SVR 4004 (ITT 241 clone) from hell

Ook op TV en videogebied heeft Philips diverse hoogstandjes op zijn naam staan. Denk aan VCR, Video2000 en de diverse onverwoestbare TV chassis. Al het tele-gebabbel kan hier plaatsvinden!

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gromsound
Berichten: 9855
Lid geworden op: 26 jun 2005, 22:58
Locatie: Haaksbergen
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16 sep 2023, 10:53

i see! very interesting indeed. one would almost think it already had a replacement VCR-LP head drum from the parallel ghhhrundiggh machine. it should be stamped on the drum, could be the bottom side.

compare with the images from Marcel who fitted a LP drum in an SVR and had the disturbance bar in the middle of the screen due to the 90 deg shifted position magnet. you know there was a double functional SVR/VCR-LP machine in this series who had 4 heads. it probably switched speed similarly to your idea, but also the heads, the gap position and the even-frame color phase coding of course. we have seen a head drum with the 4 perpared head positions here.

Afbeelding photo Marcel, left VCR-LP, right SVR
Afbeelding my own SVR drums, left one prepared for 2 extra VCR-LP heads, right one has a prepared position for the VCR-LP magnet so the casting is universal.

would be nice to find such a machine. the threading mechanism and the magnocontrol deck functions frankly are superior to the philips solution. also it brakes softly at the tape start/end in FF/REW and then advances automatically past the stop foil on the tape. saves a lot of tape accidents.
such a shame the electronics parts quality sucks and the heads wear out much faster.
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Whaka
Berichten: 49
Lid geworden op: 23 jun 2023, 16:12

16 sep 2023, 16:57

yep, i confirm i have the 4 heads ready drum.
i saw one day a website who talked about a SVR (or VCR, don't remember exactly) 5000 prototype, who had the ability to play them all.
this explain a lot indeed. the drum i have look like an original assembly, as the blue glue on the screw for the "arm" drum grounding was totally intact and i broke it when i had to replace the tantalum on the preamp.

i found what happened on the chroma board.
i very likely missed a dead blue, or it wasn't dead the first time i checked, on the power rail of the TBA510.
so the 33 Ohm safety resistor did what it supposed to do and measure 4,43 KOhm :lol:
the TBA is probabely good. i'll replace the resistor first, i wait for them and answer soon :D

edit : for the heads wear, if i remeber correctly, your SVR had a non working tape back tension sensor ?
that would explain a lot.

and i also forget, as good news sometimes don't come alone, i found another SVR, but not for free this time :mrgreen:
a grundig 4004 FR, so i'll see which drum this one have and try the same experiment.
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gromsound
Berichten: 9855
Lid geworden op: 26 jun 2005, 22:58
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16 sep 2023, 18:26

5000 prototype, who had the ability to play them all.
yes we have a prospect of ghhrundiggh in which this machine is normally presented. plays VCR and VCR-LP with the same machine and the 4 heads drum. probably no market for that thing. sources in germany state that this machine was at the very last moment not put into production due to unknown reasons. the last '4000' models are reported to have several built-in details that show '5000' optional holes/plugs/buttons. including the 4 head universal casting of the drum.

viewtopic.php?p=245409#p245409

[edit: gottem!]
Afbeelding

my tape tension was ok, just adjusted it a bit. i think Marcel had one with defective IR-led sensor.

really, change ALL blue 10mu35v tantalums, since they will ALL fail after some time under power. other values seem to be ok in our collected experience up to now.
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Whaka
Berichten: 49
Lid geworden op: 23 jun 2023, 16:12

20 sep 2023, 10:03

thanks, i vaguely remember this brochure.
i think i'll probablely replace all tantalum, as 4,7µ can also fail. it totally deserve it as it work quite well
Whaka
Berichten: 49
Lid geworden op: 23 jun 2023, 16:12

24 sep 2023, 11:00

second svr in hand now :)
i don't even bothered to plug it first (the seller already did it, as it was owner since 2020).
so i automatically replaced UA723, switch PSU to 240V, then plug, and absolutely no clock at all but it power on.
press on play, aaaaannd drum and capstan motor were going full throttle, and no attempt to thread.

ok... let's check if there's 50 Hz pilot, and of course no 50 Hz.
so dead SAJ 300T again, and also found the MC14016 (again) to be bad as on the first svr.
conclusion is the UA723 was very likely dead the bad way too in this one. i strongly encourage to replace it even on a still working machine.
this thing coast nothing and are very easy to find as they're still produced.

so after replacing the SAJ 300T clock is working again, let's try play... (and you guess what happened :mrgreen: ) shutdown.
no, it was not the tantalum in head preamp, but a 4,7µ on the servo board.

to short the story :
it also have the 4 heads ready drum, the servo board despite being the same as in my first svr don't allow me to reach VCR LP speed.
but in the first, i've replaced the LM3900N which is responsible to amplify capstan motor pulses, maybe that's why?
i swapped servo board, and try VCR LP tape, and yep... no color. no commutation point issue, but definitely no color.

edit :
it worked fine for approx. 30 min, then it lost supply reel motor regulation. tape is moving even is stop position, and no fast rewind.
something is probabely bad on the motor board.
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gromsound
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Lid geworden op: 26 jun 2005, 22:58
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24 sep 2023, 18:39

yeah probaly a small blue pea-shaped component (or more). :mrgreen:
they all go sooner or later after long standstill. but the circuit boards are easily taken out in these machines so it makes almost no difference if you choose to replace them one by one :D
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Whaka
Berichten: 49
Lid geworden op: 23 jun 2023, 16:12

26 sep 2023, 11:01

seems it was not. i've swapped motor control board, it get back to normal.
but when i put back the original board, it worked too :mrgreen:
maybe a contact issue.

i also see something else on secam variant which couldn't make them play VCR-LP tapes with color.
grundig used another transposition frequency. VCR used the same 562 KHz in both pal and secam, but grundig used 650,25 KHz in secam.
so, really nothing to hope on this point.

and a very bad news, i managed to do the worst thing that could happen : i broke a video head.
end of the road.

i guess sometimes things need to be in balance... i fixed a VCR-LP video head coil, but i killed a SVR video head tip.
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