Playing N1500 cassettes on an N1700 ??

[rbm1973]

I have an N1700 I am restoring, and 2 more I have bought.
My question is, has anyone or is there any modification to the N1700 that will allow it to play N1500 recordings, as they just show noise and slow sound. May not be possible I know, but as I will have three of them I wouldn't mind modifying one until I can find an N1500

[DangerMan]

N1700 video heads are not compatible with N1500 recordings as they have azimuth offset between heads which the 1500 does not.

[rbm1973]

Oh well I will be looking on eBay or here for another 1500

[Nicklyons2]

What DangerMan says is quite correct but that's not all; the control track is in a different place on the tape so, even if you fitted a 1500 head in a 1700 and persuaded the capstan to run at the correct speed (about 2.1X) it wouldn't read the control track so would never lock up anyway.

Try and get N1502s or, even better, N1512s (a 1502 with audio & video in/out fitted as std). I would avoid the poisonous mechanics of the N1500/1501/1520. The 1502/1512 look very similar to the 1700 but have a smaller LED clock.

[cheerfulcharlie]

The actual head drum and heads are the same on both 1500 and 1700 so you can use either in either machine,electronically they are read different of course.
You change the pulley (between 1500 and 1700) on the capstan motor to get the speed and sound correct but the video has effectively blank spaces between frames on the 1500 and frames are butted together on the 1700 with the next frame out of phase to stop interference- crudely put -sort of like that.

[DangerMan]

N1500 was to Philips VCR standard, whereas N1700 was VCR-LP. The latter had lower tape speed and therefore didn't have any naturally occurring guard tracks so it relied on slant azimuth to work.
The heads look similar but they are not the same.
Wikipedia has a decent description of the differences between the systems.
It's the slant azimuth (and control head) differences that are the killer if you want to play N1500 tapes in a 1700.... The rest is just very hard work!
A N1700 head disc will work in an N1500... It just won't play N1500 tapes, just its own non standard ones.

Pete

PS N1702 heads are the same as N1700, and N1502 same as N1500

[Nicklyons2]

Originally Posted by cheerfulcharlie

The actual head drum and heads are the same on both 1500 and 1700 so you can use either in either machine,electronically they are read different of course.
You change the pulley (between 1500 and 1700) on the capstan motor to get the speed and sound correct but the video has effectively blank spaces between frames on the 1500 and frames are butted together on the 1700 with the next frame out of phase to stop interference- crudely put -sort of like that.

This is wrong in almost every aspect: the head drums are of similar construction and, therefore, superficially look the same. They will not play each others recordings due to slant azimuth being applied on the N1700 VCR-LP system.

Electronically the machines are, in fact almost identical, (N1502/N1700) - it being the head layout which is the defining difference between the systems.

Once again even the control track head layout is physically different. The original N1500 format has two equal quality audio tracks allocated to it with a very narrow control track. This narrow control track was problematic, particularly with a format which had a moving Audio/Control head; slight misalignment would give rise to loss of servo control. Further the second audio track was only used on the 'editing' machine N1520, the other 'off air tuner' versions only used one track. The N1700 series used the area of the second audio track as the control track, giving a wider and more reliable 'pick-up'.

The only correct point made in the post above is the fact that the VCR-LP format allows adjacent video tracks to directly abutt each other with no guard band precisely because the different azimuth between heads prevents one head from reading the other's information. On the N1500 version both video heads are the same and can read each others tracks; the only way to prevent this was to separate them with the 'guard band'. This was, of course, wasteful on tape area and is why Beta, VHS and VCR-LP all adopted slant azimuth.

[P.Pilcher]

In days of yore there was a mod to enable the recording time of the N1500 to be virtually doubled by fitting N1700 heads and doing some mechanical mods to halve the tape speed. Obviously older N1500 recordings could then not be replayed, nor could recordings made on an N1700 be played on such machine either. Colour rendition was also a bit of a problem as well but the system did enable enthusiastic N1500 owners to get a longer recording time. Not long after this, Phillips brought out their new system with special cassettes which could be turned over, shortly to be followed by VHS and Betamax units so the price of N1700 units fell through the floor thus most N1500 units got scrapped. The enthusiasm of Phillips in those days to bring out successive incompatible models was a lesson well learned by the makers of VHS and Betamax machines. A VHS tape recorded on the earliest production model can still be replayed on the last machines produced before DVD and hard drive units took over.

P.P.

[cheerfulcharlie]

Originally Posted by Nicklyons2

This is wrong in almost every aspect: the head drums are of similar construction and, therefore, superficially look the same. They will not play each others recordings due to slant azimuth being applied on the N1700 VCR-LP system.

I never said that it would allow you to play both recording types without electronic modifications - I said you could interchange the head drum. but I'll tell you what, you get yourself an N1500 and N1700 and swap heads between them - and then come back and tell me I am wrong.

[greg_simons]

Had an n1500 and n1700 machine, there was also a mod you could do to the n1500 that would improve the playback definition slightly by getting the picture sharpening module for the n1700 and inserting it in the video playback chain, it really worked well, I think I got the idea from the television magazine of the time.

[Jon_G4MDC]

Is there still interest in these?
Not to break forum rules...should I be posting something elsewhere?

Sorry I can't comment on the heads issue except I am sure I once rescued an N1700 using a V.head donation from a 1500 - what model? I dunno. Possibly a modified one for 2x play time - maybe it had 17k heads fitted before?

[Nicklyons2]

Originally Posted by cheerfulcharlie

I never said that it would allow you to play both recording types without electronic modifications - I said you could interchange the head drum. but I'll tell you what, you get yourself an N1500 and N1700 and swap heads between them - and then come back and tell me I am wrong.

Yes but the OP wanted to know if, by changing the head drum he could play N1500 tapes on a modified N1700 - he can't! he would need to change the ACE head assembly as well because the N1700 can't 'see' the 1500's control track.

The bodge to which you refer will work but creates a non-std machine which will replay it's own recordings but not those of standard production machines. I could modify a VHS machine to make the head rotate anticlockwise instead of clockwise and it would record and play to it's own standard but no other machine could replay it - a working machine but pointlessly non-standard.

[cheerfulcharlie]

I never said anything about bodging anything up, I simply referred to what could be done with the tape transport and sound, with a simple explanation on why the video tracks are different ... if rbm1973 fancies experimenting with all this.
As for the ACE assembly being different -really? oh well you know eh?

[AC/HL]

Can we agree to disagree please chaps, we don't want to have to close the thread prematurely.

[whiskas]

On the subject of these machines chaps, a question for those who have experience working on them if that's OK..

I saw above a comment that the N1500 mechanics are 'poisonous' - would that mean that the N1500/1501/N1520 are a nightmare to work on? What are the pitfalls (besides AC motors) of those models vs the later N1502?
I'm hoping to get an N15xx machine soon - is the N1502 much easier to work on, more reliable etc?

I'd appreciate your advice, experiences and knowledge, chaps - thank you.

Whiskas

[Nicklyons2]

As you say the ac motors (with their eddy-current braking) appears a bit crude compared to later DC servos, however, in the 'obsolete world', they do have an advantage in that they can be more easily repaired or substituted than more specialist DC servo motors. On the minus side the 1500/01/20 use the ghastly 'fishing line' and cog/cam assembly to rotate the head drum assembly - a nightmare! and beware - the threader motor was supplied in 2 version CW and CCW rotations so you had to reverse the wiring (preferably before it drove the mech bacwards and screwed it all up!). The circuit boards were more accessible in the 1502s, easier to work on. Not that it will be of much interest now, but the timer in the 1502s was, of course electronic and with a battery back-up as opposed to a cooker timer with a mains sync movement.

For sheer 'looks' the N1501 is, IMHO the best; but if I were ordering one up for real use and N1512 - the later 1502 type but with full video (CVBS) ins and outs.