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HiFiMAN HM-901 visit pg 18. IMGS pg 19. NEW beta FW 1st page. . to the 901s. .new 901s FW . - Page 135

post #2011 of 3412
Try to use some electronic contact cleaner to clean the metal contacts of your amps

Also try to play around with the SE/balanced switch smily_headphones1.gif
post #2012 of 3412
Quote:
Originally Posted by frankrondaniel View Post
 


Yeah - same amps and batteries across all 3 units.  In the previous 2 units the amps seemed to work fine.  I'd be surprised if something happened to all three amps while waiting for the new unit.  And I won't rule out user error but I can't see what I would be doing wrong with the amp install - they make it difficult to put it in the wrong way.  Are there any installation mistakes that people have been known to make?

 

I would be surprised too that Hifiman wouldn't have checked the new unit out prior to shipping it to me. I have no doubt that the final outcome will be good - just a little frustrating in the mean time.

It is possible to not have a fully seated connection with the amp cards. Double check on that. You may also want to double check the connectors on the battery itself to ensure a good mechanical connection. One of rails on the battery is solely for the amp section, so that is a good possibility too, as it could in fact power on without that rail operating as it should. If you have a Digital Multimeter that would be even better since you can verify the voltage.


Edited by brunk - 1/21/14 at 6:42pm
post #2013 of 3412
Quote:
Originally Posted by xnuthecaveman View Post

Try to use some electronic contact cleaner to clean the metal contacts of your amps

Also try to play around with the SE/balanced switch smily_headphones1.gif

 

I'm not sure if I have anything here suitable to clean the contacts.  Does it have to be specific for this purpose or can I get away with some more generic cleaning fluid?

 

I actually played with the SE/Balanced switch as that was defective in my previous unit.  Out of curiosity, what made you suggest that?  Were there some known problems with that switch? While I was at it I played with all of the switches for good measure but unfortunately none made a difference.

post #2014 of 3412
Quote:
Originally Posted by brunk View Post
 

It is possible to not have a fully seated connection with the amp cards. Double check on that. You may also want to double check the connectors on the battery itself to ensure a good mechanical connection. One of rails on the battery is solely for the amp section, so that is a good possibility too, as it could in fact power on without that rail operating as it should. If you have a Digital Multimeter that would be even better since you can verify the voltage.

 

The amps seem like they're seated in there pretty good - as a matter of fact, they seem to seat more securely in this new unit compared to the previous ones.

Interesting comment regarding the battery. I tried both of my batteries (I purchased an backup along with the external charger) and same result with both.  Unfortunately I don't have a multimeter.  I'll take a look at the batteries connectors - anything that I could visually identify that would cause a problem?

post #2015 of 3412
For cleaning, you can use common alcohol, 70% is ok, put in on a cotton ball just enough to dampen a small portion of the cotton, and use that to clean the contacts. Just make sure you dry it well before you install.

As for the switch, it just popped out in my mind. Because, that's the component between the amps and headphones.

I don't own a hm901 yet. I'm just troubleshooting based on my experience.

Hm901 -- amp -- SE/balance switch -- headphone.

Using the lineout bypass the amp, SE/bal and headphone.
post #2016 of 3412
Quote:
Originally Posted by frankrondaniel View Post
 

 

The amps seem like they're seated in there pretty good - as a matter of fact, they seem to seat more securely in this new unit compared to the previous ones.

Interesting comment regarding the battery. I tried both of my batteries (I purchased an backup along with the external charger) and same result with both.  Unfortunately I don't have a multimeter.  I'll take a look at the batteries connectors - anything that I could visually identify that would cause a problem?

You could check the connections visually on the battery for gashes, and looseness but a DMM is the only way to verify proper operation. Your charger could in fact have a problem too if that's the case. Here's the thing: 3 units in a row experiencing similar issues is not a coincidence, I really think it's either the amps, battery and even possibly the charger damaging the batteries. I personally recommend you send it all to hifiman for a proper inspection. It's not like you can use the stuff without the 901 anyway.

post #2017 of 3412
Quote:
Originally Posted by brunk View Post
 

You could check the connections visually on the battery for gashes, and looseness but a DMM is the only way to verify proper operation. Your charger could in fact have a problem too if that's the case. Here's the thing: 3 units in a row experiencing similar issues is not a coincidence, I really think it's either the amps, battery and even possibly the charger damaging the batteries. I personally recommend you send it all to hifiman for a proper inspection. It's not like you can use the stuff without the 901 anyway.


I definitely agree that I should send everything to them this time.

post #2018 of 3412
Quote:
Originally Posted by xnuthecaveman View Post
 

 

try to use the lineout (bypass amp) to see if you can hear anything. if you can hear anything, make sure you install the amp cards correctly.

if you can't hear anything from the lineout, you might have a defective HM901. 

 

scenarios to consider:

*correct installation of amps 

*possible defective amp cards from 1st HM901

This is the best suggestion I've seen so far. Will make what i'm about to say sound a little silly but might as well try everything.

 

Have you tried updating the firmware again? Clean the connectors as well etc?

post #2019 of 3412

And do you have any friends using the 901 as well? You can use test your cards with theirs and filter out your list of what might be wrong. 

post #2020 of 3412
Quote:
Originally Posted by awry View Post
 

And do you have any friends using the 901 as well? You can use test your cards with theirs and filter out your list of what might be wrong. 

 

Unfortunately no one close by to compare.  Hifiman did ask me to send the unit back along with the amp cards this time.  Hopefully that'll show what's going on.  Can't wait to be able to actually listen to music again though!

post #2021 of 3412
Quote:
Originally Posted by frankrondaniel View Post
 

 

Unfortunately no one close by to compare.  Hifiman did ask me to send the unit back along with the amp cards this time.  Hopefully that'll show what's going on.  Can't wait to be able to actually listen to music again though!

Same here. Just sent mine back last Thursday. Older batch with the looser scroll wheel. Just wouldn't stay on anymore. They were really nice to offer me a replacement set instead of just the wheel as well as a new battery though.

 

I'm lucky enough to have a good friend, Kiats who posted above as well, who owns a 901 as well to test things out though. Good luck with your set. Do drop an update when you find out what the problem is. Would be good info to share I think. 

post #2022 of 3412
Quote:
Originally Posted by awry View Post
 

Same here. Just sent mine back last Thursday. Older batch with the looser scroll wheel. Just wouldn't stay on anymore. They were really nice to offer me a replacement set instead of just the wheel as well as a new battery though.

 

I'm lucky enough to have a good friend, Kiats who posted above as well, who owns a 901 as well to test things out though. Good luck with your set. Do drop an update when you find out what the problem is. Would be good info to share I think. 

 

My first 901 had a volume wheel issue as well - that's what started my journey down the "RMA" road!

 

I'll certainly post an update!

post #2023 of 3412
Quote:
Originally Posted by frankrondaniel View Post
 

.....that's what started my journey down the "RMA" road!

 

 

post #2024 of 3412
Quote:
Originally Posted by burtomr View Post
 

 


LOL - I don't look quite like that yet, but getting close!

post #2025 of 3412
Thread Starter 

I just got 2 of the TRRS connectors from a few pages back. Sadly, they are magnetic, very much so, so whomever tested them, didn't use a magnet. There is a lot of ferrous metal in the construction. 

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