Deathcap X2

[LOUDthud]

Back in the 70's I worked at a converted movie theater that was putting on rock and roll shows. Originally a 30's Vaudville house, the wiring on the stage was all 2 wire. The house PA's "board" was made from a half dozen or so of those little Shure mixers, all of which had an internal death cap with no switch. Due to the random connections of the power cords, there was always some voltage on the ground. More than once the sound guy had to run up on stage during the show and tape foam around the microphones to prevent musicans from getting shocked. I told them about the death caps, but it took them a while to finally figure it out. Those Union stage hands thought they knew everything.

There are special caps that are approved for use as death caps. I think they are designed to fail open when too much current flows through them.

[mhuss]

I kind of thought (at least U.S. Electrical Code) had forbidden the use of these, for the obvious reasons. I haven't seen any in new equipment. I have seen the "QuenchArc" type caps across switches to save them from excessive arcing when switching an inductive load, but not from either mains to earth ground.

How much 50/60 hz hum is a .02 cap going to reduce anyway?

--mark

[Firestorm]

On some of the amps Mike Holland used to build, he had a three-wire power cord with a proper safety ground, plus a film cap to ground on the neutral side, a film cap to ground on the hot side AND a film cap to ground from the B+ at the Standby switch. Obviously trying to accomplish something. I think they were .02s (but maybe .047s like Fender used to use). I'm not sure if they were the "official" UL-approved fail-open ones.

So what do we think Mike was trying to achieve with all those caps?

[Allynmey]

Remove them and set up a proper AC input. You can ship me those (2) .02 Sangamos and I'll male sure they never kill anyone!

[Lonely Raven]

Remove them and set up a proper AC input. You can ship me those (2) .02 Sangamos and I'll male sure they never kill anyone!

The hell you say!

Part of why I started this discussion was so I could convince myself they'd be put to better use in some sort of tweed concoction.

[muchxs]

Remove them and set up a proper AC input. You can ship me those (2) .02 Sangamos and I'll male sure they never kill anyone!

Geez Allyn, you get all horny for Sangamos? All you need to do is say so! I'll rummage through my rat's nest, erm, "carefully organized stash" (yeah, right!) of vintage parts and see what I can come up with.

Any other requests while we're at it? Those Sangamos are UGLY comared to bumblebees!

Part of why I started this discussion was so I could convince myself they'd be put to better use in some sort of tweed concoction.

Jeremy Ledford approved .022 STKs get the nod for utility use for me.

[Tonegeek]

I don't know why it's called a Deathcap ? in the 40 year's i worked on amp's i never heard of a single person here in the US getting electrocuted while playing a guitar on stage. i've seen plenty Newb's get the crap knocked out of thierself's by useing to much hand inside the amp, Seen plenty of people get shocked due to ground loop's,
But tell me, How many guy's you know that died due to this cap being in thier amp ?
Johnhenry

Not sure if the cap was the cause but I have seen stars a few times when touching a mike and my guitar at the same time. It was probably just a ground loop but even a small voltage is enough to zap you pretty good. I also saw David Lowery (of Cracker) get seriously zapped when he started the first song of a show I was doing production for 10 or so years ago. They stopped the show till he recovered. He was using a Sovtek Mig guitar amp. His guitar tech got chewed a new one for not checking for voltage before the show. Now I always touch my guitar strings to any vocal mike before I use it. If it pops, I do something about it. I have heard of people burning their strings off doing this but it is better than being dead.

[Ron Worley]

I remember seeing stars for about 10 minutes in high school after arcing my lip to the mic....

We were too stoopid to even check for ground polarity.. it was inevitable that the PA was hooked up to another circuit in the building versus the backline...

I carry a plug checker to this day to gigs for that very reason. Of course back then, none of the outlets were 3 prong, so it was like Russian roulette..

Ron

[Lonely Raven]

I remember seeing stars for about 10 minutes in high school after arcing my lip to the mic....

We were too stoopid to even check for ground polarity.. it was inevitable that the PA was hooked up to another circuit in the building versus the backline...

I carry a plug checker to this day to gigs for that very reason. Of course back then, none of the outlets were 3 prong, so it was like Russian roulette..

Ron

At the hotel I work at, when they do A/V work here, they are required to run a dedicated power line to the stage, and everything must be run off the same line. They have these HUGE breakout boxes with power lines the size of pythons for big shows. Pretty neat.

[sunnydaze]

Hi,

Been lurking for sometime.

First, I really appreciate the information some of you have taken the time to post, it has been helpful for me and I have enjoyed reading the forum. Anyway, a search for the term "deathcap" led me to this string of postings. So....

Have an old Epiphone EA 50, and I guess one of the previous owners installed a three prong plug, but they just wired the earth and neutral together and hooked it up like the original two prong, also left the sprague black beauty connected from hot to ground (deathcap). I corrected the wiring and removed the cap. This amp has an on/off knob and a volume control and is really a sweet sounding amp, although a bit on the bright side. Anyway, after removing this "deathcap" the amp was almost ice pick sounding.

As a test, I tried putting the cap from the cold side of the switch to ground using a jumper, and maybe this was just my imagination, but besides removing the very slight amount of hum, the amp sounded sweet again, no more ice pick. I only had a few moments to test, was just before leaving for work this morning. What reason, if any makes this work? Also, I can't see that having the cap on the cold side presents any danger. Comments, insight or conjecture would be greatly appreciated.

thanks
sunnydaze

[Structo]

You might want to start a new thread about your amp.

I was just looking at the schematic of this amp and the only thing I can think of why it would sound better with the death cap installed is that the filtering is very minimul on this amp.

I would replace the power supply filters soon if you haven't already.

[sunnydaze]

You might want to start a new thread about your amp.

I was just looking at the schematic of this amp and the only thing I can think of why it would sound better with the death cap installed is that the filtering is very minimul on this amp.

I would replace the power supply filters soon if you haven't already.

Thanks. I'm typing a new subject, not sure if this will create a new thread. Yes, I've replaced the powerfilters. This amp is pretty simple as you can see from the schematics. It's a little different than comparable sized Fenders in that there is no turret board, pretty much all flying leads except for a small teminal strip used for grounding on the input/preamp side. I also have a Fender Bronco (vibrochamp), but the Epi is a bit louder and more sparkly I think. The Epi uses 6AQ5's for powertubes, which I've read are electrically very similar to a 6V6, except has 7 pins. Nice thing about the 6AQ5's is that NOS tubes are pretty cheap.

I'll do a more thorough test after work and let you know if it really does sound better with the cap.

thanks
Sunnydaze

[sunnydaze]

Well,

After a more testing, I really couldn't tell much difference with the cap added back. I guess I wasn't quite awake when I tried it this morning before work - amp was laying with speaker facing the floor which pretty much wipes out the highs.....

I should have mentioned that in addition to rewiring the three three prong plug correctly, I also replaced some coupling caps. Originals were Sprague black beauties,replace with Sprague atoms. I also replaced the rectifier tube - the voltage was uneven and below specs on the first one, changing it put the readings pretty much right on target. C1 and C2 are pretty much dead on spec, but c3 is reading about 189 v should be 200 per the schematics. The voltages were about 10 - 15% low on the original first rectifier.

I had replaced the filter caps a while back, just used three Webers for in place of the original paper can 3 in one type type sprague - really couldn't tell much difference. The ice picky type sound didn't show up until I rewired the plug and replace the some of the coupling caps. Not sure why its so ice picky now.

Will post the results if I find the problem.

thanks.
sunnydaze

[sunnydaze]

Well,

After a more testing, I really couldn't tell much difference with the cap added back. I guess I wasn't quite awake when I tried it this morning before work - amp was laying with speaker facing the floor which pretty much wipes out the highs.....

I should have mentioned that in addition to rewiring the three three prong plug correctly, I also replaced some coupling caps. Originals were Sprague black beauties,replace with Sprague atoms. I also replaced the rectifier tube - the voltage was uneven and below specs on the first one, changing it put the readings pretty much right on target. C1 and C2 are pretty much dead on spec, but c3 is reading about 189 v should be 200 per the schematics. The voltages were about 10 - 15% low on the original first rectifier.

I had replaced the filter caps a while back, just used three Webers for in place of the original paper can 3 in one type type sprague - really couldn't tell much difference. The ice picky type sound didn't show up until I rewired the plug and replace the some of the coupling caps. Not sure why its so ice picky now.

Will post the results if I find the problem.

thanks.
sunnydaze

[sunnydaze]

Well,

After a more testing, I really couldn't tell much difference with the cap added back. I guess I wasn't quite awake when I tried it this morning before work - amp was laying with speaker facing the floor which pretty much wipes out the highs.....

I should have mentioned that in addition to rewiring the three three prong plug correctly, I also replaced some coupling caps. Originals were Sprague black beauties,replace with Sprague atoms. I also replaced the rectifier tube - the voltage was uneven and below specs on the first one, changing it put the readings pretty much right on target. C1 and C2 are pretty much dead on spec, but c3 is reading about 189 v should be 200 per the schematics. The voltages were about 10 - 15% low on the original first rectifier.

I had replaced the filter caps a while back, just used three Webers for in place of the original paper can 3 in one type type sprague - really couldn't tell much difference. The ice picky type sound didn't show up until I rewired the plug and replace the some of the coupling caps. Not sure why its so ice picky now.

Will post the results if I find the problem.

thanks.
sunnydaze