• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Have I permanently destroyed my amp and headphones using compressed air? Denon PMA-725R and Beyerdynamic DT990

J

JohnnyMercer

New Member
Hello!

I am very new to the audio world in terms of getting a good setup and taking care of it. I was recently gifted my father's Denon PMA-725r amplifier/receiver and was looking forward to using it with my turntable, when that arrives. However, when I turned on the amp by itself there was a lot of crackling when I turned the volume knob and I heard that cleaning it out for dust and using Deoxit would help. Now, the Deoxit hasn't arrived yet but I do have some compressed air. Today, I played the amp before opening it up and it worked fine, crackling aside. The volume was good and full and I really liked the sound. When I opened it up and saw the amount of dust, I started using my can of compressed air. Quickly I noticed that parts of the amp were turning white and upon touch were very cold. I immediately started to panic and stopped using the compressed air. I used a small brush instead and very carefully tried to brush away some of the dust. At this point I was very scared I had messed things up beyond repair.

When I put the cover back up and powered up the amp, it was awful. There was loads of static, uncomfortable scratching and an imbalance in the sound between the right and left ear. When switching inputs there's a loud crackle, almost deafening and I shut the amp off, disheartened. Now, to rule out any issues with my Beyerdynamic DT990 headphones, which worked perfectly fine before cleaning out my amp, I plugged them into my Behringer UMC404HD that is plugged into my Mac Mini M1, and was horrified to find out that somehow my headphones were damaged and the imbalance had carried over (or was always there?) to the headphones. No matter which source I use them on now, the right ear is very low in volume and lacks bass and treble, almost tinny sounding.

Firstly, is my amp permanently destroyed, can I do anything to fix it myself or do I need to just face the loss and shell out the 100€ to get a professional near me to look at it. Secondly, what could have happened to my headphones? Did I short them or blow them out? Are they also destroyed for good? I feel at a loss and very sad and frustrated that such a simple and seemingly harmful task, according to most HiFi-forums, could do so much damage to my amp and headphones.

Any and all help regarding this matter is greatly appreciated and if any further details are needed, I will be more than happy to fill in the gaps.

Sincerely,

A very heartbroken and stupid audio beginner,
Johnny
 
Register to hide this ad
Did the "ice" melt and leave moisture in the amp? I suppose it's possible a resistor, diode, or transistor froze and cracked.

Can you take a pic of the area that turned white?

Rob
 
Robisme said:
Did the "ice" melt and leave moisture in the amp? I suppose it's possible a resistor, diode, or transistor froze and cracked.

Can you take a pic of the area that turned white?

Rob
Click to expand...
Actually it seems that with time the sound issues with the amp went away, perhaps after the amp heated up. The problems remain with my DT990's, however. No matter the sound source, the right ear is a lot quieter and lacks bass and treble. The weird thing is that the right channel isn't dead (which happened on a prior of the same headphones due to a loose connection) it's just very quiet. Is it possible I shorted or damaged the headphones through the amp?

This is all very confusing honestly...

I would be more than happy to send you a picture, if that is still relevant after my newest discoveries.

Johnny
 
petehall347 said:
yep canned air turns into freeze spray if upside down ..saying that i have bought cheap cans that do that the right way up and they make moisture which isnt good .
Click to expand...
Yes I recall I did spray it at a bit of an angle, though certainly not upside down. And I did spray fairly consistently, not in short bursts. It was my first time cleaning anything using compressed air, so I suppose I should have looked up a tutorial, though I thought 'how hard can it be?' - how very wrong I was.

Johnny
 
"canned air" is usually R152a refrigerant. Makes lovely frost when the liquid comes out. It can also be used in car AC systems, but thats unrelated.

Once the frost melts you get wet mud causing weird leakage paths. Probably fine once it dries, but I'd suggest brushing or vacuuming as much of the dust out as you can.

no idea on the headphones. Suppose its possible that the cold damaged the diaphragm. Its usually some thin plastic sort of material and it may have shrunk or gotten brittle with the extreme cold.
 
gadget73 said:
"canned air" is usually R152a refrigerant. Makes lovely frost when the liquid comes out. It can also be used in car AC systems, but thats unrelated.

Once the frost melts you get wet mud causing weird leakage paths. Probably fine once it dries, but I'd suggest brushing or vacuuming as much of the dust out as you can.

no idea on the headphones. Suppose its possible that the cold damaged the diaphragm. Its usually some thin plastic sort of material and it may have shrunk or gotten brittle with the extreme cold.
Click to expand...
I use compressed air with caution. Over doing it can cause plastic to permanently discolor.

For potentiometers and slider controls, I suggest Deoxit Fader Lube. This won't dissolve old carbon tracings.

https://caig.com/fader-f-series/
 
I've used a compressor from 2ft away
very gently, no problems. On lots of gear.

The canned stuff does freeze things
used sparingly can be used to find hot components
likely failed.

I've used electrical contact cleaner
to hose off some areas on the board
My EE friend didn't think it would cause any damage
think about where you are spraying it, and the splash
You can simply lay a cloth over areas you don't ant the spray to splash on
same for the deoxit

Look for any brown spots on the board, heat damage
and check the bottom side for cracked solder joints

Worst case, pay someone a $150 to go through the receiver.

Try a different pair of headphones see what happens
 
Bubo said:
I've used a compressor from 2ft away
very gently, no problems. On lots of gear.

The canned stuff does freeze things
used sparingly can be used to find hot components
likely failed.
Click to expand...
That's the key. For 'air' you need a compressor with a water separator.
The stuff in the can is for finding components that fail when hot but work fine when cold. My dad used it to repair TV's back in the day.

Sorry for the OP. If it's still acting up after letting it dry out and come to temp then you likely froze and cracked something.
 
BillyTheKid said:
That's the key. For 'air' you need a compressor with a water separator.
The stuff in the can is for finding components that fail when hot but work fine when cold. My dad used it to repair TV's back in the day.

Sorry for the OP. If it's still acting up after letting it dry out and come to temp then you likely froze and cracked something.
Click to expand...
Sometimes I tell guys, a little dust is okay. Don't go crazy and damage your unit trying to make it shine, like a custom show car.

I don't know how many guys have asked me, "how do I restored the lettering on my amp?" After they used Windex or some such cleaner.

I tell them, "you know the saying about toothpaste, once out of the container..."

SWEATING (SMALLEST 1).jpg
 
Once I did actually wreck an amp with compressed air. Something had spilled in it once upon a time and I didn't know. That corroded the leads, and when I hit it with air those corroded leads turned to non-existent leads. I didn't realize it, plugged the thing in and blew up that channel. It made a heck of a mess, and I ended up replacing just about every single component in the power amp on that side. Some because the parts failed when it blew up, some because they were corroded and broken or about to break.
 
Well this case gets even stranger. Today, after receiving and applying my Deoxit D5. The crackle in the volume pot is gone and when I went to test a record for noise, the right ear of the DT990's worked again. Not just slightly, but was back to full functionality - back from the cusp of death. This completely baffles me and I must say, while everything seemingly worked out in my favour, I don't understand this outcome. Plenty of times have I had drivers fail or wires give out, things that could be fixed, but to have a driver to from fully functional to barely audible and then back to fully functional in the matter of three days, I have not seen before. I was so worried about my headphones that I contacted Thomann who would happily fix my headphones and send them back to me - a wonderful three year warranty is included with Beyerdynamic purchases through them. I even ordered a new pair of headphones, the Sennheiser HD58X, which I will likely keep seeing as I was interested in trying a different open-back headphone anyway.

Can anyone shed some light on this sudden resurrection of my Beyerdynamic DT990 and what even happened in the first place? Truly perplexing.

Thanks as always,

Johnny
 
JohnnyMercer said:
Can anyone shed some light on this sudden resurrection of my Beyerdynamic DT990 and what even happened in the first place? Truly perplexing.

Thanks as always,

Johnny
Click to expand...
This is WAG... but, freezing your control may have made a bad contact, worse. The Deoxit cleaned and re-established the contact.

You may have future contact issues with that control, so keep the Deoxit handy.
 
Last edited:
BillyTheKid said:
"If it ain't broke, don't fix it !' That's a tough lesson to learn.
Click to expand...
There is something to be said about units that have most of the internal parts well covered.

Keeps prying eyes and eager fingers off the merchandise. ;)
 
Last edited:
As mentioned: be certain your source of compressed air is really dry and the tank doesn't collect any water. Use low pressure only.

Head phones and buds often develop intermittent opens in the wiring. If your Beyers take another break try flexing the cable from the jack to the cans to see if anything changes. Good luck on your audio journey, JM.
 
oldflame said:
As mentioned: be certain your source of compressed air is really dry and the tank doesn't collect any water. Use low pressure only.

Head phones and buds often develop intermittent opens in the wiring. If your Beyers take another break try flexing the cable from the jack to the cans to see if anything changes. Good luck on your audio journey, JM.
Click to expand...
Thank you I will keep that in mind as well as what Mr. Boochie mentioned with future issues. It works remarkably well for now except for a pretty high noise floor and a decent bit of crackling when playing records. No complaints though, it's certainly better than having just a single functional driver.

Cheers to everyone who helped out along the way, it is massively appreciated.

Sincerely,

Johnny
 
You must log in or register to reply here.
Back
Top Bottom