Always listen to your cat before poking around a complex circuit 😊

This guy is really master of electronics. The true expert on electronics. Danyku smekám, klobouk dolu.

Fun fact: those paint-marked transistors were made by the Mikroelektonikai Vállalat (lit. Microelectronics Company). They started producing simpler semiconductors (transistors, diodes, 7400 series, etc) in Budapest in 1983. During the night of 26 May 1986 the whole factory burnt down to ashes under rather suspicious circumstances. There was an automatic fire extinguisher system in place but it was down due to maintenance. Many believe that the fire was in fact an insurance fraud as Lloyd's insured the company for some 50 million USD.

It's so good to see actual understanding and explanation of the schematic. So many new 'techs' now seem to assume the only problem anything can have is 'bad caps'. That generator is excellent!

You did very well zeroing in on two transistors, one of which proved to be the fault. Makes a huge difference having access to the circuit of course.

The voltage base to emitter isn't 1.4V, its 1.4 _bloody_ V 😁💖 Great that you managed to repair it 😊

I guess the transistor case cracked from age and moisture ingress damage the silicone die. Really strange failure. Amazing video as always 👍👍👍

Nice to see more test equipment repairs… the more of us that make this kind of video the better! You did well to compress the complex repair down to the video length you got.

Old lab equipment like this is actually easier to use than modern equipment

Nice to see a correct fix with systematic fault finding! I had quite the opposite experience with my last fix, a '70s Takeda Riken frequency counter with about 500-600 transistors in it. I had the schematic and a master's degree in electrical engineeting, but I just started poking randomly around in the device with my oscilloscope probe first. And just out of sheer luck, I found the fault in less than ten minutes. A bad 2N709 transistor and a bad old school epoxy blob silicon diode. Greetings from Germany!

Great video. Tracking down the problem by figuring out the schematic and explaining it was most intriguing.

Wow, I have the same type of function generator, good to see in your video. Greetings from Hungary..! 🙂

Interesting device. Decades ago whilst I was stuying at Uni, (Chemistry), we had a couple of electronics techs down in the basement of the chemistry building. They had a signal generator there, its brand was, “Wavetek” and its principle of operation eas much the same as this, voltage-controlled current source and current sink being switched alternately onto a bank of capacitors to generate a triangle wave…then using a comparator with wide hysteresis to get the square wave and swith from the current source to current sink. One of the techs photocopied the circuit for me so I could go away and study it in detail…that was in 1986. Since then I have acquired ownership of two Hewllett=Hewlett-Packard generators that use the same principle and have much the same ciircuit as the Wavetek. One HP is a model 3311 and it only goes to 100KHz, the other is a 3312A that goes up to 13MHz, but I knowj there is a very similar looking model that goes to 20MHz…but all the circuits are much the same, frequency pot making DC, inverting op-amp generates reverse slope DC, both DCs go to voltage controlled current source and sink respectively, a four diode matrix in between the source and sink switch the capacitor bank, (coarse frequency) alternately, comparator looks at ramps generated and sends square save cack to seitch diode array. Fancy diode-resistor clipper makes “synthetic” sine with acceptable harmonic content…you get the drift! Anyway, as I watched the video I soon realized this generator used the same principle as my HP’s and the Wavetek and the voltage controlled current source, or more succinctly, the voltage controlling it was somehow at fault and non-linear at the bottom end of the pot. Even before you took the lid off, I had swiped the model number and downloaded a circuit that looked pretty mich like my HP’s….HOWEVER, once you got the lid off and showed the actual innards and circuit…it was utterly different despite the circuit I downloaded having the same madel number! I was beyond fascinating to see all the same principles used, but UTTERLY differently. The sine shaper on this is far more complrx that my HP,s and the Wavetek which just use diodes and resistors…I reckon this clipper/shaper uses the non-linearity if complementary transistor pairs to get a sine withfar lower harmonic “hash” than my HP’s are capable…but everything else was different too…but used the same principle. I don,t know why, but whenever a transistor in a complimentary pair is buggered, it almost always seems to be the PNP…and I knew it wax the source and the source uses a PNP, (the NPN is in the current sink)…so, yes I called it about as fast as you went thhough it, but the real interesting part was the utterly different architecture of it whan compared to my HP’s, the Wavetak at Uni and a multitude of synthetic generators I have seen over the years. Definitely keep the old Soviet, Czech Tesla and other central European stuff coming. It eas funny to watch you go through that Tektronix Oscilloscope recently and have difficulty identifying “Western” components, particularlythe mil-spec tantalums…but I have the same issues with any Soviet stuff I might find..which is rare here in Australia. When yiu did the Soviet TV, the germanium PNP line output transistor with live emitter and transformer couplrd base looked like something found in a crashed UFO to me. Shango66 had a slightly different model of Soviet TV but it had almost exactly the same chassis in it…it was exactly the opposite of you inside that TektronoxOscilloscope, he was flumoxd by the Soviet components. The Czech Oscilloscope you did recently, again I pulled the circuit off the internet before you took the sides off…I saw nearly a dozen pentode valves and a fer tetrodes and diodes in the power supply…so I was REALLY Supprisedwhen you took the sides off and…NO VALVES, not even a HV diode valve in the tube supply!

Greetings from Hungary! :) Thanks for the cool - as always, video!

To je umění - umění elektroniky. This kind of failures are the most rewarding ones, beautiful job indeed! Thank you for these 25 minutes 😍

I'm totally lost during the explanation on the circuit board yet I keep watching. The hypnotic voice makes it impossible to click away! Great job on finding such a subtle fault, very impressive!

this 'weird' VCO-input is for wobbling, which is used for testing filter-settings in dependence of the input frequency. You also can generate weird sound-effects, used in synthesizers and so on..

you should not afraid to make longer videos like before. true fans of yours will be watching carefully. i will

The bloody long and bloody complex videos are the best :)

Thats a sweet multimeter man, The update on its display is real nice.

There were some old uA741 made in DIL14, later ones were made only in DIL8.

This shows the difference between knowledge and understanding. There might be many people, who have the knowledge of each of the components, they know how and what they do. But you need understanding of whole electrical circuits to be able to use proper reasoning when making a diagnosis of what most likely causes the problem. This video shows us exactly that. Describes the issue at hand, and shows it. Then breaks down the schematic to specific areas, explaining what each of them is responsible for. Using logic and reasoning to rule out what cannot be the source of the problem, because of how the apparatus behaves and when the issue becomes visible. Then, what remains, is most likely the source of the operational anomaly. We were allowed to watch over the shoulder of a true master, who explained his reasoning and found out what was causing the problem. Knowledge, understanding and practice = wisdom.

This kind of repairs are the videos that I appreciate the most. Thank you for sharing your knowledge.

Great repair video again! Its a complicated and funny mistake but you managed to find the cause and repair it! That shows you are a real electronic expert! Of course we all knew already before 🙂

BC327 and BC337 belong to my favorite transistors.

That's a nice piece of equipment

03:02 CA3140S on right hand is a high precision mosfet input metal canister operational amplifier.

Danke! Very huge Thank you. I love all this analog gadgets.. ..and how much too learn from it .. Even its AGE... AmazinG.. still working.. Sure, not easy short, but over all simple fix .. Very impressive: the amount of functions and frequency range. Well explained... understandable. Good work. As always!

EMG instruments are always described as "they have souls", very well done repair on this one. (The second thing is, they are often copies of western instruments. In fact, quite good copies, but usually lagging 5-10 years behind...)

The sine shaper circuit basically carves a sine wave out of the triangle piece by piece with 3 stages of 2 diodes and 2 transistors each. The 4 transistors on the top are used to buffer the result, and the 2 transistors on the bottom left (presumably) provide a reference of some kind. It's possible to reduce the transistor count and improve smoothness by using an overdriven differential pair with a logarithmic voltage response (though you'd need a matched pair). When I tried to recreate it, it only worked properly when I omitted the direct connection to V+ in the leftmost shaper stage (which makes sense, because then the NPN transistor would never turn on in that case).

Pěkná práce a skvělý starý přístroj, ten si tu záchranu zasloužil 😊

The more bloody long and bloody complex the videos, the better they become!

Excellent analysis to diagnosis. Kudos.

*Even more complexity!* Nice problem analysis, and also an extinguisher for burning brains of course😃

Very complex device, you analysed it nicely and found the bad transistor, strange fault!

You are definitely a very smart and patient person! Im impressed with the logic and fault finding. I did nearly pass out during the schematic part but vape and coffee pulled me through!😊

Very good analysis and repair. Always appreciate these.

Amazing how we can now replace the entire engine of this instrument with a 40MHz AD9850 DDS module, with an accuracy of a 125MHz crystal, the size of a big stamp, for less than $40!!!

Ahh its so good to see you with a good old hungarian instrument. We made so reliable ones but today they have been overtaken by their cheap chinese counterparts.

This guy is really master of electronics. Another great repair! 👋☺

Very skilled procedure. Well done. Beautifuly designed circuit. Thanks for the video.

Great troubleshooting. Fun watching you use your great knowledge and extreme logic. Thanks for the videos.

Definitely interesting failure mode. I like these :). Nice disfunction degenerator too!

Great work! Thanks for sharing your thought process. Good idea with the brush!

Thank you for didnt let them die and repaired it. Greatings from hungary.

Bloody electronic expert !

*Great Repair 👍🏻👍🏻👏🏼👏🏼👏🏼 Enjoyed Full Video ❤❤❤*

What a beautiful user interface!

We love this longer vids though, makes learning much better.

Another really great video! Thank you for so much for your efforts to make this video & explain where the fault lay for such a complex circuit design. As a repair tech I seem to also attract such failed pieces of test gear & i stupidly spend hours chasing down such similar sorts of silly faults as if it's some kind of puzzle just to exercise my aging brain for no reward other than i get to understand what some very smart designers were thinking once upon a time...

Thank you, watched every second. I, like many others, would not mind more of these longer repair videos.

Great fix.

Superb repair of a very complex instrument.

I absolutely love that device!

This is bloody insane !! Nice work man

Wow, what an interesting design, very cool, worthy of a full restoration I think...

I survived...lol. Great video, I really like how you show your thought process. Makes me feel slightly more normal when I do the same thing on repairs.

nice fix !

A most wonderful function generator. 😎 Thank you. The good old days.

Excellent repair!!! Thank for vid!!!

this is very very interesting schematic, i have similar (a gift from my teacher) it's hand build also, the triangle to sin is made with resistors and diodes and few transistors and the integrator is also with transistors, no ap amps, no full schematic, maybe even more transistors, never counted them (i can't even see all of them). oh and a digital counter with TTL 74XX, whoever build it put a lot of work.

Very interesting video, and very clever engineer. Awesome. 😉👍

Veľká vďaka za toto video, je mi sympatická táto stará technika (a to platí aj pre osciloskop v predchádzajúcom videu, aj pre digitrónový multimeter v tomto videu, aj ja mám presne taký). Aj ja som poruchu odhadoval na nejakú aktívnu súčiastku, ale tá tvoja rýchla a pritom precízna diagnostika mi skoro vyrazila oči z hlavy, neviem či by som sa ja v takejto zložitej schéme tak ľahko zorientoval. Je tu vidieť ešte jedna vec, a to úroveň elektroniky v Maďarsku a Československu v dobe socializmu, takú rozmanitosť najmä aktívnych súčiastok v československých prístrojoch, aj keď sú tiež veľmi kvalitné, proste nevidno, je vidieť že v Maďarsku bola elektronika na oveľa vyššej úrovni ako u nás. Takže toto video ma veľmi potešilo a vôbec som sa celú dobu ani na chvíľočku nenudil, priznám sa že by som ocenil viac takýchto rozsiahlejších videí na tému starej elektroniky.

I think that failing transistor is slowly dying from corrosion that has crept up the leads and is damaging the die. Old age is getting to it! Instruments like this should have a conformal coating on the board to prevent environmental corrosion. Take note of HP and Tektronix equipment. Thanks for the great job explaining the circuit. I very much looks like a Wavetek from the 70's or early 80's.

Great find. Smart guy. Excelnt!

Elementary my dear Watson Well done matey!

Watching from Hungary !

Great work!

Damn, that one has some similarities with the HP older series........great video.

They died alright, that's why they reached to the end 🤣🤣. But I on the other hand, appreciated the work done here. I don't know about everyone else, but seeing electronics come back to life, it is art in itself.

Siuuper-interesting fault-find video 👍👍 ,,Thanks for sharing Dan. All videos are very inspiring and educational //br, from norway

As of today I have my own function generator to fix, a HP 3310A function generator. I accidently touched the lead to 550V and i heard a pop and it stopped working. I found one blown transistor and a resistor got fried. I havent been able to test much but the frequency generator doesnt seem to work at all in most ranges. I am not as smart as you are, i hope that i will miraculously find the components that cause this problem and be able to replace them.... You are a true inspiration to me, I hope I can actually do it. Edit: Fixed it, the entire output stage was blown, replaced the components and it worked again. Also a filter cap on the power supply wasnt filtering correctly and replaced that.

Great explained, thank you for sharing. 😊

I hate components that sort of fail and limp along. Great video.

I love my little cheap transistor tester I do have a famcy Sencore brand but that cheap one works well !

Awesome faultfinding and repair! Maybe that transistor cracked due to some corrosion or something inside?

Fascinating!

I managed to watch to the very end, and I wish I was as intelligent as you estimated. But I'm not; yet, I'm gradually getting there, partially with listening to your explanations.

Great job, well done ☺

interesting to see failing silicon transistor faults now due to age ect , its a long time ago now for that early stuff to continue to work as in tendered ect , well done on repair ect

Wow it's interesting how this function generator works

Huge respect, I dont think that I whould be able to fix this 🤯 at least not so fast as You

I seem to recall that Wavetek 110/111 manual had a good theory section that described the effect of unbalance ( offset) in the positive and negative integrations. Just like what the low frequency behavior in this case demonstrated. Their circuit used two opposing currents, one being twice the other. But the higher one was switched, while the lower one was not. Thereby the effective current alternated from, say +1 & -0 and +1 & -2, (or +1 and -1). Based on this ancient understanding, I kept waiting when the unbalance source would be revealed. The surprise was, when one of the transistors started looking like a Darlington one. How come? I have never seen any defect developing that behavior. Something to keep pondering!

Finally something Hungarian!😃 de nem tudtam, hogy mi magyarok csináltunk jelgenerátort is.

nice work

Nice piece of kit. Imagine designing something like this from scratch, amazing really. A modern equivalent would have a dozen chips inside with a few support components and not much else. I'm struggling to think of a use for a 0.0001Hz signal though. One cycle every ~3 hours?

Very good

In hungary we still use these kinds of equipment in schools to this day

it reminds the devices I saw - when child - on my father's shop

Bravo !

I've fixed a few old oscilloscopes before and I too had super dodgey germanium components...both transistors and diodes. Can be deceiving because a quick test makes you think all is OK!

bloody clever

Another great video that did not kill me. 😂

When I saw the problem I almost immediately suspected that it was a problem with an integrator circuit becoming asymmetrical in the lower frequency ranges, indicating a problem with one half of the current-generating circuit (having experimented with similar oscillator circuits for audio synthesis applications). The specific reason it went wrong was extremely unexpected though.

Thanks!

The “sine” wave reminds me of old technical books that would approximate one using semicircles for the upper and lower half-cycles. At a glance, I don’t think the circuit is actually capable of producing a pure sine wave; still better than what passes as a “modified sine wave” with invertor manufacturers, though.

I'm here again to say we gonna die and rebirth but never going to get experience of electronic like you sir seriously NOOOOOOOOT easy to become like you 😢 Every video with new things

Nice

THX

wow this was one of.the standard equipment we used in secondary technical school in the 90s😍👌// in Hungary ofc😊 cheers for the national flag colors on the thumbnail hahahaha