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Old 18th June 2009, 06:23 PM   #1
contax is offline contax  Spain
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Default Cyrus 3 / Cyrus III amp help

Hello,

I have bought a second hand Cyrus 3. The guy who sold it told me it has been modified for working with a PSX-R power supply.

I have removed the bottom plate and tried to follow the instructions explained at http://www.rdhworld.co.uk/punbb/viewtopic.php?id=3847.

My surprise was the amp was ready for woking with the internal power supply and not the PSX-R.

I have tested it and all the controls (input selector, volume, mute, balance) work. The only problem is the output in the speakers is very low.

I have read several posts and I cannot get the service manual.

Any idea of the problem?.

Thanks for your help.

Best regards:-)
contax
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Old 21st June 2009, 02:30 PM   #2
contax is offline contax  Spain
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Default Cyrus 3 / Cyrus iii

I have read one post about a faulty Cyrus ii. It had two faulty capacitors in the NFB network.

Does anyone know if the Cyrus iii has the same capacitors?
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Old 24th June 2009, 04:34 PM   #3
anatech is offline anatech  Canada
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Hi Contax,
Yes, look at C519 and C520 (100 F). These might reduce the gain to 0dB if they were completely open. This is not likely though. I have never seen a defective feedback cap in these before, and even with the ancient Cyrus II, they don't fail at the same time.

A note to everyone considering working on one of these amplifiers:
Now for the very important things you should know about this amplifier. What I am about to say is something that should not be taken lightly. You do have a very good amplifier with very high build quality. This amp, however, is not DIY friendly at all. Beyond configuring the amp for use with an external power supply, there is nothing else I could recommend you doing with it.

The PCB is populated with surface mount components. Units I have received for service that have been worked on by other shops normally have lifted or torn off traces. This is the one type of damage that will reduce this unit to scrap. So, unless you truly are very good with working on surface mount PCBs, do not touch! I don't care if you think your skills are excellent, they must be excellent or you run a very high chance of destroying this amplifier.

There are approximately 23 surface mount transistors that might need to be replaced, depending on the manufacture date. Some should be hand matched as they form the differential pair circuits (four in each). This is a complicated job with so many parts to be replaced, all surface mount. These parts are easily mixed up too, so there is preparation before doing this work. Patience is key. Some parts are difficult to get to. It generally takes me about 2.5 hours to do this work, sometimes longer if there is a wrinkle in the repair.

It is far cheaper, and better, to send this product to the authorized service agent in your area, or back to the factory for this work. In this way, you will end up with a reliable amp using the correct parts. Any other issues would be taken care of at this time as well.

So, you know someone who can fix it cheap? What you will probably end up with is an amp that may not work properly, or is not reliable. When the proper service agent sees it, it might be damaged beyond repair due to damaged traces. I've seen this too often, and it's sad to see a product in rough shape.

I'm sorry that the news may not be what you wanted to hear, but you did get a really good amplifier. I seldom see this brand in for service, even under warranty. My advice stands. Get it to a proper service agent to protect your investment. You will then have many years to enjoy this amp.

Do I believe in this product line? Yup, sure do. I have a pair of Mono X amplifiers and the matching Preamp. I am very happy with them. I'm not easy to please either, but these make the grade easily.

-Chris
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Old 24th June 2009, 05:18 PM   #4
contax is offline contax  Spain
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Hello Chris,

Thanks for your advice.

Maybe both capacitors are faulty, but I am going to try to return the amp to the seller. He told me the unit was in full working order. I paid a good price for the amp, but the diy repair tax is too complex.

I cannot get the service manual. I cannot see the capacitors without removing the phono board.

Best regards:-)
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Old 24th June 2009, 10:32 PM   #5
anatech is offline anatech  Canada
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Hi contax,
Quote:
Maybe both capacitors are faulty
I strongly doubt that. I will accept that there may be another fault affecting both channels though.

Quote:
but the diy repair tax is too complex
There is no DIY with this product, for good reason. Most changes people might make would degrade the performance. Much like taking a race engine and "souping it up" at home. Same concept.

Quote:
I cannot get the service manual.
I know.
I am not allowed to release the information either - sorry. Not that it would do you much good. Surface mount technology is well beyond what the average DIYer can deal with. Even the soldering station (not iron!) becomes important. In fact, proper use of a hot air station would go a long way to helping someone with these. I have no doubt that there are some DIYers that do have the proper skills and equipment, but they are in the minority.

Quote:
I cannot see the capacitors without removing the phono board.
They are surface mount also.

Generally, if they short or leak, you will also see a DC offset across the speaker terminals. That is one quick check you can make.

I just thought of something. You don't have your signal source plugged into the data bus do you? Have a good look. Your amp may work just fine if you are plugged in wrong. Believe me, if that's the case, you would not be the first - or the last to do that.

BTW, these amps are very expensive new. How close to the new figure did you pay? I'll bet that fixing it may still be a very good deal. Mind you, if you bought it with the intent to change it's inner workings, this would be the wrong product. It already performs well. Much better than most examples of modified equipment I have seen.

-Chris
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Old 25th June 2009, 08:18 AM   #6
contax is offline contax  Spain
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Hello,

Are there several Cyrus III (not 3i) versions?. The fault the amp shows is like the power stage wasn't getting the correct supply.

Maybe the modification suggested by the post http://www.rdhworld.co.uk/punbb/viewtopic.php?id=3847 isn't valid for my Cyrus III model. My integrated amp has the same connectors and wire colours mentioned in this post, but has a big phono PCB over the main board.

I could take some pictures.

Thanks for your help.

Best regards:-)
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Old 30th June 2009, 08:49 PM   #7
anatech is offline anatech  Canada
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Not for major things like that.

It sounds like some faulty transistors as I mentioned earlier. All types of odd faults may occur as they become leaky intermittently. Any one of the 23 can take it down, replace all or you'll be doing them one at a time and troubleshooting each time.

If you read the bottom of that "modification" (it isn't a mod), they tell you what the error condition is if it's set up wrong.

-Chris
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Old 30th June 2009, 09:25 PM   #8
contax is offline contax  Spain
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I have got the official PSX-R modification. Some Cyrus III models have two jumpers, but not my amp.

I am going to deal with the seller and try to return the amp to him.
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Old 10th July 2009, 03:07 AM   #9
anatech is offline anatech  Canada
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Hi contax,
That isn't a modification. It's a configuration change for the optional PSX-R. It's a customer changeable thing, but they would rather the store do it, or a service center.

Along the way, Cyrus designed the amp to automatically recognize the PSX-R. The interesting thing is that the PSX-R can determine what it's plugged into and it adjusts it's output voltage to what is required for that unit.

Pretty smart engineering eh? Someone was on the ball there.

-Chris
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Old 1st December 2009, 04:54 PM   #10
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In this case this thread could be of interest:
Cyrus III power amp schematic here, but schematics of the later models wanted
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