Hello Puresound,
Re- Cyrus2 and PSX in combo.
I read earlier you removed the Cyrus mains fuse (and reconnected the mains plug for signal earthing reasons).
That would have depowered the phono section.
If you have not removed the rail fuses FS1 and FS2 as discussed by "alohka" and "Martin", this would be a necessary next step.
If the switch on noise remains then "alohka's" intuition on the grounding resistor in the PSX is certainly worth checking.
The noise from your speakers must be driving you mad by now. You can protect by using a 5 watt 100 ohm resistor between the amplifier output and either of the two speakers.
Michael Jonassen
Re- Cyrus2 and PSX in combo.
I read earlier you removed the Cyrus mains fuse (and reconnected the mains plug for signal earthing reasons).
That would have depowered the phono section.
If you have not removed the rail fuses FS1 and FS2 as discussed by "alohka" and "Martin", this would be a necessary next step.
If the switch on noise remains then "alohka's" intuition on the grounding resistor in the PSX is certainly worth checking.
The noise from your speakers must be driving you mad by now. You can protect by using a 5 watt 100 ohm resistor between the amplifier output and either of the two speakers.
Michael Jonassen
Yes michael its driving me bonkers,the noise is pushing 14v through to the speakers when power button is turned on then back to zero.
The noise is there when fusses are in when using cyrus as a intergrated ,
take fusses out and no noise on switch on,
plug psx in to cyrus (with fusses still out) and the noise rears it horrible ugly head once again!!!
ive checked / replaced all main caps in cyrus 2, checked all diodes etc. Ive just ordered the rest of caps for the board about 15 or so to see if its a bad cap.
But i cant use it due to the fact i dont want to damage my speakers on turn on.(or will it not?)
The units are in mint condition and dont want to let them go !
any more suggestions???
The noise is there when fusses are in when using cyrus as a intergrated ,
take fusses out and no noise on switch on,
plug psx in to cyrus (with fusses still out) and the noise rears it horrible ugly head once again!!!
ive checked / replaced all main caps in cyrus 2, checked all diodes etc. Ive just ordered the rest of caps for the board about 15 or so to see if its a bad cap.
But i cant use it due to the fact i dont want to damage my speakers on turn on.(or will it not?)
The units are in mint condition and dont want to let them go !
any more suggestions???
Hello Richard,
C63 and C64 are what I previously described as snubbing caps - they prevent sparking across the switch contacts at switch on.
Class Y and Class X2 are different capacitor types whereas C63 and C64 should be identical. A mix of types would indicate a repair having been made. A google search on MP3y led me to WIMA brand capacitors.
If the capacitors are not doing their job the switch contacts would suffer.
Having found a circuit diagram I can see R121 is the 15 ohm resistor mentioned by "alokha". This should be a carbon type.
The 5 watt 100 ohm resistor use was to avoid damage during testing.
Michael Jonassen
C63 and C64 are what I previously described as snubbing caps - they prevent sparking across the switch contacts at switch on.
Class Y and Class X2 are different capacitor types whereas C63 and C64 should be identical. A mix of types would indicate a repair having been made. A google search on MP3y led me to WIMA brand capacitors.
If the capacitors are not doing their job the switch contacts would suffer.
Having found a circuit diagram I can see R121 is the 15 ohm resistor mentioned by "alokha". This should be a carbon type.
The 5 watt 100 ohm resistor use was to avoid damage during testing.
Michael Jonassen
Unsurprisingly really as that's because the amp is no longer receiving any power.
The amp does thump at turn on even when new.Perhaps you can put a video of the speakers moving on Youtube and we can see if it really is that bad or just normal.
Check the link resistor mentioned by alokha.
Hi all i have now posted a video of fault for you all to watch. i turn the psx on on the video, but when using cyrus 2 as normal without psx same fault so its the cyrus2
Cyrus 2 and psx fault - YouTube
Cyrus 2 and psx fault - YouTube
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It is look like the power supply is not coming smooth. That's sound it is like the power supply is loaded coming up. That's not normal. It is sound like spring sound. At the beginning you said if you remove the PSX you didn't have the sound. Now you said that with or without you still have the sound. Which it is right?
Hello Richard,
The noise I heard on You Tube is highly abnormal.
The speaker cone moves slowly one way then the other accompanied by mains hum. The cause is a d.c. voltage which appears to correct but much too slowly.
The mains noise is impressed upon the d.c.
d.c. will burn out loudspeaker coils if applied too long. You should not use the combo with loudspeakers until you have the fault sorted.
For what it is worth, the few repairs I did on Cyrus 1's 20+ years ago were over output transistors failures.
Michael Jonassen
The noise I heard on You Tube is highly abnormal.
The speaker cone moves slowly one way then the other accompanied by mains hum. The cause is a d.c. voltage which appears to correct but much too slowly.
The mains noise is impressed upon the d.c.
d.c. will burn out loudspeaker coils if applied too long. You should not use the combo with loudspeakers until you have the fault sorted.
For what it is worth, the few repairs I did on Cyrus 1's 20+ years ago were over output transistors failures.
Michael Jonassen
Sorry for confusion . If i use Cyrus two with fusses in as normal itergrated with fusses in the noise is still heard. Take fusses out and use with psx the noise is still heard so the fault is with the Cyrus 2 i presume? Very annoying!!!!!! I have only just plugged back in to use, keeping it on all the time at the moment as there is only the noise on start up, and the dc through the speakers goes away after 2 seconds of start up. I hope it's safe for
My speakers sake!!!!!
Help!!
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Richard,
Loudspeakers can dissipate up to their rated power when they are in normal motion. This is due to a vent through the middle of the loudspeaker magnet.
Cone movement pushes air through the vent which cools the voice coil.
Without this draught the voice coil will heat up more than it would at maximum power in ordinary use and it will burn out. It is not unknown for heat to set fire to the cone, which has spread into the house.
8 ohm speakers have a voice coil resistance typically around 6 ohms. 14 volts d.c. will result in a current flow of 2.3 amps. The voice coil will have to dissipate some 30 watts as heat for a couple of seconds every time you switch on.
Presently you don't know what the fault is with your amplifier and this may put a strain on other parts and cause a more serious breakdown at any time.
The output stage is a weak point in the design in that it uses relatively paired low power devices in each output half and lacks electronic current limiting.
Any loudspeaker repair will hurt your pocket more than the cost of repairing your amplifier and you would want to avoid that by not taking any risks.
This is not all theory. It is something I had to learn from experience.
Michael Jonassen
Loudspeakers can dissipate up to their rated power when they are in normal motion. This is due to a vent through the middle of the loudspeaker magnet.
Cone movement pushes air through the vent which cools the voice coil.
Without this draught the voice coil will heat up more than it would at maximum power in ordinary use and it will burn out. It is not unknown for heat to set fire to the cone, which has spread into the house.
8 ohm speakers have a voice coil resistance typically around 6 ohms. 14 volts d.c. will result in a current flow of 2.3 amps. The voice coil will have to dissipate some 30 watts as heat for a couple of seconds every time you switch on.
Presently you don't know what the fault is with your amplifier and this may put a strain on other parts and cause a more serious breakdown at any time.
The output stage is a weak point in the design in that it uses relatively paired low power devices in each output half and lacks electronic current limiting.
Any loudspeaker repair will hurt your pocket more than the cost of repairing your amplifier and you would want to avoid that by not taking any risks.
This is not all theory. It is something I had to learn from experience.
Michael Jonassen
Did you ever try to power up with the device selector switch on mute? That will ground the input signal. If you removed the fuses how the speaker get the power to produce the big bong sound. Removing the fuses would removed the voltages to the rails. One side of the speaker it is grounded but the power transistor does not have power to produce that big bong sound. But removing the fuses does not remove the power to the PSX. It is wired directly to the transformer. In the schematic does not show how it is connected to the transformer. Can you see if it is have a connector that you can remove the PSX out completely.
I checked the PS schematic to see what may feed voltage to the speaker with the fuses out and there is a possibility that the voltage maybe feeding through diodes D9 and D10 from chassis ground. The two diodes are connected after the fuses to chassis ground. Removing both fuses still voltage can be feed trough them and the resistor R121 to the rails and to the speakers through diodes D14 and D13. The resistor R121 shorted the PS ground to chassis ground. Somebody already mentioned it. I do not remember if you mentioned to checked resistor R121 for open. Another thing what is the polarity at the speaker when you powered on the amplifier. Can you check it and post the polarity.
I have connected the test leads to output speakers and the voltage coming through is positive dc.
I have 1amp diodes so I mite just change all 4 you mensioned,also r121 is that mirrored on the other channel or is their just one?
I appreciate all the help everybody is giving me. Thanks loads
Richard
P.s
If i don't get this amp fixed soon my wife mite leave me!! Spending all my time fiddling and Internet trying to sort this problem!! Might not be a bad thing at least I won't get myther when doing it! ;-)
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Hello Richard,
I retract my earlier comments about output stage protection.
The Cyrus has quite novel protection I missed seeing it as my printer was set to portrait and cut off that section.
I have studied how this works and how it affects the circuit. I offer the following possible explanation for what is happening.
The Cyrus protection tracks the voltage across emitter resistors R107A, R107B.
It will be triggered by imbalances between output halves or when as excessive current is drawn by any of the four devices in each channel.
C57 provides an element of time delay which more or less ignores minor incidents but stores a voltage for the important ones. A sufficiently large event in one channel might disrupt its neighbouring channel.
When the power is applied both positive and negative rails are initially short circuited for as long as it takes C53 and C55 to charge. The power transistors will then start to conduct and the protection circuit will be enabled.
If there is any fault or imbalance the protection circuit will be triggered and it will short Q11 to the negative rail and turn it off. In turn that will cut off the supply negative supply rail to the differential amplifier arrangement Q3, Q5, Q7, and Q9 which is responsible for the d.c. accuracy of the amplifier.
Transistors Q7, Q3 provide a path from the positive rail to ground through R51 (75K) and the voltage at base Q3 will move from around 0 volts to some higher positive value.
This will keep the chain in the upper output section Q3 to Q41 (and partner) in a state of conduction. Q9, Q5 will follow a similar pattern, through R71 (75K) R87 (150R) and your loudspeaker to ground. Base Q5 will increase from around 0 volts to some higher positive value.
Unfortunately the change would happen at a slower rate than with Q3 due to the presence of C43 and R65 which needs to be charged to that higher value.The voltages at base Q5 will lag behind that for Q3 creating be a mismatch and the difference will appear at the output terminal. When C43 is charged and the base voltages for Q3 and Q5 equalise the balance is restored and the differential amplifier will take over and correct the fault.
Other contributors may wish to comment on the foregoing.
You can test this theory by lifting one end of D1 and measuring the d.c. behaviour at the output with a meter rather than your speakers. I recommend replacing the rail fuses with 5 watt 100 ohm resistors for that test and I would remove one diode at a time and test both channels to see if there is any cross influence.
Michael Jonassen
I retract my earlier comments about output stage protection.
The Cyrus has quite novel protection I missed seeing it as my printer was set to portrait and cut off that section.
I have studied how this works and how it affects the circuit. I offer the following possible explanation for what is happening.
The Cyrus protection tracks the voltage across emitter resistors R107A, R107B.
It will be triggered by imbalances between output halves or when as excessive current is drawn by any of the four devices in each channel.
C57 provides an element of time delay which more or less ignores minor incidents but stores a voltage for the important ones. A sufficiently large event in one channel might disrupt its neighbouring channel.
When the power is applied both positive and negative rails are initially short circuited for as long as it takes C53 and C55 to charge. The power transistors will then start to conduct and the protection circuit will be enabled.
If there is any fault or imbalance the protection circuit will be triggered and it will short Q11 to the negative rail and turn it off. In turn that will cut off the supply negative supply rail to the differential amplifier arrangement Q3, Q5, Q7, and Q9 which is responsible for the d.c. accuracy of the amplifier.
Transistors Q7, Q3 provide a path from the positive rail to ground through R51 (75K) and the voltage at base Q3 will move from around 0 volts to some higher positive value.
This will keep the chain in the upper output section Q3 to Q41 (and partner) in a state of conduction. Q9, Q5 will follow a similar pattern, through R71 (75K) R87 (150R) and your loudspeaker to ground. Base Q5 will increase from around 0 volts to some higher positive value.
Unfortunately the change would happen at a slower rate than with Q3 due to the presence of C43 and R65 which needs to be charged to that higher value.The voltages at base Q5 will lag behind that for Q3 creating be a mismatch and the difference will appear at the output terminal. When C43 is charged and the base voltages for Q3 and Q5 equalise the balance is restored and the differential amplifier will take over and correct the fault.
Other contributors may wish to comment on the foregoing.
You can test this theory by lifting one end of D1 and measuring the d.c. behaviour at the output with a meter rather than your speakers. I recommend replacing the rail fuses with 5 watt 100 ohm resistors for that test and I would remove one diode at a time and test both channels to see if there is any cross influence.
Michael Jonassen
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Hello Richard,
Re Post #57 from tauro0221.
During use D9 and D10 are reverse biased and do not conduct.
They come into play at switch off where any reversal of bias will be limited to 0.6volts -preventing capacitor damage.
The 3K9 resistors are to discharge the capacitors at a safe rate after switch off.
If your capacitors are OK and there are no switch off noises it seems a fairly safe assumption that the problem arises elsewhere.
The question of R121 has been raised before and it is still unclear if you have checked this out.
It is has a solitary earthing function in the Cyrus chassis.
alohka mentioned that there was a counterpart in the PSX and whether you checked that out also remains unclear.
I think some advice is being repeated and a few of us have lost track of the changes/tests you have made as the thread gets longer.
I am in my mid 60's and find it easy to miss something trolling through previous posts.
It would seem a good time to refresh us with the changes/tests you have made so we can at a glance the ground you have already covered.
Michael Jonassen
Re Post #57 from tauro0221.
During use D9 and D10 are reverse biased and do not conduct.
They come into play at switch off where any reversal of bias will be limited to 0.6volts -preventing capacitor damage.
The 3K9 resistors are to discharge the capacitors at a safe rate after switch off.
If your capacitors are OK and there are no switch off noises it seems a fairly safe assumption that the problem arises elsewhere.
The question of R121 has been raised before and it is still unclear if you have checked this out.
It is has a solitary earthing function in the Cyrus chassis.
alohka mentioned that there was a counterpart in the PSX and whether you checked that out also remains unclear.
I think some advice is being repeated and a few of us have lost track of the changes/tests you have made as the thread gets longer.
I am in my mid 60's and find it easy to miss something trolling through previous posts.
It would seem a good time to refresh us with the changes/tests you have made so we can at a glance the ground you have already covered.
Michael Jonassen