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Changing 220v to 120v and other questions (Groove Tubes CL1s) Channel Strips
Old 28th December 2012
Gear Nut
Doc Asbury's Avatar

Thread Starter
Changing 220v to 120v and other questions (Groove Tubes CL1s)

Hi Slutz. I just got a Groove Tubes CL1s from Korea. Does anyone know how to switch the input voltage from 240v to 120v?

There are a few threads here & on other forums requesting manuals or schematics for the Groove Tubes CL1s, but nobody seems to have any docs. If anyone does, please let me know... But my question is pretty basic and I was hoping someone would know the answer offhand.

See pics below.
Pic #1 - On the back there is a fuse compartment which opens with a small flathead.
Pic #2 - Inside the compartment is a plastic pin that can be moved between 4 slots marked 100, 120, 230 and 240. However I don't see any jumper terminals on it, and I don't see any physical connections it makes. Perhaps it's just a marker.

I set it to 120 and flipped the power on. Inside, on the power supply board, a red LED lights up, but it slowly goes dim and turns off after about 30 seconds. (I have a 2nd CL1s which is set to 120v and functions fine. When I turn it on, the red LED lights up and stays on.) The unit doesn't seem to be operating. Might this be an indication that it's still stuck in 240v mode and isn't getting enough juice?

Pic #3 - inside view of fuse/power input (I don't see any switches or jumpers)
Pic #4 - inside view of power supply circuit board (I don't see any switches or jumpers)

Any tips you could give would be really helpful. A schematic or manual would be fantastic. Thanks
Attached Thumbnails
Changing 220v to 120v and other questions (Groove Tubes CL1s)-cl1s-001_720.jpg   Changing 220v to 120v and other questions (Groove Tubes CL1s)-cl1s-002_720.jpg   Changing 220v to 120v and other questions (Groove Tubes CL1s)-cl1s-004_964.jpg   Changing 220v to 120v and other questions (Groove Tubes CL1s)-cl1s-005_964.jpg  
Old 29th December 2012
Lives for gear
Richard Crowley's Avatar

The little white indicator is attached to the end of a small PC board. We can see it in your photo #2. In many of those kinds of units, the board pulls out and you can insert it in different positions for different mains voltages.

Remember also that if you are converting the unit for different mains power voltages, you must also replace the fuses. Especially if going from 2xx to 1xx volts. The unit will draw TWICE as much current at 1xx volts. So you may have blown the fuses.

Not clear exactly what you did when you say "I set it to 120"?

Note also that you can look up the Corcom model number and that will almost certainly show the exact instructions for setting it for various voltages.
Old 30th December 2012
Lives for gear
S21's Avatar

It is common for tube gear with a linear supply to have a multi-tapped transformer. This allows the device to be configured for operation in at different voltages. The plastic slider you mentioned might be selecting different transformer taps. The photos make it look like this is the case, but there isn't sufficient detail to be sure. It looks like an active brown wire from the IEC plug goes to the top of the little bit of pcb that the slider is on, and it looks like multiple wires come off underneath that. If the rest of these wires run to the transformer (big round thing) then that's probably whats going on.

So... Make sure the slider is in the right place and check your fuses. :-)
Old 30th December 2012
Lives for gear
Richard Crowley's Avatar

The official word from Corcom (

1. Open cover, using small blade screwdriver or similar tool.
2. Set aside cover/fuse block assembly.
3. Pull voltage selector card straight out of housing, using indicator pin.
4. Orient selector card so that desired voltage is readable at the bottom.
5. Orient indicator pin to point up when desired voltage is readable at bottom (note that when indicator pin is fixed, successive voltages are selected by rotating the card 90° clockwise)
6. Insert voltage selector card into housing, printed side of card facing forward toward IEC connector and edge containing the desired voltage first.
7. Replace cover and verify that indicator pin shows the desired voltage.

And, of course, replace the fuse with a new one of the appropriate rating.
Old 4th January 2013
Gear Nut
Doc Asbury's Avatar

Thread Starter
EXCELLENT INFO, EVERYONE! rcrowley, the instructions & diagram are perfect. I didn't realize that the voltage selector card pulls out (I thought the pin just slides up & down). Voltage is now set to 120. Thanks & great job, gang.
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