To remove or not remove this 'death cap' from Music Man 2100 - 75

[westonbread]

Hey y'all.

I am fixing up a Music Man amp, model 2100 - 75.

It has went well, a transistor was shorted, I replaced them both and it is sounding great.

Should i be removing this 'death capacitor'?

My friend who uses the amp said he sometimes uses a ground lift attachment, which I told him really not safe to do. Especially with that switch and cap being able to be on either the hot or neutral.

The cap is working fine right now, doesn't look to be a cap that would be that susceptible to age.

Remove entirely?

Replace with safety new Y capacitor?

Leave it as is?

What do you guys think.

Thanks!
Dan

 

[westonbread]

Someone has to know...

 

[JohnRoberts]

I am not the guitar amp guy around here.
----
From a quick search the DVL stands for a double layer capacitor, presumably safer.

Even safer would be to wire up a 3 wire line cord, then lose the stinger cap and switch entirely. Just connect the safety ground wire to the chassis.

Alternately you could keep the stinger cap and connect it between chassis and line cord safety ground.

JR

 

[arthurdb]

I'd reckon it's pretty safe as is. The chassis is already earthed to safety ground.

However, modern safety standards dictate that only Y class capacitors be used between mains and safety earth. These are guaranteed to fail open and thus reduce the risk of anything bad happening, even if the ground is lifted (which indeed your friend shouldn't do).

 

[CJ]

That cap is to suppress noise,

I would rip it out, especially since it is rated at 125 instead of 600 volts.

There really is no need for that cap if using a three prong cord.

Ground lift - people gonna do what they do.

I have a 64 vibro champ that I have been using since , well, 1964 and I ain't dead yet. I do unplug it when not in use.

There is something to he said for floating the chassis and therefore the guitar player but I have a hard time explaining this to folks without starting a beehive of activity to the contrary.

 

[rock soderstrom]

There really is no need for that cap if using a three prong cord.

I see it the same way, I think an X2 capacitor in parallel to the mains makes more sense in terms of noise. There are also these combined (CL) mains filters, some of which are integrated into the IEC mains socket, which I have also installed without any problems.

Grounding the chassis via the PE is without alternative for me, especially for singing guitarists and bassists. I actually once saw a German bass player who suffered life-threatening injuries on a vocal microphone due to a faulty (and non-earthed) amplifier. The audience thought it was a show, but it was pure seriousness.

 

[westonbread]

Thanks guys, It seems ripping it out entirely is the consensus or maybe Y2 cap is the way. I guess the Y2 cap is compelling if the switch actually does provide any noise benefits.

Can I leave that switch in there as is without the cap? I would think its pretty harmless, although useless. Or is it necessary to remove the neutral and hot wires that go to the switch too?

Dan

 

[Electrobumps]

If you left in and killed yourself or someone else it would be annoying.

If you remove make sure you ground the mains ground to chassis. This should stop any noise issues that the death cap was designed to overcome.

I’d also personally remove the wiring and keep the switch in place. You should check out https://robrobinette.com/Amp_Stuff.htm There is loads of info on his site and has a section on the death cap.

 

[westonbread]

This amp was factory built with the 3 cord properly grounded chassis, as well as the switch and cap as far as I can tell. Early 80s.

Going to check out that link thanks Electro.

 

[westonbread]

Alright. I think i'm gonna just take the cap and out and the wiring. Seems the safest, especially if its ever used with a ground lift or shitty power wiring.

Thanks guys!

 

[JohnRoberts]

If using a ground lift adapter (don't do that) or plugged into an outlet lacking a safety ground (like my house), the stinger cap could reduce hum by bonding the chassis to 0V neutral through the 0.01uF cap.

JR

 

[CJ]

If your afraid of getting shocked you shouldn't be in the music business, jus joking

The power transformer in a guitar amp, if it has one, does a marvelous job of isolating the amplifier circuitry, and the guitar player from the power line.

When you plug in a 3 prong power cord, presto! The guitar player is now hard wired to the neutral. Gone is the isolation from the power transformer. Now, instead of getting a half a mil jolt from the "death cap", you get current flow impeded only by the sack of salt water which is your body. This means major amperage.

Most of the arguments for the three prong invoke a scenario whereby some component, such as the power cord or power transformer or power switch, enters into failure mode thereby connecting one side of the hot to the guitar player via the guitar cord. Such events, I admit, can and do occur, albeit rarely.

I have also never seen a death cap fail.

If I am a repairman and put myself in a position for a lawsuit, then I would probably want to follow the rules set down buy our wonderful friends at UL.

I use a three pronged cord on my amp for two reasons.
One is to cut down on 60 cycle hum and other artifacts.
The other is to trip the breaker when I am not at home, thereby avoiding nosey neighbors watching my house burn down with the 7 small children and the goldfish bowl.

Now if I am on stage with the big dogs at the stadium, I go wireless because there is probably 480 three phase floating around the neighborhood. And that will cook you quicker than a weiner in a Amana microwave.

 

[westonbread]

Lol. Sound logic CJ! I cut the cap and the wiring out, it has three prongs. Now to live with my decision. I think it mostly got used with the ground switch not used / in the middle, not attached to either leg of the mains anyway.

 

[CJ]

The scariest thing about the music man amps is the 750 volts on the hi/lo power switch. Brother Leo was famous for pushing the envelope. How he got the Twin Reverb standby switch past UL is beyond me.

I have pulled about a 100 of those death caps over the years. There was a time when the three pronged cord invention overlapped the two prong chassis, so you have a redundant situation where you have excess baggage that you don't want to claim.

And don't remove the flyback diodes on the power tube sockets. I found that out the hard way. Apparently they do some good in the music man amp.

 

[JohnRoberts]

If your afraid of getting shocked you shouldn't be in the music business, jus joking

shocked OK, killed not so OK

The power transformer in a guitar amp, if it has one, does a marvelous job of isolating the amplifier circuitry, and the guitar player from the power line.

When you plug in a 3 prong power cord, presto! The guitar player is now hard wired to the neutral. Gone is the isolation from the power transformer. Now, instead of getting a half a mil jolt from the "death cap", you get current flow impeded only by the sack of salt water which is your body. This means major amperage.

ASSuming proper mains outlet wiring. Safetey ground is bonded to neutral at the fuse box/power drop. But there are exceptions, ground lifts, etc.

Forgive another old Peavey story. While at a big Mexican Peavey dealer seminar (down in Mexico) a dealer shared with me that the way they knew a Peavey product was still new and not used was because the line cord ground lug was not cut off yet.

Most of the arguments for the three prong invoke a scenario whereby some component, such as the power cord or power transformer or power switch, enters into failure mode thereby connecting one side of the hot to the guitar player via the guitar cord. Such events, I admit, can and do occur, albeit rarely.

I have also never seen a death cap fail.

UL and cap makers did not come up with special classes of capacitors designed to fail safely on a lark. Consumer deaths often drive safety regulations.

If I am a repairman and put myself in a position for a lawsuit, then I would probably want to follow the rules set down buy our wonderful friends at UL.

or as a manufacturer...

I use a three pronged cord on my amp for two reasons.
One is to cut down on 60 cycle hum and other artifacts.
The other is to trip the breaker when I am not at home, thereby avoiding nosey neighbors watching my house burn down with the 7 small children and the goldfish bowl.

Now if I am on stage with the big dogs at the stadium, I go wireless because there is probably 480 three phase floating around the neighborhood. And that will cook you quicker than a weiner in a Amana microwave.

I advocate using GFCI outlet power strips for backline on stage to protect musos against energized mics, or rogue guitar amps (not the safest track record) that could harm the talent using the mic as the ground path.

JR

 

[CJ]

speak of the devil, gonna yank this guy out of a 64 bandmaster,

i bet many a gig was played with this two prong amp without incident,

been converted to three so out comes the cap, but don't throw it away!

notice the aux 120 outlet tie wrapped for your protection,
another component that could cause problems without a three prong cord,
ok, this incident right here, this funky outlet, put on my bench this morning as a miracle diguised as a coincidence, (the Big Kahuna works in mysterious ways) might be the straw that broke the camel's back as far as convincing me to stay grounded. i mean there can be no clearer way to point out how you could have a hot chassis,

 

[clintrubber]

Just freshed up my mind at the robrobinette-site, and then happened to find this thread here as well, nice.

FWIW, here's a 'topology-variation' using the ON-OFF-ON power switch, as used in old Rickenbacker amps.
Needed to go inside as this amp is blowing fuses, but while there I'll remove the 0.01 uF cap as well.