1978 Philips N1702: Another 70's VCR Repair  

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crustytv
(@crustytv)
Vrat Founder Admin

The third 70's VCR makes it to the bench for evaluation, this time in the form of an N1702.

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Posted : 09/02/2019 7:16 pm Red_to_Black liked
sideband
(@sideband)
Famed Member Moderator

I would suggest you try cleaning the audio head first. Unless it is VERY worn, that sound is typical of 'crud' on the head. It might have been twiddled of course.....!

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Posted : 09/02/2019 9:58 pm Red_to_Black liked
crustytv
(@crustytv)
Vrat Founder Admin

Spot on Rich 👍 after filming and posting the above video, I did indeed check the audio head and the full erase heads, both were discovered to be crud infested (see photo's below).I've since cleaned them up and audio is now fully restored, clear, bright and plenty of it.

No point in filming the improvement today, I will save that for part two of the next N1702 instalment, which will investigate the remaining faults. The main one being the video jittering that's going on. Well that's the plan of action for tomorrow now.

n1702audio
n1702erase

 

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Posted : 09/02/2019 10:05 pm
Jayceebee
(@jayceebee)
Prominent Member Registered

Regarding the video jitter are you absolutely certain this is not a problem with the TX9? The reason I ask is that the TX9 & 10 could suffer a common problem of no line sync, the usual cause was a leaky 1N4148 diode on the remote control/tuning board. It's purpose was to feed a voltage to one of the pins of the TDA9503 when the AV channel usually 6 or 8 was selected for video playback, this tightened up the timing eliminating the effect we called flag waving. As a short cut some field engineers would simply snip it out if the customer didn't posses a VCR, of course when they did eventually obtained one a service call came in for jitter on playback, just a thought.

John.

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Posted : 09/02/2019 11:05 pm Red_to_Black liked
crustytv
(@crustytv)
Vrat Founder Admin
Posted by: Jayceebee

Regarding the video jitter are you absolutely certain this is not a problem with the TX9? The reason I ask is that the TX9 & 10 could suffer a common problem of no line sync, the usual cause was a leaky 1N4148 diode on the remote control/tuning board. 

Absolutely certain John as its does not happen on the N1700, only with the N1702. I proved this when I swapped over the Servo PCB.

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Posted : 09/02/2019 11:10 pm
crustytv
(@crustytv)
Vrat Founder Admin

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.

n1702 a
n1702 b

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! 

n1702 c

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.

n1702 d

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.

 

 

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Posted : 10/02/2019 12:26 am
sideband
(@sideband)
Famed Member Moderator

I'm not absolutely certain since I never worked on any of these early machines but somewhere in the back of my mind there were some changes made for video editing (BBC) involving the fitting of video out and audio out sockets (I don't think the original 1700 machine had A/V out). Just thinking that might account for EE differences. 

I may be completely off track on this so take it all with a pinch of salt. I could be getting mixed up with the N1520 which WAS a special edit machine.

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Posted : 10/02/2019 8:09 am
crustytv
(@crustytv)
Vrat Founder Admin

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.

mods

p.s.
The N1700/xx would seem to have been designed to take this additional module as the case has a specific slot, lock tabs and hole blanks for the module, this verified by the other player which does not have the module but does have the aforementioned capabilities.

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Posted : 10/02/2019 10:43 am
Jayceebee
(@jayceebee)
Prominent Member Registered

I would suspect that the possibility of external video/audio in are switched in when P8 is selected hence the extra wires but whether this is by a switch on one of the external sockets or detection of a valid baseband video signal I wouldn't know. According to Mikey405's old technology website suggests the N1700/1702 differences are a four digit counter, a nine day timer and a test signal generator. I wonder if there is a switch at the rear to activate the test signal as with early VHS machines or knowing Philips could it be active when the CPU  sees no valid video signal or AFC?

More questions than answers I'm afraid.

John.

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Posted : 10/02/2019 10:57 am
crustytv
(@crustytv)
Vrat Founder Admin

Hi John,

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).

vidmod

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.

 

Edit:
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.

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Posted : 10/02/2019 11:40 am
Jayceebee
(@jayceebee)
Prominent Member Registered
Posted by: crustytv

Edit:
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. 

You read my thoughts 👍 

You may need to plug something into the DIN socket to make P8 switch from tuner to external, just an unattached cable or plug would suffice.

John.

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Posted : 10/02/2019 12:05 pm
Red_to_Black
(@red_to_black)
Noble Member Registered

In reply to JC

re: test signal and Philips, on Philips Echo deck VHS machines pressing play without a tape present/being loaded this then generated the test signal (typical Philips quirkiness), on the N17XX I have no idea though.

Ps. I also think this worked on some of the earlier Charlie deck VHS machines too

"This is my multimeter. There are many others like it, but this one is mine. My multimeter is my best friend. It is my life. I must master it as I must master my life. Without me, my multimeter is useless. Without my multimeter, I am useless."

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Posted : 10/02/2019 12:34 pm
Jayceebee
(@jayceebee)
Prominent Member Registered

Quite right Baz, you've jogged my memory on the Echo deck but I only ever came across one model, the VR6462. Pressing play without a cassette would cause the carriage to drop then the machine would FF then REW a few seconds before going into playback with a vertical white bar which took up half the screen if I remember correctly.

John.

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Posted : 10/02/2019 12:45 pm Red_to_Black liked
Red_to_Black
(@red_to_black)
Noble Member Registered

On the Echo deck machines at least the test signal logic relied on the cassette in switch (a micro switch on the FL carriage) , I know this because I once had a fault with a machine where the wire to the switch had broken and when playing a tape you got only the b&w test signal displayed on screen with the sound from the tape.

The later Charlie deck machines were slightly different in this aspect as they relied on the three cod (code) switches to determine the various logic states of the deck.

I cannot recall how the V2000 or earlier machines behaved, I had nothing to do with the N1500 machines and only ever had less than a handful of N17XX machines in the whole of my servicing career, it would be interesting to know if Philips used a test signal in a similar way on the earlier format machines.

"This is my multimeter. There are many others like it, but this one is mine. My multimeter is my best friend. It is my life. I must master it as I must master my life. Without me, my multimeter is useless. Without my multimeter, I am useless."

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Posted : 10/02/2019 2:33 pm
sideband
(@sideband)
Famed Member Moderator

A suggestion Chris...have a look in late copies of CES Service Tips (as per library) and see if anything is listed.....and to answer you question about modifications and butchering print.....yes it could happen although usually kept to a minimum. BBC engineers had their own ideas in some cases and it wasn't unknown for Philips to make modules available for them only so that they could use machines for functions beyond their domestic requirements.  

 

 

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Posted : 10/02/2019 6:29 pm crustytv liked
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