Guild superstar zapping

ok... I wonder if anyone can give me suggestions as to why my guild superstar is zapping me through my guitar strings? It happens on and off, and at times is a bit painful.

YossarianDunbar22 said:

ok... I wonder if anyone can give me suggestions as to why my guild superstar is zapping me through my guitar strings? It happens on and off, and at times is a bit painful.

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Because you have a two prong plug and the "deathcap" is failing.

Please take it to a tech and have a 3 prong plug installed and the death cap removed.

Pronto! Just google "Keith Relf"

Or "electrocution"

Default said:

Because you have a two prong plug and the "deathcap" is failing.

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Hi Yoss: from the schematic for your amp, the 'death cap' in the red circle. They were originally put in to shunt electrical interference to ground. In this case, the chassis represents ground and with a 2-wire power cord, not the ground in modern electrical panels. Over the years, exposure to voltage spikes on the incoming 120V AC power weakens the capacitor and causes it to fail. They can fail 'open' - no connection to the chassis - or they can fail 'short - creating a direct path for the 120V AC power to the chassis. Default is right; get a 3-wire power cord on your amp and remove the cap; at some point it will fail completely and you will be at risk of being shocked.

is this something i can do myself? I follow directions well. if not, anyone know a good tech in CT?

Hi Yoss; the fix is about as technically simple as it gets but you or a friend needs to know how to solder. The two incoming AC power wires are soldered in two places; one leg on the fuse, the other on the switch. These connections are un-made by heating the solder joints and tugging the old wires off. Two of the three new wires on a 3-wire cord get re-connected where the old wires were disconnected.

There are two other wrinkles.

Ground wire; the green wire is usually tied under the nut of one of the nearest transformer bolt; easy enough however good practice is to put either a crimp-on or solder-on spade connector on the end of the green ground wire and then loosen the nut, clean the chassis where the wire is going to go, slide the spade connector under the nut, and re-tighten.

Strain relief; it isn't good practice to just run the new 3-wire cord through the old chassis hole where the former cord was without some form of strain relief; a plastic or rubber bushing than creates friction between the cord and the chassis so that, when someone trips over the power cord, it doesn't rip itself away from its connections inside. Even if you find a strain relief bushing, the old hole will likely be too small for both the new cord and and the bushing. I usually have to enlarge the hole with either a reamer or a dremel bit to get it large enough.

The very cheesey work-around is to run the cord, with plenty of length to make your connections, up into the chassis and then tie a knot in the cord so that, if pulled or tripped over, the knot will take the strain instead of the solder connections. This will work but if detected by anybody, it's a giveaway for crappy practice and still leaves the cord at risk of being chafed or cut by the edge of the chassis at the hole.

If you don't want to screw with it, any electronics/TV/stereo/appliance repair shop can do the work; depending on length and type, you can get cords all over the web or just drop it off somewhere and let them find / install the cord ...and remove the cap.

If nothing else, take the power chassis out, take some pics of it, post them, and default or I can ID the problematic cap and you can take it out by cutting its legs ... with the amp unplugged. You will still need a 3-wire cord and if you go forward with the sale of this amp, you can say that it has a 3-wire cord meaning the buyer isn't stuck having to do it.

John

capnjuan said:

Hi Yoss; the fix is about as technically simple as it gets but you or a friend needs to know how to solder.

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May I say that this is yet another example of the helpful, useful and dare I say, Life Saving, advice available at LTG and I am genuinely proud to have some small association with the good folks here.

Hear, hear.

Cable here.
Strain relief here.

If you scratch around, you can probably find a longer cord. I would go 12' if I had it to do over.

Default said:

Cable here.
Strain relief here. If you scratch around, you can probably find a longer cord. I would go 12' if I had it to do over.

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Strain relief bushing needs 5/8" hole; gonna be bigger than hole in chassis now ... As a famous amp tech once said:

"I love you and I'm reaming of you but that won't do
Ream baby make me stop my reamin', you can make my reams come true.." Roy Orbison

:lol: :lol: :lol: :lol: :lol:

After reading this discussion I pulled my Superstar apart to try and find the deathcap. I have kids that play on this amp! Alas, I wasn't able to identify it unless perhaps it is on the standby switch?




If that isn't it can anyone give me a hint as to where it might be located.

Thanks,

Rich

That's it, a .047 cap, one end should be connected to ground, the other to the hot. Remove that and replace the two prong with a 3 prong with the green ground wire from the new cord connected to the chassis. There is probably another in the output section connected through the umbilical. I haven't had the pleasure of owning a Superstar, so I can't tell you where or if it has two deathcaps.

It's stuff like that where you might want to take it to a tech if you aren't used to messing around with this stuff. You can get a nasty shock, if you touch the filter caps accidentally.

Default said:

... I haven't had the pleasure of owning a Superstar, so I can't tell you where or if it has two deathcaps ...

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Yo PhillySteve ... sent you a (the?) schematic labelled 'Superstar' (it's also labelled Thunderbird :? ) .... you may call it whatever you please ... shows one cap, but - as you point out - there could be another on the upper chassis.

Hi mxaniac; you really need a grounded power cord if you're going to use that amp. CJ

Thankks for the schem, cj! According to that, there's a .05 off the power switch in the lower chassis and a .01 of the standby in the upper chassis.

Hello YossarianDunbar22.

Whatever became of Major Major ?

Welcome, and hang on for a rough ride !

Default said:

... there's a .05 off the power switch in the lower chassis and a .01 of the standby in the upper chassis.

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Thanks Steve, I missed it before;

capnjuan said:

Default said:

... there's a .05 off the power switch in the lower chassis and a .01 of the standby in the upper chassis.

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Thanks Steve, I missed it before;

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Myopia ? Stollyopia ? Puhaopia ?

coastie99 said:

... Stollyopia ? Puhaopia ? ...

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Some of this ... and some of that other stuff too! Cheers MoG!

Thanks for the replies. I have already put a grounded power cord on it, and I ran a wire between the upper and lower chassis as well.

I don't have a power switch on my lower chassis though so I'm a bit confused by references towards the lower chassis power switch.

Thanks,

Rich

mxaniac said:

... and I ran a wire between the upper and lower chassis as well.

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Hi Rich: Wire? Ground wire?

mxaniac said:

I don't have a power switch on my lower chassis though so I'm a bit confused by references towards the lower chassis power switch.
Thanks ...

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According to the schematic, it looks like there are two switches; the schematic (do you want a copy? If yes, PM me with your email address) is labeled 'Superstar-Thunderbird' but, as we have learned from buying men's socks, no matter what they say, one size does not fit all ... long way of saying that there's no guarantee that the schematic we're looking at matches your amp.

If you only have one power switch, regardless of where it is, the cap you showed us in the pic above has been removed, and you have a 3-wire cord, then you are done. If you're still being zapped, then there is DC - not AC - leaking to your chassis somewhere somehow and that would be a matter for your local tech. Good luck! CJ