Power Transformer help

[gonebytim]

Hi guys,

I have an old Pioneer SX-408 Reciever that has a dead power transformer. I'm having trouble finding any specs of the transformer to buy a suitable replacement.

I was wondering if anyone would mind having a look at the schematic for me (available here: http://www.hifiengine.com/manual_library/pioneer/sx-408.shtml) and let me know what voltage / ampage I would need to buy to replace it.

Thanks in advance!

 

[CJ]

what country do you live in? 120 or 220?

need to login to view schemo, waiting for email confirm,

 

[moamps]

My guess is 44V ct (2x22V), 3.5A, 120-140VA.

 

[gonebytim]

Thanks a lot for the replies - Australia 240v

 

[musika]

Here's the power supply schematic portion for the amp...

 

[gonebytim]

Here's the power supply schematic portion for the amp...

Yes - so it's a real shame that they don't bother labeling the output voltages of those 2 red secondary wires coming off the transformer. Because I'm not personally good enough yet to calculate what the voltages are based on the figures further on in the schematic.

I had the same issue once with another amp and someone calculated it for me and I was able to go down and buy a perfect transformer for the job.

Now I know that sounds like spoon feeding and it is - so I won't hold it against anyone who doesn't want to make my life real easy at the expense of me learning how to do these things for myself.

But I would be enormously grateful 

 

[PRR]

> what the voltages are

28V DC.

Factor is 1.414

So the AC must be 20V.

Twice.

Current:

28V twice is a 56V total supply.

Figure a totem-pole power amp driving 8 Ohms as 50 Ohms effective load on the power supply.

You may have two channels.  Double load (half resistance).

You may have 4 Ohm choice. Double load (half resistance).

So 50 Ohms/4 is 12 Ohms.

56V in 12 Ohms is 4 or 5 Amps.

Total VA is like 40VAC times 4 Amps AC or 160VA.

(You could instead look-up the Audio power output, total, and double that.)

In hi-fi, if not testing to FTC test conditions, you can probably cheat this a lot. 100VA may be too small (saggy at high volume).