Follow this procedure to bring up your CTH. You will need a digitial multimeter. If something goes wrong, disconnect the power connections immediately. You need to be reasonably skilled at using a DVM and accessing test points on a PCB. Use the Wiring Pad finder to locate the pads and pin locations on the various devices.
Board Pad Locations
|CTH Wiring Pads (300dpi PNG)||CTH Wiring Pads (600dpi PNG)|
Staged Start Up
All voltages are measured with respect to SG unless otherwise noted.
Insert all opamps be DO NOT insert the tube.
WARNING - 100VDC is significant high voltage. Every precaution for handling HV should be exercised.
Plug in the wallwart and wait for at least 2 minutes. If there is smoke turn of the amp immediately, but if not wait. The indicator should go from red to green. Whether it does or doesn't, check these voltages anyway.
- Measure between OG and SG. This should be very close to 12V. If it's not there might be a problem with the TLE2426 or with one of the devices in the rail splitter.
- If the OG measurment is good, measure OL and OR. They should also be very close to the voltage at OG. If they are the buffers and splitter are working.
- If OL and OR are not close to OG (>50mV), then either the buffer opamp is not working or one or more of the buffer BJTs are dead or the wrong hfe class.
- If OL and OR are close to OG the green light should be on. If it is not there is a problem in the ε12 or the LED RTL logic.
- Power off and let the PS bleed down.
- Set the heater switch for the heater voltage of the tube you want to insert.
- Insert the tube and turn on the amp again.
- Look for smoke. If there isn't any then . . .
- Measure TB+. It should be between 95V and 105V.
- If TB+ is ok, measure pins 1 and 6 of the tube socket. These should be approximately 80V. If they are, and if the previous measurments are correct, then your amp is ready to go.
- If TB+ is wrong there is a problem in the HV multiplier. Check diode and cap orientations.
- If TB+ is good but pins 1 and 6 are far from 80V the tube opamps may be bad or a component value may be wrong.
- If everything in the tube circuit tests good but the plate voltages are still far off, the tube is bad.