diyAudio (
-   Solid State (
-   -   Cyrus 3 Amplifier Component Mistakes? (

hexagonsun 12th September 2006 01:29 PM

Cyrus 3 Amplifier Component Mistakes?
Hello DiyAudio folk, im new to this forum and this is my first thread and post!

My main question is about R521 and R522 on the amplifier board and what value they should be, somebody has tried to repair this amplifier before me (and made a real mess) and has replaced other through-hole resistors and capacitors but im unsure of these SMT resistors, from what i can see the channels are a mirror image of each other all but these two resistors can that be right, R521 is 1.4K (1401) and R522 is 2k (2001).

Ive read other threads about getting hold of the schematic and i dont really want to pay 18 for this information.

The original symptoms where a flashing red led on the front and no life at all. I found that the output transistors had blow on one channel, both 4A fuses were blown, C519 was open, and various SMT resistors were changed in value (by damage not somebody changing them). The outputs look like they could have been changed before too, the ones i took out where D1047's.

Any light that can be put on this is much appreciated.

anatech 12th September 2006 04:09 PM

Hi hexagonsun,
If your amplifier has that much damage, plus was "struck by technician", I would get the darn manual. The troubleshooting time it will save is well worth it!

Normally these amplifiers do not suffer that much damage when they fail. It's typical to replace outputs and that's it. Drivers as well if you want to be careful, but this design seems to limit damage nicely.

The manual will contain all three versions of this amplifier (I think there are three runs). At any rate, there may be still more surprises waiting for you.

There is a test you should make. See if the smt transistors in either amp section melt when you hold a soldering iron against it. If so, there are about 24 smt transistors to replace. It's complicated but will eliminate all kinds of odd problems. You will want to send it in for that work. I kid you not!


Leolabs 13th September 2006 02:32 AM


If your amplifier has that much damage, plus was "struck by technician", I would get the darn manual. The troubleshooting time it will save is well worth it!
Agree.Rather than wasting time to reverse engineer it.

hexagonsun 13th September 2006 11:39 AM

Thanks for your replies guys, ive checked the SMT transistors and they dont melt, i didnt think any of them did?.

You may both be right about the manual. I think ill make some enquires with Cyrus. I guess i shouldn't be so tight fisted.

Ill be replacing the drivers, ive been bitten with that one on my Quad 405 well worth the precaution.

anatech 13th September 2006 01:37 PM

Hi hexagonsun,
The Cyrus III is normally quite benign as an amplifier repair. It can be a pill to service after another tech has run though it. There is nothing more destructive than a technician in panic mode.

I'll give you a couple hints to make life easier for you. Buy the replacements from Cyrus at the same time you buy the manual, buy four plastic insulators while you are at it. These are adhesive types that spoil easily. Strip the amplifier and resurface the mounting areas for the outputs on the heatsink / case. Your final sand with 600 wet / dry paper should bring an even shine. You will see what I mean when you get in there. Expect to spend between 1/2 hour to 3/4 hour. Start with a flat file and take your time. Do a really good job.

When reassembling, check the amp temporarily with mica first, apply the plastic insulators once you are sure the amp is okay. Before cleaning, remove all trances of grease or plastic insulator. I use a flat razor followed by lacquer thinner.


hexagonsun 19th September 2006 11:37 AM

Hmmm, problem, ive just got this email back from Cyrus about purchasing the schematic and parts. Thanks for your tips anatech. I dont suppose somebody could just tell me the values of R521/R522 and what output devices are used in there cyrus 3 and ill be happy to get on with the rest, theres no way im sending this amp into cyrus either i enjoy repairing things to much myself.



Unfortunately I am unable to supply you with the parts or schematics as all repairs for these need to be carried out by Cyrus approved repair centres.

If I can be of any further assistance, please do not hesitate to contact me.


Simon Bicknell


anatech 19th September 2006 12:59 PM

Hi hexagonsun,
R521/R522 are 1206 size 620R resistors. The outputs are Cyrus #PT77. That's from the manual. I am unable to supply you with any scans or copies.


Unfortunately I am unable to supply you with the parts or schematics as all repairs for these need to be carried out by Cyrus approved repair centres.
There is very good reason for this, and it has nothing to do with your skill level. Simon is not trying to be difficult. I happen to agree with this policy. History has borne this out as good practice. Simon has also ben more than helpful within those guidelines.

theres no way im sending this amp into cyrus
Wrong attitude, and I am saddened by your stance on this.

i enjoy repairing things to much myself.
So do I, but there are other things to consider some times. In this case, that would be the wrong decision. Consider that at Cyrus, they use AP-1's in the service department and test those units to new spec.


hexagonsun 25th September 2006 11:28 PM

Hello, im sure Cyrus do have all the latest technology but this is diy (do it yourself) forums, if my stance was to send it back to the maker all the time i doubt id know very much about electronics right now. Is there any way to get the schematic other than cyrus, R578/R577 are the only 620 ohm on my board.

Is it the policy of the forum to not share schematics (copyright laws ect).

If not is there anybody else out there that can give me a copy, i can pay a small fee for the trouble (5).

kind regards

anatech 26th September 2006 04:15 AM

Hi hexagonsun,
I can't because I am a warranty depot. I am just working on a 3 now. Changed a ton of smt transistors. Sadly, I am getting rather good at this.

I usually see these after another shop has had a go. The additional damage and confusion (clues are now gone) makes the repair far more difficult to accomplish. That is the case with the one I am servicing. They lifted a trace going to an smt transistor. Damn them!!!!

Something to think about. The dual differential pairs. I match all four together. Ever sit down and match the gains on smt parts? You start by buying a lot of them. Now to measure. You sure you want to? Okay then.

These schematics have not been released, but you may be able to get a copy somewhere. My hands are tied though. I can't say as I disagree in this case. I know you want to repair your own unit, but I think you should reconsider.


tiefbassuebertr 1st December 2009 04:55 PM

In this case this thread could be of interest:

All times are GMT. The time now is 03:25 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2