Hello everyone, I introduce myself, my name is Daniel and I am writing to you from Spain, I am a boy who likes everything related to analog video systems among other things. I have recently embarked on recovering a video that I found in a garbage container along with many tapes.
I have changed belts and checked and greased the main control points before operating the equipment. Change the inner fuse of the coil T2 and also fix the pulley of the belt-wire motor. I had timing problems that I show in the video and rewinding and winding (I put bicycle rubber on the capstain) but the main problem is that I cannot repair the tracking set, the power meter does not move and the tracking wheel does not It reacts when you turn it.
I have analyzed the schemes and ask the experts for advice since I have not had the pleasure of working with these machines in those years, there were still 20 years left for me to exist.
the video head seems fine, the video pause is perfect but during playback the sync doesn't seem to move the tape as fast as it should or tracking is the culprit. I put a video where the state is seen.
I apologize to everyone for not being fluent in English, I hope that everything written above is understood.
Hello oblitum, and welcome to the forum.
I'm suspecting that the tape speed is not constant, and at times in the video, the sound seemed to be a bit "wobbly" (audible 'wow'). Would you be able to to make a short recording with a constant single tone? Around 400Hz would be ideal. Picture content would not matter at this stage, but the recorder will need to be synchronised to a video signal. Ideally, if you have a pattern generator which can produce both pattern and tone together, that would be great. My thinking is that some basic 'first principals' will help us along the way.
I'm not the expert on this model of recorder, but there are members with plenty of good experience.
I'm no expert on video machines at all, but to me that looks like something mechanical causing it, as it looks to happen in a very uniform way, I'm wondering if something like an idler wheel or pinch roller has been left in one place too long and gotten a dent in it? So as it rotates it hits on the dent causing the picture disturbance? Just an idea!
Regards,
Lloyd
@katie-bush I'll try to find a signal generator to test. or I will get the signal from a computer through a vhs granador and this I connect it by IF to the vcr.
@Lloyd I have gone through all the mechanical part and it does not seem to present any lubrication problems. Any critical point?
I have reviewed three points and in two of them related to the crest and the pulse they present a signal that does not correspond to the one in the diagram. attached video.
point 410 218 and 220
Hi Daniel,
It looks like the capstan servo is running 'out of lock'. The capstan pulls the tape through the mechanism, but not only does it need to do so at the correct speed, it needs to make sure the tape is in the correct place relative to the video heads.
The capstan servo uses control pulses from the audio/ control head to achieve this. If there are no control pulses, the capstan won't 'lock', so you will get the random noise bars that you are seeing. The tracking control will also have no effect.
Servo's on early video recorders were quite complex to set up and get working correctly. There are usually several different adjustments and they need to be set up using the correct procedure in the manual. It's possible that the basic 'free running' speed of the capstan is set incorrectly- there is often a preset for this. Check that the Control head is clean and that the tape is correctly passing over it. If it's too high or too low, relative to the tape, it will miss the control track. It can't be too far out as the audio (which comes from the same head assembly) sounds OK.
I'm impressed that you have managed to get it working as well as you have so far!
Good luck with it!
All the best
Nick
@1100man Thank you very much for your support and advice. The only point that I have made has been to clean the head and all the mechanical components with IPA. I have not touched the settings of the dials, I need to print a test support to be able to work the lower pbc well.
the tracking mechanism does not respond to the dial and something I discovered is that when you run your finger over the edge of the head it loses synchronism and does not recover it again until you un-thread the tape and re-thread the tape, I don't know if it can be all related. the reference pulse of point 410 is not constant, I don't know if this is related to the already problematic transistor bc158 of point ts462
I discovered that the SK402 is split in two on all machines (another fellow on the forum spoke about that unknown) @crustytv
11/12 years ago (I was 20 years old) I was lucky enough to fix an N1700 (much simpler) because it was much further from the current experience. I am passionate about all old Video formats. my dream would be to be able to have a set of HDMAC equipment, hopefully one day I can, but for now let's make this n1500 reborn, who deserves it after saving him from death
I'm going to try to see if I'm lucky with your advice and this guide of the time. I will keep you informed.
I have disconnected the cable from the control head and it does exactly the same image problem. the peak pulse in tp221 rises and moves is not stable, in tp220 and tp218 if it is stable as shown in the photo. Can the control head be wrong? How can i test it?
218 and 220
TP221 record and play
