Marantz 240 to 110V conversion

[dantwomey]

Just recently I purchased a European 240V Marantz CD-50 with the intent of converting it from 240v to 110v operation. The reason I thought this was possible was that I already had the CD-50 service manual in hand and it had what appeared to be very clear instructions on how to do so. Well, after receiving my CD-50 and starting this task I've yet to be successful in 'deciphering' the correct steps for 110v operation. Here's my story.

Here's the schematic of the PS:


The impression the schematic gives is that the 'hot' always goes in through the switch through tap 4 and the final supply voltage is chosen by picking the appropriate secondary tap.

One example of how this works is the original 240v setup. I have a 240v test bench at work and when I connected the CD player as shown everything worked fine.



Another example is when I changed the appropriate jumper and connected it to 220V it worked fine as seen here.



Now here is where it gets tricky. Shown here is the pin out for the transformer, the chart of 'jumpers' for determining supply voltage, and a picture of the transformer traces on the main board.

When jumper 256 is installed so I'm measuring across pins 4 and 6 I get a total continuity of about 170 ohms. This makes perfect sense to me and once again when supplied with 240 volts it worked fine.

When jumper 253 was installed I'm measuring across pins 4 and 5 and I got a total continuity of about 145 ohms. Once again, when supplied with 220 volts it worked fine.

Now the chart says connect 4 and 1 for 110v operation. The problem I have is there is no continuity between 1 and 4 at all. When measuring directly at the transformer pins I get about 1 ohm between 3 an 4 but 'open' between 4 and 1 and 4 and 2. I also get an 'open' between 1,2, and 3 in any combination.

The chart suggests some interconnects such as 3-1 and 5-2 for 110v operations but I've yet to find any combination of jumper wires between 3 and 1, and between 5 and 2 that have any effect whatsoever.

Would anyone care to point out what I may or may not be overlooking here?

Regards,
Dan

[bob91343]

It may be that there is an open on terminal 1 (or 2), the one you want. Look closely at the transformer to see if there is a broken wire.

It also may be that the transformer was a special for Europe and doesn't have a terminal 1 or 2. Terminal 1 is the one you want.

[dantwomey]

Originally Posted by bob91343

It may be that there is an open on terminal 1 (or 2), the one you want. Look closely at the transformer to see if there is a broken wire.

It also may be that the transformer was a special for Europe and doesn't have a terminal 1 or 2. Terminal 1 is the one you want.

The terminals are soldered into the board. The wires are visible going from inside the transformer to the terminals. The service manual is pretty clear in suggesting that different connections on the European version will allow different supply voltages.

Regards,
Dan

[bob91343]

If you see wires going into the transformer yet those wires are open circuited, you have a bad transformer. It could be fixable but you have to get in to where the connection has failed.

[dantwomey]

Brief update. I pulled the transformer from the main board and upon inspection there are no wires on the primary side going to pins 1 and 2. Thus, the transformer is not defective. It just wasn't manufactured in the fashion the service manual indicated. This leaves me with two options. I can purchase a 110v to 240v step-up transformer or I can build multiple independent supplies from scratch. Unfortunately, not what I expected.


Regards,
Dan

[bob91343]

You can build a converter from a 1:1 transformer rated for half the power. Lacking that, you can build a 1:1 transformer from any pair of identical transformers.

Much easier than trying to replicate all the power supply outputs.

[dantwomey]

Originally Posted by bob91343

You can build a converter from a 1:1 transformer rated for half the power. Lacking that, you can build a 1:1 transformer from any pair of identical transformers.

Much easier than trying to replicate all the power supply outputs.

I'm not quite following you. Could you elaborate further?

Regards,
Dan

[bob91343]

Well I don't know how much power your unit requires, but let's assume 50 Watts. You obtain a 1:1 transformer, one with 120V in and 120V out, often called an isolation transformer, with a 25 W rating. You plug it into 120V so that it puts out 120V. You wire the secondary such that it adds to the power line so you get 240V.

If you don't have an isolation transformer, you can make one out of two 25W transformers, say 6.3V transformers. You plug one into the wall and take the 6.3V output and connect it to the 6.3V winding on the second transformer, which then will put out 120V on its primary, then proceed as before.

You can also, at fairly low cost, buy a step down transformer from many of these stores like Fry's or Best Buy and so on, already wired the way you want.

[bob91343]

Here is a link,

http://www.parts-express.com/wizards...former&x=0&y=0

They have a 100W 120/240 V converter for $20. Shipping would probably kill you but you are likely to find something like this locally.

[dantwomey]

I think I'm going to go with one of these for now. A small 115/230 toroid that'll easily fit inside the case.

https://system.netsuite.com/core/med...bd8be863ee3e38

Regards,
Dan