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Cyrus 6 vs2 Internal fault repair

I have a Cyrus 6 vs2 which has flashing per light indicating an internal problem. I'm new to this unit but have only done minor repairs to audio equipment before and some elections. Would like to sound out the problem to others and hopefully get some advice from wiser heads.
  • Headphones, one channel out, other weak and distorted.
  • Voltage output no input on speaker output is .02v both.
  • 1 of 2 internal fuses has blown.
  • All rail power at what it should be apart from -15v which is at around 1v
  • No obvious signs of damage.
  • Carried out basic continuity tests on MOSFET's and nothing seems out of order
I guess the protection circuit is active (hence the flashing red power light). Would this be responsible for the weak degraded output on the one channel that still works? Or is this an indication of another problem?
I'm reluctant to try the good fuse in the other channel to see if it works as I've not found the cause of the blow in the first place.
Anyone have any advice on what I should do now. I've only got a multimeter but have an oscilloscope on the way.
I understand that the FETs have special thermal interface pads which make the roughness of the cast aluminium manageable as a surface for thermal conduction, thinking of replacing them with something like bergquist GPVOUS pads
a huge amount to choose from though. Wondering what source I should be concerned about.
Much appreciated.
 
Download the user manual from Cyrus and you will get the different flashing led info re possible faults. You really need a full circuit diagram so I would search the net for that but Cyrus Technical info is not easily obtained. I have info on the 111, 111i and the 8xp ie before and after the 6. Unfortunately the old CU forum has gone as you may have received some help there.
Had the LS output cables been shorted ?
Isolate the power supplies from their load if you can and check these are OK. You can then check each amp, initially without power do a cold check on a comparison basis, that usually reveals any issue. You will probably have to remove the PCB from the case to do this so watch you don't damage the thermal pads
I never like delving any deeper without a cct.
Good luck
 
Thanks for the help lanmacPFM ,
The unit goes through the usual led startup then power light standby on. If I press any of the source button to bring it out of standby the red power light starts blinking. No eeprom codes flashing led's or anything. Manual says this is an internal fault.
I haven't isolated the power and have only testes the voltages on the test voltage section on the board as follows

Printed Actual
+5v +5v
+15v +15v
-15v +0.8v
+vcc +40v Amp states 37v protected by the fuse (of which neg rail fuse has blown) Am i right in assuming there must be some kind of short to allow this to read a +40v even though the neg side fuse has blown.
-vcc +0.4v Replaced fuse should correct this
+42v +34.7v Actually manual states that cyrus 6 (as opposed to 42v on the 8) is 34v for low current section of power amp
-42v -34.7v
 
Did you manage to get a circuit diagram, without one you may struggle.
The + 34.7 v and -34.7 supplies appear to be OK. Cyrus have a habit of using on card regulators to derive the + and - 15v from the appropriate 34 v rails. These regs are dissipating too many watts for comfort inside the shoebox and fail regularly. Check the -15v reg is getting -34v in . Disconnect the regulator output and see if you get -15v, remember that with most regulators there is short circuit protection so if something downstream on the -15v rail is pulling it to ground the regulator will switch off until the short is removed. it seems from what you say your fault lies on the -15v rail--But --I dont have a circuit and am driving blind
Good luck
 
Good luck by the bucket full will certainly be needed here! Not easy to work on, SMD and through hole, no technical info to be found....
 
Aha! LanmacPFM again thanks for the insight. Yes I can confirm from the manual that "+- 15v is derived from the power supply for the main amplifier via regulators VR402 and VR403." So I found those regulators and removed their snap-on heatsinks and investigated and found some damage to a trace. I'll test those regulators, replace and do my best to check for further damage. Fingers crossed.

Here's a link to the pic of the damage. imgur.com/a/VlbDUQR Can't seem to link or add pictures here.
 
So the heatsink wasn't wrapped fully in insulating tape and the corner was arcing or in contact with the trace causing that damage. Hopefully that's all.
photos.app.goo.gl/xtrfhty7E9HKky7v7
 
Thanks coredump
Fixed trace, adjusted heat sink replaced fuse and have the unit power properly and playing finely again through the headphones.
Thanks for all the help guys! Luckily it wasn't that tricky once found.
 
Excellent to read youve got it fixed.
Ive seen problems before with the clip on heartsinks used by Cyrus. The heat seems to affect the spring tension and they slip down onto track or component legs.
Do you have a full service manual, Id love a copy if you do ?
Ian
 


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