So much information that most people who service amplifiers wouldn't even do for the biasing. Absolutely bang on when covering the amp for a good hour before the correct bias points!!!!
I've recently repaired an ARCAM and found the design pretty poor. Thanks for the BIAS adjustment tip, I really like it. I've always felt I was chasing my tail if I set up the values straight to what the service manual says. I like the idea to leave it low to slowly bring the whole thing to temperature before doing the final adjustment!
Thumbs up for you sir, well explained procedure. By the way, I really like that bench multimeter; the kind of friends you need when you chase accurate measurements.
With that amount of faults a lesser amp would've probably gone into some sort of thermal runaway and self-destructed by now, so I guess in a way it is a testament to its design.. they just neglected a few key areas! I must say, the build quality though is rather nice! Good of you to take it on, as some tech's would probably make a-billion-and-one excuses on seeing one of these come in through the door!
Must have got incredibly hot to change the colour of the heatsink but no transistor failure as you say, I think these were about £1500 new so I don't mind taking on stuff like this as customers don't usually mind paying good money for something like this .
Really interesting video. It makes me wonder about the overall quality of Arcam products. Back in the 70s I had an A&R (Arcam now) A60. This was a classic stereo amp of its time, but even that used to run very hot, mainly due to its small heatsink. It sounded great and was actually built in Britain! I can’t believe how they just hold the two transistors together with thermal paste, a small spring clip would solve that problem, poor design and cost cutting if you ask me.
Thanks for the in depth video, just starting a repair on an AVR500 and nice to have some insight into what's causing it to shutdown. A service manual seems to be non-existent as I would like to monitor feedback from the amp section to the CPU to see what is exactly triggering shutdown. That heat sink compound only for thermal bonding is laughable...
checking the bias voltages are a good starting point as faulty pots cause the bias to drift, I did one of these that was intermittently shutting down but you will need the service manual , each amp has a protection circuit that measures DC offset and these are all OR gated into one single trip control line to the micro , you will never find this without the service manual as its quite complex.
@@michaeldranfield7140 I managed to find the service info for the AVR600 which appears to use the same boards albeit with some enhancements. Yes, I've grabbed a 2 pin connector from a scrap board and will look at bias as well as DC offset at the outputs. Believe the customer was looking for a cheap repair otherwise will take to arcam and I can't honestly see this being cheap unless I pull the amp block or PSU and find something silly like a cold solder joint currently causing the issue. Thanks again!
@@michaeldranfield7140 after further checks and inspection the caps and pots had already been replaced. additionally i found open 7a fuses on the centre channel and shorted output devices. given the blown channel and poor bias stability across several other channels I'm handing it back to the customer for repair directly from arcam as it looks quite involved to me. BTW, I believe my customer told me about £350 at Arcam currently.
@@leecambsuk2871 These amps are really time consuming to repair due to the construction and the fact a lot of the parts are surface mounted, last one I did had a very intermittent fault and I had it for months before i found the problem , price could well be £350 now as its a few years ago .
Excellent video, well done. I have a Harman Kardon with the same problem, shutting down as soon as it's powered up. I'm actually looking at a used Arcam ADR400, not sure I want to wade into this level of tech investigation / repair quagmire. That's the problem with these complex integrated amp systems. Once some internal function is tripped causing this, it's a real quagmire trying to solve this, could be any number of reasons, not the least of which may be installing new firmware (basically it's a computer with an amp/receiver wrapped around it). These days I'm more inclined to go for separate components that are easier to work on if needed . . . just a solid amp for driving my audio files and streams, that's more than enough.
Hi , i have just follow your advise and replaced 21 YES 21 :) tantalum capacitors around driver stage --and my Arcam ( AVR 400 model ) no overheats any more , i just want say THANK YOU VERY MUCH SIR !!!! for sharing the knowledge , brilliant .
Hi Andrzej Siwinski where did You buy the capasitors and where did you buy the capacitors and what type FKP1/2? did Ypu change the potentiometers as well ?
The exact capacitors came from Farnell components in Leeds, or you can buy them from Arcam, the pots were more difficult to get an exact match and I had to settle for the nearest I could find, in mine the pots were 100 ohms, the pots suffer from intermittent change of resistance, probably due to an oxidised wiper contact, I also have a video on the faulty pots showing the problem.
@@michaeldranfield7140 Hey Michael guess what! I've just got one of these amps, may I ask what trimmer pots did you use 120ohm or 100ohm ? Also to save me some time and help out real good did you check the resistance of the bias pots after you finished ? If so what was it im lazy and rushed :D
Hi Michael, thank you very much for your instructions. I've changed all parts as instructed but run into an issue: the front channel (central)seems to run without amplification - sounds muddy, al. Do you have any idea where to search for possible solution?
Many thanks. This is a really useful video Michael, and really clear. I bought one of these 2nd hand for around £400 and it is starting to show signs of overheating. So I'll have to try and remember my HNC electronics from the 1980s and have a bash at fixing it. What resistance are the potentiometers? tempted to try to order parts in advance of stripping mine down
The pots were 100 ohms and the correct size was difficult to find so I had to bend the legs slightly one the ones I fitted , and the exact replacement wima caps came from Farnell components in Leeds.
@@michaeldranfield7140 Thanks so much for the video and additional information. I replaced the components yesterday and it looks like the amp is no longer playing up. I've put your contact details on the Audiophiles UK facebook forum as there are probably quite a number of these amps out there that people might expensively replace when they could just ship them to you for repair.
@@michaeldranfield7140 Hi Michael. Looks like my repair did not work. The amp is still functioning, but still overheating. I probably did a poor job with the heat sink paste. I've stopped using the amp for the moment. I'm not confident I have the skills or equipment to diagnose of fix it further. Is this a job you would be interested in taking on?
I can take a look if you want to bring the amp in and leave it with me for a bit, I have just done one with a very, very intermittent fault and had it nearley 3 months due to its intermittent cutting out.
@@michaeldranfield7140 Hello Michael, I just replaced all the caps according to your advice, it looks like everything will be ok but I'm a bit worried because after an hour from turning on when I wanted to check the bias, the fans did not turn on even once, is this normal? The heatsink was warm, do you have information when the fans should turn on ? Thans a lot for Your help.
As I understand it the fans are thermostatically controlled by the 3 sensors on the heatsink and should only come on when the heatsink is very hot , but these machines were plagued with overheating when they were brand new and in an attempt to cure the overheating arcam dealers offered a software upgrade which made the fans run all the time , the live temperature data from the sensors can be called up in the service mode and displayed on a TV screen .
Hello Michael, I have fault issue in my Arcam AVR500, I searched the internet for information about it and found your video on RUclips and i think it can be useful. I found service manual for AVR600 but I'm pretty sure some of the boards are the same as in AVR500. So i have some question about potentiometers in SM for AVR6000 RV400 is 200 ohms and they set them for 6mV, so which of the information is correct. Did You change all potentiometers for the same and all of them set on the same value ?
@@michaeldranfield7140 Hello, thank you for your quick answer, I will check what I have at my boards , have you set all the potentiometers the same? Edit: I confirm the pots are 100 ohms
It's very important you change all the pots, there was some modifications in production so if your pots are 200 ohms fit the same, bias is done when the amp is warm I'm not at work today but I think it was 8mv.
@@michaeldranfield7140 Yes, that's right in the video you say 8 mV but SM for AVR 600 says: "Optimum bias at quiescent operating temperature is measured across the two 0.1 ohm emitter resistors forming R408 - it is typically 15mV at the pins of C400. When setting up from cold a good starting point to achieve this is to first turn RV400 to minimum (i.e. fully anticlockwise) and then slowly turn it up to 6mV. " But they're talking about 200 ohm potentiometers so I'm confused
345 / 5 000 Hi Michael, first of all, thank you very much for your help and advice, in my AVR500 I have already replaced all 21 caps and 7 pots, then I tried to set the bias to 8mV but on one channel when connecting the multimeter sometimes it shows proper value 8mV but once every few times shows 70mV do you have any idea whats happening? regards
What a terrible design, those transistors should be held using spring clips, rather than relying on just the thermal paste! I guess as long as it doesn't fail within the warranty period, that is OK?
A lot of money when new and yet they skimp on things like using heatsink compound to strap two transistors together when they should have used a spring clip .
Great information Michael, thanks for taking the time to do this.
Many thanks for watching .
So much information that most people who service amplifiers wouldn't even do for the biasing.
Absolutely bang on when covering the amp for a good hour before the correct bias points!!!!
Thankyou for that .
I've recently repaired an ARCAM and found the design pretty poor. Thanks for the BIAS adjustment tip, I really like it. I've always felt I was chasing my tail if I set up the values straight to what the service manual says. I like the idea to leave it low to slowly bring the whole thing to temperature before doing the final adjustment!
Glad you liked it , many thanks for watching .
Thumbs up for you sir, well explained procedure. By the way, I really like that bench multimeter; the kind of friends you need when you chase accurate measurements.
Not a cheap thing , think it was about £800.
With that amount of faults a lesser amp would've probably gone into some sort of thermal runaway and self-destructed by now, so I guess in a way it is a testament to its design.. they just neglected a few key areas! I must say, the build quality though is rather nice!
Good of you to take it on, as some tech's would probably make a-billion-and-one excuses on seeing one of these come in through the door!
Silly design mistakes and cheap critical parts.
@@glpilpi6209 Indeed, and absolutely the worst place to have aforementioned cheap components! 😬
Must have got incredibly hot to change the colour of the heatsink but no transistor failure as you say, I think these were about £1500 new so I don't mind taking on stuff like this as customers don't usually mind paying good money for something like this .
@@michaeldranfield7140 The last time I checked I think the AVR600 originally sold for $6000, not sure if that's USD or CDN.
@@marstedt yes these were very expensive when new .
Really interesting video. It makes me wonder about the overall quality of Arcam products. Back in the 70s I had an A&R (Arcam now) A60. This was a classic stereo amp of its time, but even that used to run very hot, mainly due to its small heatsink. It sounded great and was actually built in Britain! I can’t believe how they just hold the two transistors together with thermal paste, a small spring clip would solve that problem, poor design and cost cutting if you ask me.
Trouble is these days everyone's cutting cost , we have TV s with screw less backs all manor of cost cutting that in the end does no one any favours .
Thanks for the in depth video, just starting a repair on an AVR500 and nice to have some insight into what's causing it to shutdown. A service manual seems to be non-existent as I would like to monitor feedback from the amp section to the CPU to see what is exactly triggering shutdown. That heat sink compound only for thermal bonding is laughable...
checking the bias voltages are a good starting point as faulty pots cause the bias to drift, I did one of these that was intermittently shutting down but you will need the service manual , each amp has a protection circuit that measures DC offset and these are all OR gated into one single trip control line to the micro , you will never find this without the service manual as its quite complex.
@@michaeldranfield7140 I managed to find the service info for the AVR600 which appears to use the same boards albeit with some enhancements. Yes, I've grabbed a 2 pin connector from a scrap board and will look at bias as well as DC offset at the outputs. Believe the customer was looking for a cheap repair otherwise will take to arcam and I can't honestly see this being cheap unless I pull the amp block or PSU and find something silly like a cold solder joint currently causing the issue. Thanks again!
@@leecambsuk2871 I think Arcam charge about £230 to overhaul this amp so this is a job you can easily do for much less yourself . .
@@michaeldranfield7140 after further checks and inspection the caps and pots had already been replaced. additionally i found open 7a fuses on the centre channel and shorted output devices. given the blown channel and poor bias stability across several other channels I'm handing it back to the customer for repair directly from arcam as it looks quite involved to me. BTW, I believe my customer told me about £350 at Arcam currently.
@@leecambsuk2871 These amps are really time consuming to repair due to the construction and the fact a lot of the parts are surface mounted, last one I did had a very intermittent fault and I had it for months before i found the problem , price could well be £350 now as its a few years ago .
Excellent video, well done. I have a Harman Kardon with the same problem, shutting down as soon as it's powered up. I'm actually looking at a used Arcam ADR400, not sure I want to wade into this level of tech investigation / repair quagmire. That's the problem with these complex integrated amp systems. Once some internal function is tripped causing this, it's a real quagmire trying to solve this, could be any number of reasons, not the least of which may be installing new firmware (basically it's a computer with an amp/receiver wrapped around it). These days I'm more inclined to go for separate components that are easier to work on if needed . . . just a solid amp for driving my audio files and streams, that's more than enough.
Hi , i have just follow your advise and replaced 21 YES 21 :) tantalum capacitors around driver stage --and my Arcam ( AVR 400 model ) no overheats any more , i just want say THANK YOU VERY MUCH SIR !!!! for sharing the knowledge , brilliant .
No problem , many thanks for watching .
Hi Andrzej Siwinski where did You buy the capasitors and where did you buy the capacitors and what type FKP1/2? did Ypu change the potentiometers as well ?
The exact capacitors came from Farnell components in Leeds, or you can buy them from Arcam, the pots were more difficult to get an exact match and I had to settle for the nearest I could find, in mine the pots were 100 ohms, the pots suffer from intermittent change of resistance, probably due to an oxidised wiper contact, I also have a video on the faulty pots showing the problem.
@@michaeldranfield7140 Hello, thank you for the answer, but the question was for Andrzej because I think he is from the same country as me (PL)
@@lukaszstrozycki4600 ebay uk
Nice one Mike, I’ll add them Wima caps are a common failure on Cambridge audio amps quite a few of the newer ones and SMD resistors.
dont know why as Wima is usually a good quality brand .
@@michaeldranfield7140 Yeah Ive seen them in loads of devices, guess no cap is immune to high heat and stress.
@@michaeldranfield7140 Hey Michael guess what! I've just got one of these amps, may I ask what trimmer pots did you use 120ohm or 100ohm ? Also to save me some time and help out real good did you check the resistance of the bias pots after you finished ? If so what was it im lazy and rushed :D
@@MrReeceyburger123 the pots are 100 ohms and its best to replace all 7 if the old ones are black in colour and have a white insert in the middle.
Hi Michael, thank you very much for your instructions. I've changed all parts as instructed but run into an issue: the front channel (central)seems to run without amplification - sounds muddy, al. Do you have any idea where to search for possible solution?
Hello, do you have the references of the components to replace? THANKS
Many thanks. This is a really useful video Michael, and really clear. I bought one of these 2nd hand for around £400 and it is starting to show signs of overheating. So I'll have to try and remember my HNC electronics from the 1980s and have a bash at fixing it. What resistance are the potentiometers? tempted to try to order parts in advance of stripping mine down
The pots were 100 ohms and the correct size was difficult to find so I had to bend the legs slightly one the ones I fitted , and the exact replacement wima caps came from Farnell components in Leeds.
@@michaeldranfield7140 Thanks so much for the video and additional information. I replaced the components yesterday and it looks like the amp is no longer playing up. I've put your contact details on the Audiophiles UK facebook forum as there are probably quite a number of these amps out there that people might expensively replace when they could just ship them to you for repair.
Hi, many thanks for that, glad it was useful for you.
@@michaeldranfield7140 Hi Michael. Looks like my repair did not work. The amp is still functioning, but still overheating. I probably did a poor job with the heat sink paste. I've stopped using the amp for the moment. I'm not confident I have the skills or equipment to diagnose of fix it further. Is this a job you would be interested in taking on?
I can take a look if you want to bring the amp in and leave it with me for a bit, I have just done one with a very, very intermittent fault and had it nearley 3 months due to its intermittent cutting out.
Major rebuild on that item there ,is it just down to poor quality components?
Im not sure , the Wima capacitors are usually a good quality brand .
Amazing!!! Thank's!!!
Many thanks for that .
Hello, Michael, when choosing capacitors, do I only have to pay attention to the capacitance or other parameters also matter (like rated voltage)
The working voltage is also important as these high power amps run with quite a high voltage supply.
@@michaeldranfield7140 Hello Michael, I just replaced all the caps according to your advice, it looks like everything will be ok but I'm a bit worried because after an hour from turning on when I wanted to check the bias, the fans did not turn on even once, is this normal? The heatsink was warm, do you have information when the fans should turn on ? Thans a lot for Your help.
As I understand it the fans are thermostatically controlled by the 3 sensors on the heatsink and should only come on when the heatsink is very hot , but these machines were plagued with overheating when they were brand new and in an attempt to cure the overheating arcam dealers offered a software upgrade which made the fans run all the time , the live temperature data from the sensors can be called up in the service mode and displayed on a TV screen .
Hello Michael,
I have fault issue in my Arcam AVR500, I searched the internet for information about it and found your video on RUclips and i think it can be useful.
I found service manual for AVR600 but I'm pretty sure some of the boards are the same as in AVR500.
So i have some question about potentiometers in SM for AVR6000 RV400 is 200 ohms and they set them for 6mV, so which of the information is correct.
Did You change all potentiometers for the same and all of them set on the same value ?
The pots I took out were 100 0hms so I replaced with the same, some amps were modified by adding thermistors across the bias pots in later production.
@@michaeldranfield7140 Hello, thank you for your quick answer, I will check what I have at my boards , have you set all the potentiometers the same?
Edit:
I confirm the pots are 100 ohms
It's very important you change all the pots, there was some modifications in production so if your pots are 200 ohms fit the same, bias is done when the amp is warm I'm not at work today but I think it was 8mv.
@@michaeldranfield7140 Yes, that's right in the video you say 8 mV but SM for AVR 600 says: "Optimum bias at quiescent operating temperature is measured across the two
0.1 ohm emitter resistors forming R408 - it is typically 15mV at the pins of
C400. When setting up from cold a good starting point to achieve this is to first
turn RV400 to minimum (i.e. fully anticlockwise) and then slowly turn it up to
6mV. "
But they're talking about 200 ohm potentiometers so I'm confused
345 / 5 000
Hi Michael, first of all, thank you very much for your help and advice, in my AVR500 I have already replaced all 21 caps and 7 pots, then I tried to set the bias to 8mV but on one channel when connecting the multimeter sometimes it shows proper value 8mV but once every few times shows 70mV do you have any idea whats happening? regards
Poor design imo, they should have a spring clip maintaining pressure on the sense transistor.
That would have been the most sensible thing to do , it does make you wonder why it was not done on an amp costing this much money .
Great Info
What a terrible design, those transistors should be held using spring clips, rather than relying on just the thermal paste!
I guess as long as it doesn't fail within the warranty period, that is OK?
I was thinking exactly the same thing . . . how much could it cost to add a few spring clips to the assembly?
Great video.
What a badly designed pile of shit though!
A lot of money when new and yet they skimp on things like using heatsink compound to strap two transistors together when they should have used a spring clip .
Hi I have the same issue. Do you have a contact number or email?
Are you still doing repairs?
still doing repairs , just very busy at the moment , md@digifixltd.co.uk