I’m having problems, when going through the testing procedure on page 22 I am reading about 36v from the left of R33. It does say it’s supposed to see 24v or slightly higher… I doubt this is within specs though… any help would be appreciated.
Did you perform the lightbulb test ?
Does the fuse still burn when you disconnect the TIP142 and TIP 147 transistors?
As simple as a circuit as the lightbulb test is, the lightbulb oddly does not want to light up… So I’ve bypassed this.
As for the TIP142 and 147 Transistors, Disconnecting them did stop the fuses from burning.
Instructions indicate to have the leads Between the pins of the pinheader; soldering to both pins is not however specified, can you verify the correct procedure here?
Make sure TIP142 and 147 are not swapped.
Chedck that both transistors are properly isolated from the heatsink.
Solder transistor pins to both pins of pinheader.
Assembly error and/or defective part in the power amp section are most likely the causes of troubles.
Can you tell me how to troubleshoot the transistors? They are not swapped and previous to disconnecting them, I had both pins from the pinheader soldered. As for isolation, I beleive that’s what the Mica sheet is for correct? could it be fastened too tight perhaps the screws grounding to the heatsink?
You can check with a multimeter if they are properly isolated from eachother.
Also check for shorts between any of the pins. If this is the case, we’d recommend to replace them.
Careful: driver transistor will also be defective. It is best to replace all transistors of the power amp section.
If the bias potentiometer (RV3) is fully clockwise instead of counter clockwise, the voltage on R33 will be much in the middle 30s.