HELP!! Denon PMA-655R (source selector) - diyAudio
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Old 16th October 2012, 01:05 PM   #1
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Default HELP!! Denon PMA-655R (source selector)

Hi folks!

I have a problem with my Denon PMA-655R amplifier. The source input selector starts to "jump" or shift by itself suddenly. It's really annoying when listening to the Tuner and then it goes to the CD or to the Tape 1.

Any Denon user knows or had experienced this before?? How to solve this?

Many thanks in advance!
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Old 16th October 2012, 02:05 PM   #2
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walk in the park

The selector switch ""drives"" a micro processor or some IC to select the input .
Either the selector switch is dirty/warn but a more common failure for this type of switch is that the grease that existed inside the switch is so dry that the switch loose contact resulting jumping to another source or other type of failure .

You need to clean the grease from inside and apply new but not that much .

Do not try to spray the switch it will have no effect ...sorry to say but there might also be a need to totally disassemble the switch to clean it properly. ( very possible to do )

Kind regards
sakis
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SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
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Old 16th October 2012, 10:49 PM   #3
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Quote:
Originally Posted by sakis View Post
walk in the park

The selector switch ""drives"" a micro processor or some IC to select the input .
Either the selector switch is dirty/warn but a more common failure for this type of switch is that the grease that existed inside the switch is so dry that the switch loose contact resulting jumping to another source or other type of failure .

You need to clean the grease from inside and apply new but not that much .

Do not try to spray the switch it will have no effect ...sorry to say but there might also be a need to totally disassemble the switch to clean it properly. ( very possible to do )

Kind regards
sakis
Many thanks!!

After read your comment I opened the amplifier tonight and, although it was a nightmare to reach the selector switch, I was able to cleaned it. Now the problem seems to be fixed!

I though it could be the relay on the main board and I didn't want to fix it (the relay) cause this amp is quite difficult to work on.

Unfortunately it seems to affect quite few Denon amps. Someone had this same problem with the PMA-2000R. I love Denon amps but I became suspicious now with this weak part of them.

But, anyway: again, many thanks!
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Old 16th October 2012, 11:01 PM   #4
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no probs ..The dutch are always welcome !!!
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SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
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Old 29th February 2016, 10:11 AM   #5
b0gdann is offline b0gdann  Europe
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Hello,
What kind of grease did u used?

Thanks!
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Old 29th February 2016, 05:11 PM   #6
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You don't need any grease. Just flush that thing with alcohol (IPA/ethanol, doesn't matter) and it'll work as new. This applies to all source selectors of the same type. Common on 90's and 00's gear.
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Old 29th February 2016, 05:43 PM   #7
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Originally Posted by Welcome View Post
You don't need any grease. Just flush that thing with alcohol (IPA/ethanol, doesn't matter) and it'll work as new. This applies to all source selectors of the same type. Common on 90's and 00's gear.

Rubbish ....according to your suggestion you may also clean your oxidized silverware of your grandma with alcohol....

This is what happens inside the switch the silver plated contacts are oxidized and probably look almost black if you open them

You can put the switch inside a canister of alcohol together with the silverware of your grandma for a week and many things might happen except solving the oxidation ....

Farther more there is lubrication inside the switch since it has mech parts Rinse it with alcohol and will never work properly again ....it will become scratchy if not destroyed totally...

this the worst suggestion for this application /failure i heard in all my life ...
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SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
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Old 29th February 2016, 06:11 PM   #8
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been writing this a few times so far i will have to write it once more

First of all in all switches you have 3 problems
1) mechanical : switch have to feel the same after cleaning Lubrication is the key to do that You can not operate a switch especially rotary if dry ...
2) general dirt of any kind for this you can clean with any available fluid you like ...ypu may try anything even coffee without sugar or beer will do
3) oxidized silver plated contacts that go black and loose contact cause of this and very few of existing sprays may clean that but this dont come for free there is side effects

available solutions together with analysis of what they do
you have Philips type of spray red one and blue one the red is petrol ( diesel) has a good cleaning ability , partial ability to actually sweep some of the oxidation not clean it properly and totally , BUT !!! diesel sprays create the step effect especially on pots and then the pot or the switch gives a feeling that works in steps and the operation is not smooth ...Then again diesel may actually burn the plastics exist inside the switch and then you have end of story
farther more diesel left overs actually work as a magnet to dust It is common knowledge from people that used that that is a very temporary fix .....
Another issue is that left overs of this type of sprays have very high conductivity which means that cross-talk of the switch will reach astronomical numbers

the blue spray of Philips
Alike the above but based on gasoline also writing in the can the name degreaser Which obviously means that together with everything else will remove previoucly existing lubrication of your switch and YOU DON'T WANT THAT
cleaning ability of dirt is excellent while there is zero ability to remove or sweep any of the oxidation existing in the contacts ....the danger to destroy plastics is fairly low the switch will feel scratchy after that and the real problem will never be solved . conductivity of the spray is very low self evaporation also so no left overs but also NO JOB DONE

WD40
Will do exactly what diesel sprays do without destroying the plastics with lower cross talk behavior lower conductivity provide quite good lubrication but from most even though better than diesel also don't have the ability to clean oxidation

There is combination of the above from many of the manufacturers which may not be available in Greece so i dont know the behavior Deoxit is very popular here but i am not aware of teh behavior

WD 40 made a new spray contact spray WD40 specialist is called in Greece that has far better ability of cleaning oxidation together with all the other cleaning abilities , fast drying and with excellent conductivity behavior ....Still the ability to clean oxidation is not enough better than others but not enough ...

Bison has a contact spray that has excellent ability to clean everything and especially silver oxidation and its very common to get problems are that conductivity is very very high and left overs are plenty then is in the procedure that will make the difference

1) one may use any of the above sprays based on the target that except cleaning you need to remove oxidation from the contacts
2) use any of the above like degreaser which is based on gasoline and may others that are based on acetone in order to clean the left overs of the previous spray with the danger to damage the plastics inside ( mostly for acetone based )
3) apply tiny bits of classic WD 40 only for lubrication
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SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
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Old 29th February 2016, 06:27 PM   #9
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At east electronics we repair an average of above 1000 audio devices per year si we have been there a million times before testing any available chemical existing ...

The solution came 5-6 years ago in the dentist by learning how ultrasonic cleaning for teeth is working so i thought about getting one of this machines trying to modify the frequency to see if i can hit the oxidation with it to clean it

Worked like a charm but we had to create also a chemical product from scratch that doesn't have the side effect of conductivity of the existing sprays , plus the destruction of plastics from diesel sprays ...

You see for us the cleaning of the switch is one issue and the lubrication is another Problem with sprays is that these try to do both in the same can and this actually is not working .

Not to forget that the degreaser spray from Philips is made to flush and rinse the previous spray that they made the diesel one ( at the time )

here is a picture of how an open switch is cleaned before and after ultrasonic .... For sealed switches we use pharmaceutical needles to inject our chemical product inside work the switch inside out and done !! Then you have to rinse flush the ammonia based chemical and relubricate teh switch with a very small bit of WD40

For lubrication it will be enough to spray with WD40 then clean the WD40 thoroughly with pressurized air and relay on the left overs of the WD40 to do the lubrication ...most of the time is enough ....
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File Type: jpg after.JPG (178.8 KB, 26 views)
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SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr

Last edited by east electronics; 29th February 2016 at 06:39 PM.
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Old 29th February 2016, 06:33 PM   #10
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Strange that you didn't mention silicone based ones... ( I thought Philips blue was silicone based )
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