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HP 82241A charger replacement polarity
03-08-2018, 10:34 PM
Post: #1
HP 82241A charger replacement polarity
I am trying to get a replacement charger for my HP 82240A printer. The specs for the HP 882241A charger says that the voltage should be 9V DC and 1000 mA.
My question is: shall it be positive or negative polarity in the centre?

Thanks in advance,
Matti
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03-09-2018, 12:35 AM (This post was last modified: 03-09-2018 12:37 AM by brickviking.)
Post: #2
RE: HP 82241A charger replacement polarity
(03-08-2018 10:34 PM)MattiMark Wrote:  I am trying to get a replacement charger for my HP 82240A printer. The specs for the HP 882241A charger says that the voltage should be 9V DC and 1000 mA.
My question is: shall it be positive or negative polarity in the centre?

Thanks in advance,
Matti

I had a quick check of the manual, it doesn't seem to matter, as either 9V-12V AC or DC seems to be acceptable. However, I've looked online at the backplate for a HP 82241A power supply, it appears to output 9V AC, not DC. Others should contribute if they know better information.

(Post 188)

Regards, BrickViking
HP-50g |Casio fx-9750G+ |Casio fx-9750GII (SH4a)
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03-09-2018, 02:31 AM
Post: #3
RE: HP 82241A charger replacement polarity
(03-09-2018 12:35 AM)brickviking Wrote:  
(03-08-2018 10:34 PM)MattiMark Wrote:  I am trying to get a replacement charger for my HP 82240A printer. The specs for the HP 882241A charger says that the voltage should be 9V DC and 1000 mA.
My question is: shall it be positive or negative polarity in the centre?

Thanks in advance,
Matti

I had a quick check of the manual, it doesn't seem to matter, as either 9V-12V AC or DC seems to be acceptable. However, I've looked online at the backplate for a HP 82241A power supply, it appears to output 9V AC, not DC. Others should contribute if they know better information.

(Post 188)

brickviking is correct, the 82241A outputs 9VAC which is appropriate for the 82240A printer.

The 82240B requires a DC supply, like the F1011A, which also works for the 82240A and the 95/100/200LX.

So the rule of thumb is you can power an AC device from a DC output adapter, but not a DC device from an AC output adapter.

Lastly, if you have a DC powered device, the center contact is negative.

Dave
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03-09-2018, 04:08 AM
Post: #4
RE: HP 82241A charger replacement polarity
(03-09-2018 02:31 AM)Dave Frederickson Wrote:  
(03-09-2018 12:35 AM)brickviking Wrote:  I had a quick check of the manual, it doesn't seem to matter, as either 9V-12V AC or DC seems to be acceptable. However, I've looked online at the backplate for a HP 82241A power supply, it appears to output 9V AC, not DC. Others should contribute if they know better information.

(Post 188)

brickviking is correct, the 82241A outputs 9VAC which is appropriate for the 82240A printer.

The 82240B requires a DC supply, like the F1011A, which also works for the 82240A and the 95/100/200LX.

So the rule of thumb is you can power an AC device from a DC output adapter, but not a DC device from an AC output adapter.

Lastly, if you have a DC powered device, the center contact is negative.

Dave
Dave,

I have a 82240B IR printer and a 82241A mains adapter and what you said caused me to double check compatibility. Page 13 of the manual for the printer states the 82241A is the correct power adapter. Is there other information to the contrary?

The manual states that the power to the printer may be 9-12v AC _or_ DC.

Steve
In order of appearance: HP 41CV, CMT-MCGPS, HP 41CX, DM 41, DM 42
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03-09-2018, 04:13 PM
Post: #5
RE: HP 82241A charger replacement polarity
(03-09-2018 04:08 AM)4ster Wrote:  
(03-09-2018 02:31 AM)Dave Frederickson Wrote:  brickviking is correct, the 82241A outputs 9VAC which is appropriate for the 82240A printer.

The 82240B requires a DC supply, like the F1011A, which also works for the 82240A and the 95/100/200LX.

So the rule of thumb is you can power an AC device from a DC output adapter, but not a DC device from an AC output adapter.

Lastly, if you have a DC powered device, the center contact is negative.

Dave
Dave,

I have a 82240B IR printer and a 82241A mains adapter and what you said caused me to double check compatibility. Page 13 of the manual for the printer states the 82241A is the correct power adapter. Is there other information to the contrary?

The manual states that the power to the printer may be 9-12v AC _or_ DC.

On p. 12 of Edition 2 of the manual,

http://www.hpmuseum.net/document.php?hwfile=3360

it states to use only the F1011A adapter, which is DC. I incorrectly presumed that this meant that the 82240B requires a DC adapter. It's now apparent that both printers will accept either AC or DC.

Dave
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03-09-2018, 05:01 PM
Post: #6
RE: HP 82241A charger replacement polarity
I thank you all for the fast replies.
I will now try to locate one DC-power supply unit with negative polarity in the centre.

Regards,
Matti / Sweden
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03-09-2018, 05:34 PM
Post: #7
RE: HP 82241A charger replacement polarity
(03-09-2018 04:13 PM)Dave Frederickson Wrote:  It's now apparent that both printers will accept either AC or DC.
Dave

And that makes sense, since I believe that most of these printers (if not all of them) have a full bridge rectifier where its input is connected to the printer panel power plug.

This bridge of 4 diodes converts external AC power to DC with negative ground, but also converts external DC on either polarity to the correct negative ground polarity.

Basically external DC is treated as external AC.
The only small difference is that AC is converted to DC but the AC voltage nominal value results in AC times sqrt(2) DC value under no load.
Because the bridge output is loaded and the smoothing capacitor have limited capacity, the real DC value will be lower with a certain amount of ripple.
Of course this ripple must not reach the printer electronics, and this is why the bridge output is connected to a 7806 6Volt regulator.

On both AC and DC external input power supplies, the bridge will, on average, take 1.4Volt (0.7Volt per diode, as only two diodes are in series at a given time).

So, if the external power adapter is a 10Volt DC type, the regulator will get around 10-1.4 = 8.6Volt, just enough to be able to operate under its normal conditions delivering 6Volt regulated output (the common 7806 type is not a low drop voltage regulator, so it requires a absolute minimum of 2Volt higher at its input pin).

The above is true only if the power adapter have insignificant internal resistance to be able to maintain those 10Volt DC under the required printer current load.
Otherwise, we will see a voltage drop at the input of the 7806 regulator, and if this value goes under 8Volt, the printer will not be able to work using that adapter alone, and if batteries were left inside, they will supply the required energy to let the printer to continue working.

Jose Mesquita
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03-09-2018, 05:37 PM
Post: #8
RE: HP 82241A charger replacement polarity
(03-09-2018 05:01 PM)MattiMark Wrote:  I thank you all for the fast replies.
I will now try to locate one DC-power supply unit with negative polarity in the centre.

Regards,
Matti / Sweden

As the printer can accept AC, the plug can be of either polarity.
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