UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players

Notices

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

Closed Thread
 
Thread Tools
Old 29th May 2021, 6:16 pm   #1
NevilleT
Triode
 
Join Date: Mar 2021
Location: Southampton, Hampshire, UK.
Posts: 10
Default Denon Cassette Servicing Help Please

Hi All,

I have a 20+ year old Denon DR-M10HX cassette deck that I'm going to try and service.

I have aquired some test tapes and I have a scope. When I connect the scope to the L&R line level outputs I see a great deal of high frequency noise before I play the tape. Equally when I play a 3.5KHz (or any other frequency) test tape it's hard to see the test frequency through the noise.

The 3rd & 4th image shows the noise with modulation.

Any advise would be welcome.

Many thanks
Attached Thumbnails
Click image for larger version

Name:	SDS00001.jpg
Views:	77
Size:	89.5 KB
ID:	235061   Click image for larger version

Name:	SDS00002.jpg
Views:	77
Size:	112.2 KB
ID:	235062   Click image for larger version

Name:	SDS00003.jpg
Views:	75
Size:	85.3 KB
ID:	235063   Click image for larger version

Name:	SDS00004.png
Views:	68
Size:	50.8 KB
ID:	235064  
NevilleT is offline  
Old 29th May 2021, 7:51 pm   #2
Mooly
Octode
 
Join Date: May 2011
Location: Lancashire, UK.
Posts: 1,349
Default Re: Denon Cassette Servicing Help Please

I would say the first question is to see whether the deck actually plays known good music tapes correctly and also whether it records and plays OK. If it does then we have to start questioning the test and measurement setup.

A lot depends on the level the test tapes are recorded at as well.

So to begin with do not look to hard for problems... just analyse the deck as a whole as a typical user would.
Mooly is offline  
Old 29th May 2021, 9:31 pm   #3
NevilleT
Triode
 
Join Date: Mar 2021
Location: Southampton, Hampshire, UK.
Posts: 10
Default Re: Denon Cassette Servicing Help Please

That's a very good point.

I don't have any pre-recorded factory made tapes but I have some new blanks so I can make some new recordings and assess the results.

I'll report back.

Thanks
NevilleT is offline  
Old 30th May 2021, 6:00 pm   #4
NevilleT
Triode
 
Join Date: Mar 2021
Location: Southampton, Hampshire, UK.
Posts: 10
Default Re: Denon Cassette Servicing Help Please

OK as a first off I've made some recordings from the line level outputs of the deck feeding a USB sound card directly and recorded in Audacity.

The 'Not Playing Noise - Raw' recording is just the background noise with no tape playing.
https://drive.google.com/file/d/14K3...ew?usp=sharing


The 'Not Playing Noise - Normalised' is the same recording but normalised in Audacity.
https://drive.google.com/file/d/1shd...ew?usp=sharing

The 'Blank Tape Playing - Raw' is a blank tape playing (not normalised)
https://drive.google.com/file/d/1vVC...ew?usp=sharing

And here's the service manual:
https://drive.google.com/file/d/1o5o...ew?usp=sharing


What are your thoughts?

Many thanks.
NevilleT is offline  
Old 30th May 2021, 7:51 pm   #5
stevehertz
Dekatron
 
stevehertz's Avatar
 
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 8,809
Default Re: Denon Cassette Servicing Help Please

Just make 'some tapes' of your own music; from a CD, computer, radio, whatever. Then, if the results appear to be poor in any way; dull, bright, wow, flutter, dropouts, distortion, etc etc, whatever, you can then use the test tapes to help you hone in on the problem. I just think you're going about it in the wrong way if I may say so.
__________________
A digital radio is the latest thing, but a vintage wireless is forever..
stevehertz is offline  
Old 30th May 2021, 11:04 pm   #6
Ted Kendall
Dekatron
 
Join Date: Jul 2008
Location: Kington, Herefordshire, UK.
Posts: 3,657
Default Re: Denon Cassette Servicing Help Please

I'm with Steve on this - if it ain't broke, don't fix it - and as yet, you have not established that it's doing anything wrong. Just try recording and replaying some music on a decent cassette to start with and take it from there.
Ted Kendall is online now  
Old 30th May 2021, 11:20 pm   #7
TIMTAPE
Octode
 
Join Date: Jul 2006
Location: Perth, Western Australia
Posts: 1,965
Default Re: Denon Cassette Servicing Help Please

I agree with Steve. Test tapes are for very accurate and fine calibration, not for basic gross assessment. They are not for " telling me all the problems with my tape deck". Back in the day test tapes were expensive and not to be used casually. We would not let one anywhere near a tape deck before having spent time getting the deck in good basic condition such that it wouldn't damage the test tape and ruin its fine accuracy either mechanically or magnetically, if that's a word. This included carefully demagnetizing the tape path. Have you properly cleaned the tape path? From listening to one of your recordings I hear a whining noise which may be related to your digital recording setup rather than the tape deck.
TIMTAPE is offline  
Old 31st May 2021, 4:29 pm   #8
NevilleT
Triode
 
Join Date: Mar 2021
Location: Southampton, Hampshire, UK.
Posts: 10
Default Re: Denon Cassette Servicing Help Please

Hi All,

This is a short recording made on the deck. The source is a CD player connected directly to the tape deck. I recorded 6 seconds of 'silence' before the track starts in order to hear the baseline noise.

https://drive.google.com/file/d/1Uf9...ew?usp=sharing
NevilleT is offline  
Old 31st May 2021, 5:38 pm   #9
NevilleT
Triode
 
Join Date: Mar 2021
Location: Southampton, Hampshire, UK.
Posts: 10
Default Re: Denon Cassette Servicing Help Please

There are two TO220 transistors close to the bridge rectifier and smoothing caps. One is a D985 and the other is a B794. The trace below is from the emitter pins.

https://www.vintage-radio.net/forum/...1&d=1622479037
Attached Thumbnails
Click image for larger version

Name:	SDS00010.png
Views:	78
Size:	47.0 KB
ID:	235164  
NevilleT is offline  
Old 31st May 2021, 8:05 pm   #10
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
Default Re: Denon Cassette Servicing Help Please

I've never tried to diagnose cassette deck problems in this way. Scopes can reveal all sorts of strange things, which may or may not be significant.
paulsherwin is online now  
Old 31st May 2021, 9:01 pm   #11
NevilleT
Triode
 
Join Date: Mar 2021
Location: Southampton, Hampshire, UK.
Posts: 10
Default Re: Denon Cassette Servicing Help Please

Thanks Paul.

So what is the sensible forwards?

Any advise would be welcome.

P.S. I've demagnetized the head and all the metal in the area. The heads, capstan and pinch wheel has been cleaned with isopropyl alcohol

Last edited by NevilleT; 31st May 2021 at 9:10 pm.
NevilleT is offline  
Old 31st May 2021, 9:11 pm   #12
Ted Kendall
Dekatron
 
Join Date: Jul 2008
Location: Kington, Herefordshire, UK.
Posts: 3,657
Default Re: Denon Cassette Servicing Help Please

OK - on the principle of "what have we got on the ship that's good?", the WAV sounds pretty creditable - a fair facsimile of the CD track, only marred by the crackle. First thing to establish is whether it is present on playback of a blank tape, preferably one not used on this machine, and whether it is on both channels. At first listen, it sounds a bit like motor interference, not something to which modern decks ae particularly prone, but possible if the commutator is dirty or the screening can is not earthed, for instance.
Ted Kendall is online now  
Old 31st May 2021, 9:32 pm   #13
NevilleT
Triode
 
Join Date: Mar 2021
Location: Southampton, Hampshire, UK.
Posts: 10
Default Re: Denon Cassette Servicing Help Please

I bought a pack of new tapes and when I play one back the noise is there.

As soon as the deck is powered up the capstan motor starts. If I disconnect the connector to the motors the noise remains.
NevilleT is offline  
Old 31st May 2021, 9:58 pm   #14
Restoration73
Nonode
 
Restoration73's Avatar
 
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
Default Re: Denon Cassette Servicing Help Please

Please state if the noise or its nature changes if Dolby B or C is selected. It is possible
for the dedicated Dolby IC to be at fault - play mode. The only way to obtain an
absolutely silent blank tape is to use a bulk erase device.
Restoration73 is offline  
Old 31st May 2021, 10:27 pm   #15
TIMTAPE
Octode
 
Join Date: Jul 2006
Location: Perth, Western Australia
Posts: 1,965
Default Re: Denon Cassette Servicing Help Please

Quote:
Originally Posted by NevilleT View Post

As soon as the deck is powered up the capstan motor starts. If I disconnect the connector to the motors the noise remains.
. Then it's that change we need to hear in a recording. Ideally the only background noise we hear from the deck playing a new unrecorded tape is tape hiss. But there will also be the deck's preamp noise which often sounds like tape hiss. Often some hum induced by the deck's mains transformer which is probably what we hear in your last sample. But something has changed between your "not playing noise" sample and the last one. The whining has gone and the hum mentioned now appears. It's important in testing to only change one thing at a time. Otherwise things can get very confusing. Your uploads also appear to be all mono. As it's a stereo deck hearing both gives us a fuller picture. Sometimes a fault appears in only one channel. If so that should be apparent in your samples.
TIMTAPE is offline  
Old 31st May 2021, 11:55 pm   #16
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,483
Default Re: Denon Cassette Servicing Help Please

Sorry to drag things back to basics, but if this unit has a mechanical record-playback switch might it be advisable to exercise it (operate it a few times) and see if that causes the symptoms to change significantly with each subsequent operation of the switch? Up to a certain point in time the number one cause of erratic / unreliable behaviour and odd noises on cassette decks was a dirty record / playback switch.

If this particular deck has purely electronic record / replay switching, ignore the above.
SiriusHardware is online now  
Old 1st Jun 2021, 5:46 pm   #17
NevilleT
Triode
 
Join Date: Mar 2021
Location: Southampton, Hampshire, UK.
Posts: 10
Default Re: Denon Cassette Servicing Help Please

Sorry, busy life has got in the way of this for the moment.

I'll be back.

Thanks
NevilleT is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 8:18 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.