with Help two Grundig 2x4: drilling sound, machine aborts after starting playing

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Help with two Grundig 2x4: drilling sound, machine aborts after starting playing

    











BID = 779750

Perepandel

Gelegenheitsposter



Beiträge: 66
Wohnort: Miramar (Platja)
Zur Homepage von Perepandel
 

  


Geräteart : Video recorder
Defekt : Drilling sound, destroys tape
Hersteller : Grundig
Gerätetyp : 2x4 best nr. 2000
Chassis : plastic
______________________

Hi everybody!

This is my 3rd post thread in the forum. I started with one aglutinating my 4 (four!) non-working V2000. Now I think it's time to split in different posts, one for each machine/problem.

Stego, and/or some other experienced user, I hope you can enlight me!

I have two non-working Grundig 2x4 "Best Nr. 2000". One is grey/silver, lacks the closing door for the little buttons zone below the display and seems a bit old. The other one is black, shiny, in almost perfect looking condition, and seems newer. Here is a picture of them:

Bild eingefügt





The silver, old one had all belts broken/non existant, but it would turn on and somehow respond to keys pressed sometimes. The black one also would turn on, but display just garbage in the screen and didn't do anything.

After little time, the newer machine had one of his X2 capacitors from the power supply exploded. I recently repaired it, tested both "netzeil" plates and they seem to me they are giving the proper tensions.

I opened the machines. Both had their "ablaufsteuerung" half destroyed due to the "accu" defect: its acid went off of the battery and many PCB tracks were affected and gone. I've bought conductive silver "paint" from the electronic store and, with great patience, have restored the destroyed tracks. Have tested with a multimeter their continuity, also for shorts, and seem to be OK. Replaced the battery, and also replaced the thermistor from the older VCR ablaufsteuerung, which was phisically broken.

Here is a couple of pictures of the PCB after being restored. It's from the older machine; the other is inside its machine at the moment:

Bild eingefügt
Bild eingefügt





After turning on the machines, now this is what I get (after some testing and adjusting, since at the 1st moments presented some other minor problems which I as been able to 'repair'):

- Both machines turn on and show the display correctly and brightly. The clock also stores and displays the time correctly :).

- The newer machine accepts the tape, wraps it around the head and starts the act of playing. But noises comes from the mechanism, then a drilling sound (like a "Black&Decker") starts and then the tape unwraps and the machine stops.
I have investigated the "drilling" sound and it comes from the "Bremslüftmagnetschalter": the "switch plate" starts pushing very quickly like a "drilling hammer", so the entire machine vibrates very heavily and so there comes the drilling noise.
Even one time, the machine didn't stop at all, the tape continued to be "playing" for some seconds and it got totally twisted and screwed, until the machine detected something wrong, unwrapped the taped (leaving it almost unusable) and stopped.

- The older machine accepts the tape, also wraps it and then starts playing, but after 1 second or so it stops. Every other function (fast forward, slow, reverse) does the same. Rewind and fordward works well (althought the first day one time it rewinded automatically when I inserted the tape, and it also didn't stop after rewinding finished and pulled the tape out of its "tape wheel"; also, on the first day the tape didn't come out at all when pressing "cass", it stopped half the way out, but this hasn't been reproduced again).
Also it's important to note that this machine shows and "F" when it stops after trying to play the tape.

As both machines are the same (same model-number: Best.-Nr. 2000, although there seem to be some updates in the newer one: one more or less resistor here and there), I switched the "ablaufsteuerung" between both machines just to discard any problems with them. Well, the same behaviour as described above happens with both VCRs with the swapped "ablaufsteuerung", but when the older is put on the newer machine, it will show the F there, and if I put the newer on the older machine, it will stop after 1 sec playing -as usual in this machine- but without showing an F.

I don't know why one "ablaufsteuerung" is showing the F and the other not, if there are problems with them or simply the displaying of an "F" was removed in the newer model... Anyway I'm suspecting of mechanical problems on both machines: some misalignment in the tape path in the newer machine and also something wrong in the Bremslüftmagnetschalter, which by the way has his rubber washer rotten and distroyed and maybe its affecting its stability and causing its "drilling":

Bild eingefügt




In fact, all those rubber washers are broken/rotten in all my machines and I'd like to replace them (Stego, can you point me to the correct direction on the store, please? :D)

In the older machine I suspect of a mechanical problem too, but cannot imagine where and what to check. Here is a video of it showing the behaviour when playing a tape. Note it don't displays the F when it stops because it has the swapped "ablaufsteuerung":

http://www.youtube.com/embed/31zwKvJpVf8

Any hint in where to continue will be really appreciated!


[ Diese Nachricht wurde geändert von: Perepandel am  6 Aug 2011 19:42 ]

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BID = 779822

stego

Schreibmaschine



Beiträge: 2036
Wohnort: Furth i. Wald/Bayern
Zur Homepage von stego

Well, the modules "Ablaufsteuerung" are very hard damaged by the defective accus...
It is possible, that the failure is coming from this.

Both machines are, even they look like there are a lot of years between, from the same generation of V-2000.

To the "Bremslüftmagnet" (breaking magnet):

At the back side of the magnet, there is a switch. In normal position of the magnet (= the rubber pads are blocking the reel motors), the switch is closed.
At the moment, any tape drive function is activated, the magnet should pull back the rubber pads and release both reel motors. And, of course, the small switch MUST open fail-safe!
If the switch doesn´t open, the coil of the magnet will get overloaded.
In closed condition, the coil gets a voltage of app. 12 V to pull the break pads steady. After pulling the break pads, the magnet must stay active to hold the break pads. But the switch then opens, and the 12V (= pull back voltage) get down to app. 2 Volts, called the "holding voltage". With this 2 volts, the coil does not overload.

Please check, if this switch works properly.
Because, if the switch is not closed in normal position, it cannot pull at start of any tape drive, because of the missing 12 V pull-back voltage. The holding voltage of 2 V is not enough to pull the break pads.

And, please make an general check of ALL plugs on the modules! They like to break very often, and then something like with your older V-2000 can happen very easily!
It is also possible, that on your "older" V-2000 the right reel motor has occasional drop-outs.

Best regards,
stego

_________________
Für die Umsetzung meiner Tipps übernehme ich keinerlei Verantwortung! Ich sitze ja schließlich nicht vor dem Gerät. Jeder der an einem elektronischen Gerät arbeitet, muß sich dessen bewußt sein, was er/sie tut!

 

  

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BID = 780372

Perepandel

Gelegenheitsposter



Beiträge: 66
Wohnort: Miramar (Platja)
Zur Homepage von Perepandel

I haven't had a single second in the entire week to try further tests with my machine. I think I will unscrew and check the magnet; otherwise, I don't know what else to try now! Maybe I'll swap the cards/PCB from the "newer" to the "older" or viceversa to discard any electronic problems in them...

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BID = 780834

Perepandel

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Beiträge: 66
Wohnort: Miramar (Platja)
Zur Homepage von Perepandel

I switched the "DFT/servo" PCB between "older" and "newer" VCRs... Exactly the same behaviour. So I'm more and more convinced it's a "mechanical" problem, or at least it is located in the motors area, since it sound difficult to me that a problem in the "chroma" or the "tone" sections would cause a stop after one second playing...

I have now 3 "vacation" days but, unfortunately, won't be able to test as hard as I would since I still have missing belts for the "newer" machine, since my order from this store hasn't come yet... (and no news about when will it arrive)

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BID = 781067

Perepandel

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Beiträge: 66
Wohnort: Miramar (Platja)
Zur Homepage von Perepandel

I've actually swapped ALL the modules from the older VCR with others I'm almost sure they work, and the behaviour is the same... so I'm totally sure now that the problem is either mechanical or it is in some of the electronic/electric components in the tape slot part, motors, etc. Still I'm lost.

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BID = 781537

Perepandel

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Beiträge: 66
Wohnort: Miramar (Platja)
Zur Homepage von Perepandel

More updates:

I've tested ALL motors of both 2x4 machines directly with a 9 V battery. All of them work OK.

Also I disassembled the magnet of the newer machine: it looks to me OK. I've located the switch, looks exactly like the one which detects if the tape is inserted, and have verified it makes the proper contact...

Anyway, I cannot test confortably because I only have a set of belts for a couple of machines... Still waiting for my order to this store and I haven't received a single confirmaion e-mail (it's been a week since I paid the order!)

Stego, come back from vacation soon, please!!!

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BID = 781552

stego

Schreibmaschine



Beiträge: 2036
Wohnort: Furth i. Wald/Bayern
Zur Homepage von stego

Have you already tested the voltage of the magnet?
Does it pull away both rubber pads? It may be, that one of the little springs is broken or missing, then the rubber pad can touch the motor while running.
Does the switch (on the back side of the magnet) open and close correct?

This IS a mechanical problem. Or a problem with a plug and/or a cable connection.

When running, on the pcb at the magnet, there must be two voltages: 12 and app. 2 volts.
As i have already written, the pull-voltage is 12 volts, the holding voltage is 2 volts, the switch must be closed in stop position and opened in working position. If the switch is not closed, the voltage on the magnet is only 2 volts, which is too low for pulling the break pads away.
After the pads have pulled off the motors, the switch must open, then the "holding voltage" of appr. 2v appears on the magnet.

Check these things please, and also the mechanical allignment of the magnet and the rubber pads!

Best regards,
stego

_________________
Für die Umsetzung meiner Tipps übernehme ich keinerlei Verantwortung! Ich sitze ja schließlich nicht vor dem Gerät. Jeder der an einem elektronischen Gerät arbeitet, muß sich dessen bewußt sein, was er/sie tut!

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BID = 781964

Perepandel

Gelegenheitsposter



Beiträge: 66
Wohnort: Miramar (Platja)
Zur Homepage von Perepandel

Hiya, Stego!

Well, a disaster just happened.

I unscrewed the magnet to take those tests. I even had a replacement for the little rubber pad. But the part which looks like a "bullet" fell off and the little transparent plastic cylinder that comes from it broke

I tried to glue the part, but it is "ungluable". Also I suspect that this is a kind of optical device (light enters through this little transparent plastic?), so even if I could glue the broken part, it wouldn't work.

Do you think if this part is available at the store? I already got a response from them and the parts I ordered won't arrive until a month or so, so I guess I still could include it in the package (if it is available).

Or maybe you or some other user has one spare piece to sell...

I'm including a picture of the broken part:

Maybe if it's not that "light sensitive", do you think I could "repair" it myself if I find an appropiate piece of plastic (by diameter), cut it to the proper lenght, remove the remaining plastinc inside of the metal piece and put it there by pressure?




[ Diese Nachricht wurde geändert von: Perepandel am 20 Aug 2011  1:41 ]

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BID = 782000

stego

Schreibmaschine



Beiträge: 2036
Wohnort: Furth i. Wald/Bayern
Zur Homepage von stego

Hello Perepandel,

to get to a solution of this problem, i can offer you:

A complete tape drive, taken out of a 2x4 (Best.-Nr. 2000).

The tape drive had worked, but I have disassembled some parts of the electronic PCBs. So, the machine does not work anymore.

But I remember that:

All mechanical components have worked properly
The breaking magnet has worked properly too.
The head drum is missing, I have taken it for another V-2000.
Both reel motors are ok, and also the tape threading motor is ok.

So you can take parts from this tape drive.

The plastic part of the magnet has no optical function. It is only a lock ring.
But glueing is no way, because it´s not holding.

If you want to get the tape drive, please give me your address via PM (private mail, envelope symbol).

Best regards,
stego

_________________
Für die Umsetzung meiner Tipps übernehme ich keinerlei Verantwortung! Ich sitze ja schließlich nicht vor dem Gerät. Jeder der an einem elektronischen Gerät arbeitet, muß sich dessen bewußt sein, was er/sie tut!

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BID = 782015

Perepandel

Gelegenheitsposter



Beiträge: 66
Wohnort: Miramar (Platja)
Zur Homepage von Perepandel

Hi for the tip, Stego!

Knowing that it's not important the plastic to be transparent, I've almost found a replacement. I've already removed the remaining plastic inside the "bullet" and have a little cylinder of the same diameter (it's a drill from my little, Dremel-like driller :D; anyway, now that I know it's function, I'm sure almost anything of the same lenght that would fit could do the job); have yet to cut it and insert into the hole.

PD: you have PM

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BID = 782301

Perepandel

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Beiträge: 66
Wohnort: Miramar (Platja)
Zur Homepage von Perepandel

Important update on these hard 2x4!!!!!

I was giving up temporarely on the 2x4 that runs for a second and then stops with an F because I was out of ideas.

Trying to get again on the newer, the one that 'chews' tapes with a drilling sound, I unscrewed the entire tape unit. I remember once I took off the tape slot, so maybe it wasn't alligned properly (maybe not on the correct pin on the mechanism that "sucks" the tape cartridge) and that was causing the 'driller' machine and the tape chews...

Well, while performing a rutinary cleaning of the golden contacts on the top of the head drum before mounting everything again, I accidentally touched (very gently, that's the truth) one small little black rubber piece on the top of the head drum... and it fell off!!!! I'm adjunting a picture of it, with the fallen piece on my finger:

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BID = 782302

Perepandel

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Beiträge: 66
Wohnort: Miramar (Platja)
Zur Homepage von Perepandel

Important update on these hard 2x4!!!!!

I was giving up temporarely on the 2x4 that runs for a second and then stops with an F because I was out of ideas.

Trying to get again on the newer, the one that 'chews' tapes with a drilling sound, I unscrewed the entire tape unit. I remember once I took off the tape slot, so maybe it wasn't alligned properly (maybe not on the correct pin on the mechanism that "sucks" the tape cartridge) and that was causing the 'driller' machine and the tape chews...

Well, while performing a rutinary cleaning of the golden contacts on the top of the head drum before mounting everything again, I accidentally touched (very gently, that's the truth) one small little
black rubber piece on the top of the head drum (it's like a "tongue" of rubber, that comes out, vertically, from a rigid plastic piece glued/attached to the top of the drum)... and it fell off!!!!

I'm adjunting a picture of it, with the fallen piece on my finger (yellow circle and arrow):

Well, blasfeming myself just to have broken another part (anyway it was about to break by itself... I really touched it very softly), and trying to determin if it had any noticeable function... I noticed it passed trough a "bridge" (green arrow) once per revolution, blocking what is probably a light sensor, so I concluded it has an IMPORTANT function, probably to tell the system that the drum is rotating, etc...

Then a light turned on my head... I ran for the older 2x4, the one that stops after a second... was suspecting that the same piece could be broken, thus the sensor sending the signal that the drum is not rotating or whatever... and.. GUESS!!!

The piece wasn't there! Not that the little "rubber tongue" had fallen off like in the other machine... Even the plastic piece that is glued to the drum head and holds the "tongue" itself is not there! It has fallen off or maybe removed by someone some time! You can see in the picture that a hole on the head drum is visible, where the plastic piece should be:

Now I'm almost sure that is the reason why the older machine is stopping after a second... But I'm very frustrated because I have no such piece! And also broke the same piece on the newer video, so I cannot use it as a spare piece!!

I'm struggling to get an idea on how to replicate that piece, "homemadely"... or if it is also available to purchase on the store! Stego, wanna make a deal?

I'm sure this same problem has affected more people, specially the ones showing the same behaviour as me... tape threads, then the machine suddenly stop with an F... It is very easy not to notice the piece has break or it is missing!!

Maybe if precission was not much critical, I could try to replicate it with thermal glue, or some

"modelling" material...




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BID = 782323

stego

Schreibmaschine



Beiträge: 2036
Wohnort: Furth i. Wald/Bayern
Zur Homepage von stego

Hello perepandel,

now that´s a success!

This black "tongue" (of plastic material) is a part of the head drum speed indicator. Every turn of the head drum, the optical sensor indicates a short interrupt, and this signal is delivered to the servo control PCB. With this 25 Hz-signal, the servo circuit is regulating the head drum speed of 1.500 rpm.
The upper part of the optical sensor can get alligned: Loose the screw only an quarter turn, and then you can allign the light sensor according to the service manual.
If the groundig spring is not centered, it can happen, that the plastic tongue touches the optical sensor and breaks.

Then, something like on your machines happens: After starting PLAY, the machine aborts after one second, because the servo circuit gets no signal from the head drum speed indicator! The processor gets a "no head rotation" signal and stops the tape drive with a blinking "F".

In this situation the head drum spins up to much more than the correct 1.500 rpm. This may perhaps cause the "drilling" sound...

For a first check, you can use a piece of paperboard and glue it with a reversable glue (for example a hot glue).

Then, the machine must play and the head drum must rotate at its correct 1500 rpm.

If this happens, I can help you with a plastic bar, taking from one of my machines.

Best regards,
stego

_________________
Für die Umsetzung meiner Tipps übernehme ich keinerlei Verantwortung! Ich sitze ja schließlich nicht vor dem Gerät. Jeder der an einem elektronischen Gerät arbeitet, muß sich dessen bewußt sein, was er/sie tut!

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BID = 782372

Perepandel

Gelegenheitsposter



Beiträge: 66
Wohnort: Miramar (Platja)
Zur Homepage von Perepandel

Hi Stego!

What a disaster... I was writting that at 2 AM; my finger pushed "enter" by mistake and the 1st half message was published... now I don't know how to delete it! I cannot find the delete/edit message button and I'm supposed to be a programmer! Also I cannot edit the full message to put the pictures where they are supposed to!

Anyway... I can't wait to go back home at night (I have to travel 150 km every day to go working and get back for a crappy salary... have you heard about "crisis"? ) to test the "piece of paper" trick to see if I can get any image from that wonderful machine! I hope not to have manipulated it enough to definitely ruin it

Now it's a mistery to me how the "older" 2x4 lost that piece... It is not broken, it's simply missing! The "newer" one is where I broke it, but it was on its place until yesterday and that is the one that makes the drilling noise... I'm suspecting (the "newer") that machine suffers from more serious "deseases", as someone told me in youtube as a response to the video I published here that the hour is not working right, so probably its ablaufsteuerung have some defective component... also it responds differently when I put in there the "older" 2x4 ablaufsteuerung, which I'm almost 100% sure it's ok...

I'll give you more feedback on my success until I'm able to do so. Many thanks again!! I wouldn't been put in the right direction without your help

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BID = 782373

stego

Schreibmaschine



Beiträge: 2036
Wohnort: Furth i. Wald/Bayern
Zur Homepage von stego

Hello Perepandel,

To the optical sensor (the head drum speed indicator):

In the machines of the third generation (No. 2000/2000a/2200/2080/2280/2280a) the indicator is on the upper side of the head drum. The plastic "nose" or "tongue" rotates between a optical barrier and gives the 25-Hz signal to the Servo module.

In the older machines, of the first and second generation (No. 700/770 first gen. and 800/850/880 second gen.) the head drum speed indicator is located under the head drum! You cannot see it without dismounting the head drum.
The optical sensor in this machines is on the front side (looking from the front), under the spinning drum, in the stationary tape drum. It´s a black sensor, mounted with one or two screws, and the "nose" (inside) is of metal, which reflects the IR light, coming from the sensor, back to it.
This is, why the older machines have no "nose" (or "tongue") on the upper side of the head drum...

Best regards,
stego

_________________
Für die Umsetzung meiner Tipps übernehme ich keinerlei Verantwortung! Ich sitze ja schließlich nicht vor dem Gerät. Jeder der an einem elektronischen Gerät arbeitet, muß sich dessen bewußt sein, was er/sie tut!

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