I posted a thread in here about a 1964 Sano that I picked up the other day. Its got a really nice vintage tone, and I love it!! The downside is this, when the amp is turned on, it makes just a bit of hum. When I turn the main volume up, past half way it starts to hum a lot louder, and it continues to increase as I turn it up. If I turn up the secondary volume, and turn down the main volume I can get the amp a lot louder before the hum kicks in.
The amp has a two prong power cord, and it has a hum/interference knob on the back along with a polarity switch. The polarity switch changes nothing, and the hum dial corrects the hum a bit.The amp is plugged into a monster power supply/surge protector. I was thinking that there is either a bad main volume pot, or I need to convert to a 3 prong.
Another strange issue, when my buddy and I were playing our electrics,I touched one of his strings and got the hell shocked out of me. He touched my guitar string and it zapped him too. What the eff??
The amp has a two prong power cord, and it has a hum/interference knob on the back along with a polarity switch. The polarity switch changes nothing, and the hum dial corrects the hum a bit.The amp is plugged into a monster power supply/surge protector. I was thinking that there is either a bad main volume pot, or I need to convert to a 3 prong.
Another strange issue, when my buddy and I were playing our electrics,I touched one of his strings and got the hell shocked out of me. He touched my guitar string and it zapped him too. What the eff??
Does that amp have a power transformer?
If not ADD AN ISOLATION TRANSFORMER -My guess is that it does not have a power tranny,and thus no isolation from the AC line,very dangerous as you discovered.
Edit:
DO NOT add a 3-pin power cord until you verify that it is not a line-operated circuit,or else you will pop the breaker on whatever outlet it is plugged in to.
Add an isolation transformer,and then a 3-prong cord,once it's isolated from the AC mains.
If not ADD AN ISOLATION TRANSFORMER -My guess is that it does not have a power tranny,and thus no isolation from the AC line,very dangerous as you discovered.
Edit:
DO NOT add a 3-pin power cord until you verify that it is not a line-operated circuit,or else you will pop the breaker on whatever outlet it is plugged in to.
Add an isolation transformer,and then a 3-prong cord,once it's isolated from the AC mains.
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Rotus623, you need to be careful... you can take an AC voltmeter reading from earth ground to the amp's chassis (1/4" jack on guitar) and see what you get, also while trying the hum controls.
All ungrounded (two-prong powered) tube gear floats above ground depending on the leakage of the power transformer and polarity switch caps. It can be enough to just "bite" or enough to kill
- usually when musicians grab the mic (grounded) while touching their guitar. Similar to Leslie Harvey's death in 1972...
I would measure the resistance and leakage current from the amp chassis to its power cord pins. If it's a shorted power transformer, the amp should not be used until fixed.
All ungrounded (two-prong powered) tube gear floats above ground depending on the leakage of the power transformer and polarity switch caps. It can be enough to just "bite" or enough to kill
- usually when musicians grab the mic (grounded) while touching their guitar. Similar to Leslie Harvey's death in 1972... I would measure the resistance and leakage current from the amp chassis to its power cord pins. If it's a shorted power transformer, the amp should not be used until fixed.
Gotcha, so you think that the power tranny is shorted? What should my voltage reading be from the chassis to ground?
Holy **** Prarie!! I am getting 118.2 VAC from the chassis to earth ground. What does this mean?!
Now you know why KISS wear those boots. 🙄
But seriously, turn the plug around in the wall. Does the voltage go away?
But seriously, turn the plug around in the wall. Does the voltage go away?
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Hahahaha!! Yes Taj, good point, when I reverse the polarity (it actually has a switch to do so) the voltage goes down from 118.2VAC to 2.xx VAC, so phew, that's a lot better. BUT, there is still a hum at loud volumes even when the polarity is switched. Any ideas??
It's time for a properly wired 3 prong power cord and new filter caps. That's just to get the ball rolling. Better safe than sorry.
Worrrrddddd... Thanks to all guys, I'm gonna get crackin' on this big boy. I'll let you guys know when I get her all converted.
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