Hi all. New on here. Have a basic understanding of electronics.........
So.......have settled on Mission Cyrus gear for a new living room.
Have come about a Mission Cyrus 2 with one faulty channel. The previous owner tells me he had it repaired recently but has failed again and they replaced a transistor....presuming an output transistor??
I am seeking some advice -
1. Trying to find a Service Manual/Diagram for the Cyrus 2 and PSX (need to check what has been done/replaced previously as seeking to restore -not mod). Have done a search and either hitting multiple broken links or sites no longer accepting registrations, eg Hifiengine, etc; and
2. Any suggestions of someone who can assist in doing the technical work.....ideally in Adelaide SA (but not necessarily)
TIA
So.......have settled on Mission Cyrus gear for a new living room.
Have come about a Mission Cyrus 2 with one faulty channel. The previous owner tells me he had it repaired recently but has failed again and they replaced a transistor....presuming an output transistor??
I am seeking some advice -
1. Trying to find a Service Manual/Diagram for the Cyrus 2 and PSX (need to check what has been done/replaced previously as seeking to restore -not mod). Have done a search and either hitting multiple broken links or sites no longer accepting registrations, eg Hifiengine, etc; and
2. Any suggestions of someone who can assist in doing the technical work.....ideally in Adelaide SA (but not necessarily)
TIA
Thx Vunce. Tho I cant register with hifiengine. Seems he is not accepting any further registrations. Perhaps if you/someone has an existing login, then someone could send a copy?
Thx win33, I couldnt find a schema for the Mission Cyrus 2......which I believe is marginally diferent and uses different components (thos I could well be wrong there). On that, I understand some people suggest upgrading the quality of some components when/if they are replaced. Would appreciate some ideas/guidance on this, as I suspect the unit I have may well require some work....bearing in mind the focus is to restore.
Cheers
Thx win33, I couldnt find a schema for the Mission Cyrus 2......which I believe is marginally diferent and uses different components (thos I could well be wrong there). On that, I understand some people suggest upgrading the quality of some components when/if they are replaced. Would appreciate some ideas/guidance on this, as I suspect the unit I have may well require some work....bearing in mind the focus is to restore.
Cheers
@huggygood. Vunce was kind enough to send me the service manual for the Mission Cyrus 2. It covers the push button/toggle variants. You will note the amp is push button....while the PSX is toggle.
I had previous read (cant recall where) not to mix the push button/toggle models as it suggested the PSX's supplied a different voltage. Though I cant see any reference to this in manual.
Maybe someone knows.....was thinking this might be the root cause of the amp blowing transitors??!! dunno.
The units are in the mail, so unfortunately i cant check S/N or do any basic checks.
Edit Thx raymondj
I had previous read (cant recall where) not to mix the push button/toggle models as it suggested the PSX's supplied a different voltage. Though I cant see any reference to this in manual.
Maybe someone knows.....was thinking this might be the root cause of the amp blowing transitors??!! dunno.
The units are in the mail, so unfortunately i cant check S/N or do any basic checks.
Edit Thx raymondj
Ok fellas, after some advice....again....remember I am a rank amateur!!
I have received the notes from the place that last repaired the amp. All I have as a guide is component details:
1st Visit:
2 x BD243 transistors
1 x BD237 transistor
4 x banana plugs
2 x 4amp fuses
2nd Visit (6mths latter):
4 x BUV28A transistors
Now the same channel as previously is not operating. Clearly there is a root cause.
Other work may well have been completed prior.
I have looked up the various components against the Tech Manual but unable to locate them specifically. I am assuming the BUV28A transistors are the four output transistors? Can I reasonably assume these also replaced the previous 2x BD243 transistors??? Not confident the cause of the recurring fault has been fixed.
Anyway, the two local tech's I trust have either retired or moved.....and I cant seem to be able to locate a good tech!
So, I appreciate this isnt just a Oz forum, but if anyone reads this post and can suggest a great repair tech (ideally) in Adelaide, I will be very grateful
I have received the notes from the place that last repaired the amp. All I have as a guide is component details:
1st Visit:
2 x BD243 transistors
1 x BD237 transistor
4 x banana plugs
2 x 4amp fuses
2nd Visit (6mths latter):
4 x BUV28A transistors
Now the same channel as previously is not operating. Clearly there is a root cause.
Other work may well have been completed prior.
I have looked up the various components against the Tech Manual but unable to locate them specifically. I am assuming the BUV28A transistors are the four output transistors? Can I reasonably assume these also replaced the previous 2x BD243 transistors??? Not confident the cause of the recurring fault has been fixed.
Anyway, the two local tech's I trust have either retired or moved.....and I cant seem to be able to locate a good tech!
So, I appreciate this isnt just a Oz forum, but if anyone reads this post and can suggest a great repair tech (ideally) in Adelaide, I will be very grateful
OK...long hiatus.......but I haven't given up!!
I have not been able to find a local tech willing to take on repairs for my Cyrus 2. All have simply said, "it's to old....I don't work on this Noah stuff..." or something similar! The two -three semi-retired fella's who worked on this good old vintage gear have now retired, moved, etc.... Such a shame....
Remembering I am a rank amateur. So forgive me for any mis-guided comments. Plus I would prefer to not modify the amp, though given the lack of original components this may not be possible. If I am to make a change, I would prefer to optimise the sound quality rather than output. It looks like I am going to have to have a go myself....
What have found out:
-four of the output transistors have been replaced. All are on the left channel. Three of the four are from one supplier, the fourth from another - presume they may have been replaced at different times?? All the Right Channel transistors appear to be the original Cyrus PT7's;
-Q37 and Q38 are both MJE253 transistors. Q33-(L) channel is an ST BD237 , while Q34 -(R) Channel is an ??M 626 JE43??- see photo;
-the two 2A fuses have been replaced with two 4A fuses....possibly because the 2A fuses kept blowing??;
- all other components appear to be original including all the caps - as well as the Roederstein 470uf caps (the left channel one has several visible cracks in the brown coating....the right hand one is also cracked but in better cosmetic condition). Could this be the root cause???;
-The unit came with a Cyrus power supply. The previous guy stated he was using this, however the fuse is blown and the fuses in the amplifier were still in place....so unsure;
-both the amp and power supply were absolutely packed full of cat hair! I should have taken a picture....never seen anything like it. With the cover removed, it was a thick mat of hair including within all the cooling fins, etc etc, doubt was able to stay cool. Fortunately a decent vacuum and a can of cleaner has made a huge difference. There doesnt appear to be any evidence of cat piddle......but prob can't be 100% certain.
-see photos....
What else I have discovered/concluded:
-that BUV 28(a) transistors simply arent available - unless you buy them from AliExpress (and I dont have the knowledge nor equipment to determine if these are to spec). If anyone knows of a source, I am all ears;
-FJP1300TU are available and ??appear maybe?? a possible substitute (at least based on my rudimentary comparison skills) - but unsure and whether other changes need to be made. Do the other pair of transistors in each Channel also need to be replaced/complement a change to a different output transistor? Any other components also need swapping out?
-MLJ21196 (NPN) ??may also be a substitute, are available, but due to a lack of knowledge I have the questions as above.
-I have managed to source Nichicon Muse Caps for the output stages as well as the MC and MM Elna caps. But hesitant to do this yet till I have a workable solution for the transistors.
What I am still unsure about is why the output transistors are blowing.
So, seeking advice/guidance on which Transistors to source, which additional components I will need to swap out, other things to test/examine - remembering I have limited equipment (a decent Multimeter and that's about it!!).
TIA
I have not been able to find a local tech willing to take on repairs for my Cyrus 2. All have simply said, "it's to old....I don't work on this Noah stuff..." or something similar! The two -three semi-retired fella's who worked on this good old vintage gear have now retired, moved, etc.... Such a shame....
Remembering I am a rank amateur. So forgive me for any mis-guided comments. Plus I would prefer to not modify the amp, though given the lack of original components this may not be possible. If I am to make a change, I would prefer to optimise the sound quality rather than output. It looks like I am going to have to have a go myself....
What have found out:
-four of the output transistors have been replaced. All are on the left channel. Three of the four are from one supplier, the fourth from another - presume they may have been replaced at different times?? All the Right Channel transistors appear to be the original Cyrus PT7's;
-Q37 and Q38 are both MJE253 transistors. Q33-(L) channel is an ST BD237 , while Q34 -(R) Channel is an ??M 626 JE43??- see photo;
-the two 2A fuses have been replaced with two 4A fuses....possibly because the 2A fuses kept blowing??;
- all other components appear to be original including all the caps - as well as the Roederstein 470uf caps (the left channel one has several visible cracks in the brown coating....the right hand one is also cracked but in better cosmetic condition). Could this be the root cause???;
-The unit came with a Cyrus power supply. The previous guy stated he was using this, however the fuse is blown and the fuses in the amplifier were still in place....so unsure;
-both the amp and power supply were absolutely packed full of cat hair! I should have taken a picture....never seen anything like it. With the cover removed, it was a thick mat of hair including within all the cooling fins, etc etc, doubt was able to stay cool. Fortunately a decent vacuum and a can of cleaner has made a huge difference. There doesnt appear to be any evidence of cat piddle......but prob can't be 100% certain.
-see photos....
What else I have discovered/concluded:
-that BUV 28(a) transistors simply arent available - unless you buy them from AliExpress (and I dont have the knowledge nor equipment to determine if these are to spec). If anyone knows of a source, I am all ears;
-FJP1300TU are available and ??appear maybe?? a possible substitute (at least based on my rudimentary comparison skills) - but unsure and whether other changes need to be made. Do the other pair of transistors in each Channel also need to be replaced/complement a change to a different output transistor? Any other components also need swapping out?
-MLJ21196 (NPN) ??may also be a substitute, are available, but due to a lack of knowledge I have the questions as above.
-I have managed to source Nichicon Muse Caps for the output stages as well as the MC and MM Elna caps. But hesitant to do this yet till I have a workable solution for the transistors.
What I am still unsure about is why the output transistors are blowing.
So, seeking advice/guidance on which Transistors to source, which additional components I will need to swap out, other things to test/examine - remembering I have limited equipment (a decent Multimeter and that's about it!!).
TIA
Lots of reasons why output transistors could blow, ranging from owner shorted out the speaker terminals, to amplifier is oscillating or it over heated due to all the cat hair. You really need an oscilloscope to check for the presence of oscillation. Basic voltage checks, comparing left/right channels may also point to some particular fault. First start with a careful visual inspection looking for damage and previous service history.
Myalbatech does a lot of work on Cyrus products and has a clip on repair of an early Cyrus 3 amp that may be instructive.
The cyrus1 are not exactly reliable. I remember that due to an output short circuit the BD and PT bjt failed, the latter replaced with BD911(npn) and BD912(pnp)