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Hi, all.
There's a cap going to ground from the standby switch. What does this do and is it required?
TIA!
There's a cap going to ground from the standby switch. What does this do and is it required?
TIA!
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~F
"Ruining good moments since 1975" -
This subject has come up many times. Search here or Google for 'death cap".Originally posted by fdesalvo View Post
The short story: It's for noise suppression and it has to be removed for safety.
EDIT:Oppps! I misread and thought you were talking about the the grounding switch cap.Last edited by nickb; 08-22-2015, 05:47 PM.Experience is something you get, just after you really needed it. -
That's what you get for being all spicy!
Yeah the death cap is off the ground. Wondering if this is a vestigial appendage. I don't see it on some of the clone/kit manufacturer's schems.~F
"Ruining good moments since 1975"Comment
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There are two caps on the standby switch. One at the rectifier end and the other at the OT CT end. They are both power supply capacitors. They smooth out ripple current and are needed. All the clone and kit 5e7 circuits include those caps also. Though they may have it drawn in a different way that makes it look different or some may even have the standby switch located ahead of the first power supply capacitor (wrongly)."Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
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I just had another look and only see the one cap I mentioned. On Ceriatone's layout, it seems they omit it altogether.~F
"Ruining good moments since 1975"Comment
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I think you mean the .05 that is mounted right on the standby switch?Originally posted by Enzo
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A bunch of them have it - most of the tweeds with the standby in the B+ line. Mainly the E & F series... maybe an attempt to cut down thumping when switching? Doubt it's a typo or vestige, since it lasted some time...
Justin"Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
"Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
"All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -Comment
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Originally posted by fdesalvo View PostAh! I see. It's either there to filter HF transients from the line voltage that make it through the PT or to improve the HF performance of the main filter. Neither of which are consistent problems with modern line voltage or filter caps. (EDIT:Good call Justin on the standby thump possibilityOriginally posted by g1 View Post
) So I suppose it would be ok to omit that .05/600 cap. But why bother when it's not a crowded node and it won't take up much room? It won't hurt anything to be in there and costs about three bucks.
Overthinking it, it's possible that Fender experienced some magnet wire insulation problems with the input choke when the design was tested with a crappy mains voltage. Sometimes generators are used for outdoor shows. Or, back in the day and testing the amp in a facility that was basically constructed like Lego's, HF spikes could cause a problem like that. Old filters may not have had enough HF performance to protect the choke. That cap would share duty with the main filter to improve spike suppression.
Overthinking it even more... That amp had 410Vp. Which seems like a lot for the era. The main cap is a 450V cap and would almost certainly experience an over voltage condition with inrush current when the standby switch was flipped. Most caps can take this well enough but it's possible that Fender had some trouble with that cap on an amp or two and found that suppressing HF spikes, possibly made worse by inrush currents, was suitably nulled by loading a .05 cap prior to the standby switch.
At any rate I think it's likely the designer experienced something problematic and that cap solved for it. Probably not a problem with modern components BUT like I said above, it won't hurt a thing to include it."Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
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It makes sense to reduce pops on the stdby switch.~F
"Ruining good moments since 1975"Comment
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I once had a 5F6a Bassman circuit which made a loud crack when operating the Standby switch, adding the capacitor fixed it.Comment
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Hey, where's my BING BING BING BING BING??? I don't want "likes" anymore. I want BINGs.
Justin"Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
"Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
"All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -Comment
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Bing!bing!~F
"Ruining good moments since 1975"Comment
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Agh! You guys are doing it wrong!!!
It's like this:
BING BING BING BING BING !!!Originally posted by Justin Thomas View Post
Like a game show bell when a contestant wins! Sheesh! Was it that obscure? I stole it from Jim Carrey in Bruce Almighty. Maybe I shouldn't do it anymore
"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
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