PIONEER SA-606 UN VERO DISASTRO #vintage #audio
So the first thing that caught my eye that caught my eye was the condition of the fuses This is one this should be a 125 mamp fuse This here is a wire soldered on and its other companion is this same condition soldered wire I know Good morning and welcome to The River Lab today's patient is a Pioneer l'sa 606 that they sent me and that makes a relatively strange defect It turns on late but it doesn't turn on late because not when you press the switch does not light up the Veters light up and it seems to be working but the audio can be heard with a delay it can take up to 20 minutes sometimes it starts immediately and sometimes it starts with a delay and sometimes I mean it takes a really long time to start 20 minutes half an hour and we need to see why this problem here is not put in good condition all dirty inside so it will have to be cleaned and it has already been looked at and we will see In short what needs to be done so I'll make it short for you continue watching this video and see what this time too I'll combine for you the amplifier to check today is this Pioneer sa 606 which I'll tell you the truth After opening it I didn't want to close it directly I didn't want to do anything with it Now I'll show you why anyway then I decided that we'll try to repair it So when I say we'll try obviously it's me and you because because you know I'll do the repairs together with you because I'm alone then the first thing that caught my eye that caught my eye was the condition of the fuses This is one this should be a fuse of 125 mamp This here is a soldered wire I know and its other companion is this same condition soldered wire I know and already this and I mean Let's say it's not good Now I'll show you other things then the other things that catch my eye are these resistors mounted so the terminals of the old resistors have been cut and these new resistors have been soldered to them the same thing for all the resistors on the emitters you can see under the wires of the old resistors the same one next to it I'm not saying this to criticize Well I'm saying this because I actually see these works and if you allow me I can even refuse to put my hands where certain things were done because in short we are in a democracy the other thing I noticed is that stuff is missing for example where you see those three little holes the protection triac is missing and then down here another component is missing again a transistor which is part of the protection now I'll show you from underneath it's clear from the bottom in fact this is where my eye fell where At this point a component is missing here it's missing another one and unfortunately the whole amplifier has been worked on a bit. I wanted to show you that the first thing that needs to be done, unfortunately, you see, is to do a good cleaning otherwise you won't understand anything even in what you're going to do, let's say on the amplifier. But obviously this isn't anyone's fault, let's not say the person who worked on it or the owner of the amplifier because over the years these things, let's say, happen here So I cleaned the device which was the first thing to do before my audio stopped so you couldn't hear me And now let's say the appliance is cleaned I'll try to put back those mounted resistors let's say so now I'm not saying that I'll do an exceptional job and I also understand that the resistors are mounted underneath here I understand that he also did this job because it's a bad job to change them and put them back on let's say as they should I'll try to remove them anyway and try to put them back on so that you can see maybe a little less like this these welds In short, once this job has been done when it's time for it to be clean Once this job has been done I'll go and see the components that were taken away, one is down here, one was over there, here, in short, now that it's all clean, we can work on it better, we understand what we're going to touch compared to before, it was all dusty and I'll try, let's say, to understand why the protection components were removed and then let's say, we'll see each other again. I removed the resistors. Now I'll try to
reassemble them. I understand, it's a really bad job, eh. Whoever did this job did it? because it works really badly but eh mounting resistors like this let's say it's bad I don't want to say it's unprofessional but at least it's bad Let's see if I can It's not a given if I can do a little cleaner job Then another thing that needs to be done is now I have to check all the welds because I see that there are several let's say codol we used to say in codol jargon anyway that they are ruined if you see this one now they look bad eh this one for example these are ruined now I'll look for another one but there are several, now I'll come closer for a moment, I'll show you those over there better, let's see if they can be seen better. Here now, perhaps from this angle, they can be seen better if you see there is this one here which can be seen which is practically detached from this side here and there is this one here which is detached from this side here, they must be observed very carefully because you will find several of them and now I'll stand there with my glasses, I'll look at the whole printout, I'll re-seal them and then we'll see each other because there are quite a few of them, it's practically not Not only they are So in the meantime let's try to remove these fuses here that were there Jumper and we put on let's say the right fuses Now let's see how these fuses were reduced I hope they look good someone will say that I'm being polemical as usual But I ask myself and I say if there were two fuses and we put on two pieces of wire Obviously it's not the same thing okay let's continue further So fuses Changed the amplifier ready let's say for the test for the test we cleaned it I did practically nothing to it apart from cleaning and change the fuses in short these little things and put the resistors back in place So what have you seen and redo the soldering under the printed circuit obviously So um it's ready for the test if you remember the customer had said that this amplifier here started late I mean when I turned it on he heard it after a while because here the displays turned on but he couldn't hear the sound or it started late So sometimes it started earlier sometimes it started later I did the tests But the tests I had done seemed to always started and instead I realized that it doesn't always start Now I'll show you I'll put the oscilloscope here on one side and I want to point out the voltage in this case here now instead of 230 vol it is 240 V because the mains voltage is true that it is 230 V But we have a tolerance from the Enel of 10% so that means that 230 V can be 23 V higher than 230 which can even go close to 250 and here that the voltage is a bit of a dancer Today we have around 240 V I'll show you something I'll turn it on now and look at the oscilloscope I'm powering it through the lamp and as you can see the signal arrived immediately you can see the sinusoids in the darkness I'm going to turn it on Look at the oscilloscope if it doesn't make me Liar it's not starting I'm going to lower the voltage you see we have 239 V if I lower the voltage he when he arrives next it seems like 230 220 now I don't remember from here Let's see if St appear you see 230 times the sine wave has started it means that this amplifier the moting circuit that you have incorporated has a slight problem and if the voltage is higher it doesn't start or it starts with a delay then the start with a delay I understood why sometimes the supply voltage dropped and the amplifier worked but before moving on to investigate instrumentally I wanted to show you the famous explanation of how the diting circuit of this amplifier works here So let's see if I can let's say explain it to you at the start of the amplifier eh through d18 and through r104 this transistor excites immediately practically This transistor excites immediately and keeps low Eh the base of the transistor q17 q18 conducts q17 cannot conduct because the base let's say is at zero in brackets until q17 does not conduct and here on the collector through this resistor r102 we get a small negative voltage this ensures that right here there is absolutely no voltage at all so that it does not conduct and the amplifier a part of the amplifier that let's say of the preamplification if I'm not mistaken I don't have the whole diagram here now However let's say the plus B is missing and the amplifier remains silent when through r93 d19 and then there are these let's say this capacitor and this Resistor Here we introduce a delay of this negative voltage practically the negative voltage before it loads here and reaches the right voltage passes let's say about 1-2 seconds this time here eh When the voltage reaches um its negative Maximum Peak and here we have about - 1 v - 1.8 more or less at this point here Obviously this transistor stops conducting and through um this Resistance here the base of q17 is powered which can carry the + b Let's tell the amplifier that if If I'm not mistaken I think they are around 40 v or more then at this point the amplifier begins to play, let's say, it can come into operation because if the plus B is missing, the amplifier, even if the finals are powered on its own, does not receive, let's say, any low frequency signal so we have to investigate in this area here why this transistor probably doesn't get the Men 1.8 so this chain Here from r99 c72 we read this other resistor badly and what it
is because this transistor could also not work but if it didn't work it could be that it is oo always conducts so q17 It never conducts and the plus B would never be there or if it were interrupted at the start of the amplifier there would immediately be the + B the fact that it arrives late There could be a problem on these two resistors on this Resistor Or maybe even on this capacitor here because probably and then maybe the measurements make me a liar on the basis of q18 in my opinion the Men 20 V does not arrive which then obviously comes from r99 and Da this other resist which I can't see the value is lowered until it reaches let's say the minus point I think 1 times and something to ensure that q18 stops conducting let's see why and let's see what happened So before continuing in the video I wanted to show you the new printed circuits that have arrived they are in this box Here they are then at the end of the video I'll show you them better So guys this This video is sponsored by pcbway which has always been my partner for printed circuits for many years obviously long before I I could make the videos and you can make estimates online and know the cost. Obviously before placing the order with the new technologies they can make printed circuits with up to 14 layers and in various shapes, many colors and different types of material. If you want, they will mount the components directly on the printed circuit so that you save time. You will receive a product already assembled or pre-assembled and as I repeat they are a serious company. I have always found them well and that is why I strongly recommend PCBWAY. Then at the top right you see the multimeter while this resistor here that I put in this position is r99 of 27k which then leads to c72 and is used for the negative voltage that will have to drive the transistor to disable it let's see for a moment on one side there should be about 18 vol and then let's see how much there is on the other side Obviously I put the resistor in this way to show you the measurements and make you understand what the resistance was we have 19 and from here it drops to 4 we need to investigate if these 4 vol which must be here that is - 4 V on this side we have Men around 18 V and Here we have - 4 V after that another resistance must pass if I'm not mistaken from 10k to go and drive the base of the transistor But let's go and see why we give this voltage is so low at this point here that it shouldn't So I discovered why let's say it doesn't start not enough negative voltage arrives because OV Afterwards I'll show you from the diagram anyway at this point here there should be around 47-48 V but when it turns on we are at 5455 V with the obviously higher mains voltage if the mains voltage remains lower here there is a normal voltage i.e. 4748 vol and the divider works it's the divider that
doesn't work in this way yes you have to reduce the value of the Resistance I'll show you this Resistance here by a certain percentage and now let's do some math let's see I'll try to explain to you let's say my theory We went to measure Here instead of 47 V there was 50 Boh 55 it seems to me I don't remember it anymore this voltage here arrives here via this Resistance it goes to the base and let's say Here there is another Resistance and here the negative voltage arrives the negative voltage that arrives at this point here practically that would then arrive here is determined by this divider here and this practically the difference between these 20 V that arrive here and these 47 times that arrive here at a certain point at this point here there must be - 1.5 - 1.8 now I don't I remember precisely while instead it always remains a voltage of 0.6 V positive Now my theory is that since there has been an increase in the voltage of about 10% we are at 200 40 V instead of the 220 V for which the amplifier was created therefore this divider here which was made with the mains voltage changed and the mains voltage has increased here let's say it is no longer valid as it is made so we need to decrease and in my opinion we do the test anyway this Resistance here of about 10% now to be sure we can also decrease it by 15% so that then the voltage that arrives here will be let's say the right one so that nothing happens and that the circuit remains balanced and can work even if the mains voltage goes to 240 V which is easy and nothing I proceed and let's look for a moment at how much to lower the resistance In fact you can immediately see the resistance was 27k 27 for let's say 15% and around 22-23 Km let's see if we can make a divider with a couple of resistors perhaps in series or in parallel and mount it in place of r99 nothing will happen to the circuit because the drop is still small so we can forget about any damage but in that way the divider will be balanced once again between the negative voltage that arrives from here and the positive voltage that arrives from here through this other resistor and the circuit should work let's say perfectly as at the beginning. So I put two resistors in series, one of 10 and one of 12 km so as to make 22 Koh
which was about 22 22 21 km or so that had been estimated and in this way the device always starts and in addition we have at this point here that I am now going to measure you can see it in the voltmeter as soon as it turns on the voltage immediately rises to 50-odd Then as soon as the circuit starts let's say as soon as the power supply It turns on obviously there is a slight absorption and the voltage stabilizes at 48 V which is not very different from the 47 V Let's say originally and in this way Here we have solved everything Now I'll show you in the diagram where I put it I'll give you a very brief R assumption is Better to abound than to lack someone said then the matter is this here it was said that this power supply at the start passes the voltage from here this transistor conducts and this one here obviously doesn't conduct because it is forbidden then gradually that this that this negative voltage charges this capacitor here at a certain point exceeds the threshold and here at this point here yes they will find approximately - 1.5 - 1.8 I never remember its sheets here but I covered it However there will be a negative voltage in this transistor it is obviously forbidden no longer throw the base of this transistor here to Ground and this will lead producing the pub and the amplifier starts with the increase in the mains voltage which there was from 220 to 230 which then I repeat also goes to 240 and even more more this 47 V At the beginning it was much higher so this point here which is determined by this positive voltage that goes towards this base and by this negative voltage that always goes towards this base no longer combined, that is, it only worked when the mains voltage was around 230 V maximum. Otherwise here we were left with a slight positive voltage, however, sufficient to make this transistor conduct. I slightly lowered the value of this resistance here by about 15% in order to bring the correct voltage here by balancing the increase in the mains voltage so that this divider at this point R is balanced as I repeat, nothing happens. It's not a terrible change in the circuit because we're talking about a 15% drop. However, in this case, nothing happens here. The amplifier is the problem that didn't start. that couldn't be heard is solved and now we have to solve the problem of the protection of the amplifier which has been completely removed and I'll show you how to do it and we'll see together then before moving on to the protection section which has been removed I'll show you I wanted to replace this LED which would be the ignition LED Why doesn't it work So I don't have an LED like that It's a turned LED I don't know how How it is So the only solution that could be is to fit a 3 mm LED or green or blue I don't know I wouldn't like it more blue either But seeing as it was green I'll reassemble the green so all that remains is to slightly widen the little hole that is here with a pin it's almost 3 mm but if you see the LED doesn't fit in it so I'll widen it slightly now I'll take the drill and I'll widen it a little so that we can fit a normal LED instead of a contraption like the one there then this here is the little hole that was in the LED the strange one there let's call it that and it needs to be enlarged a little First of all, I'll pass a pin slightly larger than that and then I'll pass the 3mm pin through it. Yes, I'll
pass a 2 and a half pin and now I'll pass the three-point pin and then we'll see if the LED sticks it in [Music] Let's go for a minute the LED sticks it in and now I'll clean this bib here that's there and I'll come back then to clean the bib just pass a pin slightly larger than it with your hands and the pin is gone and the LED centers perfectly we can mount it on the other side please the LED there is its support let's say rubber which is also a little ruined common with a little bit of glue like it was You see here there was some more glue I'll put it back on and then let's say I'll show you the result That's it the LED has been restored and now you can see let's say how it was originally We don't notice that let's say it's been changed then as we saw at the beginning the protection of the amplifier has been removed now I'll show you where they were removed the components on the amplifier and then you have another explanation to make you understand how the protection of the speakers works practically that there is no direct current on the speakers otherwise they would be used in this amplifier which is a little different from the usual amplifiers that the Rela is mounted on let's continue So let's see a little These are the two resistors in series that I put in for the other work that was seen before then if you see stuff is missing here the triac is missing which has also been removed from the Protection here one of the two transistors which has been removed is missing now to understand how the Protection works in this amplifier I'll show you the diagram because it's a protection let's say a bit bloody compared to other amplifiers let's go and see the diagram So the protections on the amplifiers are usually put to avoid that there is a direct voltage on the speakers because if it goes short these here let's say schematically these here on the left that you see are the finals this one here on one side is represented schematically let's say the final of the amplifier Here are the two finals if one of these here two goes short not in this branch But here let's say it is connected Theoretically always very schematically I say it because then otherwise there are disputes let's say this part here goes to the speaker if one of these two short circuits positive voltage or the negative voltage of the amplifier of the amplifier's power supply because you know it works with dual voltage it ends up on the speakers on the speakers and obviously the speakers not being created to work in direct current the speakers burn out So in most amplifiers the protection is done through a Relay if the circuit senses the direct current voltage that is going on the speakers for various reasons, the most probable one, I repeat, is a blown end, the stop, the relay opens and disconnects the speaker in a way that protects it in this way the protection is done bloody in a bloody way You see here is the power transformer here is a schematic Oh obviously here is the transformer of the power supply Here is this scr that has been removed and as you can see the scr is mounted here if this scr triggers what happens is that there is an increase in current in the power transformer and it makes the line fuse solder the fuse blows So it's bloody because once that happens the amplifier stops So how is this protection made here when we say through these resistors we have on the speakers a positive or negative direct current voltage of about 8 v passes through these resistors goes direct and triggers one of the two transistors this transistor triggers if we find the positive voltage. That is, if it is burned out, in practice this transistor and this other one is triggered if this other transistor here is burned out, that is, it triggers with a negative voltage on the triac on the Gate of the triac when it senses a positive or negative voltage we know that the triac triggers with either positive or negative voltages it goes into conduction going into conduction As has been said it basically short-circuits a part short-circuit the bridge short-circuits the power supply in this way here the transformer absorbs a lot and the fuse blows it's bloody normal things instead if there is alternating voltage the classic one that goes to the speakers through this low pass filter is let's say Everything is killed and the voltage does not reach the transistors and is not driven so the control circuit is done in this way here Here the triac has been removed because it probably triggered every now and then go and see the reason Now we have to go and see if Quest This is a channel this one goes from the other channel eh the other Resistance that carries voltage from the other channel now we need to check these capacitors here if they are good the resistors have remained at the right value and then since they have removed one transistor I also remove the other one and change it and I have to find a triac that is suitable now we have to tell the truth in other amplifiers Unfortunately I have seen them remove these triacs here because every now and then they trigger for no reason so let's go and see what we say can be done Meanwhile I'm going to check all these components and then we'll talk again So I haven't disassembled anything yet I was taking a look and I noticed something strange So the strange thing let's see is this this resistance here which if my eyesight doesn't deceive me is brown black and orange so 10,000 ohm should be Brown black and red 1000 ohm is the resistance that is placed between the gate and the ground I checked the diagram several times and it should be 1000 ohm now I can see it badly however we will dismantle it and go and see if it is 10,000 ohm being a value 10 times higher is practically due to an assembly error I don't know why And this would also explain the false triggers of the triac view On the other hand if I'm not mistaken the resistor should be Quest Quest the one to be dismantled now I won't deny you that work with the camera in front and try not to block everything It's difficult for me because maybe I'm not as good as those who are used to filming I'm not that I'm a filming wizard, however I put a little bit of tin on it new and then I try to dissolder it if I get stuck and I can't do the dissal and I'll show you again after I've desoldered it So if it's said it should be this one working from afar it comes back really bad Now I'll remove it and we'll measure it together and the resistance as you can see seems to be 10,000 Ohm now we'll attach the crocodiles to it and look at it with the tester Here it is 9,990 K yes 10 K who knows how it ended up there then I change it and also check the capacitors then I dismantle the transistor I put the triac back in I also removed the transistor which was the only one left that they had left of the protection and now I will see let's say among the European transistors that I have what is most suitable to put back and the same the triac Here they are the two transistors let's say of the Protection I have reassembled these two I have to solder them again and I found some Japanese equivalents So the originals were du sa 904 And du SC 191 which were salient characteristics 90 V 0.2 W 0.05 amp I replaced them with 2 saa 99.92 2sc 1845 which are very similar but the voltage is slightly higher 120 V 0.5 W so a little more dissipation the current remains the same 0.05 amp And so let's say this too is done then
I am preparing a video I will make a video on how to replace the transistors that are no longer found Here is the triak that I mounted and the original triak the missing one was practically a 200 V 3 amp triak with a trigger current of about 30 mamp maximum Since it's not, let's say , critical, I mounted a 600 V 6 amp triac and I made sure by measuring it with the Eh test triak scr that I had shown you that I had built, you can see it in a video, I went to check that the trigger voltage and the trigger current Sorry on the Gate of this triac too did not exceed 30 me so that this thing here too let's say has been done now and then I think we can test the amplifier inside as you can see compared to when we got it, it's nice and clean We did a good job you and I always Now I'll show you the aesthetics it looks good then I'll give it a light clean here anyway aesthetically on the front it's quite clean already the cover needs to be cleaned and then we'll clean it and now we have to measure the performance then this time we'll use the HP audio analyzer which is this obviously we'll also use it to measure the power because now I've set it up so that it measures the power we've always seen it with a wattmeter and now in this way we will measure the power instead directly in watts digitally the amplifier should deliver a minimum of 40 W per channel and let's see before it reaches clipping How many watts it actually delivers look at the sinusoids when they start to cut We are at clipping And in any case now we are already at 50 W And the device continues let's say not clipping again Raise it a little we reach clipping at over 60 W I would say that in terms of power it is quiet here We are at 37 W 40 W as it should deliver completely distorted inputs and 50 W it still hasn't reached clipping yes I would say it's more than fine I turn it down and now we measure the distortion I set the audio analyzer to measure the distortion as you can see In fact you can't see it I'll show you for a moment the little button that indicates the distortion is on I raise it I put it at about half the power Let's put it around 20 W it should be like 0.05% distortion and we are at 0 vir 02 because as I tell you there is always the point in front which is as if it were a zero SCH the amplifier is doing more than well I bring it to around 35 W 0.03 and here we are practically close to clipping We are almost at we are at 45 W broken 0.04 if I go into clipping obviously As you can see we have risen to 3% distortion and the amplifier is performing as per the specifications or rather let's say as it always happens in these amplifiers here it is better than the minimum minimum specifications declared now all that remains is to clean the cover which it's really dirty and reassemble it And this amplifier is also ready. In fact before doing this this procedure here to clean it I would say that we can also measure the bandwidth this time then here we have our amplifier under test I obviously have already adjusted the volume to a volume that seemed appropriate for the measurement we want to do and let's do this test here let's now I'll also frame the oscilloscope so you can see the progress let's say work then This is the software interface that connects the HP analyzer which is this Let's say it's a very good product, but it's a bit old and it's been interfaced with a computer with a program that Walter Brollo made and I invite you to go and see his videos which are very interesting. In this way we can read the bandwidth
automatically instead of doing it manually as the audio analyzer did originally. So let's set the zero and now all that remains is to give it the Start here. We've set the zero, there's an input signal of half vol 1000 Hz and at the output we have an 11. 49 V RMS which corresponds
to approximately fifteen watts so by nose we give him the Start and he sees that it starts to run 24 Hz 28 Hz 32 Hz the analyzer you see that the numbers are moving because it is moving forward the number on the right is measuring the volts which gradually arrive so that we can then make the graph and the numbering that moves instead on the left are practically the Herz or the kilz you can also see on the oscilloscope that it is increasing the frequency practically the same the interface is telling us what it is doing and it will arrive at the maximum frequency of the analyzer which if I remember correctly is around 100,000 Hz After that it will show us the graph Here it is it has finished So let's see this graph here You know that the bandwidth, as I told you other times, is measured when there is a drop of 3db compared to the 0 DB that we have set in this in this case here so as a minimum bandwidth there is no problem. In fact it even gains by one DB and 6 but within the 3 DB above or below let's say the bandwidth is that. In fact if we go around 1000 Hz we see a little at 1000 Hz As you can see we are at 0 DB where we started at around 1000 Hz Now I move the mouse it can't be seen too well however we should have a drop of 3db which would be here and here oo an increase of 3db which would be above and here we are normal up to this amplifier there is a drop of around 3db it arrives at around 50,000 Hz it reaches around 50,000 Hz er broken So the amplifier cover is this one obviously after many years and it has accumulated there some of the dirt also as I explained to you in the other amplifier because it is rough and now I'll show you something and then it has to be washed in the sink This one is washed Soap and Water in the lid as I repeat not the whole amplifier because if you see it must come practically now you can see the difference very badly Unfortunately with the light of the camera but I can assure you that where I cleaned it Here it's a completely different matter you can see it that is I cleaned it very little Obviously compared to this part here which is dirtier Here There's all the yellow. Let's say there's dirt stuck to it.
Clearly, it's not like you can dismantle the piece of furniture and wash it in the sink. Every now and then, however, now I do it in such a way that it's nice and clean. So, as you've seen, the repair is finished. This Pioner amplifier has been put back into practically optimal condition like when I left the factory and even if the aesthetics obviously show its age , it's still in good condition, everything inside has been cleaned. Have you seen the work? Let's say that I did it and I hope that the video helps you. Obviously if you liked the video I remind you to subscribe to the channel if you haven't done so so as not to miss other videos that if you like them so if you also click the bell you will be notified and there is also the patreon channel Anyone who wants to can also subscribe there And in the meantime I say goodbye to you and we'll see you in the next video Hello everyone [Music]
2025-03-30 23:05
