As yet said in #14, Philips 22AH691, made in Singapore. Sadly, no service manual either.
Best regards!
1) clearly those sound sources do NOT put out the same level .... most normal of course.
"1 V RMS" means it can put that out, but it ultimately depends on Music program.
2) most certainly Class AB.
Class A is nice but way more expensive for the same power, so practically not used in Consumer equipment, except very very few Top Class amps.
Impossible in a generic low cost amp.
The fault could simply be a degraded contact in the signal path.
As a general precaution, clean all the switches and pots with isopropyl alcohol, let dry, and then spray contact cleaner, whatever reputed make is available.
And please do not change the preset positions, that may cause problems.
That might make a difference.
As a general precaution, clean all the switches and pots with isopropyl alcohol, let dry, and then spray contact cleaner, whatever reputed make is available.
And please do not change the preset positions, that may cause problems.
That might make a difference.
Oxidized contacts in switches and pots can also be a source of distortion as well as signal loss. Oxides can be partially rectifying - that’s why we HATE them.
I encountered this, many years ago. Lots of audible distortion, eventually traced to a pair of contacts in an old and rusty input jack. I replaced the jack, and all was well.
You can make a rectifier for a crystal radio with all sorts of odd materials. A scrap of pencil lead (graphite) pressed against a stainless-steel disposable razor blade, for instance! (I think the transparent oxide that coats the stainless steel plays a role.)
-Gnobuddy
They want 15 euros for a service manual. I don't know if I should laugh or cry...
It is a common enough circuit, look for the transistors as the search basis.
Amp using 5200 transistors with so many volt rails...that should work.
The tuner section also will have most likely Matsushita (three arrows in a triangle or stylized M), Mitsubishi, Toshiba or NEC chips.
4558 or 5532 in the pre amp section, rarely 6556.
As such, nothing very hard to find information about.
And Philips at least used good switches, pots and other materials, build quality was good.
Amp using 5200 transistors with so many volt rails...that should work.
The tuner section also will have most likely Matsushita (three arrows in a triangle or stylized M), Mitsubishi, Toshiba or NEC chips.
4558 or 5532 in the pre amp section, rarely 6556.
As such, nothing very hard to find information about.
And Philips at least used good switches, pots and other materials, build quality was good.
Too much overthinking on new transistors here. MJE15030/1 biased at 10mA will be plenty good enough.
Can I conclude that when you do not have the original or compatible transistors at hand, you can put any model and it does not matter the type of package, if they have the minimum voltage and current specifications? Of course, if they can physically fit on the amplifier board and heatsink. The final transistors do not give taste and color to the sound, just amplify?
An amplifier is supposed to amplify the sound without distortion!
If needed, put slightly more robust and newer devices, and if in doubt, this forum has many experienced and helpful members.
Also, it is working, just do the contact clean up, and see what happens.
And enough ways have been suggested to reach a solution...substitutes, to be able to fit larger devices, and so on.
Enjoy the music...
If needed, put slightly more robust and newer devices, and if in doubt, this forum has many experienced and helpful members.
Also, it is working, just do the contact clean up, and see what happens.
And enough ways have been suggested to reach a solution...substitutes, to be able to fit larger devices, and so on.
Enjoy the music...
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Within reasonable limits, and only for amplifiers which do not REQUIRE specific types. Voltage, current and second breakdown capability need to be respected. There needs to be enough composite gain between driver and output, and the replacement needs to have speed that is compatible with the circuit in question. Is it fast enough? Does it have enough, and flat enough, gain characteristic? Are they matched and how well? Did they need to be? The more refined the circuit is, and the more that is expected from it, the closer to the original types you need to be. If you put in TIP35’s where there used to be Sanken LAPTs or 80 MHz ring emitters, and now you can only get the distortion down to .08% instead of .003, that’s on you. Most of these “price point” circuits can’t get that good regardless of what you put in there - and the originals were likely chosen for BOM cost anyway. A power capability upgrade is often a good thing because the bean counters were cheaping out.
Nope.. you can't always just substitute any part... different gains and speeds can cause stability issues.
I would like to check the current quiescent and maybe adjust it, but I don't know where is the measurement points. Is it possible without the electronic scheme?
The output transistors probably have low value (<1 Ohm) emitter resistors. Measure the voltage across them and calculate the current.
If it's in the picture, 0.68 ohms, it has three pins and I don't know where to measure the voltage.
Between 1-2 and 2-3. Positive probe on 1, negative on 2: if the measured voltage is positive, this is the current of the NPN transistor, and 2-3 the PNP. Else, the other way around.