My first build from scratch...an Express

[M Fowler]

The MOV doesn't matter you can wire that either way.

Need 2A or 3A slo blow fuse.

[Bob S]

Might be that jewel indicator wiring...
There is one contact at the furthest end.
The 2 contacts closer to the chassis (1 either side) are shorted together.
I know this - don't ask how.
Took me a while to figure it out.
Hope this helps.
Bob

[donzoid]

Thanks all! I am using 2A SB now, but I "was" using FB for a few in between. I will check for short again, and look up the inrush on that bulb.

[martin manning]

Thanks all! I am using 2A SB now, but I "was" using FB for a few in between. I will check for short again, and look up the inrush on that bulb.

The bulb is what a couple of watts? I guess it's possible that just pushed it over the edge.

[donzoid]

Bob...OK I "won't" ask....heheh. Here is the type of socket I am using--they aren't like the ones you are speaking of (the Fender type). They DO take the same jewell and they are panel-mount. since it has a plastic sleeve (which granted could be a conductor under certain circumstances) there is no extra ground term. on the side. Just the two spade connects straight out the back of the socket.

Yes Martin, that bulb says its rated at 3 watts. I didn't really want to go higher on my fuse rating, as the amp runs like a champ with it cranked and other than this issue hasn't yet blown a fuse for any other reason.

I do have a 6.3v bulb and later today I might try that route...off the heaters.

[Tillydog]

Is the lamp holder rated for 125V? (What does the writing say on the side?)

Maybe the "flash" you see from the lamp is really an arc inside the holder? - Are you sure that there's nothing inside the lamp holder that there shouldn't be? (Wire clippings, or crap from manufacturing?)

Bit of a puzzle!

[donzoid]

Tilly, yes it is...I made sure all of them are (I have 4 or 5 of them). my concern was the inside spring arcing or shorting but it does it on more than one socket.

[donzoid]

Of course, I can just wire it to an AC plug and test it that way.

[Zippy]

Tilly, yes it is...I made sure all of them are (I have 4 or 5 of them). my concern was the inside spring arcing or shorting but it does it on more than one socket.

Have you checked the resistance to ground from both contacts? There may be a short to ground that is causing your problems.

[donzoid]

Good point Zippy I had checked between the two poles, but not yet to ground. Thanks I will do that.

[donzoid]

OK I have to share this: I thought I would try it again with the socket out after checking for socket internal short/short to grd. (none there) and when I flipped the switch, it spiked hard enough to cause my uninterrupted APC power supply (in the same wall circuit, my computer is running off of it) to "beep" at me and look at the fuse. Totally wasted! So I'm going to stop screwing with it and 1. try the 6.3volt route, and if that blows it too, 2. Go to either an LED or some different lamp type setup. I hope I don't have to do that....it's a mighty big hole for that fixture, AND I have a couple of very cool jewell colors I wanted to use, but not gonna be messed with any more!

[Tillydog]

Something must be shorting in there...

Not wishing to insult your intelligence, but trying to cover all the bases: Are you sure that you have the correct bulb for the holder?

The 6.3V option has its attractions! (But check for shorts first! )

[donzoid]

Gosh Tilly I'm not insulted...not at all. Befuddled is a better word. I too can't see how THAT isn't a direct short! But my meter isn't showing anything of the sort. Not on two different sockets. But I get what you are saying-- I SURE don't want that happening on my heater circuit!

Oh and since we are snowed in right now, I don't want to have to venture forth to get another pack of fuses...

[M Fowler]

Maybe it's the way the light was being wired, seems like a full load is going through the light first rather then being switched parallel with PT.

How the power switch is wired makes a difference.

I did have a light socket similiar to yours once and it burned the wires right off the sucker when I fired up my amp, but that was because it has three solder lugs and I picked the incorrect lug to wire up. Lesson learned on that light.

[donzoid]

I've had similar lessons Mark, watching lamp cord melt/burn before mine eyes with a table lamp (shorted switch). Not wanting to re-learn that one inside THIS amp...