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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 12th Feb 2008, 10:01 pm   #1
Clockwork_TV
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Default Muffled sound gets better- Tape or tape recorder?

Hi All

I've got a Philips EL3542 reel to reel and have been buying original pre-recorded tapes for it, some play at 3 3/4 some at 7 1/2 ips (stereo) from the US.

The 7 1/2 sound amazing (played thru my hi-fi amp). However the 3 3/4 are very hit and miss. UK tapes (Beatles) are of varying quality but consistent all the way through (thoug a bit wowy). But I've got a couple from the US (Led Zep) where the quality suddenly gets really good after sounding muffled for a while and some wow and flutter. Is it the tape or the machine? Can't see anything wrong with tape.
I'm wondering if it's the 3 3/4 wheel - muffled at start of tape then gets better. Is there more strain at the start of the tape?

Also this machine has a switch so you can hear the other track of the stereo. The normal track is good but the other is always more muffled. Any ideas? Should sound same as it uses the same circuit.

Or is it bit like with cassettes where sometimes they were muffled but after a rewind sounded OK again?

Cheers John
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Old 12th Feb 2008, 10:46 pm   #2
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Default Re: Muffled sound gets better- Tape or tape recorder?

It's an old machine so check the state of the heads to start with for wear & cleanliness, also check the pressure pad.
The US pre rec. tapes were excellent & were 4 track, most of the UK were from memory half track, although not all.

Start with that before you go further, if you can degauss the heads etc. that would eliminate any possible damage to your pre re. tapes.

Colin
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Old 12th Feb 2008, 11:36 pm   #3
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Default Re: Muffled sound gets better- Tape or tape recorder?

Quote:
Originally Posted by Clockwork_TV View Post
However the 3 3/4 are very hit and miss. UK tapes (Beatles) are of varying quality but consistent all the way through (thoug a bit wowy). But I've got a couple from the US (Led Zep) where the quality suddenly gets really good after sounding muffled for a while and some wow and flutter (.....)I'm wondering if it's the 3 3/4 wheel - muffled at start of tape then gets better. Is there more strain at the start of the tape?
sounds like there may be thinner tape used in some US tapes, and the take up torque on the deck is a bit high leading to skewing. try a simple test:getting a thin tape (LP or triple play type) and recording half an hour or so at 3 3/4 ips, see if you get any similar probs. that way we can try and narrow this down. though the wow and flutter is a bit of a giveaway.

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Also this machine has a switch so you can hear the other track of the stereo. The normal track is good but the other is always more muffled. Any ideas?
head wear, head dirt or skewing due to torque as described above.

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Originally Posted by Clockwork_TV View Post
Or is it bit like with cassettes where sometimes they were muffled but after a rewind sounded OK again?
I have never seen or heard of this,. rewinding evenly may improve the tape movement but will not have any effect on the tone. that's usually down to dirty or magnetised tape heads

Ben.

Last edited by Mike Phelan; 13th Feb 2008 at 8:56 am. Reason: Fixed quote tag
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Old 16th Feb 2008, 8:25 pm   #4
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Default Re: Muffled sound gets better- Tape or tape recorder?

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sounds like there may be thinner tape used in some US tapes, and the take up torque on the deck is a bit high leading to skewing. try a simple test:getting a thin tape (LP or triple play type) and recording half an hour or so at 3 3/4 ips, see if you get any similar probs. that way we can try and narrow this down. though the wow and flutter is a bit of a giveaway.



head wear, head dirt or skewing due to torque as described above.





Ben.
Thanks for the reply - I had cleaned the heads (there's only one 2 track play/record head and the erase head). I'd assume the wear would be the same on both tracks? The torque you mention might be the problem - could this be caused by a worn 3 3/4 speed wheel? Also the tape 'bounces' when I press 'play' before it gets going properly and the drive belt doesn't look great. And what is skewing?
I might have a problem recording - it didn't seem to work when I used the mic (but it does work in PA mode)
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Old 16th Feb 2008, 8:29 pm   #5
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Default Re: Muffled sound gets better- Tape or tape recorder?

Quote:
Originally Posted by DOFFERY View Post
It's an old machine so check the state of the heads to start with for wear & cleanliness, also check the pressure pad.
The US pre rec. tapes were excellent & were 4 track, most of the UK were from memory half track, although not all.

Start with that before you go further, if you can degauss the heads etc. that would eliminate any possible damage to your pre re. tapes.

Colin
Thanks for the reply - I had cleaned the heads. Don't look worn. The presssure pad doesn't look great - is there an easy way of replacing it? I managed to find my old degausser in the loft but haven't used it yet.
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Old 18th Feb 2008, 1:01 am   #6
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Default Re: Muffled sound gets better- Tape or tape recorder?

Quote:
Originally Posted by Clockwork_TV View Post
Thanks for the reply - I had cleaned the heads (there's only one 2 track play/record head and the erase head). I'd assume the wear would be the same on both tracks?
not always. on stereo machines you often notice one channel going muffly first.


Quote:
Originally Posted by Clockwork_TV View Post
The torque you mention might be the problem - could this be caused by a worn 3 3/4 speed wheel? Also the tape 'bounces' when I press 'play' before it gets going properly and the drive belt doesn't look great. And what is skewing?
I might have a problem recording - it didn't seem to work when I used the mic (but it does work in PA mode)
try this - play the tape, then stop the take up spool with your hand for a moment, see if it clears up the audio that would be an indication of excess torque. this causes the skewing - which is when the tape is not straight across the head, but is being pulled slightly upwards or downwards leading to mistracking.

if this is the small machine i'm thinking of (a pic might be useful if you can do it) then the take up i seem to recall did not start too well - think it was just the design.
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Old 18th Feb 2008, 11:49 am   #7
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Default Re: Muffled sound gets better- Tape or tape recorder?

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not always. on stereo machines you often notice one channel going muffly first.




try this - play the tape, then stop the take up spool with your hand for a moment, see if it clears up the audio that would be an indication of excess torque. this causes the skewing - which is when the tape is not straight across the head, but is being pulled slightly upwards or downwards leading to mistracking.

if this is the small machine i'm thinking of (a pic might be useful if you can do it) then the take up i seem to recall did not start too well - think it was just the design.
Thanks for the reply - I'll give it a go and report back.

This is the machine as you requested, Philips EL3542:
http://i138.photobucket.com/albums/q...erc/el3542.jpg

And even better the circuits and mechanical drawings:

http://images.google.co.uk/imgres?im...%3D1%26hl%3Den
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Old 19th Feb 2008, 3:17 pm   #8
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Default Re: Muffled sound gets better- Tape or tape recorder?

thats a much older one than i'd imagined. nice unit, good features and well worth restoring. let us know how the checks go.
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Old 19th Feb 2008, 4:05 pm   #9
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Default Re: Muffled sound gets better- Tape or tape recorder?

Hi John, I think the problem may be a worn pinch roller which causes the tape to run off line causing the tape to ride up and down. Try giving it a good clean with some proprietry head cleaning fluid. Norman
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Old 22nd Feb 2008, 11:39 pm   #10
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Default Re: Muffled sound gets better- Tape or tape recorder?

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Thanks for the reply - I'll give it a go and report back.

This is the machine as you requested, Philips EL3542:
http://i138.photobucket.com/albums/q...erc/el3542.jpg

And even better the circuits and mechanical drawings:

http://images.google.co.uk/imgres?im...%3D1%26hl%3Den
Ah -ha! Well I tried stopping the take-up reel but it made no difference. But as I was messing about I accidentally pressed the other reel (feeding the tape) and hey presto beautiful treble came in! That does it. It works for whichever speed and all my tapes - huge improvement. The more I brake the feed reel with my finger the better it sounds till it is slowing the tape speed.
So is there something wrong with the feed reel? - if I over-feed the tape the feed reel doesn't move. Should it be turning the other way?
I can't believe how good it sounds when I do this! Cheers for the pointer. But what's the problem with the mechanics then?
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Old 22nd Feb 2008, 11:43 pm   #11
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Default Re: Muffled sound gets better- Tape or tape recorder?

Quote:
Originally Posted by ben View Post
not always. on stereo machines you often notice one channel going muffly first.




try this - play the tape, then stop the take up spool with your hand for a moment, see if it clears up the audio that would be an indication of excess torque. this causes the skewing - which is when the tape is not straight across the head, but is being pulled slightly upwards or downwards leading to mistracking.

if this is the small machine i'm thinking of (a pic might be useful if you can do it) then the take up i seem to recall did not start too well - think it was just the design.
Oops - in my excitement I answered myself! Please read my previous comment which is meant to be in reply to the above comment.
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Old 23rd Feb 2008, 12:03 am   #12
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Default Re: Muffled sound gets better- Tape or tape recorder?

By slowing the supply reel, you are increasing the "bsck tension" and thus forcing the tape make better contact with playback head.

I'll leave it to the experts to tell you what's wrong. Could be pressure pads, head wear or something else
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Old 23rd Feb 2008, 1:27 am   #13
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Default Re: Muffled sound gets better- Tape or tape recorder?

I hope it's not head wear that'd mean finding another head! The pressure pad doesn't look good - is there something that I could replace it with?
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Old 23rd Feb 2008, 7:17 am   #14
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Default Re: Muffled sound gets better- Tape or tape recorder?

If you can't find one try making one out of a bit of foam and glueing it in place? I've got one that came off and I'm contemplating glueing it back on. What sort of glue should one use - spot of superglue...mmmm..?
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Old 23rd Feb 2008, 10:56 am   #15
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Default Re: Muffled sound gets better- Tape or tape recorder?

Providing the pad is felt a thin coating of a contact adhesive applied to both the felt and the mounting will hold it - make sure that you are happy with the location of the pad first as you will have difficulty relocating it if you get it wrong.

Pads seem to have been mainly felt, the variety without long hairy strands seems to stay put on mountings. Getting the correct or close to thickness is something else to take into account.

I have not had a chance to look at the mechanical view to see what mechanism is in place to give "back tension" on your deck but will do shortly.
Depending on how good you manual is we should have some clues.

On a more unpleasant note I do recall that the "rubber" used for certain parts in Philips tape recorders had a habit of degrading to a sticky black mess, in fact some belts were starting to do this in the plastic packets many, many years ago !
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Old 23rd Feb 2008, 4:10 pm   #16
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Default Re: Muffled sound gets better- Tape or tape recorder?

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Originally Posted by Clockwork_TV View Post
Oops - in my excitement I answered myself! Please read my previous comment which is meant to be in reply to the above comment.
ok no probs- at least there's some light at the end of the tunnel!
i would firstly check the pressure pads,then as oxide says, check the manual to see what if any backtension arrangement was used. good luck.
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Old 24th Feb 2008, 11:12 pm   #17
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Default Re: Muffled sound gets better- Tape or tape recorder?

OK I've tried a few things
1) I had cleaned the heads but that was a few weeks ago so thought they should be OK - but as people had suggested this as the problem I double checked. And lo and behold they were covered in tape dust. I cleaned them up which improved the sound and solved the one-sided stereo muffled sound. Now both sides are the same. But it didn't bring the treble to full quality.

2) So the sound is still improved by braking the feed reel. I tried putting pressure on the pressure pad but this didn't seem to make any difference so I guess it's not that.

3) Is it normal to have the feed spindle to rotate the opposite way to the tape direction when you press play without a tape in? When I do it on this machine it doesn't move. Only the takeup spindle rotates.
Also if I press FForward only the take-up spindle rotates. However if I do FRewind BOTH spindles rotate (in opposite directions). Shouldn't they do the same?
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Old 25th Feb 2008, 12:16 am   #18
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Default Re: Muffled sound gets better- Tape or tape recorder?

Whether the supply reel tries to run backwards in play depends on the make and model, but if yours has a pressure pad for the head, it's the pressure pad's job to make sure the tape contacts the head correctly.
If it doesnt (as shown by weak treble) then as Doffery said in the first reply either the pressure pad or the head (or both) should be suspected.

You seem to be assuming that because manually braking the supply reel temporarily "fixes" the problem that the supply reel tension is the cause of the poor treble. I suggest though, it is only pointing to a problem with the head and/or pressure pad.

Re-read Doffery's post. In my experience he's usually right!

Tim
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Old 25th Feb 2008, 6:00 pm   #19
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Default Re: Muffled sound gets better- Tape or tape recorder?

Is a worn head visibly so? It looks quite nice and shiny smooth, though it's hard to get close 'cos of other gubbins in the way. If the head is worn I assume that means the only way to fix it is with a 'new' one?
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Old 25th Feb 2008, 8:52 pm   #20
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Default Re: Muffled sound gets better- Tape or tape recorder?

First visible indication of a worn head is often a polished band over the gap. Some heads are ground that way to start with, so a certain amount of experience helps, but if you can see a vertical 'stripe' more than, say, 3mm wide, the chances are that the head is significantly worn.
Heads can be reground, but it's only financially viable for expensive professional jobs. Replacement heads to suit most decks used to be available. One such supplier was Monolith, but a quick Google returns no results, so they've probably gone, but I'm sure there must still be similar firms. Philips heads shouldn't be too hard to find ex scrap machines though.
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