cant seem to figure out the pt wiring for my express

[72fetter]

there was a speaker cab connected and i had rechecked all wiring
what portions you guys want to photograph?

[M Fowler]

I would get the right power switch and then make sure your standby switch is wired exactly like the layout.

[72fetter]

alright let me know what you guys see

[billyz]

For my 2 cents I would use a better color scheme than everything RED. Makes it very hard to trace. RED for Ground? Blue turns to RED.

[marcoloco961]

At a quick glance, it looks like the bolt under power switch is dangerously close to a hot wire. I think I would go with a shorter bolt first. When you say it sparks, where do the sparks come from? By the power switches? By the power tubes? Can you tell for sure? I think I would pull the power supply board and look for signs of burnt areas where the sparks occured, it is usually easy to spot these areas. Once I found the burnt area, I'd inspect it carefully, then deal with the problems in that area accordingly.

P.S. I would trim back the wire end off of the standby switch. You are dealing with very high DC voltages once you flip that switch and they can arc a long distance. That one could possibly arc to the chassis cover. You do know how to bleed down the voltage before you stick your hand in the chassis, correct????? If not, have someone here explain it, and practice doing it every time! Please. It could save your life.

[Noel Grassy]

Another one falls prey to the "Live Wire Sphincter Winker"!

Bring the Yellow tape...D.E.D.

[paulster]

Okay, I think I can guess where this is sparking (see highlighted section). You've got B+ at this point and it appears to be almost touching the chassis, if it isn't already. This is dangerous.

You really need to park this build and do a couple of things before you get close to applying mains power again:
1. Choose appropriate wiring colours and rewire the mains and high-voltage power supply section. Using red for hot, cold and ground makes fault-finding overly difficult and exposes you to the risk of a fundamental mis-wiring. On your DC side at least use one colour for ground connections and one for B+ connections if you're limited to a couple of colours.
2. Check your filter capacitor ratings. Since you've used a different transformer from the norm you're going to have significantly higher voltages unless you change your dropper string to get these down. Are your caps rated sufficiently highly?
3. Sort out the structural integrity of your filter cap banks. Will they move if your amp takes a jolt (being put on a cab heavily, getting bashed in the car trunk, etc.)? You've got 400V available on the ends of them so it is imperative that they're not going anywhere.
4. Fix your lead dress. I'm not even looking at the preamp side yet, but the wiring on HT side of the amp is asking for trouble, with what looks like the worst offender being the area I circled but there are plenty of other areas that really want looking at from a safety aspect (the bolt by the power switch being a good example that's already been picked up).

I'd say the easiest way to start will be to ensure your caps are discharged, lift your power supply board and then rewire that side of the amp. Once you've done that and are convinced it's electrically safe then you can turn your attention to the preamp side and see if that requires any rework.

[72fetter]

thanks guys you have been a great help.
this was a built from scraps amp so i will go back over it with a fine tooth comb.

btw the issue was the wire going to the filter caps was stupidly close to the 3w resistors that go to ground...causing a short and the sparking.

i will redo the dressing and power wiring and get back to you

[72fetter]

just saw the pic....great eye

[M Fowler]

Are those Solen Fast Caps? They are very large caps. To get the cap stack to fit you notch the power board and then they will fit if you use reasonably sized caps that is. But you were being resourceful so that is good.

You could make another cap board for the three other caps taped up or use turret stips for more durability and safety.

[72fetter]

i originally had a seperate turret board with everything but I didnt have room....they are actually siliconed to the chassis so they should be good.
I will change the power section wiring to be safer..should be good....now...how the hell do i get the type 3 master volume to work because for the life of me i cant seem to get it to work

[marcoloco961]

i originally had a seperate turret board with everything but I didnt have room....they are actually siliconed to the chassis so they should be good.
I will change the power section wiring to be safer..should be good....now...how the hell do i get the type 3 master volume to work because for the life of me i cant seem to get it to work

Here is a schematic for a JCM800, I believe. It is very similar to the wreck and has a master volume. I don't know if this is what you are calling a type 3 master volume, but see if it works for you.

[paulster]

That's a regular pre-PI master volume on the output from the tone stack treble wiper.

If you want a post-PI master then take a look at the big thread on the Lar-Mar master on the MetroAmp forum which has taken Ken's one and enhanced it.

I'm still not sure it's going to work that well in an Express but it seems to be the best master you can add to a NMV amp at the moment.