cyrus3 experts

[burbeck]

hi all,
im having problems tracking down a dc ofset problem (-12V) on a cyrus 3, i did find an open 120R fp resistor but replacing this did not help. i have tested all the non surface mount transistors out of circuit looking for leaky parts but all are ok.

from reading previous posts on this model there seems to be quite a few problems with the surface mount transistors on this unit, i am tempted to replace the lot,
cyrus say they cannot supply me with a circuit or manual, this would be very useful to me, to diagnose/trace this fault.

anyone with experiance with this unit care to offer any guidence or advice
regards
bob

[gni]

make sure all circuit paths are good and clean before attempting
the fix of surface mounts. Make sure the output transistors are
okay. . .remember they control the DC voltage in varied amounts
going to the loudspeakers. The DC could be leaking through one
of them. Is there more or less current going through a particular
output resistor. . .that should tell you which transistor is working
wrongly. . .hook up a dummy load and test the offset again. . .

[burbeck]

hi chris,
thanks for that, i have tryed the output transistor and the drivers also every other non surface mount trany on this unit
wish i had a circuit, i cannot identify the surface mount transistors even

regards
bob

[Spev]

any caps in the power amp feedback loop in the cyrus 3? I had similar dc offset problems with one of my amps and it turned out to be a leaky cap in the feedback loop - swapped it out and all was well again.

[burbeck]

hi spev,
good thought, did check the caps (where possible some are surface mount) pulled all the rest including tants.

i am convinced that i have a leaky surface mount transistor on this unit i need to identify them at least i could replace the lot, there are lots of the little beasts spread around like confetti on this board.

regards
bob

[pumba]

hi
smd transistors cross-ref
Case Type Conventional Equivalent
Marking
== ================== =======================
15 MMBT3960 2N3960
1A FMMT3904 2N3904
1B BC846B BC546B / 2N2222
1C MMBTA20 MPSA20
1E BC847A BC547A
1F BC847B BC547B
1G BC847C / FMMTA06 BC547C
1J BC848A / FMMT2369 BC548A / 2N2369
1K BC848B BC548B
1L BC848C BC548C
1P FMMT2222A 2N2222A
1T MMBT3960A 2N3960A
1X MMBT930 -
1Y MMBT3903 2N3903
2A FMMT3906 2N3906
2B MMBT2907 2N2907
2C BC849C BC549C / BC109C / MMBTA70
2E FMMTA93 -
2F FMMT2907A 2N2907A
2J MMBT3640 2N3640
2K MMBT8598 -
2M MMBT404 -
2N MMBT404A -
2T MMBT4403 2N4403
2W MMBT8599 -
2X MMBT4401 2N4401
3A BC856A / MMBTH24 BC556A
3B BC856B / FMMT918 BC556B
3D MMBTH81 -
3E BC857A / MMBTH10 BC557A
3F BC857B BC557B
3G BC857C BC557C
3J BC858A BC558A
3K BC858B BC558B
3L BC858C BC558C
4A BC859A BC559A
4B BC859B BC559B
4C BC859C BC559C
4E FMMTA92 -
4J FMMT38A -
449 FMMT449 -
489 FMMT489 -
491 FMMT491 -
493 FMMT493 -
5A BC807-16 -
5B BC807-25 BC327-25 / 2N4123
5C BC807-40 -
5E BC808-16 -
5F BC808-25 BC328-25
5G BC808-40 -
549 FMMT549 -
589 FMMT589 -
591 FMMT591 -
593 FMMT593 -
6A BC817-16 -
6B BC817-25 BC337-25
6C BC817-40 -
6E BC818-16 -
6F BC818-25 -
6G BC818-40 -
6H BC818-40 BC338-40
AA BCX51 BC636 / BCW60A
AB BCW60B -
AC BCW60C BC548B
AD BCW60D -
AE BCX52 -
AG BCX70G -
AH BCX70H -
AJ BCX70J -
AK BCX70K -
AL MMBTA55 -
AM BSS64 2N3638
AS1 BST50 BSR50
B2 BSV52 PH2369 / BSX20
BA BCX54 / BCW61A BC635
BB BCW61B -
BC BCW61C -
BD BCW61D -
BE BCX55 -
BG BCX71G -
BH BCX56 BC639
BJ BCX71J -
BK BCX71K -
BN MMBT3638A 2N3638A
BR2 BSR31 2N4031
C1 BCW29 -
C2 BCW30 BC178B / BC558B
C5 MMBA811C5 -
C6 MMBA811C6 -
C7 MMBA811C7 -
C8 MMBA811C8 -
CE BSS79B -
CEC BC869 BC369
CF BSS79C -
CH BSS82B / BSS80B -
CJ BSS80C -
CM BSS82C -
D1 BCW31 BC108A / BC548A
D2 BCW32 BC108A / BC548A
D3 BCW33 BC108C / BC548C
D6 MMBC1622D6 -
D7 MMBC1622D7 -
D8 BCF33 BC549C / BCY58 / MMBC1622D8
DA BCW67A -
DB BCW67B -
DE BFN18 -
DF BCW68F -
DG BCW68G -
DH BFN19 -
E1 BFS17 BFY90 / BFW92
EA BCW65A -
EB BCW65B -
EC BCW65C / BCW67C -
F1 MMBC1009F1 -
F3 MMBC1009F3 -
FA BFQ17 BFW16A
FE BCV46 -
FG BCV47 -
GF BFR92P -
H1 BCW69 -
H2 BCW70 BC557B
K1 BCW71 BC547A
K2 BCW72 BC547B
K4 BCW71R -
K7 BCV71 -
L1 BSS65 -
L2 BSS70 -
L3 MMBC1323L3 -
L4 MMBC1623L4 -
L5 MMBC1623L5 -
L6 MMBC1623L6 -
L7 MMBC1623L7 -
M3 MMBA812M3 -
M4 MMBA812M4 -
M5 MMBA812M5 -
M6 BSR58 / MMBA812M6 2N4858
M7 MMBA812M7 -
O2 BST82 -
P1 BFR92 BFR90
P2 BFR92A BFR90
P5 FMMT2369A 2N2369A
Q3 MMBC1321Q3 -
Q4 MMBC1321Q4 -
Q5 MMBC1321Q5 -
R1 BFR93 BFR91
R2 BFR93A BFR91
S1A SMBT3904 -
S1D SMBTA42 -
S2 MMBA813S2 -
S2A SMBT3906 -
S2D SMBTA92 -
S2F SMBT2907A -
S3 MMBA813S3 -
S4 MMBA813S4 -
T1 BCX17 BC327
T2 BCX18 -
T7 BSR15 2N2907
T8 BSR16 2N2907A
U1 BCX19 BC337
U2 BCX20 -
U7 BSR13 2N2222
U8 BSR14 2N2222A
U92 BSR17A 2N3904
Z2V FMMTA64 -
ZD MMBT4125 2N4125

[burbeck]

hi pumba,
thanks for the info
regards
bob

[tiefbassuebertr]

Originally Posted by burbeck

hi all,
im having problems tracking down a dc ofset problem (-12V) on a cyrus 3, i did find an open 120R fp resistor but replacing this did not help. i have tested all the non surface mount transistors out of circuit looking for leaky parts but all are ok.

from reading previous posts on this model there seems to be quite a few problems with the surface mount transistors on this unit, i am tempted to replace the lot,
cyrus say they cannot supply me with a circuit or manual, this would be very useful to me, to diagnose/trace this fault.

anyone with experiance with this unit care to offer any guidence or advice
regards
bob

check out this thread - there is a schematic fom the power amp section, created from me.
Cyrus III power amp schematic here, but schematics of the later models wanted

If you have schematics above IIIi, please let me know there - thank you

[anatech]

Hi Bob,
Have you inquired what the cost of repair would be from the Cyrus factory? I am told it's a reasonable amount, but I've never heard how much they actually charge.

I do warranty service for Cyrus, and I can not release the information you are requesting. However, it is with good reason that they refrain from letting the schematics out. What I can tell you is that it takes about 2 1/2 hours to properly service this amplifier, and that the work eliminates the problems. The work is very fine, so shaky hands preclude a successful repair.

Back before Cyrus was distributed in Canada again, I had to repair these without any service information. I managed to be able to fix them anyway, so if you are good enough at servicing, the same should be true for you as well. There are some transistors that should be matched when they are replaced. I do this with some adapters I built for my transistor testers. My wild guess is that you are not able to perform that operation, am I right? If you can not match these surface mount transistors, you are not going to be able to do a proper repair. It's as simple as that.

Anyway, this is a fiddly job that takes some skill to do. If you aren't careful, you will ruin the PCB traces and find yourself in a real pickle. I also happen to know the people at the factory, and can tell you they are a really good lot. Each serviced piece is also tested on an Audio Precision before it is released, so it's guarantied to meet it's original specifications and also to last.

Find out how much they would charge you for servicing your amplifier.

-Chris