the circuit i get 1 volt and testing the transformer i get -8 volts. Im so confused and need help. using the mnats revision H board.


:oops:
 
[quote author="dissonantstring"]hi line,
with the amveco transformers you have dual primaries and dual secondaries.
how do you have it wired right now?
look here for color code and here for wiring schemes.
you are wiring it for 120V primary and split secondary with CT.
hope this helps.
regards,
grant[/quote]



found the info for the color code, connected the proper wires and it registers the voltage right. thanks for your help. :razz:
 
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