Cyrus Pre - Unbalance volume

[MAT124]

Hi,

My Cyrus Pre got a problem of unbalance output in both channel. So I send it to Cyrus dealer for repair. However after 2 month, they told me that the ALPS motorized Volume is faulty but there is not replacement part for repair.

I try to search internet and find many kinds of ALPS volume available. Can anyone tell me which one is suitable for the Cyrus Pre especially the resistance value (10K, 20K, 50K, or 100K).

Many Thanks,
Clement

 

[Sonusthree]

Hi Mat, Welcome to the forum.

Have you tried contacting Cyrus in the UK? They may be able to help you directly.

service@cyrusaudio.com

Or .....
Do you have a picture of the old part?

Regards,
Martin

 

[lohk]

The older Cyrussus always had 50k pots - but the product number is written on the device, if you dare to make the repair yourself.
What is the real problem, what do you mean with "unbalanced"? (Constant, variating, etc.)

 

[MAT124]

Thanks for the replies.

I tried to contact Cyrus UK but got the same answer. The UK support guy told me that they suspect the Alps motorised volume was faulty but no part to repair.

The unbalance volume means the output in left channel is very soft while the right side is very loud. I try to adjust the balance of the amp but didn't help because the difference is so large.

I hope I can get the part from somewhere so that I can replace the component by myself. I have asked the dealer whether they will fix my Amp if I can get the part from other place but they refuse. The dealer said they will only repair the Amp with parts supplied by Cyrus UK.

Thanks,
Clement

 

[anatech]

Hi Clement,
You may easily have a problem with the Cyrus amplifier circuit. There is a large cap in the feedback loop nearest the diff pair. If it's open, it will cause this problem. Change both while you are there.

Did you troubleshoot or just guess at the control? I hope you haven't done anything to it.

-Chris

 

[MAT124]

No, I didn't do anything yet. It's the Cyrus UK support who told me that he suspect the problem was due to the ALPS motorized volume which they don't have part anymore.

I will try to open the Amp to take a look. For the CAP that you have mention, is there any easily way to check or should I just replace them?

Thanks,
Clement

 

[anatech]

Hi Clement,
I just realized you are talking about a preamp. Forget the capacitor advice.

Do look a the controls with the top off. See if they move by remote. You may have cracked solder joints on one control. Take a picture if you can please.

I service Cyrus under warranty in Canada, I'll try to help you.

-Chris

 

[MAT124]

Hi Chris,

Thanks for your help.

Attached please find the picture of the circuit board. I try to adjust the volume using the remote and seems that both volume did move. However the one near the centre do not move smoothly like the other one which near the edge. I guess this volume switch is in question.

There are some alphanumeric characters printed on the switch. Both switch got "531t 20KDB".

Thanks,
Clement

 

[anatech]

Hi Clement,
Turn the unit off and unplug it. Try to turn each control by hand. Does the one that turns intermittently feel rough?

It's possible that it's a mechanical problem or a lubrication issue.

-Chris

 

[MAT124]

Hi Chris,

Since both volumes are sitting very close, it is difficult to turn by my fingers. I use a pair of tweezers to turn them. Seem both can be turn by same amount of force.

If it is a mechanical problem or a lubrication issue, can I fix the volume switch or I need to get a replacement part?

Thanks,
Clement

 

[anatech]

Hi Clement,
What I would do at this point is remove both controls and test them outside. This means checking for mechanical issues by hand and running the motors with a variable DC power supply. You may find something simple that can be corrected, or this may lead you to look at the driver circuit for the motor. It's possible the section for positioning needs to be cleaned.

-Chris

 

[MAT124]

Hi Chris,

How much DC voltage should I apply to the motor that will not damage the motor it?

Shall I clean the motor with the CRC contact cleaner? Shall I try it before remove the controls?

Thanks,
Clement

 

[anatech]

Hi Clement,
The motor should turn with a couple volts across it. Start from zero and increase your voltage slowly. When the motor starts to turn, leave the voltage (or increase it slightly) and watch the movement of the control. It should be smooth with no nasty noises. This should help you find the problem.

Shall I clean the motor with the CRC contact cleaner?

No, please don't do that.

Shall I try it before remove the controls?

No, you want to find out what is wrong before doing anything.

-Chris

 

[MAT124]

Dear Chris,
I am going to take out circuit board from the case in order to remove the motor. Are there anything that I should take additional care so I won't make uncorrectable mistakes.

Regards,
Clement

 

[anatech]

Hi Clement,
I would need one to look at in order to answer your question.

Can you simply desolder the connections to the motor, on teh back of the motor? This would be much easier for you to do.

-Chris

 

[CRiggVA]

Bringing up an old thread as my first post. This seamed to be very similar to my issue.

My potentiometer is variating on its own, will move opposite at times from the intended direction and will sit and make sharp adjustments (motorized sounds) at various times. Does anyone have any idea who could fix this for me, if Cyrus wont touch it? I'm located on the East coast of US and would rather not ship out of the country if i dont have to.
Thanks,
Ed

 

[njansens]

An old thread indeed, however let me share my experiences.
I picked up a Pre with this problem as well.
It turned out to be one of the motorized pots.

I have no idea where to get them (note that for a single channel a double pot is used, with one log and one linear characteristic: log for the actual volume setting, the linear part for feedback of the setting)

I dismantled the pot completely and found the wiper of the feedback pot loose.
Glued it back in place, completely cleaned the pot, lubricated the mechanics and it is working fine again.

 

[tiefbassuebertr]

Hi Chris,
Thanks for your help.
Attached please find the picture of the circuit board. I try to adjust the volume using the remote and seems that both volume did move. However the one near the centre do not move smoothly like the other one which near the edge. I guess this volume switch is in question.
There are some alphanumeric characters printed on the switch. Both switch got "531t 20KDB". Thanks, Clement

The most important thing by such exotic circuit designs for volume control is the detailled schematic so as the associated circuit description. Try to order this, either by phone: 01480 435577 or by email: service@cyrusaudio.com.

An old thread indeed, however let me share my experiences.
I have no idea where to get them (note that for a single channel a double pot is used, with one log and one linear characteristic: log for the actual volume setting, the linear part for feedback of the setting)

Who was the developer from this kind of volume control ?

Which model of which from
http://www.cyrusaudio.com/product-archive/pre-amplifiers
is show in the attached pic from post #8 ?

According the URL
http://www.cyrusaudio.com/cyrus-audio-upgrading
is a service offered even for old models.