ac connection on chimpamp board, some help needed

[troublecomes]

Hello.

Im just putting together my 3886 board from BrianGT and i have a question about the transformer connection.

I bought two transformers (one for each side) which only have a single secondary - is this wrong?

I noticed on the schematic for the ps design that it is using a transformer with twin secondaries...

I hope i havent bought unsuitable transformers?

Thanks
-matt

[GeorgeBoles]

Matt,

What transformers did you buy exactly and from where? Dick Smith give you a 2 week "change your mind" guarantee.

It would be possible to use these, but you would need two of these transformers per channel, if I understand correctly.

Then you would have to be careful ensure the secondaries remain totally separate until AFTER rectification OR that any contact between the secondaries is only with them in phase.

Others on this board would be better qualified to help you out, however it MIGHT be easier, and it is certainly less bulky in your chassis, to get a refund and re-purchase.

Harbuch transformers, at least in the 300VA and 500 VA sizes, are MUCH more affordable than D.i.c.k Smith (30-40% cheaper) and Jaycar (whose prices are higher than D.i.c.k Smiths for most items), and they are locally made by knowledgable people.

Regards,

George.

I can't believe it ... the Bulletin Board appears to remove the word D.i.c.k and replace it, presumably because it looks a bit rude, hence the strange way of typing it in!

[troublecomes]

Yeah, thanks for the reply. Unfortunately there is no taking these transformers back - got them custom wound in India.

My electronics knowledge is very poor, so i think im not understanding something pretty simple.

I have the dual mono kit. I have two 22V transformers 200VA each with just one secondary on each. I was planning to have one transformer for each channel. However on the schematic it has a transformer with twin secondaries for each recifier circuit (whatever they are actually called). So my question is, can i just connect one transformer up to both sides of the power supply board (ie making a link between the terminals of the little terminal block supplied), or does this not work.

If this doesnt work do i have to use two transformers feeding one ps board, making it a stereo kit, and does it work like this?

I hope it is clear what my problem is, sorry i cant describe it properly since i dont really know much about electronics. Would love someone to tell me what the deal is.

Thanks a lot

Matt

[pinkmouse]

Yes, you can do it either way round as you suggest, though to make things simpler for you I would just use one rectifier board for both amp boards. Less chance of something catastophic going wrong.

[troublecomes]

Hello.
Thanks for the replies. Ok so i can use a trafo with a single secondary for one PS board (BrianGT), even though in the supplied schematic is used a trafo with twin secondries, each one feeding a side?

Just to make it clear what i was hoping was ok to do...i altered the schematic.... just want to make sure this wont bugger anything up and is not a problem. If its not a problem, why are trafos with dual secondaries used on a single PS board?

Thanks again
Matt

[troublecomes]

lol, thats funny GeorgeBoles with the D Smith starring, it just starred b.u.gg.er.

Its not really a bad word in Aus.

[troublecomes]

Im regretting getting these transformers a bit. Ive just found out that most transformers have an earth on the primary side and a 0V on the secondary side. Mine have neither, is this a problem?

[pinkmouse]

Nope, you use one traffo for each set of four bridge diodes.

[Arx]

I'm going to use a similar setup on mine.

I had some transformers left over from a previous experiment that are also single secondary. I think they were built for battery chargers or something.

I would recommend just using one of the rectifier boards, and hook up the two transformers as if they're each a secondary on a dual sec transformer.

I'll let you know how it goes on mine, if you're not in a huge hurry.

P.S. You've got one of the bridges backwards and would just blow up one of the caps. Also, after flipping the bridge the right way. You'll be creating a circuit consisting of only 2 diodes across the transformer.

If you tie the two grounds together (as they are on the amp board), then the current will be able to flow in through on diode of the bridge to ground, and then through the other diode bridge to the other side. POP! time for some new bridges.

-Nick