|
Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc. |
|
Thread Tools |
11th Mar 2020, 6:07 pm | #1 |
Diode
Join Date: Mar 2020
Location: Eskilstuna, Sweden
Posts: 6
|
Philips N4418 wrong speed
Anyone having problems with speed adjustments? one can adjust the speed But the are all too fast!
|
11th Mar 2020, 10:06 pm | #2 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
|
Re: Philips N4418 wrong speed
I am not familiar with this model. A quick look at the Service manual indicates that all 3 speeds can be adjusted by the relevant potentiometer/trimming resistor.
If speeds cannot be trimmed down sufficiently, then can only assume that problem may lie with the Capstan motor/Impulse head and/or the associated Speed Control Unit. |
12th Mar 2020, 12:35 pm | #3 |
Diode
Join Date: Mar 2020
Location: Eskilstuna, Sweden
Posts: 6
|
Re: Philips N4418 wrong speed
Ok thanks I have to check the speed control unit again difficult to find any faults when its working but too fast. A potentiometer in series to the motor will slow down the speed but that way the speed is not stable
|
12th Mar 2020, 9:02 pm | #4 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
|
Re: Philips N4418 wrong speed
Check the impulse head. Basically it uses a magnetic ring driven by the motor which sends pulses to the head (hence impulse head). These are fed back to the control circuit so they form part of a control loop. After all these years it's entirely possible that the magnet has become weak.
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman..... |
13th Mar 2020, 5:37 pm | #5 |
Diode
Join Date: Mar 2020
Location: Eskilstuna, Sweden
Posts: 6
|
Re: Philips N4418 wrong speed
if so how to solve that how to know if it´s too weak?
|
13th Mar 2020, 7:32 pm | #6 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
|
Re: Philips N4418 wrong speed
You need to look at the circuit...that gives a waveform which you would then check with an oscilloscope....that's how we did it at Philips 30 years ago. Don't know how you would check it without a 'scope.
Check head for continuity first.
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman..... |
13th Mar 2020, 8:15 pm | #7 |
Diode
Join Date: Mar 2020
Location: Eskilstuna, Sweden
Posts: 6
|
Re: Philips N4418 wrong speed
Thanks no problems I do have a Scope but can´t see a pulse info anyware in the schematics? I know I have a pulse
|
13th Mar 2020, 10:10 pm | #8 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
|
Re: Philips N4418 wrong speed
Hmmmm it's 30 or more years ago. We may have had more information available than just what was in the manual. I know there was a separate Circuit Description...maybe that showed the waveform. If you have pulses then it shows that the head and probably the rotating magnet is good. You need to check the feedback circuit.
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman..... |
14th Mar 2020, 4:31 pm | #9 |
Diode
Join Date: Mar 2020
Location: Eskilstuna, Sweden
Posts: 6
|
Re: Philips N4418 wrong speed
Solved!
Solved thank you all. The pulse from the head was only 20mV and the reason the wheel on the motorshaft with the magnetic ring was not in line with pickup head mounted a bit off on the motor shaft. Happy Days! |
14th Mar 2020, 11:53 pm | #10 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
|
Re: Philips N4418 wrong speed
Yes I am also struggling to see the head pulse info in the schematics.
|
15th Mar 2020, 11:55 pm | #11 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
|
Re: Philips N4418 wrong speed
....You just triggered my memory ref the low pulse fault....it was always one of the first things we checked.....a note from Eindhoven was sent to the service workshops advising us to check that the rotating magnet was in line with the head poles. It's quite possible that we measured the pulse ourselves and wrote it in the manual....it's a very long time ago. There was a separate publication called the Circuit Description which, as the title implies, explained how it all worked. Possibly THAT had the pulse waveform shown.
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman..... |
16th Mar 2020, 10:38 am | #12 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
|
Re: Philips N4418 wrong speed
That is great news, what level of pulse voltage improvement did you obtain with better alignment ?
|
19th Mar 2020, 6:43 pm | #13 |
Diode
Join Date: Mar 2020
Location: Eskilstuna, Sweden
Posts: 6
|
Re: Philips N4418 wrong speed
Around 400 mVolt
|