I've been kindly given a Cyrus Two (Issue 07) by a friend. He had a proble with it where one of the channels went down. He sent it for repair (not to Cyrus) and it came back with both channels working, but, as he described it, with reduced volume and mains hum on it.
I've only been able to test it with headphones as I don't have speaker connections to fit (I'll get some at the weekend to try it out) but I can't hear any noise and the volume seems pretty damn loud! I presume the problem is on speaker output only.
Anyway, I've had a look inside and noticed a couple of things (see photo).
One of the fuses has a small blob of solder in the centre, as if it's blown but not completely. Is this possible and could it affect the sound?
Also, R119 (I think) seems to have been replaced and resoldered - rather badly from how it looks.
Is it possible that these could be causing issues? Any ideas would be most appreciated. I'll post more info when I test it with speakers.
I've only been able to test it with headphones as I don't have speaker connections to fit (I'll get some at the weekend to try it out) but I can't hear any noise and the volume seems pretty damn loud! I presume the problem is on speaker output only.
Anyway, I've had a look inside and noticed a couple of things (see photo).
One of the fuses has a small blob of solder in the centre, as if it's blown but not completely. Is this possible and could it affect the sound?
Also, R119 (I think) seems to have been replaced and resoldered - rather badly from how it looks.
Is it possible that these could be causing issues? Any ideas would be most appreciated. I'll post more info when I test it with speakers.
That's a nice amp to receive. 
I am not sure what the problem seems to be with the amp.
One of the fuses IS a slow blow (i'm not sure about the other) and by itself should not indicate any harm. I cannot see what its rating is.
Schematics states that ratings should be 2A f.b. (thats fast blow - regular) for FS1 and FS2 and 1A s.b. for FS3 if you are on 220/240VAC grid.
Strange thing is that the rating printed on the board is nothing like the schematics state it should be.
Did the lab replace the final stage transistors ?
Are the final stage transistors original ?
Are the final stage transistors the same on the left channel as the ones on the right channel ?
Let me know if i can help with anything ...
I am not sure what the problem seems to be with the amp.
One of the fuses IS a slow blow (i'm not sure about the other) and by itself should not indicate any harm. I cannot see what its rating is.
Schematics states that ratings should be 2A f.b. (thats fast blow - regular) for FS1 and FS2 and 1A s.b. for FS3 if you are on 220/240VAC grid.
Strange thing is that the rating printed on the board is nothing like the schematics state it should be.
Did the lab replace the final stage transistors ?
Are the final stage transistors original ?
Are the final stage transistors the same on the left channel as the ones on the right channel ?
Let me know if i can help with anything ...
Your description is a bit vague.
Let me look at your images:
This amp is from the late 80ies. The headphone output is directly driven by the amp itself (via resistors) so if there is a good sound the amp is working well. These outputs maybe nevertheless overdrive a 32Ohms headphone quite easy.
The fuses MUST be 4.0A fast blow, the one with the "blob" maybe is a slow blow one. If the fast blow types break when you power on the amp something is wrong.
The lower one of the "burned" resistors should actually be a diode (D12), the parts in your photo are - as far as I can remember - the circuits for the LEDs in front. This can be very easy checked. Put out the parts just in case.
Please measure at least the power supply voltages (maybe at the fuses, ground at the black speaker output). They should be symmetrical. Do not forget to check the ground connection resistor (15R) which connects the two grounds (necessary also for the use with a PSX).
The schematics are here, the Cyrus 2 is very similar (more voltage, different output transistors and drivers, but the same schematic):
The Class-A Amplifier Site
Let me look at your images:
This amp is from the late 80ies. The headphone output is directly driven by the amp itself (via resistors) so if there is a good sound the amp is working well. These outputs maybe nevertheless overdrive a 32Ohms headphone quite easy.
The fuses MUST be 4.0A fast blow, the one with the "blob" maybe is a slow blow one. If the fast blow types break when you power on the amp something is wrong.
The lower one of the "burned" resistors should actually be a diode (D12), the parts in your photo are - as far as I can remember - the circuits for the LEDs in front. This can be very easy checked. Put out the parts just in case.
Please measure at least the power supply voltages (maybe at the fuses, ground at the black speaker output). They should be symmetrical. Do not forget to check the ground connection resistor (15R) which connects the two grounds (necessary also for the use with a PSX).
The schematics are here, the Cyrus 2 is very similar (more voltage, different output transistors and drivers, but the same schematic):
The Class-A Amplifier Site
Here is a pic of my Cyrus One. It seems that some of the components in the Two, have not been used in the One. Both fuses are 4A Fast blow.
An externally hosted image should be here but it was not working when we last tested it.
Well I've tried it out with a pair of crappy Sony speakers and it seems fine. No mains hum at all, and no distortion or lack of volume.
I think I need to speak to my friend who gave it me and get him to have a listen. He has also given me the psx but I haven't used this with it, so I'll try that soon.
Any recommendations for modern, budget speakers that could go with this?
Puffin - FYI I'm in Stockport.
I think I need to speak to my friend who gave it me and get him to have a listen. He has also given me the psx but I haven't used this with it, so I'll try that soon.
Any recommendations for modern, budget speakers that could go with this?
Puffin - FYI I'm in Stockport.
Mission Cambridge amplifier - switch
Hi All,
I am making use of this forum.
I have the above specified amplifier.
It is so nice, I upgraded it with Cardas connections,
speaker cable, 4 Black Gate capacitors.
Sounds wonderful after heating up for 1 hour.
But as the speaker cable appeared thick for this small box
I had to dismantle it many times in order to adjust the cable position inside and by doing so damaged the input selector switch .
The switch looks exactly the same as the ones on photos here.
Appreciate if anyone tells me where to find this switch .
Best to all
Aleko Markov
Hi All,
I am making use of this forum.
I have the above specified amplifier.
It is so nice, I upgraded it with Cardas connections,
speaker cable, 4 Black Gate capacitors.
Sounds wonderful after heating up for 1 hour.
But as the speaker cable appeared thick for this small box
I had to dismantle it many times in order to adjust the cable position inside and by doing so damaged the input selector switch .
The switch looks exactly the same as the ones on photos here.
Appreciate if anyone tells me where to find this switch .
Best to all
Aleko Markov
I have this amp too
And the above mentioned switch is having bad contacts.
I wanted to replace the switch so I looked for a replacement all over the internet, and when i couldn't find any I contacted Cyrus. (this was about 10 days ago).
I got hold of the service department and the technician (very kindly) explained that they no longer stock this switch, and that sadly they can't sell me one.
Two suggestions were brought up during the conversation with him, one was to dismantle the switch and clean it (I'm not sure this can help you, I'm not sure what happened to the switch during the cable installations), and the other was to use the second (record) switch as the selector switch since the both are exactly the same, and I don't use the tape's line out.
I am going to try and clean the switch soon, if I won't be satisfied with the results, I guess i'll have to look at building a preamp or a passive preamp to solve my switch problems.
hope this helps, or gives some ideas...
And the above mentioned switch is having bad contacts.
I wanted to replace the switch so I looked for a replacement all over the internet, and when i couldn't find any I contacted Cyrus. (this was about 10 days ago).
I got hold of the service department and the technician (very kindly) explained that they no longer stock this switch, and that sadly they can't sell me one.
Two suggestions were brought up during the conversation with him, one was to dismantle the switch and clean it (I'm not sure this can help you, I'm not sure what happened to the switch during the cable installations), and the other was to use the second (record) switch as the selector switch since the both are exactly the same, and I don't use the tape's line out.
I am going to try and clean the switch soon, if I won't be satisfied with the results, I guess i'll have to look at building a preamp or a passive preamp to solve my switch problems.
hope this helps, or gives some ideas...
Mission Cambridge - input selector switch
Hi Liquias,
Thank you.
Yes, indeed it does help .
I have also sent them a message today, waiting for reply.
It is a pity as you say they cannot supply the switch.
In my case the plastic rotary part is broken so now I have to turn it manually inside to select the input.
Otherwise the contacts inside are good, no problem with the sound.
I may opt to replace the input switch with the record switch .
It will be hard work to do it but it seems that I have to.
Best regards,
Aleko
Hi Liquias,
Thank you.
Yes, indeed it does help .
I have also sent them a message today, waiting for reply.
It is a pity as you say they cannot supply the switch.
In my case the plastic rotary part is broken so now I have to turn it manually inside to select the input.
Otherwise the contacts inside are good, no problem with the sound.
I may opt to replace the input switch with the record switch .
It will be hard work to do it but it seems that I have to.
Best regards,
Aleko
Mission Cambridge amplifier - selector switch
Hi lohk,
Thank you for this kind gesture.
In fact I am surprised you would take off the switches from your Cyrus 1 amplifier which is as you say in studio use.
I would not accept that you damage your amplifier so that I repair mine.
Still if you need any of those parts below please let me know.
What I have left from projects is very limited:
- one pieces of Alpha Core Guertz loudspeaker cable 1 metre;
- 6 pieces gold plated RCAs;
- some Holco 1/2 watt resistors but not complete set of values.
Best regards,
Aleko
Hi lohk,
Thank you for this kind gesture.
In fact I am surprised you would take off the switches from your Cyrus 1 amplifier which is as you say in studio use.
I would not accept that you damage your amplifier so that I repair mine.
Still if you need any of those parts below please let me know.
What I have left from projects is very limited:
- one pieces of Alpha Core Guertz loudspeaker cable 1 metre;
- 6 pieces gold plated RCAs;
- some Holco 1/2 watt resistors but not complete set of values.
Best regards,
Aleko
I have desoldered two switches of an Cyrus 1, used but in good condition. Please submit your postal adresses that I can send them.
Let us make it that way: I have no information how much the postal charges to your countries will be, I hope not too much. But I will tell you when I post the items. You can then paypal me as much as you think.
Do not worry about my studio amp. In the meantime I stripped it out of the orginal broken case and put it in a new one. One single input is now connected directly to the pot. The switches are not really needed anymore.
Aleko: What values in Holco do you have?
Let us make it that way: I have no information how much the postal charges to your countries will be, I hope not too much. But I will tell you when I post the items. You can then paypal me as much as you think.
Do not worry about my studio amp. In the meantime I stripped it out of the orginal broken case and put it in a new one. One single input is now connected directly to the pot. The switches are not really needed anymore.
Aleko: What values in Holco do you have?
Mission Cambridge amplifier - switch
Hi Lohk,
I can't believe you did that ....
Thank you!
My address is:
Aleko Markov
apt 7, entr A, 59 Haidushka Poliana St,
Lagera Est,
1612 Sofia,
Bulgaria
The Holcos are all of them having the values in the ohm region, 1/4 watt:
11.5 - 4
19.1 - 2
17.4 - 2
22.1 - 4
20.5 - 2
21.5 - 4
14.7 - 2
18.2 - 2
16.2 - 2
21 - 2
13.7 - 2
19.6 - 4
22.6 - 6
Total: 38 resistors
If you need any of them or all of them please let me have your address and I will send them over to you.
Best regards,
Aleko
Hi Lohk,
I can't believe you did that ....
Thank you!
My address is:
Aleko Markov
apt 7, entr A, 59 Haidushka Poliana St,
Lagera Est,
1612 Sofia,
Bulgaria
The Holcos are all of them having the values in the ohm region, 1/4 watt:
11.5 - 4
19.1 - 2
17.4 - 2
22.1 - 4
20.5 - 2
21.5 - 4
14.7 - 2
18.2 - 2
16.2 - 2
21 - 2
13.7 - 2
19.6 - 4
22.6 - 6
Total: 38 resistors
If you need any of them or all of them please let me have your address and I will send them over to you.
Best regards,
Aleko
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