Power supply teardown - the TR-9252/A from Fok-Gyem

[@cannesahs]

Smoke is just self cleaning feature in work. Burns excess dust, rust, dirt away

[@BogdanSerban]

Romanian neighbor here :)) BTW I have a bucket full of Romanian 2N3055

[@KeritechElectronics]

Moo. :) This power supply is just so damn beautiful! I love the vintage test equipment, it was really built to last. And it did. I was actually surprised to see an IEC C14 power connector. Very nice! The PCB design is beautiful - if only it had some solder mask, or at least a varnish coat...

[@p_mouse8676]

Aaah yes, 70's and 80's circuits. They are by far the worst to troubleshoot, hahaha Nice video about some history! There is actually an important parameter that most people overlook which you only mentioned very briefly. That is temperature and heat. Most people only think about max temperature values. It's actually a lot more difficult to keep that max temperature under control over a longer period of time. Dissipating heat in a short amount of time is easy, but keeping the performance over let's say a couple of hours and things will get complicated. This parameter is actually more important for audio amplifiers, but is also definitely and issue for professional power supplies that have to be on reliably for hours. The same goes for "delivering" enough current (power) to loads, especially dynamic loads.

[@EFazy]

Ahhhhwww! I love those PSU-s :) (Actually I have two of them (TR-9175/A and TR-9177) which still works great.) A viewer from Hungary.

[@stevenbliss989]

I love the design :) ...for the time off course, no op-amps, just discrete's!

[@FesZElectronics]

Good design does not have to be complicated. Its amazing what you can sometimes achieve with a minimal number of components.

[@DiegoColl44]

As always, excellent video. Simple and easy to understand. Great content.

[@Plons0Nard]

I like your tongue in cheek jokes 😄

[@aurthorthing7403]

Cool PSU. I like linear supplies better for some reason. I don't like PSU without big transformers.

[@FesZElectronics]

Well most often you get way better noise performance and transient response from linear supplies; The main reason for using the switching ones is size. I did notice though that some modern day higher end supplies rely on an architecture that takes the best of both worlds. They make a switching supply that then supplies a linear one - the main power conversion is done with high efficiency and noise; and then the linear supply is used to reduce the noise. But sadly there is no large transformer involved...

[@aurthorthing7403]

@@FesZElectronics I just bought a Dr. Meter branded supply and it has a huge chunky transformer. It has a few issues with noise but some clever folks have worked out the causes and modifications to make it cleaner. IDK who the OEM is of this PSU but so far it is working very well.

[@gabiold]

@@FesZElectronics There is a Fok-Gyem TR-9158A PSU, it is capable of 40V/10A. That one contains a very big transformer, but still a small heatsink for the linear regulator, because it uses a thyristor controlled rectifier (SCR) which acts as a preregulator. So sort of like a switch mode, but with the tech available in those days. I have one, it is a very reliable instrument. I killed it once though, because it does not contain reverse feed protection, and I was charging a battery with it while the power went out, and it didn't liked it. I added a reverse diode from the output to the main buffer caps, along with some other small modification I forgot already, as it is fine since, during the last 10 years of abuse. Btw. the shunts in the TR-9158 is wound bidirectionally, thus it is inductance-free!

[@gabiold]

@@FesZElectronics I am surprised when you read the company name on Wikipedia, as I was almost certainly sure that you are Hunagrian. What does 'Fesz' stands for in the channel name actually?

[@FesZElectronics]

@@gabiold I'm half Hungarian, but born in Romania. I learned the language when I was little and spent time at my grandparents. The name is short for FEri SZasz.

[@windward2818]

It is interesting that the unit control labels are in English and not Hungarian. Is it easier to engineer in English or Hungarian? or to ask the question another way, does learning and designing depend on the language used? I am a little freaked out by the fact that the output DC switch does not disconnect the supply completely from the load when off. In the USA the design would be much simpler with multiple pass transistors and having a dedicated controller, in its simplest form, for limited range, being an LM723C. The LM723C has an interesting current limit mode called current foldback which is a very nice feature which reduces power dissipation with an inverse slope but without the abrupt current limit jump made with the supply in the video. For full range down to zero volts, an op amp controller would be used with a discrete voltage reference. In other words, in the USA, in this same era, we would just dissipate the power by having more pass transistors and a larger heatsink with a cooling fan. The design would be flow through, so air would be drawn across the entire circuit board and transformer.

[@FesZElectronics]

I think the text language may have been a feature used to make the device easy to sell outside the country.

[@windward2818]

Yes, I would agree that makes a lot of sense. You seem to be well versed in circuit theory and you speak both English and Hungarian. But, when you picture electrical concepts in your head and relate them to what you have learned in school, are the concepts more easily understood in Hungarian or English? or is it a consideration to you?@@FesZElectronics

[@FesZElectronics]

I guess English or Romanian :D, I'm actually from Romania. Anyway, most technical literature available is in English, so I guess that is the language in which I know most terms.

[@windward2818]

In the USA the relative population of BSEE (Electrical Engineers) as compared to the total population is very small (0.03%) even less for professional registered engineers (0.01%). Even though our official language is English, the textbook nomenclature used is in engineering is actually very specialized, with origins usually relating to specific educational institutions in the USA. For example, the symbolic expression of Maxwell's Equations, as an approved symbol representation for ABET accredited University Degrees (University Textbooks on Electromagnetic Theory), has its roots with the Massachusetts Institute of Technology (MIT) as a matter of reference (like the Del Operator and other Vector Calculus nomenclature as adapted from W.R. Hamilton). For Electronic Instrumentation repair in the USA, specifically bench DC power supply repair, two different types of Isolated (both mains and ground) variable AC power supplies are used one for repair and one for calibration and outgoing test. This type of repair is usually done, if the equipment is under warranty, at the manufacturers repair depot. The repair isolated AC variable power supply is based on a large isolation transformer and a variac. The electronic bench is usually earthed (grounded) for personal safety and ESD, so all equipment that is tested and repaired must be isolated from mains and earth as a starting point (especially for switching supplies). I actually like to use a Fluke Scopemeter for troubleshooting power supplies because it is a battery operated scope and all of the channels are isolated from each other. So, there is really now limit on where you make measurements with the 10x probes. So, essentially both the device under test and my test equipment are isolated and floating. I also use a Fluke 289 for power supply repair, it has a low Z AC voltage range which eliminates the possibility of AC ghost voltage. For many companies the variable AC repair power supply is designed in house for their specific needs. The calibration isolated AC power supply is a large instrumentation isolated AC supply (only the line and not the ground) like the B and K 9803 or Keysight 6812C, which have a very pure sinewave output and allow setting of high and low line AC voltage at different line frequencies, along with the ability to do preprogrammed AC line transient testing if this is required for outgoing test. To calibrate a static parameter or look at performance you would use an electronic load and the instrumentation AC supply.@@FesZElectronics

[@GazembR]

Gulyás for transistors. That's mean :D

[@mihaelabortos4696]

That's funny :p

[@jamesm6951]

eating my cheese langos while watching this vid, what a treat

[@FesZElectronics]

Is there also garlic sauce on it? That always makes it better for me :D

[@rabindrasharma]

Definition of "Medical Intrument" If this drop on your foot you definitely have to visit a doctor, ;D

[@FlawlessEntropy]

When I tell people that all the engineering I know is in English they look at me sideways.

[@fraiflorin]

Interesting how they design the output voltage selection by using two knobs (2+5). 14:15 nice joke:))

[@dominikworkshop6007]

2:52 hahaha xD that's a good joke xD