While were at it
I'm looking for a 10 - 0 - 10 2.5VA transformer
if anyone can point me in the right direction, it would be appreciated
and no, a 9-0-9 or a 12-0-12 won't do, nor am I looking for any cunning solutions
Put the transformer in the basement
voltage regulator at the business end
geoff wrote: [snip]
When I was looking for a toroidal transformer with non-standard secondary voltages I found Canterbury Windings who will custom wind a transformer. For a price of course.
That might be the bit That the customer has problems with
Assuming you're happy to order several, Antrim do limited runs to your spec.
Seems to me that a switched mode PSU would be more appropriate for a Class D amp, given that a Class D amp is basically a switched mode PSU itself.
Geoff,
I understand that in your business you need to fit standard parts to stay within original design approvals but have you actually tried a
9-0-9 maybe 5 or 6 va if you have room. Generally the voltage regulation on these small transformers is quite poor and the voltage is normally quoted at rated load so you should get a higher voltage with a higher power transformer when only loaded to 2.5va. hthBob
In message , "Dave Plowman (News)" writes
That's the problem, its a one off
There are dimensional constraints in every direction. There is virtually no room to play with at all. The company that makes the transformer told me that it does need to be 10 - 0 - 10, they know the pcb it goes on. They cannot sell me a transformer as it was commissioned by their customer
In message , geoff writes
Is there a problem with the suggestions that you select a transformer which supplies the nearest voltage below, then add the requisite number of turns to get exactly what you want? It should be dead easy with a torroid.
I've had very good service from:-
Custom order seems to be the only way out of the corner you are in. Either wind it yourself or pay someone to do it for you.
Bob
I assumed it had to be like for like as a replacement for one of your PCBs? But you only expect to supply the one?
There used to be a small place in Wimbledon that would do one off transformers. I'll see if I can find the details tomorrow.
In message , "Dave Plowman (News)" writes
Yes, a one off - cheers
Unless willing to use a 12-0-12 and pass the output through a couple of diodes.
NT
In message , Tabby writes
Then into a diode bridge ?
I've not actually checked the circuit myself
It strikes me as being pretty poor design, if it's that dependent on the accurate output of the PSU
yup, a power diode drops around 1.5v conducting a high percentage of its rated i, so an extra 2 diode drops takes care of the 2v ac. Not the world's best design of course, but its an easy way to tweak psu transformers when needed.
In message , Tabby writes
No it doesn't (AFAIK), a silicon junction drops about 0.7V, germanium about 0.3V
But then the diode bridge isn't seeing a 50Hz sine wave, the smoothing cap on the output will "smooth" to a different voltage
It just feels wrong to me
In message , geoff writes
But...... With a bridge, you have two diodes in series each half cycle.
But that isn't what was said above:-
"a power diode drops around 1.5v"...
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