Here's a PDF of the CDE paper on Quench-Arc's -- I have a bag of them bought from a heavy equipment mfr in Ohio -- https://www.cde.com/resources/catalogs/HowQworks.pdf
My 1960s valve amp's switch suppression comprised a 0.022 uF, 250 VAC, polyester capacitor in series with a 220 R, 0.5 W, carbon resistor.
The capacitor failed short recently, blowing the 3 A fuse in the plug top while leaving the 1 A anti-surge equipment fuse intact. In addition, the RCD on the supply board tripped.
On opening the amp, I found the carbon resistor had been blown into fragments.
It is an arc suppression capacitor. This appears to be a TD-135? Most likely electrical in TD-124, 135 with this switch is a switch problem followed by a seized motor. Open coils are not common on E50, but not unheard of.
Does the strobe neon light? If so the motor is seized. Parts to repair if it is in fact an E50 motor are available.
To receive useful assistance it really, really helps to tell us what TT you are trying to repair, and any history you might know about it.
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It was a crap shoot.
Literally, crap shooting out of the chassis.
Lucky there was no fire.
The carbon resistor itself acted as a fuse, but it just goes to show how important proper fusing and RCD protection are.
True. If you remove the arc suppression the cap offers, you'll get, what else?, arcs. When the switch closes, depending on where the voltage is during the AC power cycle, there could be a current spike as the switch shorts the charged cap's terminals together (along with the current supplied to the device being switched) when the cycle is at a voltage maximum. Of course, chance plays a role, as you don't control where in the AC cycle the switch contacts come together after you actuate the switch's lever. And then there's contact bounce; (ouch...ouch...ouch...) I use a small resistor (10 or so ohms) in series with the cap to dissipate the energy that may be in the cap. I think that there are also cap-resistor pairs built into one package, sold as arc suppression devices that can be used for that purpose.
Actually, it's the opening of the contacts that creates a spark / arc.
I use MOVs to very effectively control this, and to extend contact / switch life greatly. They always work, every single time.
Now about this thump. I have no idea how much gain we are talking about, so the cause isn't something we can tell for sure. First steps, make certain your grounding is correct as that will make anything worse. We may have a non-issue here.
I use MOVs to very effectively control this, and to extend contact / switch life greatly. They always work, every single time.
Now about this thump. I have no idea how much gain we are talking about, so the cause isn't something we can tell for sure. First steps, make certain your grounding is correct as that will make anything worse. We may have a non-issue here.
