Hey Guys! I had an arcing sound with bright flashes in my own 100B but after checking capacitors and wiring, I put it all back together as I found nothing wrong, well the arcing had stopped. Then I had another 100B in for service with constant arcing which was down to the -70V bias wire breaking down to the +500V rail. Out of curiosity I removed the bottom plate of my 100B and sure enough the infamous Black wire was laying on the end cap of the 5k1 resistor. Careful visual inspection shows some strange discolour of the wires Black sleeving just where it lay alongside the resistor end cap.
I know it is a bit of a pain, but I would recommend you remove the 34 screws 🤬 and check, upon removing the bottom panel, that you do not have the dreaded Black wire draped on top of the 5k1. This is only a problem it seems with early models and I personally think the wire used has insufficient voltage rating. Remember it is the Right Channel but of course it is on the Left Hand side when you are looking from underneath with the front panel towards you.
Here's what can happen if you are unlucky.
http://www.g4cnh.com/public/100B_spark_up.mp4
I know it is a bit of a pain, but I would recommend you remove the 34 screws 🤬 and check, upon removing the bottom panel, that you do not have the dreaded Black wire draped on top of the 5k1. This is only a problem it seems with early models and I personally think the wire used has insufficient voltage rating. Remember it is the Right Channel but of course it is on the Left Hand side when you are looking from underneath with the front panel towards you.
Here's what can happen if you are unlucky.
http://www.g4cnh.com/public/100B_spark_up.mp4
That looks just like a bad spark plug wire that’s gone bad. I would use windex and spay it all around the plug wires, with engine running and at night time, when the wires are bad, or going bad. You get a cool *** blue light show. Lol. I showed this to a young and pretty new tech this, and that dumb *** went and grabbed a can of break clean and started spaying that **** all over, and BAMM
Whole engine compartment caught on fire with a nice loud explosion sound. The dumbass new tech totaled a brand new 40k Lexus and almost burn down the whole shop. Kept telling the service manager of the shop that I didn’t like teaching ,brand new techs that just got out of school. because they acted like they knew everything just because they had one little certification saying that they were a ASC certified mechanic. And that prove my point that just because they have that piece of paper didn’t mean that they knew Jack squat about working on cars
Whole engine compartment caught on fire with a nice loud explosion sound. The dumbass new tech totaled a brand new 40k Lexus and almost burn down the whole shop. Kept telling the service manager of the shop that I didn’t like teaching ,brand new techs that just got out of school. because they acted like they knew everything just because they had one little certification saying that they were a ASC certified mechanic. And that prove my point that just because they have that piece of paper didn’t mean that they knew Jack squat about working on cars
Having replaced the bias parts the amp was put back on test but straight away something was not right, slight smell of over heating and those 5k1 resistors in the B+ line were the ones getting all hot and bothered. The voltage across them was far too high but as there did not appear to be any circuit problems I decided to put the four 6SN7's onto the tube tester. One of the phase splitters had a heater to cathode intermittent short and I guess this was the little Imp all along. It had cooked the 5k1's which then melted the -70V wire that lay across one of them. So there you are, cause and effect all in one, the arcing being the effect. :-D