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1974 Philips N1500: Finally!  

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crustytv
(@crustytv)
Vrat Founder Admin

An offline chat with Rich (sideband) has raised a point which might be relevant. 

Rich said

"Looking at your dismembered switch when you had straightened out the contacts I noticed that some of the contacts were the reverse of others…. This means that the contacts have to be assembled in the right order. Silly question but are you sure that all the contacts are in the right place?"

I had started to wonder about the contacts, when opening SK402 it was a real struggle and all but the first 3 fell out. My assumption was to mount all contacts whose orientation was not known as shown in the photo below.  To be honest I think that's where I have gone wrong.

?

Note 1: The numbering of SK402 contacts in the photo 1-18, were for my notes and convenience. On the cct diagram they are 51-70. I have placed the real contact numbering in brackets on the photo.

Note 2: Ignore the black loop wire between 11 & 15, I rectified that mistake before reassembly as it was meant to be from pin 11 -17.

What do we know about SK402?

There are nine pairs in total

I know for certain contact pairs 1/2 & 3/4 are correct due to the first three being fixed and I matched the fourth to the other half of the third.

I'm equally confident pairs 11/12 & 17/18 are also now correct.

That leaves just five pairs

Of those five pairs four are of the up variety and one down.

A bit like the old Mastermind game, I have three correct and two incorrect.

Here are the known's. There are four pairs of "UP" and just one single set of "down". This means I have just two pair's incorrectly aligned, as to which position should have the down, I do not know. 

The pairs:-

  • 5/6 (55/56)
  • 7/8 (57/58)
  • 9/10 (59/60)
  • 13/14 (65/66)
  • 15/16 (67/68)

The fault condition is the clue to solving this puzzle and one which I've thus far failed to solve. The clue being "no la2 illumination and thus no signal". If I could suss which pair of those five pairs is related or handles that, then it should be a simple case of swapping it over with the other pair and that should fix it. So close yet so far!

Below is how the entire switch is currently set in SK402.

  • 1/2 (51/52): contact down (known to be correct)
  • 3/4 (53/54): contact up (known to be correct)
  • 5/6 (55/56): contact down 
  • 7/8 (57/58): contact up
  • 9/10 (59/60): contact up
  • 11/12 (61/62): contact down (100% certain this to be correct)
  • 13/14 (65/66): contact up
  • 15/16 (67/68): contact up
  • 17/18 (69/70): contact down (100% certain this to be correct)
sk402map

I’m stuffed at present because I cannot figure out which pair from SK402 51-70 on the circuit diagram B , that could be the cause "no la2 illumination/no signal". As a result I think the only way out of this pickle is help identifying the pair or a new SK402 as the contacts will be intact and of the correct orientation.

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Posted : 28/01/2019 9:58 am
Doz
 Doz
(@doz)
Noble V-Ratter Registered

Would it be possible to ditch the switch totally, and operate a bunch of small relays with a microswitch operated by the lever? No mean feat in itself, but I've been tempted with this solution in the past to replace a duff system switch.

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Posted : 28/01/2019 10:37 am
Doz
 Doz
(@doz)
Noble V-Ratter Registered

Oh, by the way. I'm back and hooked up my 1500 on the weekend with the intent of making a test cassette... It's got an intermittent sync problem again. What's the betting ...

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Posted : 28/01/2019 10:38 am
Terry
(@terrykc)
Famed V-Ratter Rest in Peace
Posted by: crustytv

Though I really wish I had all of the manual in English, I have some but certain pages are missing.

If you let me know which pages or parts of pages you need, I might be able to help.

When all else fails, read the instructions

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Posted : 28/01/2019 11:45 am
TVJON74
(@tvjon74)
Honorable V-Ratter Registered
Posted by: Doz

Would it be possible to ditch the switch totally, and operate a bunch of small relays with a microswitch operated by the lever? No mean feat in itself, but I've been tempted with this solution in the past to replace a duff system switch.

I suggested this last night. I think it is definitely worth looking at. I don't think it would be that difficult to implement, but will need a bit of time to work out the wiring etc. Looks like SK401 would need 8 single pole contacts for play mode and 10 single pole contacts for record mode. SK402 would need 4 single pole contacts for stop mode and 7 single pole contacts for forward mode. The relay count could be reduced by careful choosing of relay contact configurations instead of using single pole relays.

Jon
BVWS Member

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Posted : 28/01/2019 12:41 pm
crustytv
(@crustytv)
Vrat Founder Admin

Guys I don't think I need to do that, I'm not that far from solving the problem.

It is my belief that there is just one pair of contacts in SK402 (contacts 51-70) that are incorrectly aligned, though I except I could be wrong. If you read my long post (sorry for it being so verbose) at the top of this page, it explains my thoughts in detail and with evidence to support it.

If anyone can help me track down from the cct B, which pair of the identified five is associated with the "no signal la2 illumination", I reckon I will have this fault solved.

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Posted : 28/01/2019 12:46 pm
crustytv
(@crustytv)
Vrat Founder Admin

I've now located all the contacts for SK402 on circuit diagram B. Contact pairs 51/52, 53/54, 61/62 & 69/70 are I believe, 100% correctly aligned.

To view maximum size image click on image to launch viewer. Then right click image and choose open image in new tab. You will now have max size.

cctbsk402

As per my notes (see first post on this page) suspicion falls upon 55/56, 57/58, 59/60, 65/66, 67/68. Three pairs are correctly aligned, two pairs are incorrectly aligned to cause the no signal condition. Just need to figure which and this is where I really need help.

Edit: Perhaps someone with a N1500 could look down their own SK402 and  report here the contact order with regards to up down alignment of 55 thru 70 as to be honest i'm at a loss and not even sure of anything now.

sk402oout

SK401 & Sk402 need replacing as to be frank they were in a sorry state to start with. This repair pause now until I can find another scrap player as I need spares especially as I want to actively use this machine in my display room.

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Posted : 28/01/2019 3:42 pm
Hurty
(@hurty)
Busy V-Ratter Registered

Hi All, Just had a look at your N1500 rebuild Chris. When you get the replacement switches DO NOT PULL THE SLIDER OUT! If you do and re-insert the slider then most likely the spring contacts will get bent on re-inserting. A small amount of contact cleaner if needed but doubt you will need to use any. On fixing the servos which rarely fail, disconnect the eddy current break coil first and see if the sampling pulse on the ramp now goes the other way. If it is still too slow then you will be looking for a mechanical problem. Worked on these a few times in the late 70's Cleaning Philips belt goo I use Cif, gets the stuff off your fingers too.

Adrian 

 

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Posted : 08/02/2019 9:16 pm
sideband
(@sideband)
Famed V-Ratter Moderator
Posted by: Hurty

Hi All, Just had a look at your N1500 rebuild Chris. When you get the replacement switches DO NOT PULL THE SLIDER OUT! If you do and re-insert the slider then most likely the spring contacts will get bent on re-inserting.

Adrian 

Actually you should be able to pull the slider out and re-insert without any damage....that is assuming of course that the slider itself isn't damaged. When I worked for Philips, we did this all the time and I doubt that there were many that didn't reassemble OK. The leading edge of the slider is chamfered and pushes the contacts open as it is re-inserted. 

 

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Posted : 08/02/2019 10:33 pm
crustytv
(@crustytv)
Vrat Founder Admin

They say say things turn up in three's and that sentiment is proved here to be very true.

For those of you that had been following the N1500 repair, you remember it came to a grinding halt due to a complete lack of a replacement for the failed SK402 play switch. As a matter of fact I was in a very precarious position all round should the need arise for any other N1500 specific spares. The reality being I had none whatsoever and as for a set of spare heads or that scary head drum lacing cord and cog? Well that would be a wish too far.

However .....

Occurrence One; a couple of weeks ago in stepped Adrian (Hurty) with a spare used panel 45, complete with SK401 and SK402. 

parts 7

Thanks to Adrian  ? 


Occurrence Two; 1 week later, Jon (TVJon74) has an ex TV engineer mate who used to service N1500's for his bread & butter and has a stock of N1500 NOS spares. He offers to sell me a brand new pair of SK4xx switches. When they arrive unfortunately SK401's body was broken 1cm from the end, it was not due to shipping as when the chap checked his batch of NOS switches to offer a replacement, found they were all the same. Looks like age related plastic degradation. I was refunded without question the cost of that switch. I used Gorilla glue to join the body and hopefully once soldered in place will be OK but its always a worry as these switches are so very vulnerable to breakage due to plastic to metal mechanics. Having a couple extra in stock even if old now gives me a warm feeling as this N1500 is going to be put back into active service. Which moves us on rather nicely to the final event that will allow that frequent use happen.

parts 3
parts 4
parts 5
parts 6

Thanks to Jon and Jon's Mate  ?


Occurrence Three; 1 further week later, two N1500's turn up on e-bay one with a totally woodworm ridden cabinet. The other in good condition. I placed a bid on the woodworm unit and won it, today it turned up. The worm had eaten the innards, leaving  the cabinet with virtually no structural strength whatsoever. With very little effort the wood was simply snapped into pieces by hand, the bugs having chomped their way through it all. The pieces now in the refuse bin ready for collection tomorrow.

side1
side2
side3
parts 2

The chassis is complete and offers me countless spares to maintain my good condition N1500 for the next few years and what's more a spare set of heads. Also not forgetting the even rarer and super fragile head lacing cord, springs and motor gear cog. All manner of other N1500 specific parts that you need to maintain and service these wonderful old machines. 

parts 1

Thanks to e-bay for providing a constant source of useful spares for us to bid on ? 


There we go, just when you think the game is all over! So expect the N1500 back up on the bench shortly and I will be hopefully filming it on the new whizz-bang camcorder as discussed over on "The Wall"... Watch this space ..

 

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Posted : 19/02/2019 12:56 pm
sideband
(@sideband)
Famed V-Ratter Moderator

Are you sure that switch was actually broken? Looking at the panel in the first picture, the long switch looks like it's the same with a separate 1cm section at the end.....

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Posted : 19/02/2019 1:41 pm
crustytv
(@crustytv)
Vrat Founder Admin

I hadn't considered that as the only switch I had removed thus far was the shorter SK402. I see what you mean and the break is the same on mine, though I will say it does look more like a break than a manufactured section, the edges are by no means straight.

Now if it was by design, why on earth would that last section be separate, the pin spacing is not different. Even if they were surely they would have designed that fact in unless these switches are dual purpose on some other device, again doubtful as they look unique with the slider and locknut at the end.

I'm still of a mind its a flaw in the manufacturing or the resin/mould, happy to be told otherwise. If it is by design then I need to send the refund back I've been given. I would have thought though if this was bread & butter work for the engineer he might have remembered they were that way by design. To be fair though its probably 40 years since he last worked on one and how many did he have to change back in the day.

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Posted : 19/02/2019 2:32 pm
sideband
(@sideband)
Famed V-Ratter Moderator

Well I do remember seeing these sort of switches in loads of Philips products and there were some that had long sliders but with two 'bodies' and one in particular I remember in a reel to reel machine had the two bodies separated by about a centimeter. The slider however was continuous.....

I suppose if you think about it, it doesn't really matter if the end is separate...once it's soldered into place it's not going to go anywhere and will likely work perfectly. As to why a switch might be made like that.....well maybe the fixed contact part had been used in something else but extra contacts were required for use in this circuit so the extra bit was added with the longer slider, rather than manufacturing a complete new switch.....

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Posted : 19/02/2019 9:33 pm
crustytv liked
freya
(@freya)
Noble V-Ratter Registered

I think the switch body joint has failed because of poor dielectric welding, its an identical length to the next section if you look at the picture. 

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Posted : 19/02/2019 10:12 pm
crustytv liked
crustytv
(@crustytv)
Vrat Founder Admin

I've discovered something interesting with regards to the drum lacing cord configuration on a N1500 series VCR. It would appear the drum lacing is significantly different between my two machines.

The original N1500 which I've been repairing, is an earlier version  Serial No.86880 with a fixed mains supply cord. The latest machine is Serial No.87800 with a removable mains supply cord. 

I wanted to check the state of the drum lacing cord and motor transfer cog on this latest acquisition as they looked in better condition than the one in my machine.  Also it was an opportunity to study how it was strung with worry about it being the machine I want to fix.

When I removed the micro-switch plate above the motor drive transfer cog, it revealed the lacing cord disappearing off to the right then down through the chassis. I thought, "hang on a minute, that's not the same". When I checked on the underside the lacing cord after passing through the chassis, terminates onto two different sized springs that are anchored to a bracket. Checking the original machine confirms this is different. 

Now I'm aware the drum lacing cord idea was one of the Achilles heel of the N1500, I wonder if this was one of Philips attempts at improving upon the original design. The photos below show the original and then the later machine with the difference highlighted with a yellow arrow.

Quite fascinating and something I was unaware of. I wonder if it is covered in the Philips N1500 service manual, in subsequent modification supplements which are not present in the Dutch scanned version.

 

My original earlier N1500

orig15 1
orig15k 2

 

The newly acquired spares N1500

new15k 3
new15k 4
new15k 1
new15k 2

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Posted : 19/02/2019 10:54 pm
Niall
(@niall)
Reputable V-Ratter Registered
Posted by: freya

I think the switch body joint has failed because of poor dielectric welding, its an identical length to the next section if you look at the picture. 

Sorry, but I have to point out that this post appears in "Latest Posts" unfortunately truncated to "I think the switch body joint has failed because of poo"

Certainly made me open the thread to see what it really said!

🙂

 

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Posted : 20/02/2019 9:39 am
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