Power Transformer for MF NuVista CD Player

[Roy3932]

Hi,
Anyone know the value of the transformer secondary output voltage supply in MF Nuvista CD player?
The toroidal transformer in my CD player is broken. Could somebody help me to measure them. I need the value of the transformer secondary output voltage supply. The transformer is 3 inches diameter and 1 inch height. It's a multi-secondary output with a single-end 0 - ?vac and ?vac - 0 - ?vac center tapped winding. Appreciate your help.

http://www.diyaudio.com/forums/attachment.php?s=&postid=1208696&stamp=1178980143

Cheers,
Roy

 

[5th element]

This may sound obvious, but on the PCB the transformer attaches to, does it have written somewhere any voltages? If you can see a voltage somewhere BEFORE regulation you should be able to back calculate the voltage on the secondary.

Also if you can locate exactly what the transformer feeds then that may tell you something about what voltage it can fall under.

If all it powers is a few regulators, and you can identify what these devices are, and how they are wired up, then you may be able to find a voltage the circuit would be happy with.

Most regulators are happy with a range of input voltages.

 

[Roy3932]

Thanks for your reply.
I saw there is a voltage somewhere BEFORE regulation (on PCB) written 9vac-0v & 71vac-0v-71vac. May I know what's the formula to calculate the toroidal transformer secondary voltage? I'm not so knowledgable in this electrical calculation. Please advice.

Thanks.
Regards,
Roy

 

[pjpoes]

Those are the secondary ratings of the transformer I believe, and suprisingly high for a cd player. I would assume the 9 volts is for the dac and control cuircits, and I remember reading once that the Nuvistor had basicly an amplifier output stage using high voltage swings, but I assumed like 30 volts or something. Its possible that rating is after rectification, then just multiply it by .88 I believe, something like that.

Any chance you could tell me what the rating of the inductors are in the power supply? I've been trying to figure this out for a bit now and can't find any information. Would be appreciated.

By the way, I think you will need a custom transformer to match that as those are typical values.

 

[pjpoes]

I just realized you wrote VAC, thats ac, so not rectified, that is your secondary. VA is probably like 15-30va or so, but someone else might have a different opinion.

 

[Roy3932]

Thanks for the reply. Now, i've another question regarding the transformer.
For example, I've a transformer of 50VA with a 0-230V primary and dual secondary outputs of 35vac (0-35vac,0-35vac). If I want to get 0-70vac, I should connect the two secondary in series (black+yellow), is this correct?
35vac =red
0 =black
35vac =yellow
0 =orange

If i need 70vac-0-70vac single secondary with a centre tap, then I'll need two toroids transformer (0-70vac, 0-70vac). But, how do I connect two toroids to get 70vac-0-70vac?
I cannot find the component (35vac-0-35vac) in RS/Farnell.

Thanks,
Roy

 

[pjpoes]

You are correct and then you would simply tie your (0) wires together in order to turn those two transformers into the 70-0-70, however I would not go that route. I would get the transformers you need, space will be an issue.