Grundig SVR 4004 VCR owners beware!

[whaka54]

hello,

if you have a SVR 4004 and like it, i think a good idea is to preventively replace the µA723 regulating the 15V in the psu.

theses things can fail in the very bad way : not regulating at all.
so with all consequences that could lead to... 24V instead of 15.
all logic/PLL/divider/microcontroller IC's are mostly rated for 20V at very maximum.
and some are ultimate gold unobaitnum, as the TMS1100.

so better loose few cents in a µA723 i guess

[simpsons]

Bonjour Nancy

Thank you for the "heads-up" on the Grundig video 2000.

Many moons ago, Practical Television provided stock faults through its Servicing XXX pages or Les Lawry Johns.

Often published after the set came in for servicing!!

There might be an index out there showing the content pages of PT to make it easier when visiting the World Radio History site for PT back copies, but I don't know of one.

Chris

[toshiba tony]

I used to have one of these, search tuning etc. vhs was very new and on the rise, rarely rented tapes so one of these were great, never any bother except the primary of the psu. Easily sorted.

[Snarf81]

I have two of these VCRs, in the pile to look at someday. Both don't power up. I managed to modify a Philips N1700 to play the svr recordings back.

[whaka54]

Originally Posted by Snarf81

I managed to modify a Philips N1700 to play the svr recordings back.

thanks for the confirmation N1700 can play SVR tape.
i wasn't sure if the only difference was speed or if track size/azimuth were different too.

did you have a documentation on this modification ?
i have some N1700, and i'd be very happy to modify them.

[Snarf81]

I'll take a look through my files and see if I can find the instructions on how to do it. It was from an article in Television magazine IIRC.

[marceljack]

Originally Posted by Snarf81

I'll take a look through my files and see if I can find the instructions on how to do it. It was from an article in Television magazine IIRC.

In my opinion it is possible to modify a SVR machine to play back VCR cassettes but not the reverse because due to the lower tape speed the tracks of the SVR (so the heads) are thinner than the tracks of the VCR.
So in my opinion a VCR head would read adjacent SVR tracks simultaneously, but I may be wrong.

[whaka54]

Originally Posted by Snarf81

I'll take a look through my files and see if I can find the instructions on how to do it. It was from an article in Television magazine IIRC.

thanks

Originally Posted by marceljack

In my opinion it is possible to modify a SVR machine to play back VCR cassettes

might be a better option for SVR owner.
SVR are incredibly well build and so much improved compared to philips chassis, the N1700 look cheap in comparison

[Maarten]

Except for the electronics, which are said to be less reliable. I don't have the statistics, but it might mainly be a case of "beware the blue tants".

[whaka54]

Originally Posted by Maarten

"beware the blue tants".

yes, i saw them... but all i checked for now are still good.

luckily, all microcontrollers seems to have survive the 24V adventure...
the 50Hz pilot is missing, i highly suspect the SAJ300T on the servo board to be dead (rated for 16,5V max.), and also found the MC14016 dead too.
so SAJ and 4016 on the way... let's see if i can get it back to life

[collisr]

Hello Nancy,

I love the SVR machine and have 2 working models plus 2 further new-in-box that I will get round to looking at one day.

I recall lots of failed blue tantalums 😁 but never seen an issue with the voltage regulator IC.

Are these chips still available or will you use something else that is a better IC ?

Rob

[spamfritter]

Originally Posted by Maarten

Except for the electronics, which are said to be less reliable. I don't have the statistics, but it might mainly be a case of "beware the blue tants".

Les had a thing about the blue tants ! Loved reading his stories . Remember the door family ?

[whaka54]

Originally Posted by collisr

Are these chips still available or will you use something else that is a better IC ?

hello,
the µA723 is still manufactured under various references, but it is widely available.
all logic IC's are very common 4000 series, so widely available and still produced too.

the SAJ is only NOS, but easily obtainable, TDA/TBA and so are still obtainable as NOS.
the real issue are microcontroller as the TMS1100. chip itself is easy to find, but they were "hard" programmed, so no real easy way to replace except a donor SVR (maybe VCR BK3000/4000 can be donor too).
but this one seems only for clock/programming, it may live without it.

the other microcontroller is the siemens S 555B.
the machine can't live without it. but seems it can be found
as i can't find any documentation about it, i don't know if it was a custom bulid for grundig or if it's a "generic" available for who want it.

[Maarten]

I would guess the S555B is an ASIC, not a microcontroller. But older Siemens stuff can be hard to find anyway.

[whaka54]

there's a source in italy for it, but seems this shop don't sell outside italia.
and their web site is italian only.

some news :

replaced the SAJ 300T effectively bring back a lot of life.
and also permit to spot others failures, as... everybody's gonna be surprise : a shorted blue.
of course, the only hard to access in the whole machine, the one on the head preamp.

and also, capstan don't regulate at all, full throttle.
i checked if there's pulses provided by optocoupler and they work.
checked for pulses on the op-amp output on the servo board (LM3900N) : nothing, so dead op-amp.
durm is badly regulated, could also be related to the same op-amp.

that's where i am for now, but looks promising

[whaka54]

LM3900N replaced, capstan and drum are now regulated correctly.
at this point, i've still not plugged it to a TV and have no easy way to use the modulator.
it doesn't have A/V socket, so i'll have to pick them somewhere.

for now, the vu-meter level tell me there's something, but it doesn't react to tracking control.
i guess there's still some dead IC's on the servo.

[whaka54]

voilà!

tracking issue was simply a variable resistor drift (R1033).
for now color is missing, but it might also simply be another VR or capacitor drift.

and this drift was also an answer on how to turn a SVR into VCR LP.
simply by adjusting this resistor to drive the capstan at the VCR LP speed...
and adding a bit of adhesive tape on the cassette to make the SVR think it's a SVR tape.
i really don't understand why grundig did this and go alone, as it was so easy to keep compatibility.
SVR is really an UFO in video recorder history.

so very easy to add a switch with 2 variable (or well defined fixed value) resistors
i guess the same will work to turn VCR LP into SVR.

well, happy i am

[Byteman]

Turning N1700 into SVR and vice versa is not possible by 100% because of heans in SVR are placed in 180 degrees ang,e while VCR and VCR-LP uses 179 degrees. So this one degree is messing with color information, you may notice that picture is a bit "wobbling" because of fields are not aligned, and also color is missing because of phasing issue. Maybe delaying the RF signal from one of the heads for some proper time using good delay line may help to overcome this issue, but it is not easy task.

[whaka54]

i expermiented a bit, and i was able to get a perfect black and white picture.
you're right about the color "mismatch".

and for secam variant, another detail come in the game :
the subcarriers transposed frequency is not the same as it was on VCR.
so yes, not so easy specially for secam.

[ben]

Originally Posted by whaka54

hello,

if you have a SVR 4004 and like it, i think a good idea is to preventively replace the µA723 regulating the 15V in the psu. theses things can fail in the very bad way : not regulating at all.
so with all consequences that could lead to... 24V instead of 15....

I would consider installing a zener diode on that output of the PSU! Or might that cause more problems than it solved?