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VCR N1500 with various issues

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gschwab
(@gschwab)
Posts: 40
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Hi everyone,

my name is Gunther and I'm from Germany. I've had an N1500 since I was a kid, it was given to my by a friend from school in the late 80s/early 90s. With the help of my dad, I got it running. Back then, it was only mechanical issues that prevented it from working. As I had no idea what I had on my hands back then, and as I was a curious kid, I played around with the VCR a lot, put stickers on it, etc. After some years, I lost interest in it, and it disappeared in the basement. During the Covid lockdown, I remembered the VCR and made the plan to bring it back to life. 

First, I had to deal with mechanical issues again, replace the belts, fix the pinch roller, but also with some electrical issues. Several capacitors had gone bad (especially the low capacity electrolytics). After replacing them and improvising a stand to be able to make the necessary servo adjustments, it was working surprisingly well. I decided to clean it thoroughly before putting it all back together, and that's when it happened. I broke one of the video heads... Hard to believe that I managed to do now what I had not managed to do in all those years messing with the VCR. While I was able to glue the head back in place, the position doesn't seem to be perfect, so the image is much worse than before.

As I really wanted to have a well working machine, I went on the hunt for a replacement head drum or a parts machine. After a little while, I found a parts machine for a reasonable price. After picking up the machine, I was surprised at its good overall condition. It seemed to be complete, all the disintegrated belts still in place. After cleaning everything out and replacing the belts with new ones, the VCR was working from a mechanical perspective. Having replaced the critical electrolytics, I managed to play back a tape and receive the signal from a test pattern generator. Unfortunately, both were of very low quality. While the playback image was free from stripes, it was initially without color and of very low contrast. The EE signal had color, but was unstable and noisy. After cleaning some contacts, fixing a cold solder joint and replacing a missing connection. The EE signal is now stable and in color, but still pretty noisy. The playback picture is not noisy, has a bit of color now, but is still low contrast/inverted. 

As the playback picture is not noisy, I assume the modulator is working fine. Also, the heads seem to be ok, as there are no dropouts and the picture is clear. However, I don't know how to proceed in order to improve the picture. I am still waiting for a new pinch roller, as the one I have is pretty bad. I hope this should fix the periodic jumping of the image.

The EE image issue seems almost harder to fix. The automatic gain control seems to be working fine, reducing the output of the test pattern generator only leads to a noisier picture after the output has been reduced quite a bit. 

Unfortunately, I only have the complete manual in Dutch, the very helpful troubleshooting section is missing in my German version. Could anyone maybe help out with a digital copy of the English version?

Also, if any of you have any pointers, please let me know what to check! I am fairly experienced with electronics (electrical engineer) and have quite a bit of test equipment, but the N1500 makes it really difficult to proceed systematically, as everything is so hard to access.

Thanks in advance,

Gunther

 
Posted : 21/03/2023 2:46 pm
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crustytv
(@crustytv)
Posts: 11995
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Hi Gunther, welcome to VRAT.

I've just copied the Full English version of the N1500 service manual into the temporary download area of our data library. I've just fast tracked your membership to include access to this data area. I don't normally do this as we've had no end of new members turn up just after something free, never staying around to be part of the community and share their repairs with us.

It's a large file almost 1GB. Please let me know when you have downloaded it so I can remove it.

Good luck with your repairs, I have three of these machines, all in various states of repair, one nearing completion. Indeed the diagnostic section of the manual is a must have aid to assist with repairs. Parts are getting harder and harder to find and like you I've bought a number of parts machines.

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Posted : 21/03/2023 5:24 pm
gschwab
(@gschwab)
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Thank you so much for your kindness! I will download the manual tomorrow once I‘m back on my laptop. I‘d be happy to share whatever insights and pictures I have about the VCR!

 I’m really surprised that my first machine was working so much better than this one, but the second one is just in way too good a shape to be used for parts only…

 
Posted : 21/03/2023 6:54 pm
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gschwab
(@gschwab)
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@crustytv Thanks again, just downloaded the file. I'm sure this will help a lot!

 
Posted : 22/03/2023 7:35 am
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gschwab
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Well, two steps forward, one step back... With the full manual, I started on the troubleshooting section. As my VCR did not turn off after being turned on an no tape transport button being pressed, I checked that area of the device. I found that a trace on a PCB was interrupted, even though not visibly. After fixing the connection, the VCR now turns off almost immediately. The manual points to TS112 in this case, which I don't believe is faulty. The tape transport buttons are released as they should be when the device is turned off.

I suspect that C115 is being charged too fast, will have to check capacity and the resistors in that area. 

This thing is really full of surprises!

 
Posted : 30/03/2023 8:15 am
crustytv
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Posted by: @gschwab

Well, two steps forward, one step back...

That's the sort of progress I so often encounter, deeply frustrating, and Philips certainly don't make things easy.

That protection circuit is fun filled for sure, I spent some time diagnosing a fault with one of mine. If you've not read it, here's a link to the thread.

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Posted : 30/03/2023 8:30 am
gschwab
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@crustytv I actually had read your article before! It's funny how seemingly fairly simple circuits like the protection mechanisms can be so difficult to diagnose. I've also read some of your work on color TVs, absolutely amazing! Being from Germany, I'm not very familiar with Thorns and Pyes however. I just found and fixed an old Grundig 1510 where the core of the 5.5MHz trap had broken off almost invisibly...

Maybe I should have stuck with my original plan of using this machine for the good head drum only, but it was just in way too good a shape to pick it apart. I even found an original lacing drum and cord, the machine has the potential to be almost as good as new...

 
Posted : 30/03/2023 9:01 am
gschwab
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Well, not a whole lot of progress, but I still want to update this thread. The new pinch roller did not fix the unstable picture issue. However, it really seems like a mechanical issue. Synchronization works just fine when adjusting it for recording, without a cassette in the VCR. Maybe there is too much friction somewhere... However, in the time when the picture is stable, it is pretty decent, however the colors are a bit weak and there are lines across the screen sometimes. It doesn't seem to be a head issue, as this phenomenon depends on the image content, the signal seems to be overdriven.

Will try to fix the tape speed issue and see what happens. Still need to deal with the faulty protection circuit and the EE-singal issues..

 
Posted : 02/05/2023 9:39 am
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