Morley ECV to U.S. voltage?

[scotsman]

Greetings all,  I recently acquired a Morley ECV that came from the U.K.  How would I go about re-wiring it to work with U.S. voltage?  I guessing the transformer will need to be replaced - but then again, with what?  I found a schematic but it's very hard to read anything relative to the power needs.


http://www.morleypedals.com/ecv.pdf


Thanks in advance! 

[R.G.]

If it has a transformer power unit, all you need to do is replace the transformer with another transformer with the same secondary voltage, but 120Vac primary voltage and at least as much secondary current.

I would look at it for you, but Morley site is not responding right now.

[scotsman]

If it has a transformer power unit, all you need to do is replace the transformer with another transformer with the same secondary voltage, but 120Vac primary voltage and at least as much secondary current.

I would look at it for you, but Morley site is not responding right now.

I'd appreciate it more then I could ever express! 

Try this link  - seems that morley moved the file since I posted!

http://www.morleypedals.com/ecvoldes.pdf

[R.G.]

OK, morley is back up.

It uses a 78L15 regulator to power the whole mess. That gives us a couple of important items.
(1) the current it uses is less than 100ma DC, as that's all the 78L15 will do
(2) the voltage from the transformer must produce no less than 17Vdc at 100ma load and no more than about 24Vdc.

That's easy to hit. You actually have several choices.

(a) you can just add a DC-output wall wart that puts out, say 18Vdc to 22Vdc at up to 100ma. Just add a DC power jack into the hole that the AC power cord uses now, and run the DC from the wall wart to the ground and +V connections where D3 and D4 join. You can leave the original transformer in or remove it.
(b) You can add an inlet for an AC wall wart rated at 13Vac to 16Vac at more than 100ma and connect the AC from that to a new rectifier bridge. The new rectifier bridge connects its + terminal to the + side of C35, the - terminal of the bridge connects to the - terminal of C3. You can remove or leave the existing transformer and D3/D4 as you like.
(c) You can replace the transformer with a us-primary transformer. I recommend a toroidal transformer from Digikey, the TE62013-ND, $13.68. This is a dual primary, dual secondary device. You connect up the secondaries as 30Vct and then connect them as the original transformer was connected. The dual primaries let you connect them in series for 240Vac like the original, or in parallel for 120Vac for USA.

I did (c) for a Roto-Vox unit I got a few years back from the UK.

[scotsman]

OK, morley is back up.

It uses a 78L15 regulator to power the whole mess. That gives us a couple of important items.
(1) the current it uses is less than 100ma DC, as that's all the 78L15 will do
(2) the voltage from the transformer must produce no less than 17Vdc at 100ma load and no more than about 24Vdc.

That's easy to hit. You actually have several choices.

(a) you can just add a DC-output wall wart that puts out, say 18Vdc to 22Vdc at up to 100ma. Just add a DC power jack into the hole that the AC power cord uses now, and run the DC from the wall wart to the ground and +V connections where D3 and D4 join. You can leave the original transformer in or remove it.
(b) You can add an inlet for an AC wall wart rated at 13Vac to 16Vac at more than 100ma and connect the AC from that to a new rectifier bridge. The new rectifier bridge connects its + terminal to the + side of C35, the - terminal of the bridge connects to the - terminal of C3. You can remove or leave the existing transformer and D3/D4 as you like.
(c) You can replace the transformer with a us-primary transformer. I recommend a toroidal transformer from Digikey, the TE62013-ND, $13.68. This is a dual primary, dual secondary device. You connect up the secondaries as 30Vct and then connect them as the original transformer was connected. The dual primaries let you connect them in series for 240Vac like the original, or in parallel for 120Vac for USA.

I did (c) for a Roto-Vox unit I got a few years back from the UK.

Thanks R.G. - I'm opting for a transformer replacement to keep this as "original" as possible.  It's an old Tel-Ray model from California. 

I've never wired up a transformer before - any hints on getting it right the first time?

[R.G.]

Yes - get experienced help. I'm serious. The AC power line stuff has simply got to be done right or YOU ... COULD... DIE.

If you buy the one I suggested, it will have colored leads which will tell you how to hook it up. I'm looking at http://dkc3.digikey.com/PDF/T063/1805-1806.pdf in my other browser window now, and the color code is shown there.

First, locate where it will go mechanically. Look for where the lead wires have to go and try to find a place in the box where a single screw will hold it in place properly. Ideally, this is exactly where the old transformer went and you can use one of the existing holes, but drill a new hole only if you have to. If you have to drill a hole, cover all of the insides of the pedal with masking tape, sticky side up before you drill. This will catch the little metal bits that come out of the drilling and you can remove them with the masking tape. Mount the transformer in place mechanically.

Verify which red wire is connected to the green secondary wire through the winding. Do this with an ohmmeter setting on your meter. Then verify which red wire is connected through a winding to the violet primary wire. Do not mix these two reds up!!

When you have identified the red secondary wire, twist it into a pair with the brown secondary wire and solder the two twisted ends together. You now have a center tapped secondary, green -> red/brown -> blue. Solder the green wire where the original secondary went to D3 anode and the blue wire to D4 anode, like the ends of the original transformer. Solder the red/brown wire pair where the center tap from the original transformer went.

On the primary side, twist the verified primary-red and the yellow together, and black and violet together. Solder the twisted ends together on each of these twisted pairs. These pairs become the new "primary wires". Use your ohmmeter to test for continuity between any secondary wire and any primary wire. There should be many megohms of resistance between them.

Now solder the red/yellow primary into whatever contact one of the original primary wires went to, and the black/violet pair to the other place the primary went. Ideally, you would slide about 1" of heat shrink over each primary wire-pair before soldering it, do the soldering, then slide the shrink over the new solder joint and shrink it.

You will probably have to replace the power cord, or at least replace the UK style plug with a US style. Inspect the cord to see if it's worth using again, and put a new plug on it if it is. If it has problems, find a cord from something that can give its life for the cause, cut the cord off. Put the newly-liberated power cord where the original cord went, being certain that you use at least as good a strain relief as the original had. It's all this AC power wiring that I think you may want to get skilled help with. This simply has to be done neatly and well; the result if it's not is an electrocution hazard.