HP82002A replacement capacitor

[EricBlair]

I'm attempting to repair my original HP8002A charger that came with my HP45. From what I read, it is very likely that the 400uF/15V capacitor has failed. Can anyone point me to where I can buy a replacement capacitor? The size of the replacement is critical since there's very limited space on the circuit board. Also, I'm concerned that the area of circuit board under the four parallel 1/4 resistors/diodes/capacitors shows evidence of heating. That is, the circuit board is darkened. Any idea if other components need to be replaced in addition to the electrolytic?

[[kby]]

Mouser, Digi-Key, or Newark would be my normal choices for online order. There’s a local store I use here but they won’t have as many size, shape, etc. variations.

[teenix]

(05-15-2020 11:36 PM)EricBlair Wrote:  I'm attempting to repair my original HP8002A charger that came with my HP45. From what I read, it is very likely that the 400uF/15V capacitor has failed. Can anyone point me to where I can buy a replacement capacitor? The size of the replacement is critical since there's very limited space on the circuit board. Also, I'm concerned that the area of circuit board under the four parallel 1/4 resistors/diodes/capacitors shows evidence of heating. That is, the circuit board is darkened. Any idea if other components need to be replaced in addition to the electrolytic?

Look for a 470uF 25V RB electrolytic capacitor. It will almost certainly fit, but most larger component suppliers have data sheets for a lot of their component inventories so you can check this for certainty.

Try replacing the capacitor and charge the battery, with the case top in place but not fastened with the screws.

After half an hour or so, make sure you remove the mains plug, take off the cover and check how hot the components are. In general terms, I would expect to feel some warmth on the transformer and components, and maybe even a bit warmer than you think is ok, but this is reasonable. As long as they are not overly hot to the touch, they should be fine. I don't have a charger, but from memory I think the case got quite warm during charging. Over many years of use, the circuit board could have discoloured.

If the charger has a mains 110V and 230V switch it could have accidently been in the 230V position when connected to a 110V mains supply which would have caused a higher current than normal and excessive heat.

cheers

Tony

[John Keith]

On a related note, try to get a capacitor rated for 105C rather than 85C. The cap with the higher temperature rating will have a longer life in hot environments. Again check the size since 105C caps tend to be a bit larger that 85C caps of the same ratings. Modern caps are significantly smaller than the equivalents from the 70's though, so you probably won't have problems with physical size.

[EricBlair]

Tony: Much thanks for your suggestions. Try as I might Mouser, DigiKey andNewark didn't yield any results. If you can find a link I'd greatly appreciate it. I've spent lots of time looking to no avail. I did find one VERY odd listing though. If you go to <https://resi.store> - I'm not kidding that is the URL -and search on the PLU 315 you'll not only find a match, but a photo of the *exact* capacitor that's in the HP82002A! I attached a copy of the photo to save you time. They even list that they have 11 in stock. Big problem though. This appears to be a site for the Oregon State University Robotics Club and doesn't appear to be open for any sales. Seems to be student run and now, particularly with the COVID19 situation, doesn't appear to be manned/open. Any alternatives would be most welcome. The cao in the photo looks like a capacitor that has been removed from a HP charger.Really strange.

[Diego Diaz]

Hi Eric, all,

As previously noted, capacitance is not critical. Any 470uF with working voltage above 16v will fit the bill, and there are plenty of'em at the usual on-line components sites (Mouser, Digi-Key, etc.)

Choose a well known capacitors manufacturer (Panasonic, Nichicon, Elna...) and you'll be ok.

Some considerations regarding the 400uF/15v you've found:

- This is a non-normalized value, so chances are that these capacitors were either used or NOS. Any case I wouldn't recommend it. Electrolytic capacitors are renowned by "aging" even when not in use; and are more prone to leaking, loosing capacitance and increasing its ESR. (Neither of these are good things)

- Current manufacturing process has greatly improved since the HP-45 era. Any new capacitor will be smaller and more reliable than its '70s counterpart.

Good luck and keep safe. ;-)

Diego

[Dwight Sturrock]

Eric,

I sent you a forum email of a link for possible candidate for a capacitor. 470 uF, 25V, 105 degrees C.

[teenix]

(05-17-2020 07:00 PM)EricBlair Wrote:  Tony: Much thanks for your suggestions. Try as I might Mouser, DigiKey andNewark didn't yield any results.

Digikey Part no: 493-4499-1-ND

Newark Part no: 55Y9981

Jameco Part no: 158289

cheers

Tony

[EricBlair]

A big, big THANK YOU to teenix, Diego Diaz, John Keith and Dwight Sturrock. I've placed an order with Newark Electronics for part number 49W7428, a Panasonic electrolytic. As expected, the shipping cost far exceeded the cost of the caps. No complaint though. Even though the rating of the capacitor is greater than the original one, the capacitor itself is slightly smaller. I'm anxiously awaiting receiving the caps so I can restore my old HP82002A charger to life. In the interim I found, ordered, received and used a replacement item from eBay that appears to be super great. It's a Fully-Regulated USB charger cable that appears to do everything my HP Charger can do. If anyone is interested the eBay item number is 173700772484. It is a bit pricy at $40, but the delivery was fast and the Charger appears to be well built and unbelievably small.

Again, thank you one and all. My HP45 will now undoubtedly outlive me!

[BusyCalc]

Hello,

how can you measure or "feel" that a charger is not working properly and it needs a capacitor replacement?

I own a charger from a HP-80 1603S and I charge a battery back once every 2 months approx. The battery gets full and I don't think the charger gets too warm, but I'd like to know how to be sure and avoid accidents with it.

Thanks.

Kins regards,

Oscar

[teenix]

(05-25-2020 07:39 AM)BusyCalc Wrote:  Hello,

how can you measure or "feel" that a charger is not working properly and it needs a capacitor replacement?

I own a charger from a HP-80 1603S and I charge a battery back once every 2 months approx. The battery gets full and I don't think the charger gets too warm, but I'd like to know how to be sure and avoid accidents with it.

Thanks.

Kins regards,

Oscar

Hi Oscar,

It is hard to say just by the "feel".

Generally a problem will show up as battery damage due to overcharging, or batteries that appear to run down earlier than normal, indicating faulty batteries and/or a faulty charger.

I think you can only test the charger with some electronic test gear like meters, oscilloscopes and component testers.

The calculator charge plug and socket may be worn as could be the mains plug and wiring. The electrolytic filter capacitor is not rated for 40+ years of use, so it would be my first choice in new components. Then I'd have a good look at the circuit board condition followed by semiconductor, resistor, transformer checks.

cheers

Tony

[BusyCalc]

Hi Tony,

thanks for your information.

I'm a little bit worried about the "battery damage due to overcharging", because I read some threads regardind melted latch doors because of overheating in the battery.

As the charging times are so long, up to 24 hours with a 1.000 mAh battery, I'd like to avoid sleeping with one eye open.

If the capacitor were aged and faulty, wouldn't appear ripple in the output voltage? Or which is the exact purpose of the capacitor?

Kind regards,

Oscar

[teenix]

(05-26-2020 09:30 AM)BusyCalc Wrote:  If the capacitor were aged and faulty, wouldn't appear ripple in the output voltage? Or which is the exact purpose of the capacitor?

Oscar

Yes, the capacitor helps to smooth the rectified AC voltage from the transformer. If it fails, the voltage will have increased ripple and will affect the charger operation.

cheers

Tony