1977 Philips N1700

1977 Philips N1700 1

1977 Philips N1700 2

N1700 (Released 1977)

Superficially similar to the Philips N1502 both externally and internally. There were however very few components interchangeable between the two models. Slower tape-speed and a slant-azimuth recording technique (to almost eliminate cross-talk between video tracks without using tape-wasting guard-bands) made possible the longer playing time without a noticeable loss in picture quality. The mains lead was hard-wired into the machine however later releases of the N1700 had a removable lead – this would become standard on the N1702 model. Also on later models, presumably as the company had already started production of the N1702, the internal Video Head is also sometimes labelled as N1702 instead of N1700.

 

 

1977 Philips N1700 3The N1700 looks identical to the 1975 N1502, however looking a bit closer shows the controls have been re-designed. There’s a sliding tracking control replacing the rotary one, a different clock, and lower-profile control buttons. The big difference though is the “Long Play” feature.

The N1700 was an entirely new format, VCR-LP, which could record for well over two hours on a standard 60-minute VCR cassette. For the first time, an entire feature film could be held on a single video cassette.

 

 

 

1977 Philips N1700 4Philips achieved this increase using a new technique called Slant Azimuth recording, where the heads themselves were mounted on the drum at a slight angle to the track being written.

The two heads were set at opposite angles, which prevented one head from picking up interference from adjacent tracks – since these had been recorded at the other angle. So, there was now no need for ‘guard band’ gaps between the tracks, and they could be recorded much closer together on the tape. This in turn meant that the tape could be run at less than half the speed of a VCR format machine.

 

Useful and interesting information


The N1700 in my collection

Reported Fault Condition: Does not power up.

 

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Operation of the N1700 / N1702

The following text regarding operation was obtained from Oldtechnology.net to view their original article click here. The images are from my own machine

Operation of the N1700 / N1702 1The Cassette Deck

The cassette deck is concerned with the physical mechanics of moving and scanning the tape.

The first item that should be mentioned in the picture is the lacing motor. When a cassette is loaded into the VCR and the machine is switched on, it is this motor and it’s associated mechanics which drag the tape out of the cassette housing and wrap it around the drum and guide posts by rotating the entire drum assembly 200 or so degrees clockwise. The guide posts, being on the inside of the tape, pull the tape out of the cassette as they themselves are pulled round the drum.

The main circular item at the top of the picture is the drum assembly. This is divided into two sections, one stationary and the other that rotates. The stationary part (The lower drum) is the part of the assembly which sets the lower position tape as it is played. It has a special high-precision guide called the “Ruler-Edge” which, with the guide posts, ensures that the tape is positioned in exactly the correct place to be scanned by the video heads on the upper-drum. The lower drum also has the end-of-tape sensor mounted on it. This, as the name suggests, stops the tape when it has reached the end of it’s travel. It detects the end of the tape by means of a foil strip on the tape which shorts out two contacts as it passes the sensor. On top of the lower drum, is the rotating part (The upper drum). This has the video heads mounted on it 180 degrees apart. The video heads read the picture information as they scan the moving tape.

The capstan and pinch-wheel combine to pull the tape from the supply spool, past the video heads and audio / control heads and back onto the take-up spool. In the play and record modes, the take-up spool carrier has just enough torque to provide drive to take up the slack between the capstan and the take-up spool without actually dragging the tape through the mechanism itself.

Apart from the video heads, there are three more heads in the VCR. The full erase head on the left hand side erases the entire cross section of the tape before fresh audio and video are recorded. If this head is not working, then when a fresh recording has been made,vague images of the previously recorded program will be seen underneath the new recording. The audio and control heads are mounted on the same assembly on the right hand side of the VCR. The audio head records the sound on the bottom of tape and plays it back in the same way as an audio tape recorder. The control head records and picks up pulses to accurately control the position of the tape, and these are recorded on the top of the tape.

The idler on the bottom right of the picture is used to direct power from the motor to the take-up or the supply spools during fast forward or rewind.

Operation of the N1700 / N1702 2The Servo Board (Hinged Up)

The servo board accurately controls the speed and position of the drum and the tape relative to one another during record and playback.

If the picture is to be free of noise bars and tracking-errors, it is imperative that the VCR knows exactly the speed and the relative position of the tape and the heads during record and playback. This is where the servo board comes in. The VCR employs a series of sensors to control phase-locked-loops which accurately set the position and speed of the tape and the heads. The modules in the picture control various aspects of this job and are switched in and out depending on the positions of the record and play switches. (These switches are mechanically linked to the play and record buttons on the front of the VCR).

The digital lock-in circuit makes sure the upper drum is rotating at the correct speed as quickly as possible after the VCR is switched on.

Operation of the N1700 / N1702 3The FM Board (Under the Signals Board)

The FM processor board is mounted underneath the signals board on the right hand side of the N1700 / N1702 VCR. In playback it demodulates and processes the FM video signal which is supplied by the video heads via the video head amplifier. In record mode, the video signal is fed to the FM modulator and then passed as an FM signal to the video heads, again via the video head amplifier. The FM processor board also contains a recycling drop-out-compensator (DOC). The blue delay line you can see at the bottom of the picture stores one line of video information, so in the event of a drop-out (loss of FM signal due to bad tape or clogged heads etc.), the last good line of video can be displayed instead of a white blip on the screen.

Operation of the N1700 / N1702 4The Signals Board

The signals board is the most complicated board in the N1700 / N1702 VCR. It performs several tasks related to signal processing.

In record mode, the signals board takes an RF signal from the antenna socket, demodulates it using circuits very similar to most television sets, and converts it into it’s component luminance (Y) signal and composite chrominance signals (C). The Y and C signals are then amplifies and processed before being passed to the video heads for recording on to the tape.

In playback mode, the signals board takes the signal from the head, recovers the seperate Luminance and Chrominance signals, demodulates them and then combines them to form a recognisable composite video signal. This signal is then modulated and sent out as an RF signal through the antenna socket to the television.

The antenna amplifier unit amplifies the RF signals coming in to the video recorder from the television aerial and then passes them to the RF output socket.

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Belts have succumbed to the years, sticky and deformed

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Update

The belts have deformed so new ones ordered. Belt kit has arrived from Germany……..

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Update

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Some very interesting findings on this player with regards to the E-E tuning fault and some suspect dry joints on the Servo board.

Firstly, thank heavens for the microscope as my eyes even with a normal magnification bench lamp, failed to find them, a re-flow has now eliminated the jitter and my what an improvement, the picture is stable and very clear. I think this player is likely to be the better of the two.

Moving on to investigating why I cannot get E-E working. I briefly mentioned in the video that when I select a channel on the VCR, the tuning indicator light intermittently/briefly flashes then goes off. I’m therefore unable to tune the VCR to the incoming signal from my test card generator.  Also the LED clock has segments partially displaying.

To investigate these the front fascia needed to be removed. Upon doing so I noticed the channel selector bank had three additional wires soldered to one end of the board, brown, orange and purple. The other player does not have this, nor does the bare bones unit, this got me pondering why.

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Two of the wires go to the signals board where resistor R542 has one end lifted, the lifted end has the purple wire soldered to it. Where the lifted end of the resistor would been on the PCB, the orange wire is attached. The third brown wired dives off under the signals board. When the signals board was hinged up to see where it went, it revealed two things. The brown wire is joined to a grey wire which goes of to an additional module! This player has another module fitted that neither of the other two I have, Hmmmmmm!

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Under the signals board there is normally only the FM processor board mounted on the far right-hand side. However this player has an additional module and I believe the brown wire which is spliced to the grey, goes in under here somewhere.

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Its late, I’m tired so I will pick this up afresh tomorrow, perhaps those of you who know this player are currently screaming at your screens exactly what this other board is. I’ve not checked other than it seems to have some additional sockets, be they inputs or outputs, I’ve not checked. I need to consult the N1700 service manual to see if it mentions any additional modules or modifications, as I say its late so it will have to wait now. Tomorrow I will try and understand if the tuning fault and these additional wires and mods are related to the E-E problem or a red herring. If the former try and figure out why and if the latter try a replacement tuner selector bank.

Well I’ve two copies of the N1700/xx service manual and thus far I can find no mention whatsoever of the additional module in either of them.

The photo below clearly shows the places where the module has been spliced into the circuit. The module has BNC video out/in and DIN audio sockets. The additional module also has I notice, a deliberate track cut and a jump wire to another trace.

I think I’m going to revert this to standard config, remove all the tentacles from the module to the signals board and tuning module. Then revert R542 back to circuit and see if the E-E tuning can be reestablished.

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Checked and there’s no test switch on the rear so I imagine your latter assumption about being auto generated upon no signal might be true.

I’ve now had a more detailed inspection of the additional module, it again raises far more questions than answers. There are multiple track cuts, some component removal and jump wires (see below).

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What I find odd is the following; if this was a module that a company or person could order from Philips, to further extend the players video input/output options, why would it be necessary to carve up this new modules tracks? Surely if released from the factory it would be just a case of installing in the preformed slot, splicing in the various wires we see to the signals board above and the channel selector bank. Not having to resort to brutal measures such as we see here on the modules print side.

I’m more convinced now that I’m going to attempt to revert this player back to a standard N1702 player. I just hope when I do it works as intended with regards to channel selection and tuning. As mentioned last night the quality of the video playback on this player is in my opinion outstanding, well it looked fabulous last night on the Tx9.

I suppose as a test, I could feed in the test signal to the additional modules BNC video input via an adaptor, select channel 8 and see if the E-E works. Obviously I would be missing sound but at least it would show if the module is doing anything.  Don’t know, even if it does I think I’d rather it was gone.

Some further investigations were carried out today. I removed the additional Video\Audio input\output module from the N1700, desoldering it entirely from the signals board and the channel selector module.

I then tried tuning the VCR’s channels to the incoming test signal for E-E, absolutely nothing doing. The only observation I noted was upon powering up the VCR, the tuning indicator light briefly flashes.

I then decided to fit a spare signals board I had from the bare-bones N1700. Once this was installed the tuning indicator light was fully illuminated showing the VCR had recognised a signal was present, this is what you would expect. Selecting a channel on the VCR allowed me to establish E-E.  However this spare signals board has a fault all of its own, in as much as the picture is degraded on both video playback and tuning into the test card signal, well it would be too easy if it was fully working

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The conclusion to this is either there are further modifications that have been made to the N1700 signals board that I have missed, there is a fault or something else is going on. Tomorrow I’m going to put the original 1700 signals board back in but before I do that, it will go under the microscope for a full close up inspection to see if anything has been added, changed, removed, modified or broken. Needless to say there would appear to have been two issues with two of the N1700’s boards (signals and channel selector module. Well three if you count the corrupt LED clock display, though that is unrelated to the E-E fault. I wonder if that’s why the additional video output/input/audio module had been fitted to the machine as a way of getting over a fault.

the Uxxx are plugin modules in cans, little printed circuit boards that edge connect into sockets in the signals panel. All I had managed to find thus far circuit wise, were the plan views for the signals boards that show where the plugins connect via the edge connectors. There are pointers to these that show expected voltages and wave-forms. I can at least check these to see if anything looks way out.

However, I’ve also now discovered more intrigue on the signals board. The N1700 board differs from the N1702 in the reference processor module is U533 and has this built in test pattern former. Whilst the N1700’s reference processor does not and is designated  U513.

Well my board has a U513 module fitted, not the expected U533. This now fully explains why I’m not getting the test pattern generated, perhaps the wrong module is fitted. This further reinforces that someone has been in here for either good reason of bodgery, which it is, as yet I have no idea. Its difficult enough when you’re learning VCR repair without having to deal with 40+ years of other peoples agile minds either doing good or bad mods/repairs.

I’m now left with two questions and another night of dream diagnostics. Is the U513 1700 module compatible in the U533 position of the N1702 signals panel. If its not then I’m stuffed. Is the only difference the test pattern gen. If U513 is compatible in a 1702 signals board then I might have a fighting chance through diagnostics and substitution.

All fun and games and I’m enjoying the ride I hope you are too.

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It was getting late, I had spent the best part of an afternoon and evening producing, editing and uploading the video of that days work. I thought I would leave the next phase, the U513/U533 question, until the next day. I therefore just expressed what was on my mind at that point in time. As I clearly indicated in my video investigations, I was already highly suspicious that the problem was lying in the reference processor and that was where I would be next focusing my efforts and attention.

I had hoped the threads and youtube videos where showing my methodical approach to problem solving on the Philips N1500 and N1700 series VCR’s. That despite not having ever worked on VCR’s before, my approach and determination, had not only allowed me to identify the fault with the N1500 and rectify it. That I was also well on my way to identifying and solving the various faults encountered with the two N1700’s and in particular the curious additional module and lack of E-E with the 1702 signals board.

As detailed at the outset of the thread and opening video, thankfully I have the full manual. As planned for today, I checked the modifications section, in particular looking for listed differences between the 1700/02, it did not disappoint as shown below. Clearly as you also already knew the U513 is not compatible, well that’s not entirely accurate. Further investigation revealed this is permissible but as a pair U512 & U513 can be used but for it to work you need to remove D516 and D517 and finally R526.

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My 1702 signals board and it is a 1702 signals board, has a U512 fitted and D516/D517 are removed but..  ** It would seem R526 has not been removed ** (see attached below). Further investigation also shows six of the modules are N1700 and not N1702 modules. (see map below). It just gets better doesn’t it.

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N1702 Signals board: Red shows discrepancies

 

Module functionWhat should be present on the N1702 boardActually fitted
SOUNDU539U539
REF PROCU533U513
562KHzU532U512
CHR OSCU535U515
CHR AGCU534U514
SIG PREPU531U511
AGCU537U507
AMPU505U505
F-DETU506U506
SOUND FAFAU508U508

 

The investigation fog and mystery of this 1700 and its additional video module, is clearly starting to lift and reveal itself. As to why they also fitted the “Signal Splitter” module via CH8  I guess we’ll never really know what on earth their reasons behind all this were. To be honest I’m not going to try and unravel this mess!

My plan of action now is simple. I have the N1702 machine working albeit its really a N1700 now, I just need to test recording, adjust the friction drive and its finished. The first N1700 which is now missing its signals board will get the bare bones signals board that has the chroma fault, I will diagnose and fix that. This will give me two working machines. The N1702 franken-hybrid signals board will be put into stores and used as spares, after all over 60% of its modules are N1700.

The PCB’s in the modules do not have the ‘Uxxx’ designation stamped anywhere on their boards. There are some codes on the print side but these do not tie in with the U513 or U533 part codes as listed in the service manual, which is what I would have expected them to be.

I can however confirm the PCB in the U513 that came from the N1702 signals board matches identically with the other two U513 modules from the other two N1700 signals boards. All three are identical, I would say its a safe bet they are U513. For a little light relief from the technical and brain-hurt that other signals panel has inflicted, I decided to give the chassis its long needed dust down and degrease, then re-lubricate. It looks and operates now much better for it. Its actually in remarkable condition and along with the N1500, a fine example of the type of early VCR available at the start of the home recorder boom.

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Just a little update on the N1700’s progress.

I now have one machine working in what I would consider tip top condition. The belts have been changed, the rubber drive tyres and pinch roller have been treated with rubber-renew. The switches and guide posts all cleaned and the heads replaced and cleaned.

I’ve just taken delivery of a batch of 16 Philips VCR format tapes with another 15 arriving sometime next week. These tapes have come from a very well looked after collection and are in equally superb condition. They include many films, TV shows, light entertainment, news and adverts covering the period of 1978 – 1988. One tape has BBC test card F and music, many hours of fun watching whats on them. I randomly chose one which appears to be 1983, and LWT recording with all sorts but I watched the ITN news with a very young Carol Barnes  followed by the Clive James Show.

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The End

 

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