Hughes & Kettner - Rotosphere  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.

Re: Hughes & Kettner - Rotosphere

Postby blackbunny » 25 Mar 2014, 12:22

squatch wrote:Just wondering if it's safe to plug in a 15VAC adaptor? (but I'd check the output first) How much voltage do you think a MK1 would handle safely?

I wouldn't use a 15VAC supply on this pedal, 13VAC (loaded) @ 700mA - 1Amp would be the maximum. Why? All internal voltages will be be raised by about 25% if you plug in 15VAC.
The positive & negative 12VDC IC supply rails would be OK as they're regulated, the HT supply on the valve anodes will go up from 280VDC to 350VDC, which will probably be OK, but the heater supply for the valve will go from 12.6VDC to 15.75VDC, which is way too high.

Study the power supply circuit diagram I posted on the 15 May 2013 (a few posts back, on this page). You would have to replace the 2 x 1 watt 4.7 ohm resistors R209 & R210 with 18 ohm 2 watt resistors to drop the heater voltage back to 12.6VDC.
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Re: Hughes & Kettner - Rotosphere

Postby squatch » 25 Mar 2014, 14:05

Thanks blackbunny, I'll just stick to 12VAC...I've got another here
The one I was using was getting hot and buzzing so I thought I needed more than a 1 amp supply
I've got another newish 12VAC 1 amp so I'll try that, maybe the old one's kaput
Cheers, squatch
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Re: Hughes & Kettner - Rotosphere

Postby Yazoo55 » 08 Aug 2018, 18:48

OK, I've now got the full-on hots to build this. I always get this way when I got interested in a new project. I decided to use Kicad to do new layouts and get them fabricated since it is a double-sided board beyond my capabilities.

The photos have been invaluable. I've got the control board set up in Kicad and being able to see the track layout has made it a lot easier.

Any advice on wiring up the sockets/pins P01 - P06 would be greatly appreciated. I can see they relate to the Slow/Fast footswitch and the Bypass footswitch. What kind of footswitches are they?
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