Hi there
I'm a newbie to the forum - I've just hard shorted the right hand output of my Cyrus 2, from visual inspection it looks like several resistors have blown. I've been goggling for the resistor colour code but I cant seem to read it from these. Does anyone now what the direct replacements would be ?
I've included a photo of the damage
http://www.flickr.com/photos/david_warner/436340581/
http://www.flickr.com/photos/david_warner/436340547/
http://www.flickr.com/photos/david_warner/436340908/
I'm hoping someone will tell me this is a simple fix. As my Cyrus is dearly loved :-(
Many thanks
I'm a newbie to the forum - I've just hard shorted the right hand output of my Cyrus 2, from visual inspection it looks like several resistors have blown. I've been goggling for the resistor colour code but I cant seem to read it from these. Does anyone now what the direct replacements would be ?
I've included a photo of the damage
http://www.flickr.com/photos/david_warner/436340581/
http://www.flickr.com/photos/david_warner/436340547/
http://www.flickr.com/photos/david_warner/436340908/
I'm hoping someone will tell me this is a simple fix. As my Cyrus is dearly loved :-(
Many thanks
From your photos it looks as though your Cyrus is one of the earlier versions (non-metalic case). Email me and I will send you a copy of the schematic from which you will be able to determine the relevant resistor values.
It is also likely that the output transistors, and possibly the driver transistors, have also blown so you will need to check these and replace them if necessary.
It is also likely that the output transistors, and possibly the driver transistors, have also blown so you will need to check these and replace them if necessary.
Geoff
That sounds about right, Unfortunately I cant e-mail you until my account is out of moderation (not too long I hope)
Although I can solder it's been a long time, and I'm not really sure how to identify the parts of the circuit.
I was hoping to just replace the components that were visible burnt out.
Perhaps this might be a job for a profesional? Any ideas how much this would cost (just a ballpark figure would be fine)
As a sidenote, I damaged the Cyrus whilst trying to connect a mission subwoofer to the speaker outs - I have bi-wired speakers and the sub takes the signal direct from the speaker outs. After the thing blew I realised that I have the + and - of one of the bi-wire cables going into the same banna plug and something pretty similar at the other end going into the sub - silly I know, I was using flat QED cable and I got a bit confused with the labels. Do you think that would have created some kind of short?
Thanks again
That sounds about right, Unfortunately I cant e-mail you until my account is out of moderation (not too long I hope)
Although I can solder it's been a long time, and I'm not really sure how to identify the parts of the circuit.
I was hoping to just replace the components that were visible burnt out.
Perhaps this might be a job for a profesional? Any ideas how much this would cost (just a ballpark figure would be fine)
As a sidenote, I damaged the Cyrus whilst trying to connect a mission subwoofer to the speaker outs - I have bi-wired speakers and the sub takes the signal direct from the speaker outs. After the thing blew I realised that I have the + and - of one of the bi-wire cables going into the same banna plug and something pretty similar at the other end going into the sub - silly I know, I was using flat QED cable and I got a bit confused with the labels. Do you think that would have created some kind of short?
Thanks again
Go to my website. My email address is on the home page. Unless things have changed recently, Cyrus will service and repair the amp but it will be expensive (it will probably cheaper to buy another working Cyrus 2 on eBay). I am happy to talk you through the process by email (or phone if necessary) if you want to give it a go yourself.
mannotanumber said:
Absolutely! In very simple terms: The amplifier is used to 'pushing' current through a resistance of ~ 4 to 8 Ohms speakers. This is something that the amplifier works against in normal operation. When you short the outputs you take away the thing that prevents too much current from flowing through the amplifier.
It is extremely likely that this has caused the output transistors (on the heatsink) to have blown and also taken out some surrounding components.
Your amplifier should also have some (better to do all) of the electrolytic capacitors changed as well due to the age of the amp. We have seen some around here that have gone. There's no point fixing it just to have it fail again due to age.
I have 2 Cyrus Ones with similar problems so I would appreciate you posting your results here if possible. I need a bit more confidence before I dive in to mine!!
Martin.
Thanks for that,
The Caps look to be in very good condition. I got this unit on e-bay with a mission service sticker over it and I have a feeling some components have been replaced quite recently. If anyone knows where I could source any new caps, resistors etc then please let me know.
Is something Maplins can provide I've always found them to be very unhelpful.
Many thanks
The Caps look to be in very good condition. I got this unit on e-bay with a mission service sticker over it and I have a feeling some components have been replaced quite recently. If anyone knows where I could source any new caps, resistors etc then please let me know.
Is something Maplins can provide I've always found them to be very unhelpful.
Many thanks
Hi,
It's interesting that it has a Mission service sticker. I wonder what they did. Must have been a few years ago though before Cyrus became a company in their own right (independent from Mission).
Changing the caps is worthwhile if only for long term reliability. For improvements in sound I heartily recommend changing the 2 large power supply smoothing caps and perhaps upping the capacitance a little. Cyrus one and two sound a little forward at the best of times but the bass can be strangled by these old caps. But, of course, you'll need to get it working first!
I'm on a very tight budget so I generally identify the bits and pieces that I need and then do a European search on Ebay. I wouldn't get output transistors from Ebay though due to the high number of counterfeits around.
I have bought some of the more exotic items from http://www.hificollective.co.uk/.
You could probably get most of the parts from Maplin and I'd be happy to help you find them. You may find it easier just to place one order with RS components ore Farnell or .......
I'll leave it up to Geoff to advise you on the replacement transistors this is where I get lost and that is why I still have two broken Cyrus amps!!
Martin.
It's interesting that it has a Mission service sticker. I wonder what they did. Must have been a few years ago though before Cyrus became a company in their own right (independent from Mission).
Changing the caps is worthwhile if only for long term reliability. For improvements in sound I heartily recommend changing the 2 large power supply smoothing caps and perhaps upping the capacitance a little. Cyrus one and two sound a little forward at the best of times but the bass can be strangled by these old caps. But, of course, you'll need to get it working first!
I'm on a very tight budget so I generally identify the bits and pieces that I need and then do a European search on Ebay. I wouldn't get output transistors from Ebay though due to the high number of counterfeits around.
I have bought some of the more exotic items from http://www.hificollective.co.uk/.
You could probably get most of the parts from Maplin and I'd be happy to help you find them. You may find it easier just to place one order with RS components ore Farnell or .......
I'll leave it up to Geoff to advise you on the replacement transistors this is where I get lost and that is why I still have two broken Cyrus amps!!
Martin.
Sonusthree said:
Martin
Replacement output transistors need not be all that expensive, particularly if you are willing to accept a substitute. When I ordered a replacement PT7 from Cyrus about ten years ago they sent a BUV28 which I could have bought at less than half the price elsewhere.
Grandata list the BUV28 at £1.10 but they do state in their terms and conditions that most of their stock is 'replacement parts' (second sourced?). Nikko has the BUV28 at £2.75 and the BUV28A at £2.19. Cricklewood list the BUV28A at £2.50.
If you are happy with a substitute, the MJE13009 looks a good match for the BUV28. Farnell have these at £1.33 (non-RoHS) or £1.91. They are also available from RS (£1.64), Cricklewood (£1.00), Nikko (£0.82) and Grandata (£1.00).
All of these are TO-220 and so will fit all Cyrus 1s and the earlier Cyrus 2s. If you have a v7 Cyrus 1 or 2, the STW13009 available from Farnell for £0.86 looks like it might be a good bet. It has a larger TO-247 case which means lower junction temperatures and so greater longevity and, IIRC, the SOA is better so there should be less risk of failure if the output is presented with a very low impedance load.
Another candidate in a larger package (TO-3P or TO-247 depending on manufacturer) is the BUV48/48A which last time I checked was significantly cheaper than the BUV28.
Please note that, as yet, I have not tried any of these alternatives to the BUV28 in one of my amps though I intend to do so in the not too distant future as one of them is currently running on some slow 2SD6xx devices.
Geoff
Thanks Geoff, I don't want to hijack this thread but I suppose that it's relevant.
I have two broken Cyrus one amps. One plastic case neon logo and one rev 7. I'm especially interested in fixing the later model for bi-amping duties with my working Cyrus 2 (&PSX).
I bought both of these amps a long time ago very cheaply from Ebay and they both have one channel down. I tried to fix them a few years ago by substituting parts from one channel to another with no luck and, surprisingly, no further damage. I now know that this was a terrible idea!! I'd like to have a proper go at it now. The earlier model was occasionally being used to power a DIY guitar cabinet with it's remaining channel but unfortunately I knocked the case very lightly and saw a spark inside and then no sound!! It was the lightest of knocks.
What is the priority for testing for someone of my fairly limited experience? I know that I should check the output transistors and the surrounding resistors but what about all the small transistors. If I miss a dodgy one will all of my work be in vain? Is there a foolproof way to get it working?
I had considered a complete renewal of all the transistors and electrolytics. I want to keep these amps long term so don't mind the trouble and cost but can't afford to do it twice! The small transistors are many and quite expensive when added up.
My main issue is whether or not I can just substitute parts without re biasing anything. In an ideal world I would just change out all the transistors for recommended types and then relax.
Is it that easy or is it as hard as I have imagined?
My apologies to mannotanumber if I am getting in the way. I had considered starting a new thread but thought that we were essentially in the same situation.
Cheers,
Martin.
I have two broken Cyrus one amps. One plastic case neon logo and one rev 7. I'm especially interested in fixing the later model for bi-amping duties with my working Cyrus 2 (&PSX).
I bought both of these amps a long time ago very cheaply from Ebay and they both have one channel down. I tried to fix them a few years ago by substituting parts from one channel to another with no luck and, surprisingly, no further damage. I now know that this was a terrible idea!! I'd like to have a proper go at it now. The earlier model was occasionally being used to power a DIY guitar cabinet with it's remaining channel but unfortunately I knocked the case very lightly and saw a spark inside and then no sound!! It was the lightest of knocks.
What is the priority for testing for someone of my fairly limited experience? I know that I should check the output transistors and the surrounding resistors but what about all the small transistors. If I miss a dodgy one will all of my work be in vain? Is there a foolproof way to get it working?
I had considered a complete renewal of all the transistors and electrolytics. I want to keep these amps long term so don't mind the trouble and cost but can't afford to do it twice! The small transistors are many and quite expensive when added up.
My main issue is whether or not I can just substitute parts without re biasing anything. In an ideal world I would just change out all the transistors for recommended types and then relax.
Is it that easy or is it as hard as I have imagined?
My apologies to mannotanumber if I am getting in the way. I had considered starting a new thread but thought that we were essentially in the same situation.
Cheers,
Martin.
to give you a detailed reply but I will be happy to do so via individual emails, or via the forum, tomorrow (though I might need a reminder as my memory is not what it used to be - I blame the whisky for this!).Geoff
Thanks again, I was having a mad moment last night I've got the resistance now 120ohms and the 270ohms both 0.6w.
Try as I might I cant find Resistance value for R89-R96, Don't know if its my eyes ?
You have been a fantastic help mate, and I'm off to test the transistors now.
Kind Regards
Dave
Thanks again, I was having a mad moment last night I've got the resistance now 120ohms and the 270ohms both 0.6w.
Try as I might I cant find Resistance value for R89-R96, Don't know if its my eyes ?
You have been a fantastic help mate, and I'm off to test the transistors now.
Kind Regards
Dave
Martin
I can send you a copy of the earlier v6 schematic if you haven't already got one, just send me an email.
You ask "Is there a foolproof way to get it working?" and my reply has to be no, but with some care and a logical approach they is no reason why you cannot succeed.
Start at the output and work backwards, testing the transistors for a short between collector and emitter (the usual failure mode) and measuring the resistors. The resistors marked with a triangle on the v7 schematic are fusible types which are supposed to protect the associated and preceding semiconductors but, as with output transistors blowing before the rail fuses, it is more usual for the silicon to go first.
I have been lucky in that I have only lost the output transistors, the drivers have been intact and no resistors have blown. However your case may be different. If the drivers test OK then it should just be a case of replacing any failed output transistors. If the drivers have failed then you will need to check the pre-drivers (Q27/Q29 on the v7 schematic). Keep working backwards until you reach the point where nothing has failed to a short (transistors) or an open circuit (fusible resistors).
As for setting up (re-biasing) after components have been replaced, the earlier v6 has a preset for adjusting the output stage quiescent current but the v7 relies on fixed resistors with the facility to link one out to adjust the bias. When the repairs have been done and the amp re-assembled (don't forget to replace the isolation pad between the output transistors and the heatsink as this becomes less effective when reused), it is a case of checking the output stage quiescent current by measuring the voltage across one of the 0R22 resistors (or one pair of the paralleled 0R47 resistors in v6) to see that it is in the range of 50mA to 100mA.
I have not seen a recommended figure for this current published by Cyrus but my Cyrus 1s run at about 75mA. The method of adjusting resistor values on v7 to alter the quiescent current has been covered in another thread (I think the title is 'Cyrus 1 Project')
"Is it that easy or is it as hard as I have imagined?" It is as easy or as hard as you care to make it! Proceed logically in a step-by-step fashion and you should achieve a satisfactory outcome. Rush in and you may find your time and money has been wasted.
If you need further clarification on any aspect don't hesitate to ask, either here or by email.
I can send you a copy of the earlier v6 schematic if you haven't already got one, just send me an email.
You ask "Is there a foolproof way to get it working?" and my reply has to be no, but with some care and a logical approach they is no reason why you cannot succeed.
Start at the output and work backwards, testing the transistors for a short between collector and emitter (the usual failure mode) and measuring the resistors. The resistors marked with a triangle on the v7 schematic are fusible types which are supposed to protect the associated and preceding semiconductors but, as with output transistors blowing before the rail fuses, it is more usual for the silicon to go first.
I have been lucky in that I have only lost the output transistors, the drivers have been intact and no resistors have blown. However your case may be different. If the drivers test OK then it should just be a case of replacing any failed output transistors. If the drivers have failed then you will need to check the pre-drivers (Q27/Q29 on the v7 schematic). Keep working backwards until you reach the point where nothing has failed to a short (transistors) or an open circuit (fusible resistors).
As for setting up (re-biasing) after components have been replaced, the earlier v6 has a preset for adjusting the output stage quiescent current but the v7 relies on fixed resistors with the facility to link one out to adjust the bias. When the repairs have been done and the amp re-assembled (don't forget to replace the isolation pad between the output transistors and the heatsink as this becomes less effective when reused), it is a case of checking the output stage quiescent current by measuring the voltage across one of the 0R22 resistors (or one pair of the paralleled 0R47 resistors in v6) to see that it is in the range of 50mA to 100mA.
I have not seen a recommended figure for this current published by Cyrus but my Cyrus 1s run at about 75mA. The method of adjusting resistor values on v7 to alter the quiescent current has been covered in another thread (I think the title is 'Cyrus 1 Project')
"Is it that easy or is it as hard as I have imagined?" It is as easy or as hard as you care to make it! Proceed logically in a step-by-step fashion and you should achieve a satisfactory outcome. Rush in and you may find your time and money has been wasted.
If you need further clarification on any aspect don't hesitate to ask, either here or by email.
As a first post, may I offer the tip that has served me well in the past faulting solid-state amps. Generally these will run with around 20 to 30 volts rail positive and negative and will have fuses which will probably keep blowing until you fix the fault.
Ideally you have a current limited dual-stabilised power supply to use for testing purposes, great if you have one, no help if you don't.
My suggestion is that you pick up some old dual filament 45watt P45 headlight bulbs from a car breaker - shouldn't cost much and you may already have some. These will have two 12 volt filaments in each glass envelope. If you ignore the common connection and connect to the other two you have a light bulb that takes 24 volts and needs about 4 amps to light up. Put one (i.e. a separate bulb with two filaments in series) across where each of the low voltage fuses should go. Do not try this in place of a mains fuse - you have been warned.
These will not go bang if there's a fault, they just light up. If the current is <<4 amps they won't affect normal operation due to the temp coefficient thing viz the resistance is very low until they carry 3 or 4 amps. I sometimes found that you could change a Transistor and all seemed to go well until you put a load in place and then you draw excessive current so I would leave them in until you are 100% through with testing into a real load. The two filaments in series might also be used as a makeshift test-load at about 6.5 ohms, though clearly a lot less than this until current starts flowing.
One other tip - use any NPN power transistor to replace the dud and only when it all works worry about getting an exact replacement and finalising the bias settings etc. - you may take more than one attempt to get it right.
Ideally you have a current limited dual-stabilised power supply to use for testing purposes, great if you have one, no help if you don't.
My suggestion is that you pick up some old dual filament 45watt P45 headlight bulbs from a car breaker - shouldn't cost much and you may already have some. These will have two 12 volt filaments in each glass envelope. If you ignore the common connection and connect to the other two you have a light bulb that takes 24 volts and needs about 4 amps to light up. Put one (i.e. a separate bulb with two filaments in series) across where each of the low voltage fuses should go. Do not try this in place of a mains fuse - you have been warned.
These will not go bang if there's a fault, they just light up. If the current is <<4 amps they won't affect normal operation due to the temp coefficient thing viz the resistance is very low until they carry 3 or 4 amps. I sometimes found that you could change a Transistor and all seemed to go well until you put a load in place and then you draw excessive current so I would leave them in until you are 100% through with testing into a real load. The two filaments in series might also be used as a makeshift test-load at about 6.5 ohms, though clearly a lot less than this until current starts flowing.
One other tip - use any NPN power transistor to replace the dud and only when it all works worry about getting an exact replacement and finalising the bias settings etc. - you may take more than one attempt to get it right.
Well I am both happy and slightly embarrassed! I opened the Issue 7 Cyrus and found no shorted transistors. I saw a few suspicious solder joints so reworked them. I also noticed that the ribbon cable wasn't looking very secure at the point where it joins it's push fit connector so I removed the connector and soldered directly to the PCB. It now works!!!
As a side issue I usually run an Issue 7 Cyrus 2 with PSX. These have been 'upgraded' and modified but the stock Cyrus 1 has the best 'speed' by a country mile. My usual Cyrus 2 rig only wins out in terms of lower frequency authority. I WILL find a way to Biamp with both Cyrii. I've heard many arguments about speed and PRAT but in this case I am referring to the clear superiority of the Cyrus 1 when, for example, following very fast and intricate piano. My C2/PSX sounds dull by comparison. I am, therefore, scared to mod the Cyrus one with more capacitance or a better pot. I guess I should start a whole new thread about this ....
Back on topic:
My plastic Cyrus one has a more serious problem. It keeps blowing fuses and two of the output transistors are missing entirely. (Yes, seriously) I think I'll stick to BUV28/48 if they are supplied by Cyrus but I cannot see a preset to adjust the bias but I haven't had a proper look yet. I'll have a good poke around later and post my findings.
Geoff: Please could you send me a v6 schematic to fivelitrebucket(at no flippin spam please)aol.com. I will also try to contact you by forum mail but I find it to be terribly unreliable.
Kind regards,
Martin.
As a side issue I usually run an Issue 7 Cyrus 2 with PSX. These have been 'upgraded' and modified but the stock Cyrus 1 has the best 'speed' by a country mile. My usual Cyrus 2 rig only wins out in terms of lower frequency authority. I WILL find a way to Biamp with both Cyrii. I've heard many arguments about speed and PRAT but in this case I am referring to the clear superiority of the Cyrus 1 when, for example, following very fast and intricate piano. My C2/PSX sounds dull by comparison. I am, therefore, scared to mod the Cyrus one with more capacitance or a better pot. I guess I should start a whole new thread about this ....
Back on topic:
My plastic Cyrus one has a more serious problem. It keeps blowing fuses and two of the output transistors are missing entirely. (Yes, seriously) I think I'll stick to BUV28/48 if they are supplied by Cyrus but I cannot see a preset to adjust the bias but I haven't had a proper look yet. I'll have a good poke around later and post my findings.
Geoff: Please could you send me a v6 schematic to fivelitrebucket(at no flippin spam please)aol.com. I will also try to contact you by forum mail but I find it to be terribly unreliable.
Kind regards,
Martin.
Sonusthree said:
I have found exactly the same. The Cyrus 2+PSX only comes into its own when in a large room and/or feeding inefficient speakers. That is of course unless one is using the phono stage when the separate power supply for this can be a benefit.
The presets RV2/3 for setting the quiescent current are hidden under the ribbon cable.
Done.
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