Carvin X-100 Guitar Amp OPT

probably a 1982 vintage Carvin tig welder on the bench,

couple a state of the art transformer off the Shumacher bench with B+/Plate circuit board traces which are located 1/16" from the metal chassis and you have yourself a repair job.

got a nice 1/2" blue arc off the blu lead of the transformer trace to ground, so we rip up the traces and run wires, problem solved......


not!

amp comes back and we are out of solutions, seems to run fine on the bench,  wtf, over?

gotta be the transformer. 

so what if the amp comes back, what is a slight ding to the rep compared with an excuse to do a complete teardown on a vintage Carvin? are you with me so far or do we need to break it down further?

hear is the victim>

layered paper job on a    125 EI,  2 lams this-a-way, two that-a-way, (Lap 2)

looks like some sectioning going on, (notice jumpers)

looks like some bi-fi action

somebody short-lammed us, look at that wedge, what about the leakage folks, can you spare us 7 more lams so we can get the leakage down a bit? 

complaining to dead people again.

leads

more leads

ok  we see a problem right from the git go,

can you see it?

stare at this pic for a while

answer in next post....

answer:

they wind maybe 5 or 6 coils on a single mandrel.

then the pull them off the mandrel and some joker takes them to the band saw room.

then they slice em like cheese at a deli, only this guy sliced it wrong, there is practically no margin for the high voltage on the right side of the coil, remember, this is layered paper, no nylon flange to guard against creepage.  if you got 100 K Hz bandwidth at 300 volts rms then you are gonna get some corona if the amp goes crazy on a high note,

pri leads.

sec wind spaced out

primary wind, no margin at all, wire falls of edge of coil, there is no end insulation on the coil where it crosses under the core, Kapton coated wire might work under these conditions, but doing that with a single build is kind if risky,

bi fi wound secondary section, why red and green? easier on the eyes, easier to catch a cross-over on a multiple coil wind,

why we don't like it?  differences in diameter, DCR, and toughness between red and green,

try scraping red and green with a pen knife and tell me what you think?

this is a pretty slick coil, kind of like the famous Altec-Peerless job for the Williamson, 16489 or whatever,

could use a bigger core, saturates at 60 watts-20 Hz, Carvin says it will do 100 watts but the math does not agree. you either need more turns or more lams.

here is  print #1, the winding print is 11 sections so we need an extra sheet,

here is the winding print, might tweak some wire sizes when we rewind, like 28 to 29,

why does the inner secondary  have 1 less than it's cousins?

less linkage away from the center of the core, so less voltage and thus less current, saves the inner wind from overloading, distributes the high current speaker power more evenly,

Where's the like button?  Where's the Guinness? 

CJ said:

could use a bigger core, saturates at 60 watts-20 Hz, Carvin says it will do 100 watts but the math does not agree. you either need more turns or more lams.

Click to expand...

It's a guitar amp, so 20Hz is out of scope. Rated power increases with frequency, so 100W at 40 Hz is not unconceivable; can even do bass.
I have one of those and I always feel nervous when I switch it on, knowing how overstressed it is, but I like it when I want a kind of 1980's sound.