Originally posted by Enzo
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Fender Blues Jr 3 noise
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Originally posted by Enzo View PostThe little TO92 black plastic transistors, like 2N3904, may look opaque, but they are not. To IR light, they are little windows. Also LEDs and other diodes can be sensitive to light. SO when your chassis is out, fluorescent or other strobed light sources can bleed into circuits by shining through the walls of a transistor or into an LED.
nosajsoldering stuff that's broken, breaking stuff that works, Yeah!
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To a certain extent all transistors are phototransistors. Inside a TO3 it would never matter, but light hitting the junction can be picked up like a tiny current. Noise, hum, signal interference.
This is not something that commonly causes us trouble. But possibly.Education is what you're left with after you have forgotten what you have learned.
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Originally posted by nevetslab View PostI never knew that! Amazing what you can learn browsing thru the posts on any given day! Very interesting tidbit of info, Enzo!!
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Originally posted by Enzo View PostTube, solid state, doesn't matter, any sensitive amplifier circuit can pick up interference.
My AT&T wireless desk phone sent all manner of noise into amps when I had it sitting right next to me at the bench. I had to move it away. Yes, cell phones often make clicks and pops as they check themselves in and out of the world. A sump pump in the basement used to send hash about the house to pick up.
I once had a baffling buzz that went for several seconds once a minute. It was only a stroke of luck that it was a warm day and I left it running to step out on the front step for fresh air, and I could hear this at the same time I noticed the traffic signal at the end of the block. The yellow light on one direction had a noisy triac in the circuit, so whenever that yellow was lit, noise went out on the power lines in the area.
My dad had a little fish tank heater, and it had a simple bimetal thermal switch inside to set the temperature. Every time it cycled on or off, the thermal switch contacts sparked, and I picked it up in my shop. Fish tank was on the other side of the wall of my shop in that house.
I had a CD player whose display send out digital noise to anything around it. I discovered that one day it was blinking 88:88 off and on, and the hash in my stereo exactly following along.
Noise could be coming in through the power line, but it could also be radiated. Plug the amp into a FILTERED power strip. Not just surge limited, but actual filtered. ANy change?
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Enzo.....I was looking locally but the only thing around here is the surge protect garbage.....I do have a bunch of filtering units that were removed from gaming terminals such as what is found in a casino........the AC cord would plug into the filter and the other end had a bunch of chokes and caps for filtering out noise....then the back end was just connected to the power supply ckt with those spade connect/dis-connect connectors and the unit is encased in a metal casing..........I have these in two different physical sizes.....one is about the size of a pack of king size cigs......the other type is about half the size.....I will dig them out over the next day or so and take a quick pic so you can have a look......as I have to find them among all the stuff I have stashed away....maybe if I rigged up one of these to a power bar that might work??? anyway, I will get back to you with a few pics......
Cheers
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Originally posted by bsco View PostOK Enzo....I found the larger unit..this may not be suitable but here is a pic......[ATTACH=CONFIG]52590[/ATTACH]Logic is an organized way of going wrong with confidence
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Originally posted by nevetslab View PostThat's essentially what's inside a well-filtered power strip. I find them as the power inlet module on test equipment. For bench applications, you could build it into a 3-gang die-cast box made for mounting duplex power outlets & wall switches. Since this is only rated for 5A 125VAC, it would only be suitable for the amp being serviced. Getting the power into this thru the box.....you could chop the male plug off a molded IEC power cord, pass the open end thru the strain relief of the box. The other end gets wired to a Duplex outlet. The cover plate....you should be able to find one that has two duplex outlets and a wall switch. You might be able to find a dummy plate to cover the unused outlet holes on the cover plate. Verify the line and neutral connections between your added power plug that gets attached to your cable that gets plugged into the filter, so you don't reverse the Line & Neutral on the duplex outlet.
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Originally posted by bsco View PostThank you for your reply.......It sounds like this would work then...........the fact that it is only rated at 5A won't be a problem...at least I don't think it would be.....as these interference issues will be at zero volume level......so the only current that will be drawn will be the idle current of the amp in question....please correct me f I am wrong here......CheersLogic is an organized way of going wrong with confidence
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Originally posted by nevetslab View PostYou're correct. You can, of course, use it under full power of most amps that draw under the rated current of the filter. Truth be known, I've used one of these with just an in-line AC Female outlet cable, where it's feed end was terminated into insulated crimped Fast-on connectors and plugged onto the outlet terminals, with the ground connected with a crimped terminal. Not what I'd do for a permanent safe-and-sane bench unit, though. We all have to cobble something together in a pinch to solve a problem.
Cheers
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I used to work in the arcade industry, and every video game had one of those silver box filters on the incoming AC mains. That is exactly what is inside a filtered outlet strip, thought they might make the circuit up from caps and coils instead of buying the silver box. Same difference. I am sure the casino video games are no different from the arcade videos I worked with. I don't know who is in the casino game these days, but in my day Bally was a big name in both arcade and casino.
A lot of processing gear we use, like rack DSP units will have an IEC power connector, the typical "computer" power cord, and the filter is built into the power connector.
Remember, a mains filter is only going to tell us if the noise is riding the mains into your system. It won't affect radiated noise.Education is what you're left with after you have forgotten what you have learned.
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Originally posted by Enzo View PostI used to work in the arcade industry, and every video game had one of those silver box filters on the incoming AC mains. That is exactly what is inside a filtered outlet strip, thought they might make the circuit up from caps and coils instead of buying the silver box. Same difference. I am sure the casino video games are no different from the arcade videos I worked with. I don't know who is in the casino game these days, but in my day Bally was a big name in both arcade and casino.
A lot of processing gear we use, like rack DSP units will have an IEC power connector, the typical "computer" power cord, and the filter is built into the power connector.
Remember, a mains filter is only going to tell us if the noise is riding the mains into your system. It won't affect radiated noise.
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FANTASTIC technicians.......and there are many.....J.M. g1...Jazz....nevetslab......The Dude......Randall....yourself included.....etc........etc.......there are too many to remember......all you guys are great....you really and truly have no idea of how much you actually help..seriously.....the info that is tossed around here will never be taught in an electronics course...no amount of money will buy it....and newcomers to this aspect of electronic repair, like myself would never figure out some of this shit.....just look at post #16...nevetslab sums it up great.....keep up the good work.....
I agree !!!!!!!Last edited by shortcircuit; 02-19-2019, 10:07 PM.If you don't know where your going any road'll take you there : George Harrison
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