How to find out polarity of device

Reply

  #1  
Old 05-01-12, 01:01 PM
Member
Thread Starter
Join Date: May 2012
Posts: 2
How to find out polarity of device

I have a audio recorder (Edirol R-09HR High-Resolution WAVE/MP3 Recorder) need to use ac-dc adapter.
There is no any marker to tell me polarity of input in this device.
(I check the adapter from amazon.com for this device which I do not have, there is no marker as well)
I have a Radio-Shack ac-dc adapter which I can adjust polarity.
The porblem is how to find out this audio recorder input polarity, that is, is pin "+" or "-"?
 

Last edited by aspfun; 05-01-12 at 01:32 PM.
Sponsored Links
  #2  
Old 05-01-12, 01:47 PM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
The porblem is how to find out this audio recorder input polarity, that is, is pin "+" or "-"?
Does this recorder have a power-in jack? The best I can tell, the "plug-in power" is for power out to an external device:
"The unit has plug-in power with adequate voltage to power my Sonic Studios DSM-6S"
- from a review at Amazon.com
What does the paperwork with it say? Have you tried contacting Roland?
 
  #3  
Old 05-01-12, 01:57 PM
Member
Thread Starter
Join Date: May 2012
Posts: 2
find out this audio recorder input polarity

Yes, this device has power-in jack but no "+" or "-" mark at all.
I just call Roland at 3238903740 and customer service tell me that I have to buy special adapter which made from Roland. I can not use the adapter from Radio Shack. (I do not think this is true)
 
  #4  
Old 05-01-12, 02:25 PM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
just call Roland at 3238903740 and customer service tell me that I have to buy special adapter which made from Roland. I can not use the adapter from Radio Shack. (I do not think this is true)
Let's say you're right. Do you also think that Roland won't consider it a violation of their warranty agreement if you use a power adapter not made by them?
 
  #5  
Old 05-01-12, 02:40 PM
Member
Join Date: Feb 2002
Location: port chester n y
Posts: 2,117
A digital multi-meter that can both measure the value of DC voltages and indicate the polarity. You can test the polarity indication of the multi-meter by measuring the voltage of a battery that has definite polarity marks to ID the + / - ends of the battery.

if you have the Positive meter lead on the Negative side of the battery , the meter may indicate " - 12 " ( 12-volt battery ).
 
  #6  
Old 05-01-12, 04:05 PM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 9,750
Thumbs up Welcome to our forums!

You need to consider that all 12 volt adapters are not created equally!
The voltage of different adapters can widely vary even when marked at 12 volts.

If you are not using the mfr's adapter you would do well to check the open circuit voltage.
You would need to make a judgement call if the voltage was much higher.
If the output voltage was high and the load you were placing on the adapter is very low compared to its output capacity the voltage may not drop much when connected.

You could take a shot at carefully probing the pins on the recorder with a voltmeter while it is operating to see if voltage is present........this may tell you what the polarity is.

Pretty much all the 12 vdc devices I have are center pin positive.
 
  #7  
Old 05-02-12, 06:01 AM
Member
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,239
The Roland power supply is regulated DC, so a basic wall-wart from Radio Shack won't do the job. It's 3VDC and must deliver at least 400 milliamps.

One way to tell polarity is to use a multimeter set to ohms. Pull the batteries. Touch one lead to one of the negative battery terminals and the other to the outside metal part of the power input jack. If you get OL or OPEN on the meter, touch the lead to the other battery terminal. (The batteries are in series, so only one of the two terminals is common to the power supply.) If you still get an OL or OPEN reading, touch the other lead to the center pin on the power jack and repeat the process with the battery terminals.

At some point you should see a very low ohms reading. When you do, the power jack pin you're touching is DC negative.
 
  #8  
Old 05-02-12, 09:24 AM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
Assuming the battery terminals have a direct connection to the power-in jack, I would just do a continuity test with the center pin of the jack as one contact. Most multi-meters can do this.
 
  #9  
Old 05-13-12, 11:36 PM
Banned. Rule And/Or Policy Violation
Join Date: Jan 2010
Location: KS
Posts: 1,896
Originally Posted by Nashkat1 View Post
Let's say you're right. Do you also think that Roland won't consider it a violation of their warranty agreement if you use a power adapter not made by them?
Look up the Magnusson-Moss Warranty Act. A manufacturer can't void your warranty for simply using a 3rd party accessory. They have to prove that the accessory in question caused damage.

Originally Posted by Rick Johnston View Post
The Roland power supply is regulated DC, so a basic wall-wart from Radio Shack won't do the job. It's 3VDC and must deliver at least 400 milliamps.
The RS multi-volt warts (the ones with the slider switch) ARE regulated.

Originally Posted by Rick Johnston View Post
One way to tell polarity is to use a multimeter set to ohms. Pull the batteries. Touch one lead to one of the negative battery terminals and the other to the outside metal part of the power input jack. If you get OL or OPEN on the meter, touch the lead to the other battery terminal. (The batteries are in series, so only one of the two terminals is common to the power supply.) If you still get an OL or OPEN reading, touch the other lead to the center pin on the power jack and repeat the process with the battery terminals.

At some point you should see a very low ohms reading. When you do, the power jack pin you're touching is DC negative.
Originally Posted by Nashkat1 View Post
Assuming the battery terminals have a direct connection to the power-in jack, I would just do a continuity test with the center pin of the jack as one contact. Most multi-meters can do this.
That very rarely works. Most dual-power products use a 'switching' power jack, which isolates the power jack from the batteries - this is to prevent inadvertent charging of non-rechargeable batteries. Some devices do provide a charging function in this manner (it is not usually a direct connection to the jack either), but the R-09 is not one of them. It says so right in the manual.

To the OP..

Originally Posted by aspfun View Post
Yes, this device has power-in jack but no "+" or "-" mark at all.
I just call Roland at 3238903740 and customer service tell me that I have to buy special adapter which made from Roland. I can not use the adapter from Radio Shack. (I do not think this is true)
The R-09HR calls for a Roland PSB-6U adapter, which is 3v @ 300mA, tip positive, 4.00mm OD × 1.70mm ID (Adaptaplug tip "B"). You will be fine using the adapter you currently have, as long as it has a 3v setting and the Adaptaplug is installed in Tip Positive position. All manufacturers will tell you that you can't use something other than THEIR accessories with their product. They want you to give THEM the money.
 
  #10  
Old 05-14-12, 08:54 AM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
Look up the Magnusson-Moss Warranty Act. A manufacturer can't void your warranty for simply using a 3rd party accessory.
Indeed. I hadn't known that before.
Warrantors cannot require that only branded parts be used with the product in order to retain the warranty.
Source: Magnuson–Moss Warranty Act
That very rarely works. Most dual-power products use a 'switching' power jack, which isolates the power jack from the batteries - this is to prevent inadvertent charging of non-rechargeable batteries. Some devices do provide a charging function in this manner (it is not usually a direct connection to the jack either), but the R-09 is not one of them.
As I suspected. Thank you for clearing it up.
 
  #11  
Old 05-14-12, 01:54 PM
Member
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,239
Originally Posted by JerseyMatt
That very rarely works. Most dual-power products use a 'switching' power jack, which isolates the power jack from the batteries - this is to prevent inadvertent charging of non-rechargeable batteries. Some devices do provide a charging function in this manner (it is not usually a direct connection to the jack either), but the R-09 is not one of them. It says so right in the manual.
Not meaning to be argumentative (too late!) ...

Every one I've ever seen switches only the +V side, leaving the ground connected to both batt pack and power input jack. That's why I suggested metering for DC negative (which in this case is also common ground).

Speaking of negative, that has been my experience with cheepo RS power supplies on guitar processors and other devices that require filtered, regulated power supplies. Unless you like to hear hum in the audio. The "real" Roland PS also has an RF choke on the low-voltage side.

The other confusion exists over whether the PS needs to deliver 300ma or 400ma. Every cheepo PS I've ever tried to use that's rated the same as the device has exactly no headroom, which turns them into little heaters.
 
  #12  
Old 05-14-12, 02:38 PM
Banned. Rule And/Or Policy Violation
Join Date: Jan 2010
Location: KS
Posts: 1,896
It's kind of tough for it to switch +V in a tip-positive configuration when the switch in a coaxial plug is on the 'sleeve' contact... Not only that, but there will also undoubtedly be diode isolation between the jack and batteries to prevent power backflow.

The hum/noise comes from unfiltered switched-mode power supply (SMPS) adapters. Switched-mode adapters are the tiny ultra-light kind that are used for cell phone/laptop chargers and such. They are highly regulated by design, but noise suppression is only absent on the absolute cheapest chinese junk. Most of them do have filtering circuitry. The multi-volt RS adapter is linear, not switched mode. Linear adapters have the heavy e-core wire transformer inside. It is also regulated, and regulated linear supply is also filtered by design. Again, only the very cheapest linear supplies are unregulated. The ones from RS (the old white ones anyway, not sure of the current generation) - including the 300mA multi-volt and the fixed volt models - are all regulated. The old 1500mA multivolt was the only unregulated one they carried.

And the reason the 'real' Roland PS has the RF choke is because it has to. It's a SMPS, and SMPS circuitry generates a lot of RF noise which must be trapped before it gets to the device. That's something you'll find on any SMPS. The ferrite bead may be internal (like on a cell phone charger), but it's there.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes