Philips N4450
 

A few days ago I bought a Philips N4450 (the complex one, 3 motors, 6 heads, autoreverse, etc). It's now in bits on the bench, and I have a few questions.

I have downloaded the English service manual, but I have also found a 2-part service manual in German. Part 2 of the latter seems to be the same as the common English service manual, part 1 looks to be theory-of-operation and contains things that are not in the English manual, like the circuit of the capstan motor. Does anyone have Part 1 of the service manual in English (I can't find it with Google)?

The user manual states that the machine will either stop at the end of the tape or can be set to record/play left-to-right, then autoreverse, do the same right-to-left and then stop. It goes on to say that if you want continuous operation (autoreverse at both ends of the tape) to see your dealer. I assume there was a modification to do this, does anyone know what it involved? I can't see anything about it in the English service manual

Re: Philips N4450
 

Hi Tony,
I bought the service manual in the early 70s and it did come in 2 parts. Since then I have downloaded every available manual for this machine. However Philips did produce yellow updates but these seem even rarer. Can't say that any one included info not available in any of the others. Unfortunately can't put my hands on the original to check.

I have also searched in vain for the continuous reversal mod for 40 years now, I really don't think it was ever actually published. I mentioned it some years ago on this forum and nobody ever commented.

Good luck with the machine, I really must get around to restoring mine! Oddly enough the original belts only lasted about 11 years. Perhaps that was good going for Philips.

See if I can find the manuals....

Peter

Re: Philips N4450
 

Hi Tony,
I have both parts of the N4450 manual, long hoarded but for which I've no use. There aren't any supplements with them, and at a glance I can't find any mention of mods, but if you PM your address I'll post them (2 x large letter!).
PS some things are in both manuals, but they are largely different.

Re: Philips N4450
 

Thanks for the offer of the manuals, I have PM'ed you my address.

As I said, I've found the 2 part manual in German, so have downloaded that too. I don't read German but can follow the circuit diagrams etc. It does sound like the manual you have in that some stuff is in both parts. Part 1 seems to be the theory of operation/description, part 2 is the repair information.

I wonder if the continuous-run mod ever existed. I was hoping it was just a 'move this wire' sort of thing, but it might well have been that there was going to be a replacement for the reset/reverse PCB. That would be trivial to fit if you had the PCB (so any dealer
could do it) but of course without the PCB or information on what it consisted of it's more work than I intend to do at this stage.

Re: Philips N4450
 

Yes it was and it worked but I no longer have any information on these. When I was working at Philips, I used to repair a lot of these....they were treated as something of a specialist item. We only had a few requests to modify for continuous auto reverse and I did at least one but it was over 40 years ago......

I really can't remember if it involved fitting an extra sensor or an additional board as well. I do remember it coming as a kit. I honestly don't know if the technical bods that worked in the audio development dept at Philips are still around or even if they would still remember anything about it. Chances are the parts to modify it would be unobtainable now anyway. It was one of those 'parts available on request only' so chances are it was very limited.

I do know someone (ex Philips) who has or had one of these and I'm fairly certain that it had been modified so I can try and get hold of him. No promises though.....

Re: Philips N4450
 

Looking at the circuit diagrams (again), I don't think it would need any more sensors or mechancial parts. There are already end-of-tape (foil detection) sensors on the deck, and that's all that's needed.

But I can't see any way to make the reset/autoreverse module act as a toggle flip-flop. So my guess is that the kit was (at least) a replacement for that plug-in board. I could probably work out something to do it, but most likely it would not be the offical way.

Other than the (bare) PCB, I would think the electronic components (on said PCB) were all standard (there's nothing custom in the control circuity at all).

Re: Philips N4450
 

Very interesting to hear that there was an official mod, maybe the full details will come to life after all. One problem I can see is that if modded then continuous reversal will be the default, it won't be possible to switch back to the original since the reverse switch is only two position. Not a problem until you are recording, then unless you are watching the tape will reverse and record over what has been recently recorded. I certainly made recordings where automatic reverse was used. Presumably this is why Philips chose to make reverse once, the default setting.

Tony: if I can find my manuals perhaps we can exchange notes after you receive those from AC/HL?

Peter

Re: Philips N4450
 

The 'Operating Instructions' (user manual) which I downloaded from HifiEngine state (section 1.11, page 11 of that .pdf file) :

'The reverse function is performed only at the end of the tape transport to the right. If continuous reversal is desired, please consult your dealer'

So that's why I assumed there was an official modification, at least planned.

And yes, continuous auto-reverse could be a right pain in record mode, and I guess that's why it wasn't the default. Pity they didn't have a 3 position 'reverse' switch (stop at tape end, reverse one, reverse continually), but I can't believe the modification involved changing all that.

You could, of course use an endless tape spool (the machine is documented as supporting those) if you can find one.

I am, of course happy to chat about this machine and any faults I find/cures. At the moment I am just looking over it and then will partially dismantle the mechanical side (nothing that will upset the head alignment!) to clean off the Evil Goo from the old belts...

Re: Philips N4450
 

Regarding potential endless play and record mode, in a machine such as this, I would have expected that it would fairly easy to design it so that the endless mode would only function in play but not in record mode. Or that there would be an electronic interlock so that record mode could not be entered if endless were selected.

Re: Philips N4450
 

I just found this old thread from 2008 and I commented on the continuous auto-reverse then:
http://www.vintage-radio.net/forum/s...0+auto+reverse

It seems there was an extra panel fitted but it became unavailable after 5 years.....

Re: Philips N4450
 

Sorry, I see that there were some very useful comments at the time. After 9 years I had forgotten.

Peter

Re: Philips N4450
 

I changed the belts in my N4515 for the first time last year - after 37 years of service.

Re: Philips N4450
 

The belts in mine (and in my N4510) have turned to evil goo. I am going to have to take a lot of the machine apart to clean things. It appears (without dismantling things yet) that the pulley on one of the reel motors is 'glued' to the chassis by the remains of one of the belts.

Re: Philips N4450
 

The service life of these machines (the time in which spare parts are guaranteed to be available) was 10 years......

Re: Philips N4450
 

Some more on this...

I dislike (intensely!) having parts I will have to repeatedly remove (like the rear cover and the deck chassis) held on by woodscrews. I'd only removed them twice and they started to feel loose. So I have spent a couple of days making and fitting tapped metal blocks for this.

I've also cleaned enough of the decayed belts off that the motors will turn freely by hand. So it is probably time to apply power and see how well the transport control system works. There are AC128s on the flip-flops (you may remember I had to replace those in my N4510) and a lot of lockfits which are also not know for reliabilty now. I will probably have to order some BC54x and BC55x transistors.

One other minor problem. It appears that there was once a trim strip glued to the plastic cover, about half way down where it hinges. That is missing. What did it look like?

Re: Philips N4450
 

It was just a black strip, but with a 'rough' texture...not sure what the finish is called.

Re: Philips N4450
 

Thanks. So similar to the rexine-type stuff that covers the case?

Re: Philips N4450
 

No it was spray-painted...come to think of it, probably similar to the finish of the head cover of the N4511.

Re: Philips N4450
 

After some digging, I found this (not very good) picture of a 4450 with cover. You can just see the black strip.

Re: Philips N4450
 

OK, thanks. I suspect I'll just use a strip of black plastic, if I fit anything there. But I want to sort out the mechanical and electronic faults first.