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Thanks for watching. The Y class capacitor is supposed to fail to an open circuit for protection but of course these RIFA caps fail in the worst possible way. There is a good article on class-I and II power supply differences here www.emea.lambda.tdk.com/il/KB/What-is-the-difference-between-Class-I-and-Class-II-power-supplies.pdf

@@EriksElectronicsWorkbenchThanks a lot for the Appnote - it really is a great resource of knowledge! What I wanted to say is that the more expensive class-I devices generally have branded and (except maybe the old RIFAs) high-quality Y-caps, though their shorting mostly only leads to a tripped breaker. The tons of dirt-cheap consumer SMPS, like chargers or other wall warts, directly endanger the life of the user. That's why, in my opinion, if we talk about dangerous Y-caps, we should never forget the class-II devices.

Thanks for watching! The fuse is factory installed in that position across the switch.

Thank you!

Glad you found the video helpful!

Thanks and yes they sure did make some quality heavy duty power supplies.

Thanks for watching and glad you are enjoying my videos!

Thanks for watching! Yes you need to know the limits of your test equipment. I did check the voltage and waveform across the ceramic surface mount capacitor. It is a 94 KHz very narrow spike waveform with the spikes going to about 5 volts and it is riding on 3 volts DC. Note this is voltage across the cap, not referenced to ground, measured with a Fluke 199C isolated ground scopemeter.

Hi, my guess is the impedance or matching between the transformers is not ideal and may be setting up some distortion on the AC waveform making the transformer growl or hum. And some transformers are just more prone to making noises. Even at no load, there is some current between your isolation transformer and variac. A properly sized/rated capacitor across the AC line between transformers (power factor correction) could possibly help correct this but the noise is not damaging to the transformer unless it is so extreme the transformer is running hot (could be indication of other problems too).

@@EriksElectronicsWorkbench Thanks Eric, I'll get the maths hat on and give it some consideration. I guess all the loading it sees at the moment is inductive so there could be something in it. The toroid is double-insulated as it came from an out-door-functions company and has no earth reference at all. Having the variac first also means I can have the earth ground on its metal case connected.

@@grahambambrook313 It seems placing the bulb for current limiting last is the best option (as I show in the video) and the order placement of the transformer and variac is about a toss up with some advantages on each way. Arrange how it works best for you and the components you are using. Yes one transformer driving another is a very inductive load to the first transformer (or variac) although in my own set up I have not had any issues.

@@EriksElectronicsWorkbench 👍

If you want to limit the inrush current surge a single component can do this, called the NTC Thermistor, you can find them here www.mouser.com/c/circuit-protection/thermistors/ntc-thermistors/ you have to choose the proper resistance and wattage rating among other things. Keep in mind some motors cannot be current limited as they will not start up correctly and will overheat.

Simpson Electric still manufactures them in the USA. Their website is simpsonelectric.com/products/test-equipment/vom-multimeters/ The new production meters top out at 1000 volts AC/DC. That is standard on modern meters and a high voltage probe is needed for over 1000 volts. Regular test probes are never safe over 1000 volts! Analog multimeters are very useful on noisy AC measurements that make digital meters unreadable from gibberish number displays, and for measuring changing voltages that make digital number displays hard to track. The analog meter can give a better understand on the rate of change. These meters do not require battery power, except for ohms, so that can add to reliability.

@@EriksElectronicsWorkbench Thanks for the info, it's really interesting, I didn't know the company was still in business ! I still use analog meters and my favorite it my electronic Simpson really similar to the 260-6XLM on the Simpson's Web site, that I bought used in the 70's, you can inverse polarity no problem and the meter is rather accurate.

It can generate any AC voltage up to 300 volts so think of it as an electronic version of a variac. Any frequency DC (0 Hz) to 1 KHz so you can test 50 Hz and 400 Hz equipment or check how frequency variation affects a device's performance. Measuring abilities built in so you can monitor performance of a device being tested. Isolated output from main AC line which helps add safety during testing. Clean and stable output waveform for testing sensitive devices that you want to isolate from line fluctuations.

@@EriksElectronicsWorkbench how much is used one cost or to refurbish one ?

@@kevinedwards5719 Used checked working $1500 and up. Parts (complete boards) can run into the many hundreds or another thousand if you are trying to repair a unit. Non working or "unknown condition" units can be around $500 which is the description my unit had.

You're welcome and the donation is appreciated. Thanks :)

Yes correct that the transformer secondary does not have a ground reference which is what the "isolation" is referring to. Since the transformer's secondary does not reference either side to ground, if a fault occurs, for example, in the variac making some part of it live to one of the isolated AC lines you would not be shocked because no return path exists from the user through ground and back to the transformer's secondary. This is also why you should not use a ground referenced oscilloscope on the isolation transformer's secondary (on DUT). If you introduce a ground path on any part of the transformer's secondary then yes a shock hazard will exist.

@@EriksElectronicsWorkbench thank you for the detailed response I really appreciate that.

@@johnc.4625 Happy to help with questions and thanks for the donation. :)

Could you please clarify what you mean about the ground referenced oscilloscope? Are you suggesting having the oscilloscope connected to an isolated supply and not a grounded mains?

@@msouthwe1 AC mains powered oscilloscopes have the probe ground tied to chassis ground. You should not float an AC mains powered oscilloscope on an isolation transformer as there can still be a shock hazard if you contact a metal part of the scope and part of the circuit you are testing. In situations where the scope ground can't be tied to circuit ground potential the only safe way is to use an isolated ground scope like a Fluke Scopemeter or a differential scope probe.

In typical bench testing there are fuses but they are in the variac and also the isolation transformer. There are two fuses on the variac, selectable for the expected load. The devices in this video are just for an example and not used in my regular bench setup.

Both channels were turned on and active. That is shown by both channel traces being displayed. The reason only the Ch 1 indicator light was on is that shows which channel the vertical controls will affect. Notice the scope does not have two sets of vertical controls on the panel.

Glad you liked the video and thanks for watching!

The amp's circuit design is based very closely to the 555MkII design and I have not heard of the issues this amp had being a problem in other SE or MKII models. There are some transistors that run quite hot on the main circuit board (this model and previous model) and there is speculation that the heat can lead to problems. I was surprised the SE didn't have heatsinks on those transistors. The noisy transistor is probably an isolated failure. The instability (oscillations) are an easy fix with 4 components if an amp is found to have that problem.

I know how it goes with too much to fix and so little time! Mag-amps are rugged so it makes sense they would be used in welders. I have seen them in gen set engine control governors and DC power supplies for preregulation. I have some audio equipment repair videos so if you have an interest in that equipment check them out. Thanks for watching!

It does not have those features, it was not designed to be paralleled with other generator sets.

Yes I had a similar problem in my Sencore capacitor tester where the fuse went intermittent. Fuse looked ok but had no continuity because the end cap connection broke.

Glad to know you found the video helpful, thanks for watching!

Have you tried unplugging the inputs on the amp and see if the problem goes away? If so the amp is not the source and the interference is being picked up in the cables or preamp or some other audio component. Any strong radio transmitters nearby? They can induce interference.

Glad you enjoyed the video, thanks for watching.

Thanks for subscribing and happy to know you enjoy the content on my channel.

Thanks for watching!

This series 4 version and other earlier version models used a standard D cell and four AA's. Later models starting at series 6 and newer used a D cell and 9volt battery.

Any examples?

@@RPike-bq3xm Yes, zero EMI emission environments. One in particular I know of was a physics lab conducting experiments to measure the EM emissions from various materials under various conditions. The detection system needed to be calibrated using equipment that had zero EMI emissions, for obvious reasons.

Obviously you don't have much experience in electronics because then you would not ask.

Wow, I didn't know that, I found a place where they sell it (ITM) probably made in China ? same quality ? is there a market for that ? I have an old Simpson 303-Xl, still working, I love it.

@@levent8208 They are Made in USA. Still a market for them. Several areas still use them. A couple are power monitoring and in EMI free testing environments.

Thanks for watching and I'm happy to know you enjoy the content on my channel.

The military service manual is dated January 1967 so these meters were made in the 60's and 70's. Not sure if they built them into the 80's. They were built under contract for the military. There is no date on this unit so I don't know exact date of manufacture.

@@EriksElectronicsWorkbench Thank you Erik, it's a very nice instrument, I have myself and old Simpson electronic multimeter I acquired in 1978 or around that date when I was studying electronics, I love it and they are rather accurate.

@@EriksElectronicsWorkbench And I have subscribed, I live in Montreal.

@@levent8208 Simpson makes very nice meters that do last a long time.

@@levent8208 thanks!

I agree the component placement was sloppy. I have worked on several other Adcom devices and they did not have this build issue. Not sure what happened in this case.

Yes NAD and Proton were/are related and shared similar designs.

The metal box with the isolation transformer outlets should not be earth grounded. The reason is, suppose a wire comes loose and contacts inside the metal box. And suppose the box were grounded. Now one side of the isolation transformer has a ground reference and a shock hazard exists from the opposite secondary winding end to ground which completely defeats what the isolation transformer was supposed to protect against. With the box not grounded, suppose a wire comes loose and contacts inside the box. A shock would only occur if you touch the metal outlet box and at the same time the opposite secondary winding end which is very unlikely to occur (but of course not impossible). Regular testing of the whole isolation system for such faults is needed and if you prefer a plastic outlet box can be used. I will try to be more clear when pointing to the meter scales as to which tic marks I'm using but I did mention the AC voltage is taken on the red scale.

The entire POINT of an isolation transformer is to isolate the connection from ground for safety. That way you cannot get shocked by grounding yourself out accidentally. The only way you get shocked is by bridging the two legs of the transformer. If one of the wires from the isolation transformer contacts the metal box, it's fine because the only path back to the transformer is through the other leg of the transformer. However, if you connect ground to metal box and one of transformer legs also touches the metal box, then ground becomes a path back to the transformer and you can once again electrocute yourself by accidently grounding yourself.

Yes the secondary of the isolation transformer is just as dangerous as the normal AC line voltage. If you contact between both ends of the transformer's secondary you will be shocked. The protection or isolation the transformer offers is that there is no longer a ground reference which reduces the shock hazard. In other words, if you contact ONE SIDE of the transformer's secondary (and assuming the transformer and wiring is set up correctly) there is no path the current can take through your body to ground.

Yes, but the second important benefit of an isolation transformer is that on mains powered test gear, the probe return wire is usually connected to ground. By making your test gear float you can protect both your test gear and yourself by preventing a live-earth short during testing.

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Yes LED's require very little current to operate (compared to an incandescent bulb) and with necessary current limiting resistors they are fairly high impedance loads.

Free: unfortunately not, while it is very little energy it is measured by the utilities meter.

@@Janktzoni I did say : ALMOST free .... this tiny glow would probably cost about ( ? UK , £1 ) for the whole year , which is VERY affordable ( Ha - Ha ! ) ........ DAVE™🛑

The capacitors are basically turning into resistors as the dielectric breaks down so they start passing excessive current which heats them up.

In order to remove the "ghost" voltage, there must be a load impedance significantly lower than the output impedance of the "ghost" voltage. That lower impedance can but does not have to be provided by the meter itself. You can simply add an appropriately sized resistor in parallel to the meter to provide enough load to pull down the "ghost" voltage.

@@timharig Thanks for the insight timharig! Impedance is still a little bit mysterious for me in some situations, but discussions like this help with my understanding. Appreciate it.-jrh

@@robharley9838 Don't let the word scare you. For the purposes of this video, since there is only one frequency involved and we are not dealing with reactive components, you can treat impedance just like resistance. Ohms law for impedance is the same as for resistance: V= IZ Serial impedances are additive: Zt = Z1 + Z2 + Z3 + ... Parallel impedances follow the same rule as parallel resistances: Zt = 1/(1/Z1 + 1/Z2 + 1/Z3 + ...) The voltage dropped in series impedances drop in proportion to their impedances: V1 = V*Z1/(Z1+Z2) V2 = V*Z2/(Z1+Z2) etc. If you have a 120V ghost voltage with an output impedance of 2Meg ohm and you connect a meter with a 10Meg ohm input impedance, then the voltage that the meter measures will be the drop across its 10Meg ohm input: V = 120*(10Meg/(10Meg + 2Meg)) = 100V If however, measure the same 120V@2Meg Ohm ghost voltage with a meter that only has a 100k Ohm input impedance, then most of the voltage is dropped across the ghost voltage's impedance and the meter will only measure: V = 120(100k/(100k + 2Meg)) = 5.7V If you have a 10Meg ohm meter and you want to reduce its apparent input impedance, you could take the 100k ohm resistor and connect it in parallel with the meter. Then the meter's apparent impedance is: Zm + Zr = 1/(1/100k + 1/10Meg) = 99k ohm If you wanted to further remove the ghost voltage, then you could use an even lower value resistor. Assuming a 1k ohm resistor: Zm + Zr = 1/(1/1k + 1/10Meg) = 1k V = 120(1k/(1k + 2Meg)) = 60mV Note however, that if the voltage being measured is NOT a ghost voltage and the output impedance of the REAL voltage was say 0.1 ohm, then the current flowing through such a small resistor could be significant: V = 120(1k/(1k+0.1)) = 120V I = 120/1k = 120mA That is enough to make a small resistor warm and enough to interfere with the operation of lower power circuits -- which is why volt meters usually try to have as high of an input impedance as possible. Also note that if we ARE dealing with reactive components (inductors [coils] and capacitors) then the equations above still work; but, we have to treat impedance as a complex vector and we need to be concerned with how the impedance of reactive components changes with frequency.

@@timharig Many thanks for the lesson! OHMs law rules. I'll be pondering this for sure. -jrh