ThinkJet 2225B battery pack question

[hfischer]

Hello,

I just successfully re-activated a 2225B ThinkJet hp-il printer - the only issues were an internally corroded on/off switch (disassembled, cleaned, working) and a dry print head (alcohol didn't help, hot water did). The complete disassembly of the device thus wouldn't have been necessary, but was instructive :-)

The printer came with a modified battery pack, which contains rectifier, capacitor and voltage regulator, all on a rather hand-made looking raster board. It is fed from an external W&W-labeled transformer, a bit larger and much heavier than the usual hp power supply, but with an original hp connector.

The printer runs nicely on this supply, but I might consider rebuilding the battery pack. Is a schematic available somewhere?

Thanks in advance,

Helmut (Germany)

[Dave Frederickson]

Couldn't find a schematic, but here's an article that should help.
https://www.hpmuseum.org/cgi-sys/cgiwrap...i?read=563

Here's a pic of one of my battery packs showing the orientation of the six sub-C cells and the pico fuse.


Here's how the PCB is wired in the pack. It contains an input transformer, four diodes forming a full wave bridge rectifier, and a resistor whose color coding bands have fallen off. It measures about 5.5 ohms.


Here's a close up of the PCB.


And the circuit side.


No load output of the PCB is about 10.7 volts.

It's not mentioned in the article, but the original cells were 1200 mAh NiCd. The cells can be replaced with high-capacity NiMH cells but with capacities up to 5000 mAh they take a lot longer to charge. I use a Tenergy 1006 smart pack charger.
http://www.tenergy.com/01006

Also, new-formula ink cartridges are available.
https://www.hpmuseum.org/forum/thread-14...#pid130884


Dave

[John Keith]

Judging from the first picture the resistor is 4.7 ohms. 5.5 ohms seems high but will include the resistance of the meter leads unless you compensated for it. Also the coil is probably a filter choke, not a transformer.

[Dave Frederickson]

(05-12-2020 04:07 PM)John Keith Wrote:  Judging from the first picture the resistor is 4.7 ohms. 5.5 ohms seems high but will include the resistance of the meter leads unless you compensated for it. Also the coil is probably a filter choke, not a transformer.

I did compensate for the lead resistance, but I agree with your analysis. Further inspection reveals that the inductor is indeed a choke and not a transformer. I see no part number and I don't have an LCR meter.

The bands on the resistor are yellow-violet-gold-gold, so, yes 4.7 ohms.

EDIT: The diodes are marked 010 704 which I take as an abbreviation for 1901-0704 which crosses to a 1N4002 diode.

[hfischer]

Dave and Keith,

thank you for your answers - the photos and the link to the 2005 post by Etienne were extremely helpful!

Looking at all the photos, I came to the same conclusions as Keith: choke and 4.7 Ohms (the colour code yellow - violet - gold can be "guessed" on one of the photos).

I tried to roughly calculate the inductance of the chokes and arrive at something like 1 Microhenry. On Etienne's photos there are two chokes, the colour code of which might say 10 Microhenries. No idea how critical this may be, and whether the chokes are present to block spikes from the mains into the printer or whether they are meant to block spikes coming from the printer's internal voltage converter.

Anyway, I had just finished a tentative simple circuit diagram when your posts came up (see attachment). For Etienne's battery pack the chokes would be after the rectifier.

   

(hope this works - I can't see the attachment ...)

BTW: today I received a 2225C, cheap and intended for spare parts. The case is in a better shape than that of my 2225B, and this printer also works, at least the self test. And in a locker at my former workplace, a while ago I discovered a box full of inkjet paper which nobody wants :-)

Thanks for the links to ink cartridges and charger!

Stay healthy,

Helmut

[Dave Frederickson]

(05-12-2020 04:46 PM)hfischer Wrote:  Anyway, I had just finished a tentative simple circuit diagram when your posts came up (see attachment).

It's a detail, but the fuse should be located between the 4th and 5th cell from the top. If someone could explain why this is of concern I'd be interested.

[hfischer]

(05-12-2020 05:25 PM)Dave Frederickson Wrote:  It's a detail, but the fuse should be located between the 4th and 5th cell from the top. If someone could explain why this is of concern I'd be interested.

Ah, I didn't look at your first photo closely enough! I have corrected it in the diagram.

   

In my view, it would make sense to place the fuse there if it were temperature-sensitive and actuated also as a thermal protection against overheating. I had checked this already in some Picofuse specs, but couldn't find anything in this direction.

Helmut

[John Keith]

Looking at your diagram, does the choke consist of two separate windings on one core? If so, it is probably a common-mode choke which is used to filter out line noise.

[hfischer]

(05-12-2020 09:27 PM)John Keith Wrote:  Looking at your diagram, does the choke consist of two separate windings on one core? If so, it is probably a common-mode choke which is used to filter out line noise.

Yes, this can be seen quite nicely on Dave's third picture: looks like about 20 windings of two adjacent wires on a small helical core. The core looks like plastic, not ferrite.

[Dave Frederickson]

(05-13-2020 08:48 AM)hfischer Wrote:  The core looks like plastic, not ferrite.

The choke has been dipped in epoxy, so it doesn't look like ferrite, but it's not plastic and from the weight I think it's ferrite.

[hfischer]

(05-13-2020 02:13 PM)Dave Frederickson Wrote:  The choke has been dipped in epoxy, so it doesn't look like ferrite, but it's not plastic and from the weight I think it's ferrite.

Initiated by this thread, I just received a donation in form of an empty (no batteries, no Picofuse, but with PCB) battery tray - THANKS!

The PCB looks like in your pictures. The choke reacts with a degaussing device, so I assume the core is ferrite.

I already ordered sub-C cells and Picofuses. One question remains: should the Picofuse be slow or quick (I have ordered both kinds)?

Helmut

[Dave Frederickson]

(05-25-2020 09:02 AM)hfischer Wrote:  One question remains: should the Picofuse be slow or quick (I have ordered both kinds)?

I don't have a definitive answer, but after comparing images of many pico fuses, I've been unable to find any pics of a slow-blow fuse like the one pictured in the tutorial. So I'm going to say it's fast-blow.

If I'm wrong, worst case is you'd experience nuisance blows. If that happens then switch to the slow-blow fuse.

I did find some info on NiCD and NiMH Pack Design.
http://www.dalitech.com/Resources/NiCd%2...Design.pdf

Paragraph 7.3.4 states that thermal fuses "... open at elevated temperatures caused by run-away current. They are a fail-safe measure since the battery will become inoperative once the fuse has opened. These fuses are recommended, if absolute termination of current is needed for safety concerns only."

Dave

[Steve Nichols]

I recently acquired a 2225b printer in very good condition except that the battery died after very little time. Can the battery be replaced with a power supply that converts the AC supplied by the 82059 converter to the DC that the printer needs?

Steve N.

[Bab]

Hello Steve
Last year i tested successfully my hpil thinkjet with a laboratory power suply directly plugged to the springs + and - of the printer.
It is not perfect but it can be useful for testing the printer.

Bab

(A not very good english-speaking)

[KimH]

I have reenvigorated several batteries for ThinkJets and 9114 drives. They are not the same (2225 is NiCad & 9114 is LeadAcid)

As they are not the same, but has similar power-requirements, I made experiments similar to what you are considering here.

The short version is, both devices require the battery as a power source even with the 82059… The charger is just that, a charger. The power needed to supply comes from the batteries.

There is a lot (!!!) more power required than the charger can give.

So, one of 2 options.

Powerful external power supply - as in 5-10 amps (peak) at the voltage required
Or
Rebuild the battery from the components available, as similar as possible, to what was in the battery-pack.

(01-20-2024 10:04 PM)Steve Nichols Wrote:  I recently acquired a 2225b printer in very good condition except that the battery died after very little time. Can the battery be replaced with a power supply that converts the AC supplied by the 82059 converter to the DC that the printer needs?

Steve N.

[Steve Nichols]

Does anyone know the amps and volts a 2225b needs out of a power brick that takes as input 110 volts AC at 60hz and replaces the battery or what available power brick would do the job?

Steve N.

[Dave Frederickson]

What we know about the battery pack:
1. A good battery pack fully charged outputs 8.5V
2. Typical output is 7.2 to 7.6V
3. The Power LED will indicate a low battery and flash if the voltage drops to 6.2 to 6.5V
4. The fuse is rated at 5A.

If the fuse was derated by 25% then the output would be 3.75A.
So a power adapter with an output of 7-8V at 4A should work fine.

[Jeff_Birt]

(01-26-2024 01:03 AM)Dave Frederickson Wrote:  What we know about the battery pack:
1. A good battery pack fully charged outputs 8.5V
2. Typical output is 7.2 to 7.6V
3. The Power LED will indicate a low battery and flash if the voltage drops to 6.2 to 6.5V
4. The fuse is rated at 5A.

If the fuse was derated by 25% then the output would be 3.75A.
So a power adapter with an output of 7-8V at 4A should work fine.

Be very careful about trying to run a battery-operated device from the charging connector. Most often there is a current limiting resistor in series. This is part of the charging circuit but if you try to pump the full operational current through it the voltage drop and power dissipated will both be too high.

[Steve Nichols]

To be clear regarding what I am thinking of doing, I just received a 9114b disk drive with a power brick that has its output wire running through the socket where the charger would normally plug in. I am sure that the battery in the battery pack has been removed and the wire from the power brick is connected directly to the plug that plugs into the socket on the disk drive. I received my 9114b from a well respected dealer in used HP calculator items. The disk drive is working well, and I believe will continue to work well. Therefore, I hope to create a similar arrangement for my Thinkjet.

There is a problem that the power brick has no markings to identify its specs. If I could I would look for the same power brick, assuming that the 9114 and ThinkJet use the same voltage. I am left with attempting to match the specs that have, kindly, been provided.

Steve N.

[Dave Frederickson]

(01-26-2024 02:15 AM)Steve Nichols Wrote:  There is a problem that the power brick has no markings to identify its specs. If I could I would look for the same power brick, assuming that the 9114 and ThinkJet use the same voltage.

They do not. The 9114 uses a 6V lead acid battery and the power brick I'm using is only 3A.

My suggestion is to gut your old 2225B battery and run the output of the power brick through the empty case. EXCEPT, you should add the 5A fuse.

Dave