Toroidal Power Transformer Questions

[Hercdriver]

Is anyone familiar with the McLaren Audio 602 preamp? The company went out of business in New Zealand several years ago.

I recently purchased the McLaren 602 from someone in Germany and had it shipped to USA. It is currently rigged for European electrical outlets. Of course, the German and USA electrical requirements differ.

This unit has a toroidal power transformer and the original brochure stipulates that the power requirements are: 110-120/220-240VAC; 50-60HZ; and 8VA.

I want to be able to use this unit in the USA without purchasing an external step-up transformer.

My questions are as follows:

1. Is it possible that the torroidal transformer is a dual voltage unit? Mind you, there is no visible internal/external switch for voltage regulation and the unit was built in 1987.

2. If so, is there an easy way to test for internal dual voltage capability without damaging the unit?

3. If the transformer is strictly 220-240V, can I simply replace the transformer with one that favors US voltage? Is it more complicated than that?

Any help anyone can provide would be much appreciated.

Thanks,

Herc

[K-amps]

If it has dual primaries chances are you can use it for 120 and 240 volt mains... does it say anything on the Toroid?

For 120 v the primaries are wired in paralell and in series for the 240v.

Not sure if this helped....

[Hercdriver]

K-amps,

Thanks for the response. The Toroid has no markings, but since the brochure said that the power requirements were:

a) 110-120/220-240
b) 50/60Hz
c) 8VA

I 'm assuming maybe there are dual primaries. Upon looking at the side of the board directly under the toroid, I noticed a simple wire connected to 2 solder points. This could be the "hard-wired" series set-up for the 2 primaries making it a 220-240 capable unit.

Question: If our assumptions are correct, do I need to do anything extra for unit to accept 110-120V, since we know it can handle twice that amount of power? I'm thinking (I may be wrong) I could just plug the unit into the wall and "go for it".

Thanks,

Herc

[K-amps]

I would...

BUT


Use a 100 watt bulb in series with the primaries. Once powered up, check for buzzing or high current draw (the bulb should not light up at all, except when first powered up ).

Then check the secondary voltages if they are what you's expect, I'd say you are fine.

keep the bulb in series till you have the PSU (Caps and bridges completed).

My 2 cents,

[Hercdriver]

Many thanks, K-amps. - - Herc

[K-amps]

Good Luck and anytime!

[HDTVman]

I would suggest finding a manual for the unit and seeing what it tells you to do. If the dual primaries are wired in series for 240vac operation then the wiring will need to be changed to parallel for 120vac. Unless it uses a switch mode power supply most dual voltage units I have seen require the wiring to be changed via a switch or jumpers.

Later BZ

[Hercdriver]

HDTV,

You may have a point. I did notice a short wire soldered at both ends on the back of the board, directly under the toroid. Perhaps this is the "jumper" wire connecting the primary and secondary in series.

The torroid has no markings and the unit was manufactured circa 1987.

Here's a really dumb question. Without taking the toroid apart,
is there a way to use a voltmeter to determine which solder points (on the back of the board) connect to the primary and which ones connect to the secondary transformer?

Here's another dumb question. If the primary and secondary are connected in series via a hard-wire/jumper to become 240 VAC unit, does one simply disconnect the jumper/break the hard-wire to establish 2 parallel units for a 120 VAC unit? Do you tie those loose ends somehow?


Thanks,

Herc

Herc

[sam9]

Go to www.plitron.com
Click on <Products>
Click on <Standard Power Transformers>
Scroll down to "Inputs"
Click on <Schematics>
Look at the illustration of "Type 7 Primary"


This is most likely your arrangement. You can identify wires even if color coding is different by using an ohm meter on you DMM.

UNPLUG THE UNIT ! ! !

Using the above illustration, the part on the right, as a guide the resistance between"white" and "black" or between "brown" and "orange" will each be about 1/2 the resistance you measure between "orange" and "black". Regardless of the actual colors you can figue out which is which by measuring each combination and writing them down. It is important to writ them down since it is easy to get the permutations confused. Once you figure it out and confirm that this is valid description of what you are dealing with, you need to find a way to reconnect it in to the configuration on the left. Whithout seeing it we would just be guessing on the best way to do this. One way to check for correctness after you have dne this is to measure the resistance between "black" and "orange" - it should be about 1/2 of what you measured (and wrote down !!) when you measured "white" and "black" in the original configuration.

WARNING: This is mains voltage. Doing it wrong can (eventually will) kill you. If you are not sure about your abilitities in messing with this get a tech to do it. Even a mom & pop TV repair joint should be able to handle it .

[Hercdriver]

Sam9

Thanks for the info. I did the ohm meter tests and there appears to be 8 solder points beneath the Toroid. Suprisingly, I tested every combination of pairs and just like you said, there were some pairs that were approximately half the resistance value(48) of another pair(94). However, there were some pairs with halved values that were approximately 1/10th the value (4.6) of another pair (9.0).

Perhaps this is more like a Plitron type 7 vice Type 5?

Herc