Philips (Black Tulip) N5748 HIFI Cassette Deck

[mae]

NP designates a bipolar (non polarised) electrolytic.

[Michael 5of9]

NP designates a bipolar (non polarised) electrolytic.

Thank you; so I am looking for a bipolar type; not a polarised type, which means it can be fitted either way. The existing is a 15μf x 16v radial.

[Michael 5of9]

by Harrie » Fri Apr 01, 2016 1:53 pm
Why replacement ? Are the heads damaged ? When just cleaning them is o.k. don't
replace them.

The reason for wanting to renew the heads; was a loss of sound performance on play, this was about 8 years after buying it. I cannot recall the exact observations; it was as if the play heads were dirty, that kind of performance loss

Update: Blue Electrolytic Capacitors; have removed one by one, tested and replaced, on all the small boards. The results; most 4.7μf gave 5.62μf, 68μf gave 99μf, 100μf gave 128.7μf, the readings were well above the stamped value

I have a 47μf x 10v that gives 45.4μf on board U407 Indicator/Peak board; I intend to replace this one

Have come across; two yellow capacitors on each board U302 and U406 C736, C737 marked 4.7μf 35v; have removed and tested and all gives 4.75μf.

One navy/grey capacitor on each board U412-15, C732 marked 10μf 25v, this has the same value’s as the two blue ones on the same boards.

I am assuming they are Electrolytic; why are these yellow and navy/grey, in with the blue caps; is it as Thomas said “Philips used whatever they got their hands on at the moment”

U405 Main board, are all alright, so far only one cap is below, I take it caps over the stated value are good

I just have the caps on board U410 Recording Pre.Ampl to check.

Advice would be much appreciated

[Michael 5of9]

I had 4 wires to unsolder from U405 Main PC board and remove the 4 screws securing the front section; to be able to turn over U410 Recording Pre.Ampl PC board, to remove and check the Blue Electrolytic Capacitors.

The meter gives 7.35μf on a 4.7μf; on this board they all varied down to the lowest reading of 6.75μf.

The four 100μf caps gave 158.4μf, 247.4μf, 155.4μf and 164μf; these are much higher readings than the stamped value, I need advice on these now whether to replace them and with what
I have finished testing all of the Electrolytic Capacitors apart from Motor 1 which has a bipolar electrolytic

I tested with my meter with some new Electrolytic Capacitors 150μf gave 163.2μf and a 22μf gave 22.50μf which would suggest they are within the tolerance value and my meter is good

[Michael 5of9]

This Capstan Motor; with a bipolar type “NP” electrolytic capacitor 15μf 16v redial fitted.

I would like to replace this cap; however, finding a 15μf cap has proved to be a challenge!
There is a choice of fitting a 10μf or a 22μf; please advise
I haven’t remover and tested because it is heavily/well soldered and likely to cause damage to the cap.

[MGf]

Capacitance measurement functions in regular multimeters tend to give a higher reading in most cases.
But my experience is that Philips capacitors frequently give a higher capacitance reading when they age.
The thing with capacitors and electrolytic capacitors in particular, is that there is much more to them then only their capacitance value.
ESR (Equivalent Series Resistor) is one very important one, but their influence depends largely on the function of the capacitor in a certain schematic.
The capacitance measurement method gives a reading when measured with a certain frequency.
Different frequencies could give other readings on your meter. The most ideal measurement is to measure the capacitor using the frequency close enough to the frequency the capacitor is used for. Like for power supplies use 100Hz/120Hz and for audio use 1kHz, 10kHz. But to be able to measure like that, you will need a much more advanced capacitance/ESR meter or a LCR meter.

[Michael 5of9]

by MGf » Sat Sep 15, 2018 11:08 am
Capacitance measurement functions in regular multimeters tend to give a higher reading in most cases.
But my experience is that Philips capacitors frequently give a higher capacitance reading when they age.

I’m pretty sure that we can call these old caps now and with old technology. The comments I have read on some websites https://www.hificollective.co.uk/compon ... hicon.html regarding the new types of electrolytes, boasts of achieving higher sound quality in audio devices and are constructed with select materials to create superior acoustic sound.

I’m looking forward to hearing “refreshing sound quality” by replacing these old ones; this is what I am aiming for.

Can I assume Philips made or had these electrolytes made solely for themselves back in the 1980’s; when they were producing top of the range audio equipment and that they now, no longer are leaders in this area of the market

Thank you MGf for your input; much appreciated.

[Michael 5of9]

A sample of the new Vishay electrolytic capacitors to be fitted; after the stamped value is the letter “M” which stands for the tolerance value, being ± 20 %.

[Michael 5of9]

With turning over the U410 Recording Pre.Ampl PC board several times to work on it; the tension from one of the wires has broken the copper print.

I used an aluminium offcut from a cap to make the repair.

[Michael 5of9]

Here you can see the old and the new with the rear side afterwards.

[Michael 5of9]

U405 Main PC board and U410 Recording Pre.Ampl PC board, with new Vishay Blue Electrolytic Capacitors, I have managed to keep uniformity on these boards.

[Michael 5of9]

One of four Boards (U412-15) with New Vishay Blue Electrolytic Capacitors

Have replaced all the difficult to reach caps whilst the unit was disassembled.

Boards U406 (the two yellow caps are still there), U407 (four 4.7μf 40v redial caps are still there) U409 (the two yellow and two 4.7μf 40v redial caps are still there) all the rest have been replaced, sadly not all Vishay some Nichicon, Multicomp and Panasonic.

It would be good to have a mentor to check and adjust all the Potentiometer before testing?

[Michael 5of9]

I have the unit working again; no sound coming from the left side, this is with either connection at the headphone socket or when connected to the amplifier via the 5 pin round DIN socket, I need help, thanks

[Michael 5of9]

No sound on the left side outputs; both VU meters are responding very well whilst playing a tape. The service manual gives a few voltage readings that can be checked on certain transistors, have done this, some of the left side voltages are down, you can see my results via the link below.

https://1drv.ms/b/s!AuQDAPiShOjc83VEyP6uYzBqquiZ

Transistor: Advice has been given; that the problem is likely to be a Japanese made transistor, not the BC/BD ones. I have come across some that reads C1737 95B; I did a Google Search and another search from a very useful website (see below) that has identified from the service manual all the existing transistors and gives there properties, but not the C1737 95B, well it’s not important to know this now.


https://alltransistors.com/transistor.p ... stor=23410

https://www.electronics-notes.com/artic ... istors.php


http://www.bustedgear.com/faq_transisto ... ution.html

[Michael 5of9]

Gears replaced: This post comes in out of chronology; the instructions were a must, I used a well-fitting socket screwdriver on both sides to give support whilst pushing both of the gear onto the shaft, I cannot remember which one, there is one that you need to remove a further steel plate to gain access for giving support!

The instructions stipulate “At this second gear wheel as far as you push through to the Fergie about 1 mm above the wheel.” it would be helpful to create a stop inside the pushing socket to stop the gear from going beyond 1mm, it’s not easy at all having to back/reverse it out to the critical position.

I have noticed that this second wheel whilst in the play mode does not have full alignment with it’s mating gear.