Philips compared to Pioneer. Terminally confused. listening, service, better, having

tom

Ok, I give in.

I've a rebuilt SA-8800. CD's played on a Sony Playstation series one sound great. Good bass and middle but very slightly hazy treble, which I put down to the speakers (CS-99A). Then having taken the Philips (720) out of service, just for the fun of it I put it back in. I know sound is subjective but fed from the same source, to my ears the damn thing sounds better than the Pioneer. At first I didn't think it had the bass response of the Pioneer but listening more to the music it has the bass alright, but does not sound as if it has any bass lift. If the music has bass at low volume, low volume is what you get.

I've not found a circuit diagram for the Philips (yet) but everything I've read here suggests that simply because of its age a re-cap could be in order. On the other hand, if it works and sounds as good as it does, even if the caps have drifted from their original value, as long as they are not going to cause terminal damage I'm thinking I should maybe leave them alone.

Faults? Short duration speaker thump when turned on (it's not effected by the volume setting and I've been told that the thump is normal), very slight hiss at maximum volume and no signal input. This is effected by the volume setting. Having said that, with the rats nest of wiring going round the back of a 24 year old Sony TV, a bit of noise is hardly surprising.

I know I've posted about the Philips before but it is a puzzle. A warm running external heatsink about half as wide as the case. Heats up slowly but if anything, with the volume at zero it runs slightly warmer.......

When an amp is aging, a number of sound detoriating issues grow slowly over the years:
- the ESR value of electrolytic capacitors increases, with different effects depending the function of the capacitor (signal path, rail decoupling, power supply, etc)
- small trim pots (like bias adjustment) have surface corrosion, dust etc, resulting in bias offset, signal distortion, etc)
- some transistors start 'rotting' inside, notably the ones that are in continuous class-A, such as current sources and sinks on the main amp board (not the output ones)
- then there are lots of mechanical contacts that start having surface corrosion (all the switches, speaker selection, protection relays, etc.)

Removed my reply because it was not relevant to philips receiver, see posts here after

Just curious. Is your Playstation an SCPH-100X model? That is the best one.

I'll offer two short points:

1. If the Phillips is more that 25 years old you should recap it.  It won't sound worse, and it'll be more reliable.

2.  There can be synergy between speaker and amplifier.  I had some Cerwin Vega D-5s for about 15 years.  I never though much of them, and I tried them with 4 or 5 different amps.  I hooked them up to my 70s Kenwood KR-6160 and they absolutely sang.  It blew me away how different they sounded.  Maybe your CS-99As react better to your Phillips than your Pioneer.  Remember - the speakers are the most critical link in the audio chain, but they aren't the only one.


Originally Posted by OilmasterYou can find the SA-8800 service manual here:

download...r_SA-8800.html

If you're not familiar with this site: it's offered in multiple parts: see the line quot;multipartsquot; : 0, 1, 2. On each page, click on gt;gt; please, click here ! lt;lt; in the bottom section, then unrar them together....

Well, this is not the average amp reading this manual, hence I would not play with the adjustments myself if your not into it (see page 20).

If you are into it, you could do a couple of investigations, but they are potentially damagingthe amp if you slip with the probes, hence I would connect the probes before switching on:

- the differiential amp in the beginning of the power amp section (Q9) has a current sink below with Q11. Both transistors are special ones with two transistors in one package, and are known to become naughty

- the current sink (Q11) should preciously divide the current indicated above (0.5mA) in two. Any offset means potential noise and offset in the output stage

- first: verify if the total current of 0.5 mA is actually 0.5 mA by measuring the DC voltage drop across R65 on top; this should be U=IxR = 0.5m x 91k = 45.5 volt (put volume knob at zero)

- secondly: as indicated in the schematic, the DC voltage at both basis of Q9 should be 0 mV. If not, you've got a problem.

- thirdly: verify the individual current per tail in the bottom across R61 and R63, the voltage drop across these resistors should be exactly the same. If not, then the transistors need replacement (but hard or impossible to find, unless you have a donor unit)

- if all is ok, then verify all the other DC voltages as indicated in the schematic.

The feedback loop does not contain an electrolytic capacitor as I suggested earlier, only an ordinairy film cap C45, so this is not a suspicious component.

As you can see, there is no series capacitor at the output of the amp, hence the switch on thumb may not be quoted as quot;normalquot;; rather the opposite !

The tone amp section has a surprising number of differiential amplifier sections as well (FET input stage, hmm, hard to find parts), so same tests and issues to be looked up for. Anyway, this amp has a high level of special transistors and circuit topology, difficult to repair when getting older. But the warming up heatsink issue can only origin from the power amp stage, noise and poor high tones from any place though.

Or if you are willing to sell this amp to me, I would be happy  

ozzyThank you Oilmaster and everyone else who has given me help with this. I think my original post was unclear; it is the Philips receiver that gives the 'thump'. Someone who knows this model well told me it is class A, and provided the thump is not excessive it's normal. The Pioneer is very quiet at all times. When I bought it, it blew the main fuse whenever it was turned on. A friend of mine writes a Vintage section for a Hi-Fi magazine and he gave the Pioneer to the man who does his Tech work. The report came back that transistors had shorted out on one channel. Exact originals were no longer available, so to get it working and keep it balanced, he rebuilt both channels.

Does the Philips have 'bias'? I've been told that with class A amps, bias might not be an issue. Does this make sense?


Originally Posted by Coconuts 500Just curious. Is your Playstation an SCPH-100X model? That is the best one.

I'm sorry to have taken so long to reply, it's SCPH 5502, sold in the U.K. I've read (I think on AK) that it uses the same processor as the 100X.

If your Philips receiver is the model listed below, then you are talking to the right man; this is homefront hifi gear for me ! And this gear has a large fanclub in Holland as well, so it took me only 3 minutes to find all details, including superb service manuals.... this is a very lucky shot, the manuals are not found for sale on the internet: I know this because I obtained 7 years ago a copy of the 22RH521 amp (not receiver) myself via a friend working at Philips HQ, who could access Philips' archive library .

About the model designation you provided by email: a 22RH521. This is in principle an amplifier without tuner. However, a family member with tuner exist with the label '720' on the front panel, but the model number should consequently be 22RH720. Anyway, you can quickly check what you've got by these websites:

The 22RH521 amplifier:
Vissenoge.../521%20new.htm
amplifiers/22rh521.htm

and the 22RH720 receiver:
Vissenoge.../720%20new.htm
receivers/22rh720.htm

on the quot;sites you can directly download the service manuals.  Hail hail these folks, they must be retired Philips technicians.

I assume the 720 website is your 720 ??? I just remembered that I actually do have the 521 amp myself when I hit these websites (totally silent, that's why I got the schematics, but never started the repair). In Holland they were popular nicknamed quot;fish eyesquot;  in those days.

Ok, studying the quot;720 receiverquot; schematics:

1) this chap does have a output capacitor at the output of the power amp, because it does have a single power rail, which is know to give a quot;houmpquot; during switch on amp; off (charging and discharging current can only go through the speakers). Such single rail design was normal those days, because complementary NPN-PNP transistors were not readily available those days, so only PNP transistors were used, requiring single power rail, and an output capacitor.

2) it's not pure class-A, it's a class-AB amplifier, meaning that it is in class-A at low volume levels, and in class-B at higher volume levels. But that requires accurate bias adjustment, and that is probably the problem in your case: one or both channels are running more and more in class-A, which means more constant current draw through the output transistors, thus heat. Oh yeah, it sounds better, but output transistors and heat sink are not designed for it, and you should not make it run many hours like this.

3) a recap wouldn't be a luxury, the schematics show plenty of caps and many type of caps in the signal path, plus the power supply caps are definitely quot;end of lifequot;. Please be aware that I found several units reported with burned-out transformer, which is due to failing power supply filiter capacitors. Again, don't use it too much, the transformers are very very difficult to obtain (donors club only ), they are a special Philips cookie.

4) this equipment is also wanted by a very special elite group of audio fanatics: the MFB freaks (serious clubs and events in Holland). MFB stands for quot;Motion FeedBackquot;, the special speaker series from Philips late 70s and early 80's. These speakers have accelaration (g-force) sensors in the speaker cone, providing true feedback signal to the amplifier stage from the last component in the music chain, instead of a feedback signal from the output of the amp stage. These speakers have a build-in power amplifier, but they need the other philips gear as pre-amplifier (source selection, tone control, etc.) and they like the model you have, although not specific MFB gear. Very special and very interesting stuff. It's all in dutch, but your receiver is somewhere there:


Originally Posted by OilmasterIf your Philips receiver is the model listed below, then you are talking to the right man; this is homefront hifi gear for me ! And this gear has a large fanclub in Holland as well, so it took me only 3 minutes to find all details, including superb service manuals.... this is a very lucky shot, the manuals are not found for sale on the internet: I know this because I obtained 7 years ago a copy of the 22RH521 amp (not receiver) myself via a friend working at Philips HQ, who could access Philips' archive library .

About the model designation you provided by email: a 22RH521. This is in principle an amplifier without tuner. However, a family member with tuner exist with the label '720' on the front panel, but the model number should consequently be 22RH720. Anyway, you can quickly check what you've got by these websites:

The 22RH521 amplifier:
Vissenoge.../521%20new.htm
amplifiers/22rh521.htm

and the 22RH720 receiver:
Vissenoge.../720%20new.htm
receivers/22rh720.htm

on the quot;sites you can directly download the service manuals.  Hail hail these folks, they must be retired Philips technicians.

I assume the 720 website is your 720 ??? I just remembered that I actually do have the 521 amp myself when I hit these websites (totally silent, that's why I got the schematics, but never started the repair). In Holland they were popular nicknamed quot;fish eyesquot;  in those days.

Ok, studying the quot;720 receiverquot; schematics:

1) this chap does have a output capacitor at the output of the power amp, because it does have a single power rail, which is know to give a quot;houmpquot; during switch on amp; off (charging and discharging current can only go through the speakers). Such single rail design was normal those days, because complementary NPN-PNP transistors were not readily available those days, so only PNP transistors were used, requiring single power rail, and an output capacitor.

2) it's not pure class-A, it's a class-AB amplifier, meaning that it is in class-A at low volume levels, and in class-B at higher volume levels. But that requires accurate bias adjustment, and that is probably the problem in your case: one or both channels are running more and more in class-A, which means more constant current draw through the output transistors, thus heat. Oh yeah, it sounds better, but output transistors and heat sink are not designed for it, and you should not make it run many hours like this.

3) a recap wouldn't be a luxury, the schematics show plenty of caps and many type of caps in the signal path, plus the power supply caps are definitely quot;end of lifequot;. Please be aware that I found several units reported with burned-out transformer, which is due to failing power supply filiter capacitors. Again, don't use it too much, the transformers are very very difficult to obtain (donors club only ), they are a special Philips cookie.

4) this equipment is also wanted by a very special elite group of audio fanatics: the MFB freaks (serious clubs and events in Holland). MFB stands for quot;Motion FeedBackquot;, the special speaker series from Philips late 70s and early 80's. These speakers have accelaration (g-force) sensors in the speaker cone, providing true feedback signal to the amplifier stage from the last component in the music chain, instead of a feedback signal from the output of the amp stage. These speakers have a build-in power amplifier, but they need the other philips gear as pre-amplifier (source selection, tone control, etc.) and they like the model you have, although not specific MFB gear. Very special and very interesting stuff. It's all in dutch, but your receiver is somewhere there: Thank you oilmaster. I once (only once) heard a pair of large 3 way Philips MFB speakers. They might have been tri-amped (the owner didn't let me get close enough to check this; probably thought I was showing too much interest) but in a room about 40ft by 30ft they sounded extraordinarily good. The owner was a strange guy. We had just sold him one of the last Seeburg 45 players and he was like a child. quot;What's this, what's thisquot; (poke poke). quot;Thisquot; was a 500 volt supply line to a very large (200 watts per channel) stereo amplifier. I'm sorry to digress, but we at last got the cover back on before he killed himself. We wanted his cheque to clear before he got that cover off again.............


Originally Posted by CombworkI'm sorry to have taken so long to reply, it's SCPH 5502, sold in the U.K. I've read (I think on AK) that it uses the same processor as the 100X.

They all use the same processor, but the SCPH-100X (which was also sold in the UK) has the best, and most desirable DAC. 550X has a similiar DAC, not quite as good, but close. All the other models are inferior.


Originally Posted by Coconuts 500They all use the same processor, but the SCPH-100X (which was also sold in the UK) has the best, and most desirable DAC. 550X has a similiar DAC, not quite as good, but close. All the other models are inferior.

Thanks Coconuts. To most people these old Sony game machines are still unknown. Much more likely to be found in a skip than a shop

Another thing to know is that your Philips receiver has DIN input/output. DIN type signal are actually current driven signals instead of the voltage driven RCA interfaces. To quot;convertquot; the current signal back into voltage, you can see at the schematic that there is directly a resistor bridge at the back of the DIN input connector (for any given brand/model).

This may explain why a certain CDplayer/amp combination may sound better then another one. In case of the RCA voltage interface, the impedance of the amp must be very high, otherwise the source must supply too much current as it ought to be only a voltage without current (or said differently: the source is loaded too much). So, in your case, the Pioneer SA-8800 with the RCA voltage interface may actually load your cd player (or Sony play station, whatever) too much, seriously influencing the sound. Despite that the DIN interface is current driven, it might be a lower load (higher impedance) for your cd player, and therefore influence the sound much less (or not).

The advantage of the current driven (DIN) interface between equipment is that distance between equipment doesn't really matter, as opposed to voltage driven interfaces. However, home hifi gear is always close to each other. Eventually, the Japanese won the race with the RCA voltage interface and the DIN interface disappeared from domestic hifi gear.

But of course, the Philips might just sound better then the Pioneer, notably because the Philips is at Class-A at low volume levels, and the Pioneer is ice cold Class-B.

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