Also from NZ Auckland. 50 years in the audio and repair industry Have worked on the same model Rotel Clean of dirt and dust and some water spillage. Needed some capacitor replacements to restore equal channel levels and frequency response. Enjoyed your video. Nicely presented
I DONT HAVE ANY FORMAL TRAINING IN ELECTRONICS, BUT I STUCK TO YOUR VIDEO FOR THE WONDERFUL WAY YOU EXPLAINED EVERYTHING, NOT THAT I UNDERSTOOD EVERY TECHNICAL DETAIL. BUT THANKS FOR THIS TREAT.
Thank you Peter, I hope the video was helpful to you. This is quite a common issue with these amplifiers but a very easy thing to solve even for none technical people.
Hello Michael, You prove why companies shouldn't be age bias, Undoubtedly one of the best engineers i've come across. The UK is heading the same way with adverts. Love your videos, you do them so well, better than people more than half your age in fact. (not an insult a compliment). Just shows "there is no education like experience".
Great concise video, Michael. I've one of these babies, but the elder brother.. the RA931MK.II.. Some 20 yrs old today. Still works like a charm. Always stitched on, for my internet TV, and marantz CD2000 CD player! I've tons of CDs.. driving my British made Rogers LS1 "bookshelf" loudspeakers. Only had it repaired once .. blown fuse one side. That was 10 yrs ago. Volume pots and Selectors are as noisy as hell...bought a can of WD40 Contact Cleaner in 2017. . Removed cover and blasted them ALPS potentiometers for all they're worth.. today, Dec 2020, still no crackles and pops. Wonderful stuff, this WD40 contact cleaners!! Hope my el'cheapo hifi setup can last for another 15 yrs.
Thank you for the kind words, yes sorry I cannot just pop over to fix it for you. Good luck in getting it fixed, probably worth the effort. Most Rotel stuff is pretty good.
@@MichaelBeeny How lovely to have a swift and pleasant reply, I have a fair few rotel bits and they have always been excellent for the money. I'm hoping that I can get it fixed to allow it to live on in a new role. Kindest regards from the South coast of England.
I was born on the (almost) south coast. Kent in fact!! well I know it's not really the south coast!! but a lot closer than New Zealand. Well, it's 25 c today, so in my T shirt and shorts, off now to get some lunch and a nice coffee. It's a tough life but some ones gotta do it!!
Hi thank you for this, however I have the same amp and its been intermittently distorting the one channel and it normalizes if you switch the amp off then on again quickly then it eventually does the same thing again
If you can track the fault to the pre amp or the amp it's self by feeding a signal directly into the amp. If it's the preamp only, more likely to be a capacitor. Not many caps in the power amp so more likely to be a transistor in the drive circuits. The output transistors are not so temperature sensitive, they tent work or not. Could be not easy to find the problem. Might be worth looking at the PCB under a lens for poor joints, that would be temperature sensitive. Good luck, it's a bit far to pop in to help!!
Hi Michael, thanks for an easy to follow video, I assume you just switched out the fuse in the end? I have a Rotel 820BX3 which was in perfect working order before I shorted the speaker channel (one Side) I've checked over for anything obvious, looking at the 2 fuses near the power supply, they both look intact, but I'm not sure how to check with my multi-meter (doorstop) could you advise please? that is if you still check this thread. many thanks
It might be OK. Some amplifiers have built in protection. As you have a meter, before you re connect your speakers, check you have no DC on the speaker terminals. Should be less than 50mV or so. If it's OK connect the speakers and test it's working. If not, then some damage has beeen done. Good luck.
@@MichaelBeeny thanks for the reply, I'll check the DC, but the amp does only give out one channel sound, I'll check again but I recall even the headphone-out gives only one channel. On the video you checked a couple of things, were you checking DC also? re the fuses, could one have blown even though they both look undamaged? Sorry to ask a lot, but I'm frustrated and can't find anyone to look at this near me, I don't want to sell it as junk if its a simple(ish) fix.
@@paulsmith721 It's very simple to check the fuses, remove them from the circuit and use your test meter on resistance to see if they are open or not. If one has blown, replace it and switch on. Often shorting the speakers will blow the fuse without more damage but often the fuse will blow after the amplifier has been damaged. If that's the case, you have a big problem. I cannot help further in that case.
Hi Dave, I don't generally offer a repair service on vintage equipment due to the difficulty here in NZ of getting replacement parts. However, tell the problem and your location. If I can help I will. Probably better to contact me here tas.audio49@gmail.com
Fuses only fail for 2 reasons. Old fuses can fail through fatigue but if they blow on every switch on, you must have a short circuit or blown output transistors. Obviously I cannot fault find from here in NZ. Probably not the best project for a newbie.
Hi. Great video. I’ve got a new version of this the 971 mkII. MY QUestion is what would cause the thump when I turn it on. I’m guessing speaker relay switch possibly. When I first turn on I get the thump through speakers. I do hear a click right after turning it on. It’s pretty quick click that I think is the relay switch but it’s a lot quicker than other clicks I get from different gear like Teac and Technics. I went ahead and ordered a new relay for it anyways seeing was cheap. Thoughts?
I doubt it's the relay itself faulty, sounds more like the relay is closing to fast, before the amp is stable, hence the pop. I would look at the caps in the relay timing circuit. Dried out electrolytic caps! Should be about 3/5 seconds.
@@New-England-HiFi-Guy I have not looked at this circuit for over 5 years. It does not in fact have a relay protection, just a fuse. You will get a bit of a thump because of this. As you talked about changing the relay, I was miss lead a little, I do see dozens of amplifiers per month, cannot remember all the circuits. So do you have a problem?? Maybe not.
@@MichaelBeeny thanks for feedback. No actual problem then I guess. Just wasn’t sure if this had a protection relay and if it could of been faulty. Ty again.
Hola Michael,me gustaría que me ayudaras a ver como puedo resolver un problema o dos que tengo en mi rotel RA-930AX.Me explico. La primera duda me surge que cuendo enciendo el apmlificador los bafles hacen un pequeño ruido,como un "PLOF" un sonido grave pero no muy fuerte, eso si. Este sonido al apagar el amplificador lo hace mas menos fuerte ..¿Es esto normal?: La segunda duda es que a veces al encender el amplificador o tras un rato funcionando, o bien alguno o los dos canales no suenan o bien crepitan .He observado que vuelven a la normalidad correcta si giras el selector de tono y lo vuelves a su posición original. ¿Cuál puede ser la falla? ..¿Necesito llevarlo a un técnico ?Tengo el esquema del aparato Gracias por tu ayuda Hi Michael, I would like you to help me see how I can solve a problem or two that I have in my rotel RA-930AX. Let me explain. The first question arises that when I turn on the amplifier the speakers make a small noise, like a "PLOF "A serious sound but not very strong, yes. This sound when turning off the amplifier makes it less loud .. Is this normal ?: The second doubt is that sometimes when you turn on the amplifier or after a while working, either one or both channels do not sound or they crack. I have observed that they return to the correct normality if you turn the tone selector and return it to its position original. What can be the fault? ..Do I need to take him to a technician? I have the schematic of the apparatus. My language is Spanish and I have problems following your explanation of the video.Thanks for your help
Hi Jose, I'm sure you must appreciate that making repairs on a amplifier I don't know from 10,000 miles away is near to impossible. However a number is things I would look at first is switches, clean them. Also if the amplifier has relays on the speakers, these may have contact oxidisation. Other than that, I need to have the amplifier in front of me with a test meter and scope at least. Sorry to be unhelpful but I do have limits. After the covert thingy, a first class flight and a weeks hotel might be tempting!! lol PS your English is 99.9% better than my Spanish.
@@MichaelBeeny First of all tell him that my English is not good, since it is a translation made with the google translator. I saw his video and activated the subtitles, and copied them and passed them through the translator to understand what he was saying. I made a summary that if you think we could review what is in the video. We open the cover of the amplifier and observe the main capacitors that they do not have faults in the form, that they are not credited. All this without turning on the amplifier. Next we put the multimeter on the scale of 2 volts of direct current and we turn on the amplifier without signal, and we measure at the output of the speaker when it is turned off. The estimated value must be at 0.094 volts, right? The next step would be to test the 4 fuses, with the continuity element of the multimeter and the amplifier turned off, or I suppose that removing the fuses and testing them, in my case the F601 and F602 of 4 Amps and the resistors 633 and 634 of 33.2 K. In the case of the video, the 603 failed. Now measure between tp2 and tp4 and between tp1 and tps about 5 mv of direct current, I suppose that with the amplifier on. I can give you my diagram .. Is everything correct? Thank you www.manualslib.com/manual/897752/Rotel-Ra-930ax.html Antes de nada decirle que mi ingles no es bueno,ya que es una traduccion hecha con el traductor de google.Vi su video y active los subtitulos,y los copie y los pase a traves del traductor para entender lo que decia. me hice un resumen que si le parece podiamos repasar sobre lo que cuenta en el video. Abrimos la tapa del amplificador y observamos los condensadores principales de que no tengan fallos en la forma,que no esten abonbados. Todo esto sin encender el amplificador.A continuecion ponemos el multimetro en la escala de 2 voltios de corriente continua y encendemos el amplificador sin señal,y medimos a la salida del altavoz cuando este se apaga. El valor estimado debe de estar en 0,094 voltios ¿no?. El siguiente paso seria testear los 4 fusibles,con el elemento de continuidad del multimetro y el amplificador apagado,o supongo que extrayendo los fusibles y testeandolos,en mi caso los F601 y F602 de 4 Amperios y las resistencias 633 y 634 de 33,2 K.En el caso del video fallo el 603.Ahora medir entre tp2 y tp4 y entre tp1 y tps unos 5 mv de corriente continua ,supongo que con el amplificador encendido.Le puedo pasar mi esquema..¿Es todo correcto? Gracias www.manualslib.com/manual/897752/Rotel-Ra-930ax.html
Hi I'm working on a RA-820 amp and have 86mV out of one channel and 109mV out the other channel. This amp has a problem with the left channel fuse that blows after 20 minutes.
That offset is not over high. If it takes that long to blow the fuse could be thermal runaway. I think I would remove the speaker or load resistor, connect your meter to the output, switch on and monitor the output. You do not say if the fuse is in the speaker line or a power supply line. Obviously not a short, something is drawing to much current over time. Does the heat sink get hot under no load conditions? If it does could be biasing. Almost impossible to to suggest more really, bit far to pop over to help, sorry!! Good luck Kevin.
Thanks for sharing your knowledge Mike - this is really helpful. I'm trying to fix my amp (ra931) which has a similar problem with just one channel working. A fuse has blown and i think it is likely due to a shorted diode in the power amp - marked d901 on the board. I want to replace the diode, but i'm not sure what to buy. Any ideas?
Fuses can fail just through long term use. If you replace the fuse and it fails again it could probably be one or both of the output transistors short. If the diodes are in the power supply that will make the fuse fail but a diode in the amplifier is unlikely to fail for no reason, more likely to be the result of other faults. Sorry to be un helpful but it is almost impossible to fault find without the unit on my bench with some test gear. Diodes within an amplifier tend to be on the biasing circuits.
Hi Michael 👋 I’ve just fixed my recently acquired Rotel RA-920X after that video so thank you for the upload 🤙 I’m very new to electrics and your video helped me understand so much! Mine had the same problem on the function switch where it wasn’t working correctly so I’ve sprayed it with contact cleaner and it’s much better. I also have a Rega planar 3 which after a minute or so stops turning clockwise and starts turning anti clockwise which I think would be the capacitor? It seems to have a large crack and has expanded like you mentioned in the video. Any suggestions on what it might be?
Dear Michael, thanks for this hugely informative video. I have the same issue for my RA 930 AX and I replaced the fuse on the left hand output. Unfortunately it seemed to blow again almost immediately so I was wondering if that indicates something else. Thanks
+dominic doyle Hi Dominic. If the fuse blows instantly, sadly that could be the output transistors, one or both. At lest you have one working channel so with a simply multi meter you should be able to compare reading. Again sadly even if you find that one of the output transistors have blown, sometimes it can take the driver also.
+Michael Beeny thanks. Do you recommend a novice goes further with this in an attempt to repair it myself or should say goodbye to this old friend? I will have to order the multi meter and then work from there. I don't really have any repair options locally.
+dominic doyle If you have little knowledge with electronics I would suggest you have really little chance of fixing the Rotel yourself. Because of it's vintage you could probably sell on line as a not working unit. There is always someone that will love to repair it and either re sell or use. I would personally not just dump it. You might be surprised how much you could sell for, depending on your country of course.
+Michael Beeny I'm in Italy. I'm going to get my hands on a multi meter and check the things in your video more out of curiosity than hope and see. All of the online help basically resolves this issue with a new fuse. Cheers again.
It's been a few years now to remember the circuit but if it's only the phono not working could be the selector switch or the phono pre amp it's self. As it's a self contained unit make sure you have voltage . I have just looked at the video again and it does have a single IC for both channels, either the IC is dead or no volts getting to it. Good luck.
Hi i have found only now this very nice video because there is a guy here selling one for cheap. I have seen at the schematic. I really do not know why Rotel place an op-amp in front of the actual power amp stage (a stage with a Vgain of 18 times ... it is already a lot with cd players). I am pretty sure that bypassing that op-amp could lead to an even great sound. The pot impedance i guess should be lower like 10kohm for instance. What i mean it is that there is a really great potential for even better sound. What do you think ? Thanks a lot and kind regards, gino
Hi Gino Older amplifiers were somewhat more sensitive as tuners, tape/cassette players tended to need about 100mV where as a CD player would often put out 500mV or even up to 1 volt. I doubt this would be an issue, just means the volume pot will be a little more cramped. I doubt you will detect any difference by passing the IC, of course ANY extra stages MUST degrade the signal but by how much? I don't think I would bother.
@@MichaelBeeny Good morning and thank you very much for your kind and precious reply Actually a 0.1V signal is really low and I understand now why the higher gains (about 10 times) of the old line preamps. Personally I am always looking for an amplifier with not many watts because I listen at low SPLs with rather efficient speakers but that is still capable of giving a nice punch in the bass, a result of a good power supply. They advised me to look at the power capacitors because they are the ones who provide the energy during the transients. I like this Rotel very much because the design is simple and classic. I could make a little change. Add a pair of rca connectors on the back and plug them right downstream the volume pot before a dc blocking capacitor so to have an additional main in input. I'm currently playing with some cheap little tube preamps and some don't sound too bad. I would be curious to hear one in comparison with the line stage of the small Rotel. To finally have a kind of hybrid integrated. I have a feeling that hybrid amps can sound very good. I remember some reviews of solid state pre+power amp combinations. Often replacing the ss preamp with a tube preamp was improving the musicality. It seems quite a challenge to make a good sounding solid state preamp. And the very good ones often they are also very expensive. Strange. Instead very good sounding power amps are more common. I really do not understand why. Thanks again and best regards, gino
Hi. Are you a native New Zealander? I was a bit surprised to learn that you are in NZ for your accent would suggest you were from the UK. Nice video, you seem to be an expert in what you do!
+Michał Chyliński Hi Michal, you are very good with accents, no I have only been in NZ for 14 years. Still training to be a real Kiwi!! As you thought I am originally from UK. Thank you for your kind words however. My profile has a little info about myself should you be interested.
Thank you MIchael i have the Exact Same Amplifier With the Same output !! 25 years old Aswell lol Will look @ the Fuses Check it out I lived NZ in 1982 in CastorBay Area close to Takapuna where are you ? thank you for your Valued info i think i have saved My amp i let you know ! lol
I am a maintenance technician......Allways check fuses first :) well done anyway. By the way if you want some good radio without advertising and very little talking try radio paradise internet radio it streams in FLAC CD quality. Have fun.
Also from NZ Auckland.
50 years in the audio and repair industry
Have worked on the same model Rotel
Clean of dirt and dust and some water spillage. Needed some capacitor replacements to restore equal channel levels and frequency response.
Enjoyed your video. Nicely presented
Welcome Ross, thanks for watching, not quite Auckland but Hamilton area.
I like your clarity when speaking about these repairs! Thank You for this!
Thank you J for your kind words.
i know it is pretty randomly asking but do anyone know of a good place to watch newly released movies online ?
@Zachary Cohen Flixportal
@Israel Bryce Thanks, I signed up and it seems like a nice service :) I really appreciate it !
@Zachary Cohen No problem :D
I DONT HAVE ANY FORMAL TRAINING IN ELECTRONICS, BUT I STUCK TO YOUR VIDEO FOR THE WONDERFUL WAY YOU EXPLAINED EVERYTHING, NOT THAT I UNDERSTOOD EVERY TECHNICAL DETAIL. BUT THANKS FOR THIS TREAT.
Fixed my (fairly expensive) charity shop purchase with a 20p fuse (t4l 250 vb) by the left speaker output thanks to your videos. Cheers.
Enjoy how precisely you explain the details. Thanks Michael.
Thank you Peter, I hope the video was helpful to you. This is quite a common issue with these amplifiers but a very easy thing to solve even for none technical people.
Hello Michael, You prove why companies shouldn't be age bias, Undoubtedly one of the best engineers i've come across.
The UK is heading the same way with adverts.
Love your videos, you do them so well, better than people more than half your age in fact. (not an insult a compliment).
Just shows "there is no education like experience".
Thank you for your kind words, I really appreciate them.
Good video. Thanks for sharing your repair process.
Thank you for the most detail video. 👍👍👍👍👍👍👍👍👍👍👍👍
Hello Michael, very impressed about your knowledge , i'm now a new subscriber from France, thank you for your channel, i learn a lot, bravo !
Thank you for the kind words, much appreciated.
Great concise video, Michael. I've one of these babies, but the elder brother.. the RA931MK.II.. Some 20 yrs old today. Still works like a charm. Always stitched on, for my internet TV, and marantz CD2000 CD player! I've tons of CDs.. driving my British made Rogers LS1 "bookshelf" loudspeakers. Only had it repaired once .. blown fuse one side. That was 10 yrs ago. Volume pots and Selectors are as noisy as hell...bought a can of WD40 Contact Cleaner in 2017. . Removed cover and blasted them ALPS potentiometers for all they're worth.. today, Dec 2020, still no crackles and pops. Wonderful stuff, this WD40 contact cleaners!! Hope my el'cheapo hifi setup can last for another 15 yrs.
What an excellent video, thank you. Shame you are not round the corner to fix mine.
Thank you for the kind words, yes sorry I cannot just pop over to fix it for you. Good luck in getting it fixed, probably worth the effort. Most Rotel stuff is pretty good.
@@MichaelBeeny How lovely to have a swift and pleasant reply, I have a fair few rotel bits and they have always been excellent for the money. I'm hoping that I can get it fixed to allow it to live on in a new role. Kindest regards from the South coast of England.
I was born on the (almost) south coast. Kent in fact!! well I know it's not really the south coast!! but a lot closer than New Zealand. Well, it's 25 c today, so in my T shirt and shorts, off now to get some lunch and a nice coffee. It's a tough life but some ones gotta do it!!
Michael Beeny good for you! Enjoy it, it s**t here. Lol.
@@MichaelBeeny A quick thought, and it might help others too, is the fuse a T4L250v ?
Hi thank you for this, however I have the same amp and its been intermittently distorting the one channel and it normalizes if you switch the amp off then on again quickly then it eventually does the same thing again
If you can track the fault to the pre amp or the amp it's self by feeding a signal directly into the amp. If it's the preamp only, more likely to be a capacitor. Not many caps in the power amp so more likely to be a transistor in the drive circuits. The output transistors are not so temperature sensitive, they tent work or not. Could be not easy to find the problem. Might be worth looking at the PCB under a lens for poor joints, that would be temperature sensitive. Good luck, it's a bit far to pop in to help!!
Hi Michael, thanks for an easy to follow video, I assume you just switched out the fuse in the end? I have a Rotel 820BX3 which was in perfect working order before I shorted the speaker channel (one Side) I've checked over for anything obvious, looking at the 2 fuses near the power supply, they both look intact, but I'm not sure how to check with my multi-meter (doorstop) could you advise please? that is if you still check this thread. many thanks
It might be OK. Some amplifiers have built in protection. As you have a meter, before you re connect your speakers, check you have no DC on the speaker terminals. Should be less than 50mV or so. If it's OK connect the speakers and test it's working. If not, then some damage has beeen done. Good luck.
@@MichaelBeeny thanks for the reply, I'll check the DC, but the amp does only give out one channel sound, I'll check again but I recall even the headphone-out gives only one channel.
On the video you checked a couple of things, were you checking DC also?
re the fuses, could one have blown even though they both look undamaged?
Sorry to ask a lot, but I'm frustrated and can't find anyone to look at this near me, I don't want to sell it as junk if its a simple(ish) fix.
@@paulsmith721 It's very simple to check the fuses, remove them from the circuit and use your test meter on resistance to see if they are open or not. If one has blown, replace it and switch on. Often shorting the speakers will blow the fuse without more damage but often the fuse will blow after the amplifier has been damaged. If that's the case, you have a big problem. I cannot help further in that case.
great video thanks! what caused the fuse to blow do you think? Speaker wires touching?
A short on the cable is probable but general fatigue, after so long is also probable.
Great video. Thanks!
I don't suppose you'd like to help another Brit in New Zealand out with a NAD 3020 that's driving me nuts, would you?
Hi Dave, I don't generally offer a repair service on vintage equipment due to the difficulty here in NZ of getting replacement parts. However, tell the problem and your location. If I can help I will. Probably better to contact me here tas.audio49@gmail.com
hi michael brill video fuses keep blowing in mine im new to dis where do i start thanks.
Fuses only fail for 2 reasons. Old fuses can fail through fatigue but if they blow on every switch on, you must have a short circuit or blown output transistors. Obviously I cannot fault find from here in NZ. Probably not the best project for a newbie.
thanks for the reply mike could you do a quick video and shows how it's done I would really appreciate that thanks.
Hi. Great video. I’ve got a new version of this the 971 mkII. MY QUestion is what would cause the thump when I turn it on. I’m guessing speaker relay switch possibly. When I first turn on I get the thump through speakers. I do hear a click right after turning it on. It’s pretty quick click that I think is the relay switch but it’s a lot quicker than other clicks I get from different gear like Teac and Technics. I went ahead and ordered a new relay for it anyways seeing was cheap. Thoughts?
I doubt it's the relay itself faulty, sounds more like the relay is closing to fast, before the amp is stable, hence the pop. I would look at the caps in the relay timing circuit. Dried out electrolytic caps! Should be about 3/5 seconds.
@@MichaelBeeny I opened her up and I don’t even see a relay protection switch at all.
Also yours kicked right on when you hit power button.
@@New-England-HiFi-Guy I have not looked at this circuit for over 5 years. It does not in fact have a relay protection, just a fuse. You will get a bit of a thump because of this. As you talked about changing the relay, I was miss lead a little, I do see dozens of amplifiers per month, cannot remember all the circuits. So do you have a problem?? Maybe not.
@@MichaelBeeny thanks for feedback. No actual problem then I guess. Just wasn’t sure if this had a protection relay and if it could of been faulty. Ty again.
thanks mate. fixed mine, was also a bad fuse. thanks
As you have seen on my video, it's often the simple things that go wrong. Sadly not always the case.
Hola Michael,me gustaría que me ayudaras a ver como puedo resolver un problema o dos que tengo en mi rotel RA-930AX.Me explico. La primera duda me surge que cuendo enciendo el apmlificador los bafles hacen un pequeño ruido,como un "PLOF" un sonido grave pero no muy fuerte, eso si. Este sonido al apagar el amplificador lo hace mas menos fuerte ..¿Es esto normal?:
La segunda duda es que a veces al encender el amplificador o tras un rato funcionando, o bien alguno o los dos canales no suenan o bien crepitan .He observado que vuelven a la normalidad correcta si giras el selector de tono y lo vuelves a su posición original. ¿Cuál puede ser la falla? ..¿Necesito llevarlo a un técnico ?Tengo el esquema del aparato Gracias por tu ayuda
Hi Michael, I would like you to help me see how I can solve a problem or two that I have in my rotel RA-930AX. Let me explain. The first question arises that when I turn on the amplifier the speakers make a small noise, like a "PLOF "A serious sound but not very strong, yes. This sound when turning off the amplifier makes it less loud .. Is this normal ?:
The second doubt is that sometimes when you turn on the amplifier or after a while working, either one or both channels do not sound or they crack. I have observed that they return to the correct normality if you turn the tone selector and return it to its position original. What can be the fault? ..Do I need to take him to a technician? I have the schematic of the apparatus. My language is Spanish and I have problems following your explanation of the video.Thanks for your help
Hi Jose, I'm sure you must appreciate that making repairs on a amplifier I don't know from 10,000 miles away is near to impossible. However a number is things I would look at first is switches, clean them. Also if the amplifier has relays on the speakers, these may have contact oxidisation. Other than that, I need to have the amplifier in front of me with a test meter and scope at least. Sorry to be unhelpful but I do have limits.
After the covert thingy, a first class flight and a weeks hotel might be tempting!! lol
PS your English is 99.9% better than my Spanish.
Thank you for your kind response, I will follow your advice .. greetings
@@MichaelBeeny First of all tell him that my English is not good, since it is a translation made with the google translator. I saw his video and activated the subtitles, and copied them and passed them through the translator to understand what he was saying. I made a summary that if you think we could review what is in the video.
We open the cover of the amplifier and observe the main capacitors that they do not have faults in the form, that they are not credited.
All this without turning on the amplifier. Next we put the multimeter on the scale of 2 volts of direct current and we turn on the amplifier without signal, and we measure at the output of the speaker when it is turned off. The estimated value must be at 0.094 volts, right?
The next step would be to test the 4 fuses, with the continuity element of the multimeter and the amplifier turned off, or I suppose that removing the fuses and testing them, in my case the F601 and F602 of 4 Amps and the resistors 633 and 634 of 33.2 K. In the case of the video, the 603 failed. Now measure between tp2 and tp4 and between tp1 and tps about 5 mv of direct current, I suppose that with the amplifier on. I can give you my diagram .. Is everything correct?
Thank you
www.manualslib.com/manual/897752/Rotel-Ra-930ax.html
Antes de nada decirle que mi ingles no es bueno,ya que es una traduccion hecha con el traductor de google.Vi su video y active los subtitulos,y los copie y los pase a traves del traductor para entender lo que decia. me hice un resumen que si le parece podiamos repasar sobre lo que cuenta en el video.
Abrimos la tapa del amplificador y observamos los condensadores principales de que no tengan fallos en la forma,que no esten abonbados.
Todo esto sin encender el amplificador.A continuecion ponemos el multimetro en la escala de 2 voltios de corriente continua y encendemos el amplificador sin señal,y medimos a la salida del altavoz cuando este se apaga. El valor estimado debe de estar en 0,094 voltios ¿no?.
El siguiente paso seria testear los 4 fusibles,con el elemento de continuidad del multimetro y el amplificador apagado,o supongo que extrayendo los fusibles y testeandolos,en mi caso los F601 y F602 de 4 Amperios y las resistencias 633 y 634 de 33,2 K.En el caso del video fallo el 603.Ahora medir entre tp2 y tp4 y entre tp1 y tps unos 5 mv de corriente continua ,supongo que con el amplificador encendido.Le puedo pasar mi esquema..¿Es todo correcto?
Gracias
www.manualslib.com/manual/897752/Rotel-Ra-930ax.html
sir can you use a stick to point the diagram so we can see clearly .
Hi I'm working on a RA-820 amp and have 86mV out of one channel and 109mV out the other channel. This amp has a problem with the left channel fuse that blows after 20 minutes.
That offset is not over high. If it takes that long to blow the fuse could be thermal runaway. I think I would remove the speaker or load resistor, connect your meter to the output, switch on and monitor the output. You do not say if the fuse is in the speaker line or a power supply line. Obviously not a short, something is drawing to much current over time. Does the heat sink get hot under no load conditions? If it does could be biasing. Almost impossible to to suggest more really, bit far to pop over to help, sorry!! Good luck Kevin.
Thanks for sharing your knowledge Mike - this is really helpful. I'm trying to fix my amp (ra931) which has a similar problem with just one channel working. A fuse has blown and i think it is likely due to a shorted diode in the power amp - marked d901 on the board. I want to replace the diode, but i'm not sure what to buy. Any ideas?
Fuses can fail just through long term use. If you replace the fuse and it fails again it could probably be one or both of the output transistors short. If the diodes are in the power supply that will make the fuse fail but a diode in the amplifier is unlikely to fail for no reason, more likely to be the result of other faults. Sorry to be un helpful but it is almost impossible to fault find without the unit on my bench with some test gear. Diodes within an amplifier tend to be on the biasing circuits.
Hi Michael 👋 I’ve just fixed my recently acquired Rotel RA-920X after that video so thank you for the upload 🤙 I’m very new to electrics and your video helped me understand so much! Mine had the same problem on the function switch where it wasn’t working correctly so I’ve sprayed it with contact cleaner and it’s much better. I also have a Rega planar 3 which after a minute or so stops turning clockwise and starts turning anti clockwise which I think would be the capacitor? It seems to have a large crack and has expanded like you mentioned in the video. Any suggestions on what it might be?
Dear Michael, thanks for this hugely informative video. I have the same issue for my RA 930 AX and I replaced the fuse on the left hand output. Unfortunately it seemed to blow again almost immediately so I was wondering if that indicates something else. Thanks
+dominic doyle Hi Dominic. If the fuse blows instantly, sadly that could be the output transistors, one or both. At lest you have one working channel so with a simply multi meter you should be able to compare reading. Again sadly even if you find that one of the output transistors have blown, sometimes it can take the driver also.
+Michael Beeny thanks. Do you recommend a novice goes further with this in an attempt to repair it myself or should say goodbye to this old friend? I will have to order the multi meter and then work from there. I don't really have any repair options locally.
+dominic doyle If you have little knowledge with electronics I would suggest you have really little chance of fixing the Rotel yourself. Because of it's vintage you could probably sell on line as a not working unit. There is always someone that will love to repair it and either re sell or use. I would personally not just dump it. You might be surprised how much you could sell for, depending on your country of course.
+Michael Beeny I'm in Italy. I'm going to get my hands on a multi meter and check the things in your video more out of curiosity than hope and see. All of the online help basically resolves this issue with a new fuse. Cheers again.
Hello Michael. I have bought a rotel 840bx and phono input is not working:( would you have any suggestions what should I look for it. Thank you
It's been a few years now to remember the circuit but if it's only the phono not working could be the selector switch or the phono pre amp it's self. As it's a self contained unit make sure you have voltage . I have just looked at the video again and it does have a single IC for both channels, either the IC is dead or no volts getting to it. Good luck.
@@MichaelBeeny Thank you for your reply.
Hi i have found only now this very nice video because there is a guy here selling one for cheap. I have seen at the schematic. I really do not know why Rotel place an op-amp in front of the actual power amp stage (a stage with a Vgain of 18 times ... it is already a lot with cd players). I am pretty sure that bypassing that op-amp could lead to an even great sound. The pot impedance i guess should be lower like 10kohm for instance. What i mean it is that there is a really great potential for even better sound. What do you think ? Thanks a lot and kind regards, gino
Hi Gino Older amplifiers were somewhat more sensitive as tuners, tape/cassette players tended to need about 100mV where as a CD player would often put out 500mV or even up to 1 volt. I doubt this would be an issue, just means the volume pot will be a little more cramped. I doubt you will detect any difference by passing the IC, of course ANY extra stages MUST degrade the signal but by how much? I don't think I would bother.
@@MichaelBeeny Good morning and thank you very much for your kind and precious reply Actually a 0.1V signal is really low and I understand now why the higher gains (about 10 times) of the old line preamps. Personally I am always looking for an amplifier with not many watts because I listen at low SPLs with rather efficient speakers but that is still capable of giving a nice punch in the bass, a result of a good power supply. They advised me to look at the power capacitors because they are the ones who provide the energy during the transients. I like this Rotel very much because the design is simple and classic. I could make a little change. Add a pair of rca connectors on the back and plug them right downstream the volume pot before a dc blocking capacitor so to have an additional main in input. I'm currently playing with some cheap little tube preamps and some don't sound too bad. I would be curious to hear one in comparison with the line stage of the small Rotel. To finally have a kind of hybrid integrated. I have a feeling that hybrid amps can sound very good. I remember some reviews of solid state pre+power amp combinations. Often replacing the ss preamp with a tube preamp was improving the musicality.
It seems quite a challenge to make a good sounding solid state preamp.
And the very good ones often they are also very expensive. Strange. Instead very good sounding power amps are more common. I really do not understand why.
Thanks again and best regards, gino
Enjoyed the video, thanks.
+WestonWood Thank you for you're kind words.
Hi. Are you a native New Zealander? I was a bit surprised to learn that you are in NZ for your accent would suggest you were from the UK. Nice video, you seem to be an expert in what you do!
+Michał Chyliński Hi Michal, you are very good with accents, no I have only been in NZ for 14 years. Still training to be a real Kiwi!! As you thought I am originally from UK. Thank you for your kind words however. My profile has a little info about myself should you be interested.
Thank you MIchael i have the Exact Same Amplifier With the Same output !! 25 years old Aswell lol Will look @ the Fuses Check it out I lived NZ in 1982 in CastorBay Area close to Takapuna where are you ? thank you for your Valued info i think i have saved My amp i let you know ! lol
vielen Dank!
@11:59 lol!
è gia il secondo rotel di cui vedo la riparazione qui su YT ed entrambe risolte sostituendo il fusibile
I am a maintenance technician......Allways check fuses first :) well done anyway. By the way if you want some good radio without advertising and very little talking try radio paradise internet radio it streams in FLAC CD quality. Have fun.
I knew what the fault was before I made the video, it's made to be informative and entertaining.
@@MichaelBeeny It Was. Thank you.
MB "New Zealand is a bit like America for radio: shit."
This video makes me not want to buy older gear. What a hassle
Well Max, at least older gear CAN be repaired. A fault on modern gear is a death sentence.