questions about HP 802059 wall warts

[4ster]

I just acquired a new (to me) 802059D (edit: 82059D) charger that came with an HP 9114B disk drive. I have always wondered why HP decided to have their wall warts supply AC voltage when most other wall transformers/chargers supply DC. Now, please understand that I can by no means be labeled as someone knowledgable in electronics. Knowing HP, I'm sure there was a good reason. Anyone know the reason?

The manual for the disk drive states that an 82059B charger should be used. This one is a 82059D. The no load AC output, measuring across the terminals, is 12+ish VAC on this one and on my other two 8205B chargers as well. I am assuming that the D model is a later manufacture than the B and that they are interchangeable for 40 series accessories. Is this correct?

[rprosperi]

(05-06-2017 02:20 PM)4ster Wrote:  I just acquired a new (to me) 802059D charger that came with an HP 9114B disk drive. I have always wondered why HP decided to have their wall warts supply AC voltage when most other wall transformers/chargers supply DC. Now, please understand that I can by no means be labeled as someone knowledgable in electronics. Knowing HP, I'm sure there was a good reason. Anyone know the reason?

The manual for the disk drive states that an 802059B charger should be used. This one is a 802059D. The no load AC output, measuring across the terminals, is 12+ish VAC on this one and on my other two 80205B chargers as well. I am assuming that the D model is a later manufacture than the B and that they are interchangeable for 40 series accessories. Is this correct?

The 82059B and 82059D are compatible. (Note you have an extra 0 after the initial 8).

As to why HP chose that, it's impossible to say for sure now, though it's likely folks that know about this stuff will chime-in with technical insights. The key advantage I can see is it's a simple transformer electrical design, and these adapters have been extremely reliable as a result, I have many of them, use daily, and have never had one fail.

[Dieter]

(05-06-2017 04:34 PM)rprosperi Wrote:  [ Why AC? ]
As to why HP chose that, it's impossible to say for sure now, though it's likely folks that know about this stuff will chime-in with technical insights.

I am definitely not one of these folks, but I'd say that AC is the most versatile option: it can be used for devices that run on AC, pulsating DC or "pure" DC – the required conversions are trivial.

(05-06-2017 04:34 PM)rprosperi Wrote:  The key advantage I can see is it's a simple transformer electrical design, and these adapters have been extremely reliable as a result, I have many of them, use daily, and have never had one fail.

I have two European versions (82066A) for charging the HP41 battery pack. The first one from 1981 soon had a problem with a bad cable or plug making unreliable contact. Later I found another one (NIB) in the dump bin of a local electronics store. The price was very reasonable: 2,50 DEM, which at that time was not much more than 1 USD. $-)

Dieter