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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 9th Aug 2017, 9:12 am   #41
TonyDuell
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Default Re: Philips N4450

Yes, that lever is a standard feature, metioned in both the user and service manuals. As the capstan motor is electronically controlled, the timer is the only part that depends on mains frequency.

The lever moves the timer motor (which will happily run off 50Hz or 60Hz power, just at different speeds) so that its worm engages with different gears on the next shaft, thus giving different reduction ratios for the 2 mains frequencies.

I've now got the timer back together, and it seems to work properly when I turn things by hand. The contacts close when they should, the 'carry linkage' from minute to hours now snaps over nicely.

Now cleaning the contacts on the record relay, then will put all the boards back in the amplifier. Then take enough of the deck apart to get rid of the Evil Goo (I do not want it dripping on the amplifier again.)
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Old 10th Aug 2017, 8:00 pm   #42
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I've put some photos of the N4450 timer (dismantled) and the way the slider controls work in the same album that I gave the link for in post 21.
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Old 10th Aug 2017, 10:41 pm   #43
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Interesting to see the photos. After the time and dedication you are putting into the restoration you should have a machine at least as good as a new one! The heads look excellent. I have to say that the timer was not a facility I used more than once or twice. I was always at home when it was time to record the charts on a Sunday.

I have heard stories that the power supply was under specified and prone to failure. Certainly if you turn up the volume the take up spool will slow and then stop as the dc motor is drained of power. When I finally get around to mine I intend to replace the many incandescent bulbs by LEDs to reduce power consumption. When the original bulbs began to fail (40 years ago now) I had great trouble finding wire-ended replacements and had to make do with adapting MES bulbs.

I was very surprised and disappointed when I found that the "professional" slider controls were just modified rotary pots.

Always thought that the black finish was a bit austere so I added some wood veneer to the sides, better to fit into the domestic environment.

Plenty more stories about this great machine, will save them for another time.

Peter
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Old 11th Aug 2017, 4:06 am   #44
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The bulbs in mine are all good at the moment. Whether I would replace them with LEDs I don't know -- I don't like using components/technology (like white LEDs) that were no around when the machine was made.

I probably won't have too many problems with the PSU. I assume you were using normal 8 ohm speakers. If I use the power amplifiers at all, I will be using a pair of Philips MFB speakers (which I will start another thread on if I want to discuss them). These have an internal power amplifier, they can be driven off the outputs of another power amplifier (so can be used with this recorder) but have an input impedance of around 100 ohms in that mode. So they will only draw about a twelfth of the current of standard speakers.

I doubt I will ever use the timer other than testing it. But I like to have everything 'right' when I rebuild a machine.

The slider controls are curious. The simpler machines like the N4510 and N4418 use normal slider pots. I can't find this odd gearing in any other product. Whether the rotary potentiometers were more reliable I don't know. I assume there was a reason for not using slider pots in this machine. But I am glad they did, it's a lot easier to clean or repair a rotary pot. And I am not sure why you were disappointed in them, they work, there's not excessve backlash in the gearing.

I don't have a 'domestic environment', thankfully. 19" rack cabinets everywhere, 'scope in the kitchen, etc. So the black finish doesn't upset me. In any case I care more about what's inside the box than the trim.
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Old 13th Aug 2017, 1:43 pm   #45
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And today's lesson is 'Don't cut corners!'.

Having got the amplifier back together I tested it to find it was dead on one channel. An imput signal got as far as the monitor socket but no further. Testing signals on the amplifier motherboard suggests more potentiometer trouble. Possibly squirting propan-2-ol into them moved some muck onto the track/contacts.

So I have stripped the amplifier again and am cleaning and testing all the pots and switches (might as well do the latter while it's apart. Then I can look for real faults!.

The pots are not in good condition though. The wiper is a pair of contacts in parallel and in a couple of cases one (fortunately not both) has broken off. If I could get replacements I would fit them.

Also Philips left long bare ends on the wires after soldering them. I am cutting those off as a couple looked as though they might short to something. They can't have any electrical purpose.
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Old 13th Aug 2017, 3:04 pm   #46
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Default Re: Philips N4450

Quote:
Originally Posted by TonyDuell View Post

I probably won't have too many problems with the PSU.
The rectifiers used to fail on these with monotonous regularity. They are BY164 types and the official Philips mod was to fit one more in parallel with each so there were four in total (eight altogether). The advice was to drill 1/32" holes alongside the existing ones to take the extra BY164's. No more problems after that.

Quote:
Originally Posted by TonyDuell View Post
And today's lesson is 'Don't cut corners!'.

Having got the amplifier back together I tested it to find it was dead on one channel. An imput signal got as far as the monitor socket but no further. Testing signals on the amplifier motherboard suggests more potentiometer trouble.
I seem to recall that the 'A-B switch was troublesome. Back in the day, I just used to replace them. Now you may have to remove the slider and use switch cleaner sparingly. If you remove the slider, note that one end is tapered. Insert the slider tapered end first....that taper opens the internal contacts otherwise the contacts will be wrecked.
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Old 13th Aug 2017, 4:54 pm   #47
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Yes, I noticed the tapered end on the switch slider.

Today I took the amplifier chassis apart again, dismantled all the pots and cleaned them Then took all the switch sliders out (one at time!), including the ones on the equalisation PCB (the speed control switch) and cleaned those. Put it all back together, and...

.. The amplifier now seems to work properly on both channels. So it was just bad contacts somewhere. I suspect I can't get much more done on this machine until I get a belt kit (they are available on Ebay).
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Old 13th Aug 2017, 5:01 pm   #48
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I also had trouble with the A-B switch within quite a short space of time after buying it. I don't know if switch cleaner will fix the problem, I just don't think the switch is up to the job, it got used a lot.

I also had problems with the tracks lifting very easily on the board that contains the A-B switch when soldering.

One interesting little issue on the earlier machines is oscillation of the sprung tape guides during playback/record. Can get violent enough to affect the sound quality. Philips fixed this by attaching a damping mechanism to each guide consisting of two disks with a viscous liquid between. Sadly my machine did not have them.....

I have to say that in nine years of hard use very little went wrong.

Peter
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Old 13th Aug 2017, 5:13 pm   #49
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The A-B switch is on the amplifier motherboard. In fact the only one of these slide switches that is is the speed selector.

I've had problems with tracks lifting on the flip-flop boards in this machine and the N4510 when I replaced all the AC128s. I now take things very carefully and am prepared to add bodge-wires... That is more of a problem with the switches which rely on the soldered joints to the tracks as a mechanical fixing.

To clean the switches I removed the slider and wiped it on both sides wth propan-2-ol. Then sprayed that into the housing, put the slider in and worked it backwards and forwards. Took the slider out and cleaned it again. Then put it all back together. I don't know if it will last, but it has cured some problems.

I dont think I have the dampers for the tape guides either.

As regards the rectifier, is there any good reason not to fit a higher-current one if it fails? I can't see it would be a problem.
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Old 13th Aug 2017, 5:27 pm   #50
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Hope the switch continues to work for you.
I've heard that suggestion about the rectifiers before, can't see that replacing with better spec' diodes isn't a better idea?
To be honest I was hoping that Doffery might join in the discussion with the benefit of his huge experience with recorders. I know he has experience of the N4450.

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Old 13th Aug 2017, 8:20 pm   #51
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I see no reason why a higher rating bridge rec cannot be fitted. It was probably only for ease of fitting that the extra BY164's were suggested. If a bigger rectifier(s) were fitted, it may have been a major job. As it stood, the mods took about 15 - 20 minutes to implement.

I'm quite sure suitable modern recs can be fitted...even separate diodes wired in bridge mode. There's no restriction on 'approved parts only' being fitted nowadays!
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Old 19th Aug 2017, 3:00 pm   #52
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The latest on this project: I've now got a new belt kit (4 belts) and thus the next job is to dismantle more of the deck and then fit them. There's sticky grease on some of the brake linkages that needs cleaning out, for example.

Electronically it still seems to work, the cleaning of the pots and switches has cured the problems.

I've noticed what others have said about marginal power supplies. When testing the amplifier, the switch illumination bulbs do go dimmer when I turn the volume up into a loudspeaker load. But I probably won't be using normal speakers with it, as I mentioned I have a pair of Philips 22RH541s to use. Those have an input resistance of around 100 ohms, so shouldn't load the amplifier as much.
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Old 19th Aug 2017, 5:44 pm   #53
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I seem to recall that there are brushes that run against the capstan drive belt (the big one between the two flywheels). They will probably need cleaning as well or replacements fabricated.
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Old 19th Aug 2017, 5:52 pm   #54
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There are those brushes ('belt dampers' in the service manual) for the capstan belt and each reel belt. I have already removed them and cleaned them. They weren't too bad, looks like the belt fell away from them and ended up on the amplifier motherboard, etc.
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Old 17th Oct 2017, 4:07 pm   #55
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I've gone back to this machine after a brief pause to do other work...

Spent the afternoon stripping and cleaning all the mechanism, the brakes, pinch roller brackets, etc. All that is back together apart from one retaining clip that broke up. See my thread in 'bits wanted' for more details.

Now the original mains lead is somewhat hardened with age, so I will replace it. The original is 2 core, inside the machine they go to a little tagstrip near the strain relief bush (which oddly is fitted from inside the chassis, it works better that way, but is not as neat. I can't believe anyone has taken it out and turned it round, so I'll keep it like that).

But on the same bracket is an unused screw labelled with the 'chassis earth' symbol. My first thought is that I could fit a 3 core lead and connect the earth continuity conductor there. There is a lot of exposed metalwork on the machine after all. The downsides to so doing are (a) it's not original; (b) I would be liable for any problems (but I am going to be the only person to use it) and (c) possibility of hum from earth loops when I connect it to other equipment.

Thoughts? Leave it as it is or fit 3 core?
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Old 17th Oct 2017, 9:25 pm   #56
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Default Re: Philips N4450

Make a quick lash-up first with 3-core cable, just for testing. If you get hum problems, and if it's reasonably easy to do so, try swapping the connections to the power transformer primary.

However, unless you get a tingle from the chassis when the signal cable is disconnected, it's probably well-enough insulated to be safe with a 2-core lead.
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Old 18th Oct 2017, 4:16 am   #57
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I have run the machine with the original (2 core) cable and didn't get any tingles, nor did the RCD in the consumer unit here trip. There was also no significant leakage from the mains wiring to chassis using my insulation tester (OK, I have never had it calibrated but I have checked it against a few resistors, and it does seem to give sensible results. It tests at 1000V which should be OK for mains)

The problem is that the N4450 has an internal audio power amplifier and also line level outputs. It could be used as the central part of an audio system, driving the speakers directly, and fed from other units (also normally with 2 core mains leads), or it could be linked to another amplifier (which would normally be earthed with a 3 core lead). In the former case it would be a reasonable to have a 3 core lead on the N4450, in the latter not.

My feeling (after a night's thought) is to fit the 2 core cable as it was originally. It's what the manual shows, it's what Philips considered to be right.
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Old 18th Oct 2017, 3:48 pm   #58
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Another thought I had :

The mechanical design of the mains input means that the mains cable is fed through a fairly large hole in the bottom cover. This hole is large enough for a continental mains plug but not for a BS1363 one. So to avoid having the cover hanging on the cable when I remove it for servicing/repairs (and driving me (in)sane)), I fitted one of those 3 pin in-line flex connectors. The plug of that will easily fit through the hole in the cover. So I can unplug it and remove the cover.

Now, I could wire the plug part of the connector to the machine with 3 core cable. And then either make up 2 mains leads (one 2 core, one 3 core) to use as appropriate. Or a 3 core mains lead and a short plug-to-socket cable with 2 core cable to be put in if I need to remove the earth for any reason.
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Old 18th Oct 2017, 6:41 pm   #59
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Default Re: Philips N4450

For what it’s worth, when I was using my N4450 regularly it was connected to a Goodmans 1-10 which had a three core cable and thus earthed through the mains. I have a vague feeling that when the recorder was not connected to another piece of equipment there was that tingling feeling when brushing the back of a finger against the metalwork. This disappeared when connected to the 1-10.
I would agree with Philips and retain the two core cable.

Oddly for the next generation of Philips’ machines (N4504/6) two core cable was retained but the figure-of-eight connector was used. I wonder what criteria manufacturers use to determine whether a removable or captive mains cable is fitted?

Peter
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Old 18th Oct 2017, 7:02 pm   #60
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I've not done anything yet, but my current (!) thought is to fit a 3 core cable. There is a clearly marked earth screw inside the machine (not on the outside where it might have been for earthing, say, a pickup arm cable). As I mentioned I don't _have_ to use the earth wire externally.

Thinking some more, I feel that the common method of avoiding earth loops by using the audio cable screen as the earth continuity conductor is plain wrong. There has to be a better way to do it! I am happier if things -- particularly things with a lot of exposed metalwork as here -- are earthed.
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