I was given a Crack kit by someone who tried to build it, but ran into problems and gave up. After sitting on the shelf a while, I finally got a pair of headphones nice enough that I'd like to sort this thing out. I've done a fair amount of digital electronics repair, so I have a scope, isolation transformer, meter, etc, but this is my first time digging into an amplifier. I wasn't given any documentation, but was able to find a manual online.
When I got it, I was told that it had been powered up, had a hot smell, and blew the fuse after a few minutes.
Comparing the chassis to the build instructions, I saw that the wiring for the 150V secondary had been reversed, bridging the 150V and 0V lugs instead of 150V - 150V / 0V - 0V. Also, the wiring from the transformer to terminals 18/19 were reversed. I suspect it doesn't matter, since it's the input to the bridge rectifier, but I corrected it anyway.
Nowhere in the documentation does it state what the fuse rating should be. I saw that the input jack itself is rated for 10A. I stuck a 4A SB fuse in, since I had one handy and it seemed like it'd be in the right ballpark.
I didn't see any other issues, so I went through the resistance check from the manual (passed), and powered it up with the tubes removed to check the heater and B+ voltage; both looked good, the fuse didn't blow, and I had no hot smell or other indication of malfunction. From there, I reinstalled the tubes and went through the power up and voltage check from the manual. The 12AU7 lit up, but the 6080 didn't. Checking the voltage on terminal 2, it was around 220VDC instead of 170V.
I pulled the 6080 and checked the heater, it seems to have a very high resistance (megaohms), so I'm afraid it got toasted when it was powered up before. Also looks like terminal to connects to its socket, so that may explain the voltage test result. I went ahead and ordered a replacement.
Any other things I ought to check, or does it seem likely that the 6080 is the problem? I'd hate to toast another one.
