Philips (Black Tulip) N5748 HIFI Cassette Deck

De compact cassette was een schitterende uitvinding van Philips en werd een wereldwijd succes. Ook bandrecorders blijken een tijdloos populair medium.Kun jij ook geen genoeg krijgen van die sfeervol draaiende spoelen? Deel hier je magnetische passie!

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Michael 5of9
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Lid geworden op: 06 sep 2014, 11:48
Locatie: CUMBRIA in ENGLAND
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01 dec 2018, 13:38

The fault with no sound on the left has been identified; it is transistor TS448 BC 548 B fitted on the U405 main board, directly above it, is board U411 which slots in and it looks like it has contributed to the 2 broken solder joints on the board.

These have been refitted in a way to give more clearance from U411.
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The new relationship between TS448 BC 548 B and U411 gives a little more space.
The new relationship between TS448 BC 548 B and U411 gives a little more space.
The relationship between TS448 BC 548 B and U411 was stressful.
The relationship between TS448 BC 548 B and U411 was stressful.
TS448 BC 548 B two solder joints have bridged the board.
TS448 BC 548 B two solder joints have bridged the board.
Kind Regards Michael
Heating & Electrical Engineer
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Michael 5of9
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Lid geworden op: 06 sep 2014, 11:48
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14 feb 2019, 12:33

Rewinding Issue; I think this is a known problem and someone knows how to resolve this, that is if it can be or maybe it just requires a small amount of service/maintenance :think:

With a C60 (30min each side) cassette inserted and ready, fast forward works very well, rewind works, but tires towards the end of the tape, then stops, short of finishing the rewind.
The tape is free to turn; so the tape in the cassette is not tight.
The rewind voltage is correct +6v to +7v although it does rise to +8v when tiring.

When rewinding there must be something that provides a small amount of braking/clutch/tensioner on the supply spool (maybe item 174 left or 181 right, see page 9 of the service manual; Cassette Mechanical Mechanism) so that there is some tension on the tape.
Thinking about the two spools as two pulleys with a belt between them.
At the start of the rewind the take-up spool will be small and will become larger and it would need a small amount of brake on the supply spool.
Near the end of the rewind it might need a little more brake or just the same on the supply spool :think:

You can see a video of the issue; the flywheel is rotating anticlockwise; https://1drv.ms/v/s!AuQDAPiShOjc9mao0c5Rkbl_epQP

More information including page 9 of the service manual; https://1drv.ms/f/s!AuQDAPiShOjc9mGIHDHkXizetz5t

Many thanks;
Bijlagen
174 left or 181 right, see page 9 of the service manual; Cassette Mechanical Mechanism
174 left or 181 right, see page 9 of the service manual; Cassette Mechanical Mechanism
Kind Regards Michael
Heating & Electrical Engineer
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HermanH
Berichten: 3598
Lid geworden op: 22 mei 2015, 20:39
Locatie: Omgeving Breda

01 mar 2019, 17:37

Zijn hier nog experts die nog eens naar dit probleem willen kijken ?
Binnenkort uitverkoop
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Remi
Berichten: 9914
Lid geworden op: 16 jun 2005, 20:04
Locatie: bij Arnhem

01 mar 2019, 17:54

sorry, your links don't seem to work here, maybe due to my vpn?
I would think there is to much friction in the tape transport, could be the cassette itself or maybe the motor isn't 100% ?
There are new gearwheels mounted i believe, can they turn freely?

I can't think of anything more causing this problem.
"Hoezo nu wel genoeg? D'r is toch nog plek!" jaja, waar dan? "Ha! d'r kan nog wat in de auto!"
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Michael 5of9
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Lid geworden op: 06 sep 2014, 11:48
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01 mar 2019, 18:16

Remi schreef:
01 mar 2019, 17:54
sorry, your links don't seem to work here, maybe due to my vpn?
Hmmmm; both links not working?
They both work from this end?

I wonder if anyone else is experiencing this weblink issue, or knows how to make it work, they are to my original OneDrive?
Kind Regards Michael
Heating & Electrical Engineer
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PatrickVB
Berichten: 2781
Lid geworden op: 07 mei 2007, 21:36
Locatie: Hengelo/Twente/OV/NL
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01 mar 2019, 19:17

Here both links work.
ADK2525/541(3)/752/762/580/690/421/720/4307/4308(2)/4407/4510/4511/EL3787/EL3302/N2511/DCC900/EM2200(3)/GA212/GA312/GA532/CD1380/CD1482/AR9123/4000DS/4000DSMKII/GX630D/CS1225
N1700/VR2120/VR2220/VR2220F/VK4001/RS2340/VR2350
http://www.tessatronic.nl
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Remi
Berichten: 9914
Lid geworden op: 16 jun 2005, 20:04
Locatie: bij Arnhem

01 mar 2019, 19:46

on my smartphone it says i need to log in with my microsoft account. i don't believe i have one so there you go, no picture for me
"Hoezo nu wel genoeg? D'r is toch nog plek!" jaja, waar dan? "Ha! d'r kan nog wat in de auto!"
airmax78
Berichten: 151
Lid geworden op: 09 dec 2015, 21:02

01 mar 2019, 20:50

Hello Michael,

I hope, my english is not too bad, but maybe we got something to laugh about it.
I have many of these decks here but I never have encounterd this particular issue. In my opinion, it's more a mechanical problem, the electrical part seems to be fine. At first, make sure that the brakes at the reels are not applied during rewind or fast forward. At second, remove the belt to the tape counter and see, if this makes a difference. However, the main belt seems to be too loose... normally the main belt should never slip on the end of the tape (or before). The reel motor is controlled by a current sensing circuit on the motor control PCB which must cut off immediately when tape end is reached. I know, the main belt is hard to find (I guess 1,5 x 50mm) but the belt that comes together with the new CDM9 tray gear fits perfectly. Also the counter belt should not to be too thick or too tight.
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Michael 5of9
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Lid geworden op: 06 sep 2014, 11:48
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02 mar 2019, 15:24

Remi schreef:
01 mar 2019, 19:46
on my smartphone it says i need to log in with my microsoft account. i don't believe i have one so there you go, no picture for me
Let’s try accessing via my Google Drive Account for those who haven’t a Microsoft account?

You can see a video of the issue; the flywheel is rotating anticlockwise; https://drive.google.com/file/d/1do1iV ... p=sharing

More information including page 9 of the service manual; https://drive.google.com/drive/folders/ ... =sharing

The tape is about 2/3rd through rewind and the voltage has increase to just over 8.05v and then as it is tiring-out the voltage decreases to 7.74v (the voltage on rewind does not drop significantly near the end of a rewind); it’s 1 volt over specification, is this will be due to the extra load on the motor?

Watching and listening to the motor; you can hear that there is something struggling and just before the end if you stop the video at 40 seconds running (and it is running anticlockwise) if you look at the top side of the pulley on the motor can see the torque that has been produced by the belt being stretched in a way that you can see that it isn’t being taken round by the large plastic flywheel because of the friction produced on the running gear and tape, this is the problem area.

I don’t know how you are listening to these videos; headphones give a better hearing?
Kind Regards Michael
Heating & Electrical Engineer
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Michael 5of9
Berichten: 47
Lid geworden op: 06 sep 2014, 11:48
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02 mar 2019, 15:43

airmax78 schreef:
01 mar 2019, 20:50
At first, make sure that the brakes at the reels are not applied during rewind or fast forward.
Yes I think a brake is being applied; I am hoping that someone who knows all about this problem will step in, as I need to be fully instructed before dismantling :think:
airmax78 schreef:
01 mar 2019, 20:50
At second, remove the belt to the tape counter and see, if this makes a difference.
Yes I will try this and report back
airmax78 schreef:
01 mar 2019, 20:50
However, the main belt seems to be too loose... normally the main belt should never slip on the end of the tape (or before). The reel motor is controlled by a current sensing circuit on the motor control PCB which must cut off immediately when tape end is reached. I know, the main belt is hard to find (I guess 1,5 x 50mm) but the belt that comes together with the new CDM9 tray gear fits perfectly. Also the counter belt should not to be too thick or too tight.
These belts are new; I bought them from this website's shop, of which I am most greatfull, they are identical to my original ones. There isn't any slipping via pulley and belt.

Thank you airmax78 for your input :)

https://www.cse.iitk.ac.in/users/amit/c ... tents.html
Kind Regards Michael
Heating & Electrical Engineer
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Remi
Berichten: 9914
Lid geworden op: 16 jun 2005, 20:04
Locatie: bij Arnhem

02 mar 2019, 16:26

yes, this works :D

there is slipping of the pully, in the last clip you can hear the motor pulling just before the automatic stop.
This combination of a running motor and a stopped travelindicator (the black flywheel) suggest a broken tape or end of tape.
It is perfectly ok that it will stop now.

As said by airmax78, try without the tapecounter belt, or just to have tested it, try the original belt on the winding motor.
It seems a bit loose. All and all i believe there is a mechanical issue, there is not enough pull by the motor, first thing is it should not slip.
"Hoezo nu wel genoeg? D'r is toch nog plek!" jaja, waar dan? "Ha! d'r kan nog wat in de auto!"
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Michael 5of9
Berichten: 47
Lid geworden op: 06 sep 2014, 11:48
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06 mar 2019, 15:38

Rewinding Issue; it has been on my mind what airmax78 said and Remi had identified “there is slipping of the pulley” this I hadn’t picked upon; even after watching and studying the rewinding many times, I still say there is too much torque being produced by the brake.

A new video concentrating on the wind motor pulley; at 43 seconds into this video you can hear the pulley making a slipping noise as the belt has come to a stop and just briefly see the pulley spin without the belt going round, thanks airmax78 and Remi, sorry, video not quite focused. Video link - Wind Motor Pulley Slipping https://drive.google.com/file/d/1dZwiV ... p=sharing

I removed the counter belt and tried rewind; rewind almost finished to the end. I thought it best for the next step to measure the original and new belts, to see the differences, and bearing in mind what airmax78 and Remi said, concerning the motor belt being loose, it then became obvious that the belts were on the wrong pulleys.

I changed over the belts; the tape counter belt looks a bit loose, as you can see in the picture, it does the job with no slipping and the wind motor, rewinds all the way now, there is too much torque on the motor for my liking Hmmmm! Video link – Belts Fitted Correctly This Time https://drive.google.com/file/d/1LWp5 ... p=sharing

The original belt sizes giving internal diameter and thickness;
Tape Counter 60mm approx. x 0.93mm, square section.
Wind Motor 63mm approx. x 1.40mm, square section.

New belts;
Tape Counter 61mm approx. x 1.24mm, square section.
Wind Motor 56/7mm approx. x 1.54mm, round section.
Bijlagen
New Tape Counter Belt 61mm approx. x 1.24mm, square section.
New Tape Counter Belt 61mm approx. x 1.24mm, square section.
New Wind Motor Belt <br />56/7mm approx. x 1.54mm, round section.
New Wind Motor Belt
56/7mm approx. x 1.54mm, round section.
Kind Regards Michael
Heating & Electrical Engineer
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Michael 5of9
Berichten: 47
Lid geworden op: 06 sep 2014, 11:48
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06 mar 2019, 16:44

I am getting Interference noise; whilst playing a cassette, it sounds something like crackle/popping in the background, like when you turn/pull out the headphones from the socket, this isn’t a continuous noise, it just happens once every few seconds, is this a suppressor problem :think:
Kind Regards Michael
Heating & Electrical Engineer
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Remi
Berichten: 9914
Lid geworden op: 16 jun 2005, 20:04
Locatie: bij Arnhem

06 mar 2019, 17:46

allright! who would have thought the belts were mixed up?
it seems rather loose on the counter now but if it works it works. More tension will only stress the pulleys.

don't know about your new problem, bad capacitor? bad transistor? try to wiggle the removable PCB's in their slots?
"Hoezo nu wel genoeg? D'r is toch nog plek!" jaja, waar dan? "Ha! d'r kan nog wat in de auto!"
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Michael 5of9
Berichten: 47
Lid geworden op: 06 sep 2014, 11:48
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06 mar 2019, 18:01

Many thanks Remi
Remi schreef:
06 mar 2019, 17:46

don't know about your new problem, bad capacitor? bad transistor? try to wiggle the removable PCB's in their slots?
I have also been very fortunate to have a lot of help from LesJones on All About Circuits
https://forum.allaboutcircuits.com/thre ... 885/page-9

Interference Noise I removed the playback pre-amplifier board U409 and the noise had stopped.
As I am intending to renew all the transistors in this unit I replaced the ones in this board next, yes, the noise has gone.

I have been keeping a record of the reference voltage and hFE (current gain or amplification factor of the transistor) readings, look at the low readings on U409) they are shown in the file called Philips N 5748 Transistors 24April19 these voltages have improved after renewing each board of transistors, all the transistors have been replaced now. The two photos show transistor BC337-16 which should give 100 hFE min.
https://drive.google.com/file/d/1DT2D7X ... sp=sharing
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Transistor BC337-16.jpg
Transistor BC337-16 ..jpg
Kind Regards Michael
Heating & Electrical Engineer
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