Grundig Videorecorder VCR Videorekorder HIFI  2280 a

Reparaturtipps zum Fehler: Noisy picture

Im Unterforum Reparatur - Video-Geräte - Beschreibung: Videorecorder, Camcorder, DVD-Player und alles was mit Bildaufzeichnung zu tun hat.

Elektronik Forum Nicht eingeloggt       Einloggen       Registrieren




[Registrieren]      --     [FAQ]      --     [ Einen Link auf Ihrer Homepage zum Forum]      --     [ Themen kostenlos per RSS in ihre Homepage einbauen]      --     [Einloggen]

Suchen


Serverzeit: 20 7 2024  00:12:10      TV   VCR Aufnahme   TFT   CRT-Monitor   Netzteile   LED-FAQ   Osziloskop-Schirmbilder            


Elektronik- und Elektroforum Forum Index   >>   Reparatur - Video-Geräte        Reparatur - Video-Geräte : Videorecorder, Camcorder, DVD-Player und alles was mit Bildaufzeichnung zu tun hat.

Gehe zu Seite ( Vorherige Seite 1 | 2 | 3 Nächste Seite )      


Autor
Videorecorder Grundig 2280 a --- Noisy picture
Suche nach Videorecorder Grundig 2280

    







BID = 803673

stego

Schreibmaschine

Beiträge: 2461
 

  


Hi Alexander,

now that is REALLY a good news from you! Congratulation!

I´m really glad, that your V-2000 works again, and no other faults have resulted from your watch.

The adjustment of the tape drive:
If EVERY adjustment screw is still sealed (with blue paint), please don´t turn around on them!!!
Because, if they are still sealed, the tape path is alligned in best condition! Any of the image interferences have their cause elsewhere - but not at the tape guides. This robust mechanism doesn´t disadjust itself!

First of all, the pressure roller has to be ok, next check the back-tension of the tape (as I have already written: under the copper heat sink on the module "Ablaufsteuerung" there is a trim-potentiomenter. With this trimpoti, you can allign the back-tension of the tape.
Also check the first tape lever, if this lever turns out correctly.

And, not to forget: The capstan belt! If this is worn, it may be, that the tape is transported unbalanced, what may result in image interferences (and also sound up and down).

Best regards,
stego

_________________

Erklärung von Abkürzungen

BID = 816760

Byteman

Gerade angekommen


Beiträge: 17
Wohnort: Belarus, Minsk
ICQ Status  

 

  

Hi, all!

Now I'm ready to continue repair of my V2000 VCR. I've repaired old pinch roller on the special equipment at work, and now it is like a new one. Now tape doesn't go up and down along heads. That's OK.

But now I have another two problems... Even three....

Problem #1. There are two resistors at the top of the DTF/SERVO board. What function do they do? The problem is that when I've placed all cables to their places, I broke one resistor I've changed it with another one (4,7 KOhms), but when I rotate it, nothing on the picture changes (I've even checked FBAS-output signal with oscylloscope, but nothing changes). I'm just want to know, what function these two resistor do, and how to tune them onto correct positions (which testpoints to use).

Problem #2. I'm digitizing old V2000 tapes. There are drop frames very-very often. But it looks like a system. When I press play, the drop frames go for about two minutes. Then it stabilizes and capturing is good. It is not my trouble (not is doftware or capture hardware), it is trouble with VCR. On VHS systems I usually tune up syncho-head, and it works good arter it. But on V2000 there are no syncro-head... On oscilloscope it looks like bag V-sync pulse (when there are many drops). Then it normalizes, and capture goes good. It looks like that VCR cannot syncronise with frames/fields written on the tape (fields are swapped too when frames are dropped). Even on fresh-recorded tapes from ideal black-burst generator there are dropped frames when digitizing (a few minutes, then all is good, 25,000000 fps framerate). What regulators are for sync-tuning on this VCR?

Problem #3. When I bought this VCR, head-switching pin on the head was broken. I've made a replace for it, using photos. Maybe, it is a trouble of bad syncing... I don't know.

Please, help me. I just wand to digitize all of those old tapes... There are really interesting things, like old German news about Berlin Wall break, and other interesting thinga (like ARD testcard and others)....

I have oscilloscope and I can make screenshots of certain oscillograms at certain testpoints.

Thanks in advance!

Erklärung von Abkürzungen

BID = 816796

stego

Schreibmaschine

Beiträge: 2461

Hello and welcome back again!

1. Which restistors do you mean? Do you have a service manual? In the sm, all allign points (for service) are described, and those having no description MUST NOT get disadjusted! They are adjusted in GRUNDIG factory after production and can not get alligned by "normal" technicans.

2. It looks like a) the video heads are worn, so the DTF signals (recorded with the video signal) are read faulty. V-2000 works without a "normal" sync track, like VHS or Betamax. V-2000 has 5 different frequences recorded on the helical scan tracks. In play mode, these five signals get to the DTF-control, then the DTF module serves the DTF voltages to the piezo elements, on which the video heads are mounted.

This is, why V-2000 can offer perfect clear picture search FF and REW.
It is a really difficult "dynamic track following" system, and some troubles have not been removed entirely until the end of the system V-2000.

Now, after more than 25 years, the tapes have get older as well as the machines. It is nearly impossible today, to play a V-2000 tape in the same perfect quality as it was recorded. Even a new recording - the tape material is old!

I hope, you have checked all of the voltages coming from the power supply. This is a general presuppose for correct working of the VCR.

What about the DTF voltages (Oscilloscope on the pickup-shoes)? In normal mode (play), the voltages must not drift up or down very much. The oscilloscope should display a relative straight line.

If the drop-outs appear, is the picture still present? Or does it disappear in this time? Check the DTF-voltage, when the image interference appears.

3. The pin for the photo sensor (video headdisc speed indicator) is a little too wide! Original, this pin is only about 5 mm wide.
Perhaps, the servo control gets too long sync pulses because of the "big" pin on the head drum.

Best regards,
stego

_________________

Erklärung von Abkürzungen

BID = 816839

Byteman

Gerade angekommen


Beiträge: 17
Wohnort: Belarus, Minsk
ICQ Status  

Hello, Stego! Again and again you help me to repair this VCR! Thank you for your help!

1. I don't have SM none in electronic or paper variants The resistors are R1194 and R1217. They are on the top of DTF/SERVO board (you can see broken one on the third photo).

2. If I understand correctly, DTF system works good, becsause there are no visible glitches on the picture, FF and REW works perfectly, PAUSE is perfect too. On TV the picture is very-very clean. But VirtualDub drops frames because of non-correct V-sync pulse. When drop occures, picture is good, but DScaler in that cases shows "2:1 Bad Pulldown", I'll post oscillograms of "good" (when there are no drops) and "bad" sync which goes from VCR. It looks like VCR is out of "sync-window" (like on floppydisk-controllers), and when it synchronises, there are no drops after that. On TV-set picture looks line about one line up or down, and fields are swapped (looks like "jerking picture"). RF-signal from head-amplifier is straight level, I'll make and oscillograms too at the evening...

3. Ok, I'll make this pin shorter, now it is about 7-8mm wide

Thank you for your Great help!!! I hope, thet together we will manage with this old V2000 VCR

Best reagrds,
Alexander

Erklärung von Abkürzungen

BID = 816881

stego

Schreibmaschine

Beiträge: 2461

Now I see the two varaible resistors! As far as I know (without looking into my machine or into the sm), these are the two allign points for the correct DTF voltage (voltage output stage), one for each head. Every head has its own piezo element and its own output stage on the servo/DTF-board.

For calibrating this voltage correct, you must own the original Service cassette - and this is a problem now today, because this cassette is avilable NOWHERE !

I will take a look into the sm, how the adjustment is best without the service cassette. Wait until tomorrow!

Both variable resistors are of the same type (is there a print on it? Like "10k" or so?)

Perhaps the sync signal drops out because of the old recordings. But the machine itself has 25 years or more of age! Most of the electrolyt caps are out of tolerance, I guess. If such a V-2000 machine should work as new, most of the electrolyc caps must get changed and the whole circuit has to get alligned new.

Best regards,
stego

_________________

Erklärung von Abkürzungen

BID = 816923

Byteman

Gerade angekommen


Beiträge: 17
Wohnort: Belarus, Minsk
ICQ Status  

Oh.... Service Cassette.... Noooo.... I'll tried to calibrate voltages in FF mode, just measured DTV voltages and set them at same levels. Rewinding and pause are good. Clean picture, without disturbs. Both resistors are 4,7KOhms.

About the sync: where I can read about all the sync methods of V2000 standard? I've found no literature on the web... Only some words about the lack of control track... What regulators are for sync tuning?

I'm sorry for bad photo quality, tomorrow will make better photos. The first corresponds to "good" sync (small "zero level" before V-pulse), second - for "bad" sync (no "zero level" before V-pulse).

Erklärung von Abkürzungen

BID = 816953

Byteman

Gerade angekommen


Beiträge: 17
Wohnort: Belarus, Minsk
ICQ Status  

The first photo is with good sync pulse, the second - with bad pulse.


[ Diese Nachricht wurde geändert von: Byteman am 23 Feb 2012 21:56 ]

Erklärung von Abkürzungen

BID = 816976

stego

Schreibmaschine

Beiträge: 2461

I have forgotten:

Are all of the allignment screws still sealed with blue paint?
Or has someone turned around on this screws?

The FM packets look not very constant, especially when the picture is noisy...
It looks a bit, as if the tape does not drive correct at the run-out of the head drum.

Is the tape path ok after your work on the pinch roller?
There must be no crinkles in the whole tape path, and the tape has to turn around the white roller (tape guide) after the capstan/pinch roller very constant, even in Picture search forward and reverse!
If the tape gets up or down turning around this white roller when switching between forward and reverse, the tape path must get alligned.

This is what reminds me at the moment.

The service manual has a lot of description of the whole circuit - but only in german language!
Perhaps, somewhere in the internet, there is a service manual in english language. I don´t know, sorry!

Best regards,
stego

_________________

Erklärung von Abkürzungen

BID = 816978

Byteman

Gerade angekommen


Beiträge: 17
Wohnort: Belarus, Minsk
ICQ Status  

Tomorrow I'll try to make photo of RF-packet directly from head-amplifier. All the tape path is aligned as "from factory". I've only tried to change pinch roller pressure (because roller became thinner).

Erklärung von Abkürzungen

BID = 817228

Byteman

Gerade angekommen


Beiträge: 17
Wohnort: Belarus, Minsk
ICQ Status  

Hello! Here is RF-packet looks like....I don't know, if it is good or bad. Here are some sample videos which I had digitized some months ago. You can notice drops on those videos. Some tapes have many drops, some are fewer, but picture quality on all records is the same... I can't beleive that V2000 standard was so critical to tape quality... Maybe this is misaligned tape path, or some troubles in sync-module. On TV the picture is almost perfect (sometimes picture goes some lines up and down, very fast, seems like sync errors).... I can't guess what to do the next step... I think that I'll have to buy another V2000 VCR, digitize all tapes on it, and sell it again

But if to be serious, I really want to know all details of V2000 standard, because it is more interesting thing, that usual VHS...

Best regards,
Alexander.

Erklärung von Abkürzungen

BID = 817409

Byteman

Gerade angekommen


Beiträge: 17
Wohnort: Belarus, Minsk
ICQ Status  

Hello, Stego!
I've tried another tape, RF-packets are more straight, like on VHS-machines. It only has a head-switching gap (if I understood correctly). On VHS this gap is abnormal and should be eliminated by tuning head-switching signals. And what about V2000? Is this gap normal?

Erklärung von Abkürzungen

BID = 817458

stego

Schreibmaschine

Beiträge: 2461

Hello Byteman,

I don´t know off-hand, if the oscillogrammes are ok that way.
If I get time today, I will take a look into my service manuals. Some oscillogrammes are shown there.
When finding anything interesting for you, I will scan it and upload it here.

The head switch-over point is alligned with the optical sensor on top of the head drum. (Sliding the sensor unit). But for correct allignment, the service cassette is neccessary again...

Best regards,
stego

_________________

Erklärung von Abkürzungen

BID = 817604

stego

Schreibmaschine

Beiträge: 2461

Sorry, I didn´t have ONLY ONE minute time the last weekend!
These are days, where I have to work without any end!

Perhaps, next weekend I manage to take a look into my service manuals, but I can´t promise you anything at 100 %...

Sorry again and best regards,
stego

_________________

Erklärung von Abkürzungen

BID = 817634

Byteman

Gerade angekommen


Beiträge: 17
Wohnort: Belarus, Minsk
ICQ Status  

Hi, Stego!

I'll wait for necessary time, because it doesn't matter for me, will I repair it today, or some months later Thanks again

Best regards,
Alexander

Erklärung von Abkürzungen

BID = 817647

stego

Schreibmaschine

Beiträge: 2461

Hello Alexander,

now - I have found a Service manual in PDF!!
But: it´s about 100 Megabytes of data size!
I don´t know, where I can upload it for you...

You can try to download it yourself here:

http://freeservicemanuals.info/en/s.....280a/

After download, you get a file named "2x4" without .pdf, so you must rename it to "2x4.pdf", then you can open it with Adobe Reader.

Unfortunately, it is only in german language.
But I don´t really know, if the sm´s were also printed in other languages.

If your download is not successful, we must search for a alternative for uploading my PDF-file.

Best regards,
stego

_________________

Erklärung von Abkürzungen


Vorherige Seite       Nächste Seite
Gehe zu Seite ( Vorherige Seite 1 | 2 | 3 Nächste Seite )
Zurück zur Seite 0 im Unterforum          Vorheriges Thema Nächstes Thema 


Zum Ersatzteileshop


Bezeichnungen von Produkten, Abbildungen und Logos , die in diesem Forum oder im Shop verwendet werden, sind Eigentum des entsprechenden Herstellers oder Besitzers. Diese dienen lediglich zur Identifikation!
Impressum       Datenschutz       Copyright © Baldur Brock Fernsehtechnik und Versand Ersatzteile in Heilbronn Deutschland       

gerechnet auf die letzten 30 Tage haben wir 14 Beiträge im Durchschnitt pro Tag       heute wurden bisher 0 Beiträge verfasst
© x sparkkelsputz        Besucher : 181688539   Heute : 24    Gestern : 4667    Online : 503        20.7.2024    0:12
3 Besucher in den letzten 60 Sekunden        alle 20.00 Sekunden ein neuer Besucher ---- logout ----viewtopic ---- logout ----
xcvb ycvb
0.220559835434