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Post subject: three way on off switch (old school) question
Posted: Wed Apr 20, 2011 3:39 pm
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If an older tube amp has a On/Off/On switch and it works fine one way but sparks the other, would your first thought be that it needs a new switch ?
I can't find a short anywhere in the circuit ????

Crazy !!!

Arjay ???

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Post subject: Re: three way on off switch (old school) question
Posted: Wed Apr 20, 2011 3:42 pm
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blues bondsman wrote:
If an older tube amp has a On/Off/On switch and it works fine one way but sparks the other, would your first thought be that it needs a new switch ?
I can't find a short anywhere in the circuit ????

Crazy !!!

Arjay ???


Absolutely!

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Post subject: Re: three way on off switch (old school) question
Posted: Wed Apr 20, 2011 3:51 pm
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Martian wrote:
blues bondsman wrote:
If an older tube amp has a On/Off/On switch and it works fine one way but sparks the other, would your first thought be that it needs a new switch ?
I can't find a short anywhere in the circuit ????

Crazy !!!

Arjay ???


Absolutely!


+1!!!

The contacts within are shot.

Replace it immediately and do not use this amp until you have done so.

I'm not comin' to your funeral......I want you at mine!

:mrgreen:

Arjay

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Post subject: Re: three way on off switch (old school) question
Posted: Wed Apr 20, 2011 3:54 pm
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Maybe not just a new switch, but a different kind. I know that people use these type switches in lieu of an off-standby-on, but the spark occurs when the switch is switched from on to the middle (open) position, and you have to go through the middle position to get to standby from on. Using a capacitor on the AC part of the switch might help, as I'll bet that is the section that is sparking, the collapsing field of the power transformer has no place to go. :idea:

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Post subject: Re: three way on off switch (old school) question
Posted: Wed Apr 20, 2011 3:56 pm
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Should I just replace it with a one way ?

There are two large caps on the switch.

(Old Peavey by the way)

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Post subject: Re: three way on off switch (old school) question
Posted: Wed Apr 20, 2011 4:14 pm
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blues bondsman wrote:
Should I just replace it with a one way ?

There are two large caps on the switch.

(Old Peavey by the way)


See shimmilou's remarks above. Could be that a pair of new caps will cure the problem. Many old Ampegs had a similar switch arrangement.

Regardless, the amp needs attention immediately.

Arjay

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Post subject: Re: three way on off switch (old school) question
Posted: Wed Apr 20, 2011 4:19 pm
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A "one-way" on-off switch will eliminate the standby position. The standby part of the switch allows the tubes to warm up before slamming the high voltage on them. You would probably still have the spark with the one way switch. Since you already have capacitors on the switch, I would check them to see if one or both are shot. If the contacts in your existing switch were "shot" then the amp wouldn't come on, and the contacts being shot would be a symptom, not the cause of the problem. Damage to the contacts would be caused by the sparking, not the sparking caused by bad contacts. :idea:

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Post subject: Re: three way on off switch (old school) question
Posted: Wed Apr 20, 2011 4:33 pm
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no standby on this old girl, on/off/on one single switch, i believe it was two different grounds.

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Post subject: Re: three way on off switch (old school) question
Posted: Wed Apr 20, 2011 5:23 pm
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Are you referring to the power switch? If so, one of the on positions is likely a standby, supplying power to the transformer but leaving the DC voltage to the output tubes off. If one of the on positions is a standby position, then the amp will power on but have no sound out in one of the on positions, and will have sound out in the other on position. If your switch is wired this way, one of the on positions powers the tranny, and the other on position powers the tranny and the DC. Which Peavey do you have? I have a few Peavey schematics and I would have a better idea of the switch wiring by looking at the schematic if you know the model. :idea:

Edit:

Perusing some Peavey schematics, I saw one that had a switch as you've described with the two capacitors (.01 uFd). On that amp it is just a polarity switch for the power transformer input. Not sure why that would be necessary as the schematic shows a 3 prong grounded power plug, but that is how it is shown, this may be what you have also. Either way, I would still say that one or both of the caps are suspect. :idea:

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Post subject: Re: three way on off switch (old school) question
Posted: Wed Apr 20, 2011 6:40 pm
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shimmilou wrote:
Not sure why that would be necessary as the schematic shows a 3 prong grounded power plug, but that is how it is shown, this may be what you have also.


Well into Fender's silverface era, most if not all of the amps were equipped with a grounded 3-conductor power cable yet still featured a 3-position polarity switch on the rear panel (excepting the Champ, Vibro Champ, Bronco, and Musicmaster Bass Amp). A perfectly-good Carling switch, with absolutely nothing to do.

Weird!

:shock:

Arjay

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Post subject: Re: three way on off switch (old school) question
Posted: Wed Apr 20, 2011 7:08 pm
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Sounds like they weren't sure that the whole "safety" ground thingy would catch on. :lol: Do you think that blues bondsman would be better off with a simple on-off switch, sticking with the polarity that doesn't cause a spark? :?:

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Post subject: Re: three way on off switch (old school) question
Posted: Wed Apr 20, 2011 7:14 pm
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If the amp is currently (and correctly) grounded, probably.

But if the switch also performs a "standby" function, that would be terrible feature to lose, given today's cost for quality tubes.

Arjay

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Post subject: Re: three way on off switch (old school) question
Posted: Thu Apr 21, 2011 5:44 am
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Blues Bondsman, try here for replacement switches and anything else electronic.
http://www.mouser.com/?cm_mmc=google-_- ... 5QodkwXyHA

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Post subject: Re: three way on off switch (old school) question
Posted: Fri Apr 22, 2011 6:37 am
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Thanks !!!
I knew you guys would point me in the right direction.
I'm sure its a polarity option and not a standby.

it is one of those 6L6 run amps with SS preamp.

it is a peavey Classic VT Series 100

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