Mark IIc+ "death cap" removal

[LesPaul70]

Looking at this schematic (can't vouch for its overall accuracy):
http://tubefreak.com/mk2cpwr.gif

Am I correct that the so-called "death cap" would be the cap in the bottom left corner?
Just wondering what would be the ideal way to eliminate it if I need/want to. I'll be very grateful for any pointers and suggestions.

 

[MrMarkIII]

And why would one call them (I count 8 to 10) a "death cap"?

 

[sduck]

Why do you want to "eliminate" a capacitor? You can't just get rid of a capacitor because of some nickname someone's given it. BTW, I've never heard of a death cap before, although I've been aware for many decades that certain undischarged capacitors can indeed kill you if you're dumb enough to mess with them in the wrong way. Perhaps you are wanting to learn how to properly discharge the caps so that you can work on the amp?

 

[LesPaul70]

Not referring to the general precautions here...I have some experience and I'm aware.

The ground switch cap on vintage amps is sometimes called a "death cap" because if it malfunctions, it can connect AC to your amp chassis. (You figure out why and under which circumstances this would be bad.) Looking at the linked schematic, it seems to me that the ground switch is in the bottom left corner and the cap there could do that if it shorted.

Not saying that the risk is very probable, but I've read here that some people have removed the 'death cap' from their Marks. Because I never have, I was just interested in knowing what would be the correct way of doing that. (If I ever wanted or needed to.)

 

[Restless Rocks]

As you can see in the schematic, the ground switch is what we call an "on/off/on" type. In other words in the middle position the cap is not connected to either the hot or neutral ac line. Same as being removed.

 

[shytfayse]

As you can see in the schematic, the ground switch is what we call an "on/off/on" type. In other words in the middle position the cap is not connected to either the hot or neutral ac line. Same as being removed.

+1

I would not remove it. If the outlet is properly grounded, and the "death cap" shorted, and the ground switch was in the on position where the hot/line side was connected to the switch it would probably blow the circuit breaker. There may be a pop and you may sh!t your pants, but, you will most likely survive. The "death cap" was more problematic in the 50's and 60's where grounded outlets and polarized 120 volt plugs did not exist. I think the possibility of the cap shorting is very slim.

That said, the "death cap" is the capacitor in the lower left, and, you could just snip it out with some diagonal cutters. Then you could sleep at night not thinking about it.

- Pat.

 

[sduck]

Ah, now I see the issue. And, as Shytfayse has mentioned, caps, and especially the electrolytic types used for this application have improved considerably in the last few decades. Current electrolytics are designed so that any kind of failure will not result in a short, except in very rare cases. However, some of these are old amps, and may still have the original caps - probably time to replace them!

 

[LesPaul70]

...just wanted to pop in to thank everybody who responded. Good point about the switch being "on-off-on" type. Yes, I agree, that's a better solution than physically modifying a relatively valuable vintage amp.

One of our regular band jam venues still has no grounded outlets (yeah, just how backwards is that? but that's the way it is), which is why I asked in the first place. But I now know I have several options how to avoid the potential problem, which is great.

Case closed. Thank you all again.