Denon DRA-F109DAB flashing red light repair

hi guys and girls on YouTube and welcome to my channel in this video we're going to be look at this little Den high-fi system um it's a Dr f19 dab um now one of the problems with modern HiFi equipment is um if you haven't got the service manual you're absolutely stuffed you very very little chance of finding a fault without the service manual um so we'll just plug it in and uh see what the fault is and then I'll explain why the service manual is so important on uh modern Hi-Fi equipment right so here we go plug it in uh it's completely dead and then after a short pause um we've got flashing light on the front so the actual power Supply um the connectors are here I don't know if you can see it down there they're all marked the first one's CPU 5vt uh that's the first thing we need to measure there and as you can see we got 5.19 Vols uh now all these other um pins here are all if we tap onto another one they're all completely dead um also the amplifier Supply the high power what is it 30 1 32 volts on there um that's all got no voltage on either um so without a service manual that's all you can do now um and the reason is with a lot of Hi-Fi equipment when something goes wrong um it switches into a safe mode it switches off um and it just won't do anything no matter what you do this won't do anything and that's why it's so important you need the service manual um because what we've got to do is got to put this into into the um into the uh service menu uh and it should tell us on the front there what the problem is uh and in some circumstances um some rails will be powered up so we can make additional measurements um so let's get the service manual first right so I've got the service manual and that tells me to um enter the um service menu we press the power and you press the preset recall P them both down while you plug it in the mains uh and it should tell us on the front then what the problem is right so I'll just set the camera up in front of it I'll just um unplug it to reset it and then it says you hold that down and that down and we power up at the same time right now it's come on and it says there protection power um so there's a fault on the the power supply that's actually uh shut this thing down um but you can't do anything with it until you cancel this protection um so even if you find the fault um by accident without a service manual um it still won't work because you've got to cancel this error out of the memory before you can go any further and so now that should enable us um to check all these power rails are correct because it's like in a safe mode now right so now I think I see what the problem might be uh I've clipped onto the plus 12vt rail there and we've only got 9.27 and if we measure the uh minus 12vt rail uh we've only got 10.3 volts uh so what I'm going to do is I'm going to leave that connected like that we're measuring the voltage and I'm just going to unplug it which will cancel the service mode um and then it should make the power supply dead again uh that should drop back down to zero uh and not come back on when we try and repower up so let's just unplug it first like that yeah that rail's dropped down now plug it back in uh wait till it starts flashing yeah it's in protect and as you can see that rail now has gone completely dead um so without a service manual that tells you how to get into the service mode you wouldn't have a hope in Hell of fixing this uh because this isn't going to work even when we fix the fault until we cancel this error protection error out of the memory um now there appears to be three different power supplies here so I'm going to stop the camera and study the manual um with uh a plus and a minus rail both been low you would have thought that the possibility uh of two capacitors on the secondary is very slim I would imagine we're looking at a primary side uh problem here but anyway I'm going to stop the camera now and study the service manual right so if it was a capacitor on the primary side it's more likely to be that one uh but what I'm going to do is we're going to move over here to the Plus+ 12 and minus 12 volt rails I'm going to check these four capacitors here um and see where we go from there but it is um a pretty simple power supply um I don't think we'll need a new board it shouldn't be uh too difficult to repair this right now unusually um these capacitors all check out all right so um and the other suspect on the primary is this one here that also checks out all right so what we need to know now is what voltage is on pin eight of that chip uh and it's switched through there and it comes from a line p v CC so we need to find the source of that first and then I'll uh I'll download the data sheet for this chip and we'll check what the uh minimum supply for correct operation should be there right so where's the data sheet for the switch mode power supply uh Chopper control iy uh and we're looking at a typical Supply voltage of 13.5 uh the minimum of 10.3 for it to start so we need to check that first now of course you have to measure this voltage with the uh in the service mode otherwise the power supply will be dead uh but we got 13.88 vol there um so that is not the source of the problem right so um just before we move on I'm measuring here the main amplifier output rail presume it's a Class D chip under there and if you look we've got 3193 volts so let's just call that 32 Volts for the main amplifier uh and this is where it gets really strange and uh it's nearly time to go home I've had a stressful day um I'm going to come back to this on Monday when I thought about it but let's just have a look why this is strange 32 volts and the amplifier Supply right so if you look at this all these supplies are coming off one Transformer driven by one I uh so the main High current rail for the amplifier 32 volts that is absolutely correct uh the rails we've got faulty are these I've actually measured these three now and they're all wrong uh the 12vt output from that 12vt regulator uh we've only got 1242 volts in so that's not enough overhead for the regulator to work so I'm assuming going to have probably 14 or 15 volts here um and on the plus 12vt rail here I've only got 9.3 Vols and on the - 12vt rail uh I've only got 10.3 uh but how strange is that um these three rails are wrong this rails right and they're all coming from the same Transformer yeah so I'm going to have to uh I'm going to have to leave this till next week and come back to it very strange that right so it's Monday morning now I've spent half the morning actually looking at this power supply I cannot see any problem whatsoever um why the power suppli has got a low output but I've actually downloaded the data sheet for that IC there uh and it tells me that the IC can run in a low uh load mode uh now I'm wondering if these outputs are actually wrong um because we don't have any loading on the main rail um because we don't have any speakers connected so all this time I've spent looking at this power because the rails are wrong might just be a red herring um the actual switch mode controller might be throttling back the power supply because there's not enough load on it uh so what I'm going to do now um I can't see any problem with that I'm going to connect a pair of speakers to it and we're going to cancel the protection mode and then see what happens right so that's a pair of speakers connected um let's just start this in the service mode right and then I've just got to have a quick look at the service manual and see how we cancel this right so it says to uh disable the protection history we just hold the preset call button down for 5 seconds and there we go that's protection cleared right let's see what it does now then right so that's not actually um altered any voltage on the power supply that's the minus 12vt rail that's still showing as low um I'm just going to turn this off at the mains turn it back on again and then um if it doesn't go immediately back into protect uh we'll put some music through and see what happens right so I've actually decided we're not going to play music it we're going to play this uh Focus CD for CD players uh it's just a 1K sine wave uh and then we don't get any problems with YouTube uh copyrights using other people's music so uh it's powered up now um I've got this plane that's the minus 12vt rail we're still monitoring and uh look at this uh that's that's your 1K um sound from both speakers it's working absolutely fine um now look what I've just um discovered on here um it was as I thought the power suppli is in sort of um some low power mode because the more you turn the volume up the more the rail Rises up so that's the Min -12 I'll just turn the speakers around then we'll turn this up a bit so I'll just turn the speakers around so it doesn't deaf me let's get in the camera and turn this up and watch this this is Theus 12vt Rail and when he turn the sound back down it drops down to 10.38 um so the rails r up with the amount of volume so what a waste of time that's been why doesn't it say in the manual that the power supply rails rise with the amount of volume so back to the service manual um if you look at that + 12 - 12 no mention there that these rails are actually variable depending on the volume level so guys and girls on YouTube lesson learned um and we still don't know why this has actually tripped out in the first place because it's running absolutely fine um it said power fault uh the no reference if it was a fault with the amplifier it to say uh amplifier protection so obviously whatever was wrong with this um it was a power supply that tripped it but uh it's running absolutely fine uh what I'm going to do is set it up on a bench and just uh run it for an hour or so and then uh just have to send it back um but anyway hopefully um viewers on YouTube won't make the mistake I've made um of trying to look why the rails appear to be low all right guys and girls on YouTube I'll catch you in the next video many thanks for watching goodbye

Channel: Michael Dranfield

Views: 4,667

Keywords:

Id: NTZk67lI0lI

Length: 14min 4sec (844 seconds)

Published: Mon Oct 16 2023