Important Electrical Safety Tips!
Added 2025-01-17 06:34:40 +0000 UTCHere are some important electrical safety considerations while working with line operated devices. Every device has it's own design, so covering all aspects is difficult, this video talks about the more common issues you may encounter.
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Comments
I worked for a German company and we installed machinery both in Canada and the USA as well as all the other countries and the most fun I've ever had was trying to get our equipment through Ontario hydro we did not Bond DC power supplies negative too the chassis nor did we Bond one side of AC tto the chassis
Chauvin
2025-06-25 17:46:40 +0000 UTCI seen a power supply that used a 0.1 safety capacitor paralleled with a 1M resistor on the ground leg of the plug. This was used for a current transducer that has extreme sensitivity to ground loops. I understand some of the thinking on this practice but am dubious of how safe it is.
Allison Rae Barnhardt
2025-03-15 23:07:01 +0000 UTCHow would you go about sizing a fuse, for that Radio?
Jonathan Hughes
2025-02-23 22:35:10 +0000 UTCPaul how do all these mistakes and contradictions between schematics, parts lists and actual equipment happen. Isn't there someone doing quality control that checks for such mistakes before printing up paperwork?
John E Barron III
2025-02-20 01:14:09 +0000 UTCwhat brand was that power supply so I know not to buy that brand?
John E Barron III
2025-02-20 00:55:01 +0000 UTCOMG Mr. C I love the idea you pointed out how bad some schematics can be. I too have come across some that are incredibly messed up. Such that schematics have inconsistencies with board diagrams component values mixed up or different between the two different diagrams showing the same thing but connected differently. Such confusion is the bane of learning for beginners like me.
John E Barron III
2025-02-20 00:49:38 +0000 UTCSince variacs and isolation transformers are often used together, why are there no "all-in-one" units to purchase?
Tony Vassil
2025-02-08 16:17:29 +0000 UTCRestoring and using and old scope is fun. It forces you to think about controls, settings, voltages to be measured. As a side note I like to use old VOMs as well as the new DMMs. Better pay attention to loading, polarity, etc.
Richard Goebel
2025-02-03 18:16:42 +0000 UTCI didn't see it mentioned. Just a reminder (ask me how I know...) some SMPSs have hot heat sinks... I've come across high voltage on a heat sink before and didn't much care for it...
Brad Wilmot
2025-01-31 00:37:36 +0000 UTCI saw one isolation transformer which had a center tapped secondary, and the CT was connected to the safety ground. This means both ends of the secondary are 60V hot, with opposite polarity with each other. This would be good for noise isolation, but not for servicing directly line connected circuits. To use this transformer for such servicing, the CT, and perhaps the safety ground of the secondary isolated output receptacles(s), should be disconnected and insulated from everything, including each other. The safety ground of the primary line cord should be kept intact, being still connected to the transformer's core, metal housing, and the Farady shield between the windings of the transformer, if it has one.
Michael Kiley
2025-01-26 23:06:17 +0000 UTCFor my Isolation Transformer I have a small grey adapter plug that plugs into 3 terminals (female) then the plug in is only 2 connections on the other side. This avoids destroying the original plug that comes with the Iso Transformer . This temporarily disconnects primary ground from secondary ground.
Timothy A Holder
2025-01-24 21:00:08 +0000 UTCYou've brought back some great memories of working on gear on my father's basement workbench. He was a WW2 radar tech and repaired TVs as a side job. I was his assistant to hold a soldering gun or to help search for those elusive screws or nuts that would fall off the bench. e would take time to explain some things to me, kindling my interest and my future in electronics. Thanks for a great video!
Jeffry Blackmon
2025-01-22 08:22:48 +0000 UTCWhen I was in high school (1970-72), I took electronics as an elective. The teacher was really cool, very interested in having his students learn. Anyway... The school had 3 EICO 'scope kits, and he let me have one of them. I built it, and it worked for about 15 minutes, and burned out the transformer. I went through and burned out the other two transformers before I caught a clue and figured out what was going on. They had all the tube filaments wired in parallel, drawing about 8 amps on a 2 amp filament winding. Too bad I didn't figure that out before we ran out of transformers.
Steve A.
2025-01-22 07:55:43 +0000 UTCWould love to see a video of that Eico scope brought up on a variac and restored. Maybe you could do another video with that AA6 radio with a blue tooth module.
Reid Braswell
2025-01-22 01:18:54 +0000 UTCLooking forward to your AA 5 bluetooth video.
Robert Harris
2025-01-20 16:25:05 +0000 UTCI am speculating that the reason the radio uses only 3 screws to connect to the cabinet is that the filter capacitor on the short side of the chassis is potentially in the way of the 2 screws that would normally go on that side of the chassis to make it similar to the other short side of the chassis.
Robert Harris
2025-01-20 16:24:32 +0000 UTCYep, I know that now, but that was almost 50 years ago, and I was just learning.
Gary Nations
2025-01-18 22:33:05 +0000 UTCPretty decent sound (just by turning the variable capacitor manually through the ten or so music stations still on the AM band here), but it doesn't hold a candle to the mighty (also Canadian-built) Philips CM-60A.
Chris Blair
2025-01-18 20:07:29 +0000 UTCLove your channel and joined Patreon last month
Bill Martin
2025-01-18 19:32:17 +0000 UTCSo, did you recap the Canadian radio? I kept waiting as I've got a Zenith AM/FM six tube using a selenium rectifier that I'll have to figure a drop resistor or use Zenier to correct the voltage. One big plus is the chassis is isolated via plastic screw holders on the bottom, very simple and effective.
Bill Martin
2025-01-18 19:31:43 +0000 UTCAlthough here in the UK we use 240V, construction site tools are required to be 110V, fed from a centre-tapped & grounded transformer. So the most you get to ground is 55V AC.
Ross Thompson
2025-01-18 19:28:05 +0000 UTCYes that is one way to achieve isolation, but one issue can be reactance of the windings which will mean less than 100% power transfer across the two transformers. Capacitors can be used to improve the power factor. Otherwise losses can generate more heat in the windings and affect the output regulation. Larger expensive single transformers perform better but normally require current inrush damper circuits.
David Moule
2025-01-18 18:26:39 +0000 UTCI agree, that would make a great video!
tmorgan0630
2025-01-18 16:51:15 +0000 UTCPaul, in the oscilloscope example, you mentioned a "safety cap" and "third lead" to ground. Perhaps you could expand on that. What makes a particular cap a safety cap as opposed to what we saw there? What would the third lead be for?
Tony Vassil
2025-01-18 15:56:07 +0000 UTCThank you for sharing your knowledge with us Mr C. As usual, lots of info packed into these videos. Looking forward to the conversion board
Chris
2025-01-18 15:53:30 +0000 UTCI've heard varying arguments back and forth about whether or not it's a good idea to add a safety ground to the chassis of a transformerless set. Perhaps you could address this in a follow up video
Alan Drury
2025-01-18 15:03:35 +0000 UTCCould you do a video about how to create a safe workbench. With am isolation transformer, variac, earth leakage circuit breaker, ground lift etc.
Dave Achterberg
2025-01-18 11:51:19 +0000 UTCyes PE should be connected in the Hausanschlusskasten to N -- what I mean is that the two contacts in the connector are not polarized, so you dont know which one is N or L and though which is connected to PE --- also some dangerours connectors from china are existant, wher the PE is open in the distributor, but this against the VDE etc... in sum never rely on this be careful as said.
Dipl. Ing. Rolf-Dieter Klein
2025-01-18 08:33:10 +0000 UTCYes, true!
Patrik Lindahl
2025-01-18 08:24:54 +0000 UTCSounds like a neutral in the US split phase system
Sean Glennon
2025-01-18 07:30:18 +0000 UTCWhen I was a teenager I built a radio xmitter. The final had a tuning capacitor with a plastic knob and a barely sunken metal screw. Thevxmitter was on the end of the bed and fortunately the door was open because I became antenna and leapfroged into the hallway . So watch out for those screws on the plastic knobs.
Greg Richard
2025-01-18 04:16:30 +0000 UTCWe have zero control of how the home wiring the set goes home to is wired.I have seen many receptacles wired with hot and neutral reversed, or in the case of our first house (1926), 2 wire, 2, 60A. fuses! That was all.
Tom Harris
2025-01-18 03:15:00 +0000 UTCNote book open, Pen in hand. So much to learn and so much fun to follow along. Today I learned loads about working on older radio sets and the Scope was awesome. The safety thinking on grounding and isolation is the best. Thanks for another great class.
Jared Kusner
2025-01-18 00:01:20 +0000 UTCGreat video Paul, safety is the number one issue . I myself always check the internal state of electrical equipment that i purchase that is second hand and twice i have found in modern equipment that people have intentionally wired it to deliver a nasty shock when switched on. In these instances it should be a criminal offence to be honest because someone could lose there life. Also it may sound like a silly thing but i was looking for a Voltage Tripler in that oscilloscope for the CRT , hasn't it got one?
David simpson
2025-01-18 00:00:29 +0000 UTCI *LOVE* my old scopes. New digital scopes make me mental as they pixelate the waveform.
Benjamin Hall
2025-01-17 22:08:13 +0000 UTCI have made my own isolation transformer, but I use a “virtual ground”. 230v in 2x120v out, I put my output “ground” on the middle of those two taps with fuses on the two phases. Has been working well, but not sure if it’s considered a proper way to do this.
Patrik Lindahl
2025-01-17 22:08:06 +0000 UTCIn germany, the PE is ALWAYS connected to N, usually via a N-PE-bridge insde the Hausanschlusskasten :) The secondary output of insulaton transformers usually doesn't have a PE-terminal, so the ground/chassis of the DUT is floating. In one of my insulaton-variacs, I installed a switchable PE-connect, so I can ground the DUT if necessary. I have a red warning light that reminds me of the additional danger of having ground (and N-)-potential on the chassis of the device I am working on. It's mportant to always be extra aware, that with a grounded chassis in most cases all secondary DC-voltages are also PE-related - and can be dangerous. Ths means: connecting the chassis of the DUT to ground basically eliminates the safety-functon of the insulaton transformer.
Tante Lilo
2025-01-17 22:04:48 +0000 UTCGreat topic that I've learned you can't study enough! One example that comes to mind is all the consumer devices out there that use capacitive dropper supplies. They can sure ruin your day if you mess with them without an isolation transformer! Thanks for all the knowledge that you share. - JRH
James R Harley
2025-01-17 21:30:49 +0000 UTCHey Paul There are also variacs around, that DO have a seperate primary winding - and so they are insulating variacs. i have one in my workshop...
Tante Lilo
2025-01-17 21:29:38 +0000 UTCWhen I was 13 or 14 I made my own isolation transformer. I went to radio shack and got two 12 volt at 3 Amp transformers and turned them back to back. As long I I wasn't pulling too much current they worked just fine.
Gary Nations
2025-01-17 19:19:23 +0000 UTCI loved the video as I Always learn very useful information. I have a variac but not the isolation transformer yet and now know what to watch for. Thank you so much.
george
2025-01-17 15:44:32 +0000 UTCI'm wondering if that "30R" annotation on the resistor in the 'scope really means "30 ohms". The schematic has a general notation that resistances are in ohms unless otherwise stated, and all of the other resistors less than 1K are just notated with a number (no unit), for example two cathode resistors near the upper left of the schematic. Furthermore, the use of "R" in resistor ratings it relatively recent, with people noticing that it is easy to miss a decimal point and so using the "M" or "K" in the decimal-point position and needing to introduce "R" for this purpose for values under 1K. I believe EICO units were kits, so it might be necessary to consult the kit assembly instructions to really know what this annotation means. Changing this resistor would alter the bias of the CRT cathode relative to all the other electrodes
Kevin Martin
2025-01-17 15:13:30 +0000 UTCYes! I love all your videos!
Tom Hogan
2025-01-17 15:10:29 +0000 UTCI really like those old oscilloscopes! They are fun!
Kenny Fidler
2025-01-17 15:06:04 +0000 UTCVery good discussion. I always pick up some thing from these. I have a side suggestion for some future video. I'm working on a Zenith 12H670 radio. (I plan on using the ideas from this video on it, even though this radio has a transformer) But I have trouble understanding dual purpose tubes. My Zenith has a Detector/Amplifier tube 7B6. I noticed the All American in this video also has a tube 12AV6 like this. These tubes have a common cathode, for the diode and the triode. Can you explain how the signal moves through this tube in some future Video. Thanks, I appreciate your work.
Mike
2025-01-17 14:51:10 +0000 UTCAnd the part with "lots of politics around it, but not so much knowledge" got me very well 😄
Andrus
2025-01-17 13:38:40 +0000 UTCThe 35W4 is drawn that way, as we used to say at KB, is to "Confuse" the competition. Also, that scope doesn't show the second anode on the schematic? Doesn't have one?
David Kuhn
2025-01-17 13:32:12 +0000 UTCVery good bite sizes of knowledge and learning.
Andrus
2025-01-17 13:18:31 +0000 UTCWe used to own that same model radio. But when it stopped working properly in the 80’s we got rid of it. We used to always have CBC radio on in the morning.
M. Perry
2025-01-17 10:14:32 +0000 UTCon the 35w4 -- it looks like it only used for the filament to add as a division in series for all filements to sum up to the line voltage and the middle filement serves to divide for the lamp attached to the 35w4 - the tube of couse is not used otherwise. -- In germany teh connectors to line voltage are not polarizes, this makes adaption dangerous also 240V ... isolation transformers are always needed. and the PE usually not connected to neutral (which cannot be mechanically distinguished).
Dipl. Ing. Rolf-Dieter Klein
2025-01-17 07:48:35 +0000 UTCI'm looking forward to hearing how it sounds.
Mr Carlson's Lab
2025-01-17 07:18:48 +0000 UTCPaul, I have that exact Electrohome Roland Series radio on the bench right now. Works great, I just need to restring the dial.
Chris Blair
2025-01-17 06:44:17 +0000 UTC
