More on the Super-rare Grundig SVR4004. A format of only one model.

[@TigerBoyRS]

This is "just" cheer electro investigative drive, a rare sport... Must be praised for the patience, courage and honesty. When this early video machines were made, I'm sure no one would ever think that 40+ years later, a clever brit would diving into German junk like this. Someone's footage on that rare vintage format, will be thankful, when brought back to existence and digitized to "eternity". Video empowers people! Cheers 📼

[@RinoaL]

Despite me not having time to watch this from start to finish, thank you for filming it!

[@allanbroadfield5121]

Your videos are great, I love anything video, and remember agonising over beta or vhs. back in the day. I wish I understood the technicalities, but a little too long in the tooth to learn now!

[@mrnmrn1]

I've had sooo many cascading faults with dipped tantalums that at this point, if the unit is 30 or more years old, I start with replacing all of them before even attempting a power up. If it's a DC rail decoupling cap, I replace it with a low-ESR electrolytic, if it's a low value coupling capacitor in the signal path, I use a film capacitor. SMD tantalums last longer because their epoxy coating is much thicker. I have two NOS video waveform monitors, when I powered one up, a dipped tantalum smoked. It was on the 5v rail, I've cut it out. Then the next one smoked, rinse and repeat ~15 times. When all the tantalums were removed from the 5V rail, the unit started working. For about a minute, then an other tantalum, this time on the 15V rail shorted out. I haven't powered up the other one, as I want to make a video about it. It will probably be a smoke machine just like the other one. And they are not even that old, from 91 or 92 IIRC, and the tantalums are KEMET or some other good brand, rated 16V on a 5V rail. They were stored in a damp basement, their cardboard boxes are moldy, so their aging was accelerated. One of the big enemies of tantalums is moisture, it slowly gets through the thin epoxy coating. The other enemy is oxygen, which also penetrates through the coating. Hermetically sealed metal can tantalums on the other hand, are everlasting, as long as they are protected from voltage surges.

[@Knaeckebrotsaege]

Had similar issues with vintage PCs (286-486 era). Having a tantalum on the 12V rail with a dozen or so amps behind it blow up sending glowing shards flying everywhere _while you're leaning over the board_ on a test bench (to check something unrelated) ain't exactly fun. I've started replacing those (insert lots of swearwords that would get my comment deleted) before applying any power ever since then

[@crumplezone1]

Perseverance will always win rewards, great content

[@TheRealHarrypm]

Be wonderful to see this manual scanned and OCR'ed for translation with DeepL etc (but what would be more wonderful would be getting some FM RF captures of that format to impliment a decoder for! 🤤)

[@alyro-ls1dv]

thank you for the video. thank you for showing how precise one can chase a fault which turns out to be a working component. it is part of the process and not giving up to easy. the desintegrating plastic parts are a real pain with some manufacturers products. others might say they were not so as long as the company expected this machine be of use for anybody but you repairing and using this prooves these voices being wrong.

[@randomsteve4288]

The problem with disintegrating plastic is not only with Grundig it is with Philips and other mfc too. And I would rather have some connecting plugs break apart, where you can always solder the wires directly, than have crucial parts of the mechanism disintegrate like on the Philips Turbo Drive.

[@more.power.]

Thank you Colin tricky repair,

[@TTVEaGMXde]

There are still many blue tantalum capacitors and FRAKO electrolytic capacitors in the device.

[@randomsteve4288]

Oh you gotta love them molded plastic ERO/FRAKO firecracker electrolytics. Short on arrival... The alliance between Grundig and Roederstein (ERO) may have been a nice touch in the "Made in Germany" departement, but came to bite them... Same goes for Grundig's silly idea to go to the lengths of reinventing signal IC and microcontrollers and have them custom built exclusively by Siemens in the long obsolete MOS technology, making them prone to ESD, where similar ESD protected chips where already available from Philips/Valvo and used by almost any other manufacturer. Dunno how many Grundig TV I had to scrap because the elusive TDA6200 audio controller had kicked the bucket upon someone plugging the VCR without turning both sets off. The Philips TDA8420 chip based sets never gave any trouble in that regard. But in that regard Grundig was much like Sony; staying with national suppliers and always reinventing the wheel...

[@TTVEaGMXde]

@@randomsteve4288 In 1986 I had one of the first 24" Panasonic TVs with a full square tube that was sold in Germany. The service center (also in Hamburg) asked me if I had ever connected anything to the Scart connection (DIN AV was also available) because it wasn't working. I hadn't, but I got the TV from the largest department store in Hamburg from the service center because in the store the device didn't have any color. So if people think that the powerful 15V Z-diode is overkill for the video output amplifier that I developed for the Philips VCR N 1700, they now know the "origin". Later, the device also received a new Mullard (PHILIPS) picture tube, since the white areas were already colorful when the shadow mask was cold. Doming was a major problem with PHILIPS flat square picture tubes from 1985-1989 (beginning of nickel addition in shadow mask). I hope I corrected Google Translate correctly😉

[@tremorist]

Max Grundig wanted this format to be built, so it was built. Market analysis did not matter to him, he followed his "stomach" feeling. Much to the disadvantage of the company.

[@randomsteve4288]

That is true to some extent. But Max Grundig also sported the idea to produce extraordinary gear that outperformed the rest. And to some degree he achieved that. Both in the 50s 60s and 70s. His idea to introduce modules in TV starting with the CUC series along with extensive tech support in the form of a factory refurb service for said modules made the sets not only easy to service but also cut down on repair cost and downtime. And spraking for Germany the only other company that would rival Grundig in terms of quality and performance was Saba. And even in the booming market of VCR Grundig made an impression. If one looks at Grundigs Video2000 and compares it to the VHS or Beta machines of that same time, Video2000 wins in all regards from features to picture quality. Some even outperforme the Video2000 VCR of Philips. The feature of dynamic track following of Video2000 producing a noise free freeze frame was not introduced to VHS until decades later. What broke the neck of Grundigs Video2000 over VHS was the sheer complexity they put into it to produce a top quality image and its pricetag, while JVC was swamping the market not only with cheaper drives, but also taking a jumpstart in the booming market of VHS rental tapes(!) by striking alliances with the film studios, while Video2000 and other formats still focused almost only on the customers demand for making home recordings from TV programs.

[@mlluke7506]

Your ability to trace the faults is very impressive.

[@joligrunlaub3412]

I have a printed original version of the service manual with an appendix. Grundig changed the pinout ofB1 and B4 during production. They turned it around. 1 is now 10 and 10 is 1. In the sve 4004el there is another schematic of the power supply.

[@video99couk]

Yes I saw the EL version has an updated power supply with some components deleted.

[@randomsteve4288]

40:03 I hate to throw a wrench into your troubleshooting, but there should not have been any smoke escaping at this point. The 15V regulator is protected by a feature called electronic fuse "ELEKTRONISCHE SICHERUNG". And this electronic fuse is build around the thyristor/scr TY447 2N5081G. And this protection works as follows; TY447 monitors the voltage drop across the resistor R451 (0R22). If the output current rises the voltage drop across R451 increases. If that voltage across R451 exceeds the Gate to Cathode trigger voltage of TY447, the SCR conducts and puts a positive voltage from the raw 22,6V line via R443 onto the node of R446/R447 and thus effectively pulling pin 2 of the uA723 high. As a result the uA723 has to immediately switch off any base drive to the pass transistor T449, and the whole 15V output will shut down. The cleverness with this circuit is that it latches the supply in the shut off mode and will not let it come back up, even if the short disappears. Why is that so? Because like any thyristor SCR TY447 will stay conductive as long as it has any Anode to Cathode current flowing through it, even if the Gate drive (hence excessive output current thru R451) disappears. As a result after an overcurrent trigger event, the pin 2 on the uA723 will stay pulled high and the 15V supply will stay shut down until the whole VCR is fully power cycled. I wonder where we did see this behavior... Oh right, the previous Grundig SVR 4004 did exactly behave like that; the 15V line IMMEDIATELY shut down on the overload caused by the bad tantalum and stayed shut down until a power cycle. What this means for this VCR is, that either this powersupply board is a different revision missing this electronic fuse feature (I hardly think so), or the SCR TY447 is bad or was disabled by a previous tech troubleshooting, or the "NEW" uA723 that you fitted does not handle the signal to pin 2 correctly, meaning it is a fake. The latter can be proven easily by upon proper operation passing voltage from the 22,6V rail thru a 1,5k resistor into the node of R446 and R447, and watching if the 15V line shuts down. Whatever you do, Bottomline is; The 7V you saw on the 15V rail before the smoke escaped should never have happened. The overload shutdown should have kicked in instantly and lasted until cycling the power. Just like seen on the previous 4004. Seeing how these VCR are prone to problems with tentalums on the 15 Volt line shorting out, I strongly suggest investigating into why this powersupply did not shut down the 15V rail on overload properly, unless you want to fit a fuse in the 22,6V rail to make up for that protection feature not working. Side note; Why didn't you use a current limited(!!!) bench powersupply to externally feed the 15V rail? You could have easily seen how much current was drawn and which module was the culprit.

[@video99couk]

I am concerned about fake UA723 chips and will buy some from a reputable supplier, so could replace that later. The smoke was certainly a bad thing and I would want to avoid that risk again. I will be working on the machine again very soon: I'm fairly sure that the failure to operate deck functions is caused by another tantalum capacitor having failed. I'm not keep on using the bench power supply route, it could result in currents flowing where they should not since the machine's design may assume some 15V rails are only present when others are.

[@janosnagyj.9540]

Wow, what a trip! Yeah those 723s are always a pain in the arse... when you show it the first time on the diagram I was like noooooo... a 723 😅 But it's strange why something was smoking, on the top part of the circuit there is an "electronic fuse" which through that SCR disables the output in case of overcurrent - at least, it should do that...🙄 So basically we had a dead 723 to begin with, and then that tantalum got shocked when it saw again some electrons after who knows how many years of total darkness 🤣And now something else gave up again. Maybe another tantalum had enough? 🙄 Can't wait the next episode 😅

[@video99couk]

The smoke should not have happened with the SCR in there.

[@robertlloyd-jones4310]

Great video Colin, I love these in depth videos about real vintage technology. You have a lot of patience! You’ve inspired me to take another look at my machine (when I have a lot of spare time). The main fault on mine is that the capstan pinch wheel solenoid doesn’t engage in play. Any ideas which voltage might be missing? Cheers, Rob.

[@video99couk]

You'll have to wade through the service manual, especially around page 90 where all the timing diagrams are, to see why it's not being actuated.

[@Ragnar8504]

B4: 1. Permanent -26 V 2. GND 3. 4. Motor Control Board 13 (I assume pin 13) 5. Locating hole 6. To clock 9 7. Permanent +12 V 8. Syscon board 23 9. IF fine tuning +15 V R - active when the machine is on and a function key has been pressed, relay is latched +15 V E - active when the machine is powered on but idle

[@chillidogkev]

I've not much experience of tantalum caps but doing a Google search of them for info it says basically that they are used when large capacitance is required in a small package AND ultra reliability is paramount such as in medical equipment. Ironic then that so many you find have failed. What are your thoughts on this?

[@video99couk]

They are not good at handling current surges, so should not be used for decoupling a power supply. It's not that they are bad capacitors, rather that they were incorrectly used.

[@chillidogkev]

@@video99couk Many thanks 👍

[@normanmackenzie8130]

That one was a bummur..but, you WILL fix it, no doubt about it. Excellent stuff.

[@norman200]

Thanks for another excellent repair video. I remember a mate of mine had one on the 1970s?

[@chillidogkev]

I could have put money on the fact that one of the kids was going to barge in and drop a parcel in his hands containing the actual manual.

[@mikaelgranquist821]

More Video 2000, please?

[@midiaaudioevideo]

I wanna see you working on a shotgun microphones, specially Sennheiser, thanks for your patience

[@Matt_Quinn-Personal_Account]

You have a faulty shotgun mike?? Don't think I've ever known one to go down, myself.

[@frankowalker4662]

Bloody Tanty's. (and light bulbs. ha ha)

[@video99couk]

Cold resistance of a small light bulb was a bit lower than I expected!

[@guimbadriver]

wow i never saw it in my short life...look this mechanics 4 heavy driver motors two big motors must be drum and capstan others one must be reel and loading

[@video99couk]

Actually two reel motors with electronic back tension.

[@guimbadriver]

@@video99couk wow professional tape transport looks like my JVC CR 850 U U matic VCR

[@DavidMander-rs4uk]

Are you going to put that in the obselete junk museum? 🤔

[@video99couk]

Kind of missing the point? I run a video transfer business. So I will be using it to transfer customer's tapes.