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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 6th Oct 2019, 9:31 pm   #61
TonyDuell
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Default Re: Philips N4450 Reel to Reel Tape Player

Do you get the same loss of signal level (and quality?) in both directions? If not then it points to a head (or head switch, the switch on the PCB that the heads connect to, that is operated by the pinch roller levers) problem. If the problem is the same in both directions then while it could be that both heads are giving problems it is more likely to be an electronic fault on the amplifier chassis.

You could also try swapping the track 1 and track 3 head connections (either on the back of the heads or on that PCB I mentioned) to see if the fault moves or stays on the same channel. If it moves, then the heads are suspect (as now the head handle the othe channel), if it stays the same then it's head trouble or similar.
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Old 9th Oct 2019, 7:47 pm   #62
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Default Re: Philips N4450 Reel to Reel Tape Player

Thanks Tony. I will follow your thought process verbatim tomorrow and report back. I have spent more money on a "new" reel to ensure that this is not to blame.

I really dont want it to be the heads, but have a spare machine.
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Old 9th Oct 2019, 8:22 pm   #63
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Default Re: Philips N4450 Reel to Reel Tape Player

Can you take a good close-up picture of the front of the heads? Don't forget the pressure felts in front of them. They used to wear frequently and it does also depend to some extent on the type of tape you use.
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Old 9th Oct 2019, 10:53 pm   #64
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Default Re: Philips N4450 Reel to Reel Tape Player

If it uses pressure pads, then back coated tapes could pose a problem.
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Old 10th Oct 2019, 7:00 am   #65
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Default Re: Philips N4450 Reel to Reel Tape Player

Track 1 or the left track in a quarter track machine notoriously loses the treble after significant head wear. Often it's just because dirt congregates in the "corner" of the wear ridge. Cleaning is difficult as the cotton bud often rides right over the dirt, missing it completely. The dirt needs to be very carefully removed without damaging the head. If this is the case, having removed the dirt, you'll just have to keep removing it periodically.

With serious audio work, the head would never have been be allowed to get to that state as both recording and playback become unreliable.

Also, as record heads wear, they tend to become overbiased, which robs the recordings of treble. I've lost count of the recorders I've rebiased to restore the highs in record.
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Old 12th Oct 2019, 7:11 pm   #66
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Default Re: Philips N4450 Reel to Reel Tape Player

I found time to clean the heads and take a picture:

https://www.vintage-radio.net/forum/...pictureid=4285

https://www.vintage-radio.net/forum/...pictureid=4284

https://www.vintage-radio.net/forum/...pictureid=4283
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Old 13th Oct 2019, 12:12 pm   #67
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Default Re: Philips N4450 Reel to Reel Tape Player

They look pretty good and it's also been fitted with the better (harder) heads during its lifetime. If you play a known good tape and VERY GENTLY apply pressure to the pressure pads, see if the treble or play level improves. If it does then it's probably pressure pad wear but it could be an alignment problem if the particular head(s) is(are) not completely perpendicular (90 degrees).

In the good old days we had precision jigs for checking these things........
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Old 14th Oct 2019, 2:52 pm   #68
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Default Re: Philips N4450 Reel to Reel Tape Player

Thanks Sideband. Will try this, this evening.
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Old 15th Oct 2019, 11:10 am   #69
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Default Re: Philips N4450 Reel to Reel Tape Player

Morning all . Sideband - the treble is slightly improved when i lift the pressre pads.

Where can i buy new pads? Or do you think that the heads need aligning?
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Old 15th Oct 2019, 12:10 pm   #70
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Default Re: Philips N4450 Reel to Reel Tape Player

Alignment of the heads on these is a tricky job without the proper test gear. There was a dedicated alignment tape for fine adjustment and a jig for the initial course adjustment plus we also had a special fluid (called Indicord) to paint onto a standard recording tape so that we could see the recorded tracks and check that they were positioned correctly. None of these things are available now unless you are lucky enough to find the jig and alignment tape on eBay or elsewhere.

All you can do these days is play a known good tape recorded with 1Khz and 10Khz test tones from a correctly aligned 4 track machine and adjust the heads for best output..... You need a dual beam scope and you play the 1khz test tone to adjust phasing and the 10 Khz for maximum output.

I don't know about the availability of pressure pads. You may find some on eBay (try German or Dutch eBay). Alternatively you may have to make some.
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Old 12th Nov 2019, 7:03 pm   #71
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Default Re: Philips N4450 Reel to Reel Tape Player

Hum - Im still stuck and am starting to think that the back coated tape i have might be to blame.

Does anyone have a known good tape they would sell to me please?
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Old 12th Nov 2019, 7:40 pm   #72
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Default Re: Philips N4450 Reel to Reel Tape Player

You do need some “standard” tape, back coated should not be used on machines that need pressure pads. On later Philips machines such as the N4504, N4406 and N4422 the pressure pad can be retracted when using back coated tape.
Unfortunately reel tape, even used, seems to have increased in value over the last few years sometimes to daft prices.
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Old 12th Nov 2019, 10:05 pm   #73
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Default Re: Philips N4450 Reel to Reel Tape Player

Quote:
Originally Posted by Reelman View Post
back coated should not be used on machines that need pressure pads.
Yes that's correct....I was momentarily taken back to around 1979 to the Philips workshop (604 Purley Way, Waddon) when we had a customer come in with one of these with worn out pressure pads. We asked him what tape he was using. 'Professional' he replied and showed us a sample. We told him he couldn't use it on a machine with pressure pads. The backing is like sandpaper to pressure pads and they wear very quickly.

We had to point out that the N4450 wasn't professional....apparently his father worked for the BBC and used to obtain the professional tape. I think he eventually settled on Ampex tape and asked if we could optimise the bias for it.
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Old 27th Nov 2019, 6:36 pm   #74
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Default Re: Philips N4450 Reel to Reel Tape Player

Ok, making progress.....

I bought a new head assembly from ebay for 35 and also a capstan motor control board for the parts machine. My father is an electronic engineer (GEC, Marconi and Plessy) and is slowly sorting the problems on these machines.

I have now spent 300 on these machine inc purchase price. Perhaps I should have just bought a Revox or Fostec to start with?

More updates once the parts arrive.

Does anyone on this forum sell belts for the N4450?
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Old 30th Mar 2020, 3:41 pm   #75
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Default Re: Philips N4450 Reel to Reel Tape Player

My father has been lumbared with three N4450 machines now. Two of mine and one of my uncles. My dad also has his own machine which he looks after.

He has got most machines working now, but they all seem to be effected by a recording issue.

I have asked him to write out what he has tried to date in hope that someone (@Sideband) can help with what to look at next.....

Monitored the recording using the “B”efore and “A”fter switch
The Recording for the LEFT speaker is very LOW when recording in either LEFT or RIGHT direction
The Recording for the RIGHT speaker is FINE in both directions

CHECKED SO FAR
1: Measured Power supplies
VOLTAGE Measured
48V 39V (Changed C507) Now 45V
26V 24V
-27V -24.6V
2: Swapped P4 and P104 boards - NO Difference - Boards OK
3: Swapped the Tracks 1-4 and 2-3 on the record head - NO Difference - Record Heads OK
4: PRE RECORDED tapes fine in both directions – Playback heads OK

Any ideas what could be wrong? If we can get to the bottom of it on one machine, all remaining machines are sorted.
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Old 30th Mar 2020, 5:27 pm   #76
TonyDuell
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Default Re: Philips N4450 Reel to Reel Tape Player

A couple of quick checks that might help to isolate the problem :

1) Do you get a normal indication on both level meters (or is the left hand one much lower than the right)?

2) Do you get a normal signal when monitoring in the 'before tape' position (i.e. not off the tape, just via the electronics)? Or is the left hand signal weak there too?
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Old 30th Mar 2020, 5:35 pm   #77
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Default Re: Philips N4450 Reel to Reel Tape Player

If the tape is played on another machine are both the left and rights channels recorded correctly or is the left still quieter?
My N4450 soon developed an intermittent A-B switch from new and was never ever completely solved. Be careful, the tracks on the circuit boards are quite fragile. Removal of a component can also take part of the track with it!

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Old 31st Mar 2020, 11:50 am   #78
Ray_Singh
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Default Re: Philips N4450 Reel to Reel Tape Player

Thank you - I have gone back to Dad to see what he thinks. He has answers for Tony and will check your suggestions Reelman.


@TonyDuell -

1: Do you get a normal indication on both level meters (or is the left hand one much lower than the right)?
No, During recording and the switch in “After Tape” only the Left meter shows lower level.
Right meter shows no loss in Before After switch position
Noticed some loss in treble on the Right channel in After position

2: Do you get a normal signal when monitoring in the 'before tape' position (i.e. not off the tape, just via the electronics)? Or is the left hand signal weak there too?
In the “Before Tape” both meters show good signal levels (through the electronics). The sound quality is also very good.
Also Note: Prerecorded tapes play with good sound quality
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Old 31st Mar 2020, 2:53 pm   #79
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Default Re: Philips N4450 Reel to Reel Tape Player

Sounds like something is wrong with the LH record amplifier, you could try swapping the L and R record modules and see if the fault changes channel.
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Old 1st Apr 2020, 11:03 am   #80
Ray_Singh
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Default Re: Philips N4450 Reel to Reel Tape Player

Thanks Michael Maurice - We swapped these and it made no difference....

@Reelman - Investigations ongoing....
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