Philips N4450 Reel to Reel Tape Player - UK Vintage Radio Repair and Restoration Discussion Forum

nicola.ghinassi · 13th Feb 2020, 12:54 pm

Hello everybody, I'm new to the forum. I received a Philips N4450 as a gift, and I am proceeding to put it back into operation. I replaced all the belts, checked the contacts and circuits. Two problems: when I turn it on, there is a continuous background noise, I was unable to understand its origin. In addition, the REC key always remains on. Could it be the flip flop card and its transistors? Everything else seems to be working well. I am in your hands to ... find a solution.

Thanks in advance, Nicola

TonyDuell · 13th Feb 2020, 6:16 pm

A function 'stuck on' (like REC in your case) is very often due to the AC128s on the flip-flop boards.

julie_m · 14th Feb 2020, 7:54 am

BC327 will substitute OK for the AC128 in this case. It's a silicon device, but in this application only the PNP polarity is important.

nicola.ghinassi · 14th Feb 2020, 9:14 am

Thanks a lot for the reply, so I would say that I will proceed with the replacement of the AC128. The thing I noticed, when I start with the ON button, is that there is an annoying and continuous noise, like a bell trill, of which I can not find the origin at all. It is present both at standstill and when PLAY, FF, FW and PAUSE are started. In short, always .... any ideas? Thanks in advance, Nicola

TonyDuell · 15th Feb 2020, 6:26 am

There are two things that run all the time (when the machine is on) : The clock timer and the capstan motor.

You can disconnect the timer motor with the 2 push-on terminals next to it (these are 'live', so unplug the machine from the mains, disconnect the wires, then plug it in again). I seem to remember that the capstan motor is turned off in 'Amplifier' mode, so try selecting that with the slide switch.

Do either of those remove the noise?

nicola.ghinassi · 17th Feb 2020, 3:07 pm

I proceed to a check, as suggested. As soon as I have checked everything, I will let you know. thank you

nicola.ghinassi · 2nd Mar 2020, 10:34 am

Hello everyone, solved the problem of noise similar to a "bell": disassembled the rotors, a nice clean thoroughly with alcohol, reassembled the belts. Otra only feels the engine running, nothing else. Unfortunately the old nails had completely melted, they got everything dirty, I had escaped the minimum residues from the first cleaning.

Antonello · 3rd Mar 2020, 9:20 pm

Quote:

Originally Posted by TonyDuell

There are two things that run all the time (when the machine is on) : The clock timer and the capstan motor.

You can disconnect the timer motor with the 2 push-on terminals next to it (these are 'live', so unplug the machine from the mains, disconnect the wires, then plug it in again). I seem to remember that the capstan motor is turned off in 'Amplifier' mode, so try selecting that with the slide switch.

Do either of those remove the noise?

Tony in my 4450 Philips if I put amplifier mode the motor does not stop but starts to turn at very high speed. What could be the cause?

I have already changed the BD135 without solving. I replaced all transistors on the control board

If I disconnect the card and put the amplifier in mode, the motor remains off.

13th Feb 2020, 12:54 pm	#1
nicola.ghinassi Diode Join Date: Feb 2020 Location: Bologna, Emilia Romagna, Italy Posts: 5	Philips N4450 Reel to Reel Tape Player Hello everybody, I'm new to the forum. I received a Philips N4450 as a gift, and I am proceeding to put it back into operation. I replaced all the belts, checked the contacts and circuits. Two problems: when I turn it on, there is a continuous background noise, I was unable to understand its origin. In addition, the REC key always remains on. Could it be the flip flop card and its transistors? Everything else seems to be working well. I am in your hands to ... find a solution. Thanks in advance, Nicola

13th Feb 2020, 6:16 pm	#2
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Philips N4450 Reel to Reel Tape Player A function 'stuck on' (like REC in your case) is very often due to the AC128s on the flip-flop boards.

14th Feb 2020, 7:54 am	#3
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Philips N4450 Reel to Reel Tape Player BC327 will substitute OK for the AC128 in this case. It's a silicon device, but in this application only the PNP polarity is important. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

14th Feb 2020, 9:14 am	#4
nicola.ghinassi Diode Join Date: Feb 2020 Location: Bologna, Emilia Romagna, Italy Posts: 5	Re: Philips N4450 Reel to Reel Tape Player Thanks a lot for the reply, so I would say that I will proceed with the replacement of the AC128. The thing I noticed, when I start with the ON button, is that there is an annoying and continuous noise, like a bell trill, of which I can not find the origin at all. It is present both at standstill and when PLAY, FF, FW and PAUSE are started. In short, always .... any ideas? Thanks in advance, Nicola

15th Feb 2020, 6:26 am	#5
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Philips N4450 Reel to Reel Tape Player There are two things that run all the time (when the machine is on) : The clock timer and the capstan motor. You can disconnect the timer motor with the 2 push-on terminals next to it (these are 'live', so unplug the machine from the mains, disconnect the wires, then plug it in again). I seem to remember that the capstan motor is turned off in 'Amplifier' mode, so try selecting that with the slide switch. Do either of those remove the noise?

17th Feb 2020, 3:07 pm	#6
nicola.ghinassi Diode Join Date: Feb 2020 Location: Bologna, Emilia Romagna, Italy Posts: 5	Re: Philips N4450 Reel to Reel Tape Player I proceed to a check, as suggested. As soon as I have checked everything, I will let you know. thank you

2nd Mar 2020, 10:34 am	#7
nicola.ghinassi Diode Join Date: Feb 2020 Location: Bologna, Emilia Romagna, Italy Posts: 5	Re: Philips N4450 Reel to Reel Tape Player Hello everyone, solved the problem of noise similar to a "bell": disassembled the rotors, a nice clean thoroughly with alcohol, reassembled the belts. Otra only feels the engine running, nothing else. Unfortunately the old nails had completely melted, they got everything dirty, I had escaped the minimum residues from the first cleaning.