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  • #16
    Originally posted by Enzo View Post
    The 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.
    I never knew that! Amazing what you can learn browsing thru the posts on any given day! Very interesting tidbit of info, Enzo!!
    Logic is an organized way of going wrong with confidence

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    • #17
      Originally posted by Enzo View Post
      The 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.
      What would light sources bleeding into the transistor do to the circuit? noise?
      nosaj
      soldering stuff that's broken, breaking stuff that works, Yeah!

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      • #18
        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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        • #19
          I had fun one day, aiming a little pen laser at various parts on a powered up circuit....
          If it ain't broke I'll fix it until it is...
          I have just enough knowledge to be dangerous...

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          • #20
            Originally posted by nevetslab View Post
            I never knew that! Amazing what you can learn browsing thru the posts on any given day! Very interesting tidbit of info, Enzo!!
            That is the reason why I had joined this forum....The people here are very experienced and have had to deal with all kinds of wild and wacky issues....I too also read through various posts to see what I can learn......and I can say I have discovered all kinds of info that I would never find anywhere else.....Keep up the good work......

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            • #21
              Originally posted by Enzo View Post
              Tube, 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?
              I do not have a filtered power strip.....By the looks of it, I will have to invest in one....by the way, I tried to just highlight that last line in your post but ended up posting the entire thing....

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              • #22
                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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                • #23
                  OK Enzo....I found the larger unit..this may not be suitable but here is a pic......Click image for larger version

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                  • #24
                    Originally posted by bsco View Post
                    OK Enzo....I found the larger unit..this may not be suitable but here is a pic......[ATTACH=CONFIG]52590[/ATTACH]
                    That'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.
                    Logic is an organized way of going wrong with confidence

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                    • #25
                      Originally posted by nevetslab View Post
                      That'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.
                      Thank 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......Cheers

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                      • #26
                        Originally posted by bsco View Post
                        Thank 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......Cheers
                        You'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.
                        Logic is an organized way of going wrong with confidence

                        Comment


                        • #27
                          Originally posted by nevetslab View Post
                          You'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.
                          Ok then.....when I get some free time......and this is an understatement......I have a metal box here that I can install this unit into and install a regular electrical wall outlet. ...actually I have a single 3 prong outlet that came from some of the scrapped casino machines that I can install.....the box is made from alumium so it will be pretty easy to drill and cut..........that way I can plug the AC power into the filter and plug the amp into the receptacle at the other end........and I can also install an ON/OFF switch on the top....but for now, like you said I could just cobble something together just to see if it works first......many thanks for the reply......
                          Cheers

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                          • #28
                            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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                            • #29
                              Originally posted by Enzo View Post
                              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.
                              Enzo.....Thank you for your reply.....I was hoping that you would jump in.....Yeah...the video game industry is somewhat similar to some of the arcade industry....Bally was a BIG pin ball thing here...back when the games were full of relays...and I believe Bally is still big here in the pin ball area....though I could be wrong..........the casino industry of course was electronic.....but used CRT monitors, dot matrix and drum type printers as was found in the Canon cals.....only they were metal drums....not the rubber ones which were wrapped around a plastic form....the casino brands that we had here were Hi-Tech; Merit; VLC (video Lottery Consultants) Spielo...(which was a Canadian company based in Moncton, N.B.) and G-Tech who were mostly in lottery ticket sales..... the VLC in particular had this device installed......and the one that is in the pic came from a VLC unit.....and that machine ran on a Motorola 68000 uP.......Some of the G-tech stuff ran on a Z80.......anyway, I am getting away from the topic at hand.....I realize that it won't do anything for radiated noise.....like what I am getting from the cordless phone......this device won't filter that out.....but the other noise such as motors, deep freeze, furnace, etc should be filtered out.....and that brings up a second question.....what would you use to kill the radiated noise......I have had to resort to putting caps across the input of an amp through the jack cord... to kill radio freqs....20pF or so......correct me if I am wrong.......and by the way....DO NOT leave this forum......for fucks sake......I look at all the posts here and there are a lot of people here who I think are 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.....

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                              • #30
                                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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