I refilled a catridge 4521 f, but toner is getting leaked at the one side of the toner, n whereas drum is perfectly good.

The toner cartridges have electronic chips on them that tell the copier when they are used up since all you did was refill the cart and did nothing with the chip then copier still sees a used cart get a OEM cartridge install it correctly

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

I would not recommend trying to refill a toner cartridge, you don't want to breath in the fine toner powder.
I suggest you purchase a new toner cartridge or a cheaper alternative, a re-manufactured toner cartridge for your model printer.

Clean the powder with inside with the blur. clean the toner drum from all the sides. shake a bit if still there is a power leakage then there is a problem in the toner,that needs to be fixed.

there are some possibilities for this problem. i will explain it. 1) First of all check out if the toner is full ,half or near to empty. There is no exact procedure to check the powder left in the toner without opening the toner.but in one toner there comes about near to 1500 copies.if you have got about 1200 to 1300 copies.then its quite possible that the power left is near to empty so the streaks comes on the paper due to less powder left.many times in this case removing and shaking the toner then reinserting the toner again and checking the printout helps. 2) But if you are sure that toner is not empty then other possibility is.in the toner cartridge there is a aluminium drum.its easily seen in the cartridge.once you remove the cartridge. if that drum is got very much used then due to that drum the streaks appear.fox example.if the drum is new the print is very dark.if the drum gets old the print gets very light or with streaks or faded print. 3) Now if drum and toner powder both are proper and still the problem then its the fault in the printer.in your printer there is some toner powder got spilled out on the inner parts from where the printing paper passes.so when the paper passes from the part where the powder is fallen or got collected then the streaks comes.in this case the printer needs internal cleaning and servicing. 4) but in some cases it has been noticed that internal powder of the toner becomes moist and very hard to come out from the toner for printing.in this case either toner needs to be refilled or toner needs to be replaced.you can get the toner refilled from local cartridge refilling store or local stationery shops dealing in cartridge refillings.The cartridge refilling shops also have the same printer for checking the cartridge.so at the refilling shop it will be confirmed whether the fault is in cartridge or printer.
This will help. Thanks please keep updated. please please do rate the solution positively .thank you for using fixya

r u a professional??
if so pull out the toner cartridge, unscrew from both side, gently remove the drum & the magnetic mesh roller, be careful that the teflon cover is not affected n there is spring on one side, clean the drum with a soft cotton cloth n keep aside, now clean neatly the container vessel & magnetic-mesh roller using a brush, refill using 'original' refill pack, don't refill till brim, reassemble all, after reassembly, clean all toner spills using soft cotton cloth, blow some heat on the drum using a hair dryer..itz ready
..always hv an expert supervision n always use genuine spare n refills..dis will make ur pc last long....

you can fill it by yourself.
1. buy good qulity magnatic toner powder.
2. basic for oppening 12a toner is 2 SIDE SMALL PIN, YOU CAN EITHER PUT THESE PINS INSIDE THE TONER WITH THE HELP OF HAMMER AND NAIL.OR OTHER TRICK IS TO FIRST OPEN THE GEAR SIDE TWO screw BY PHILIPS SCREW DRIVER and pick up drum then with the help of l type sharp longe nail try to pull pins from inside to out side this by process you see you get two part of toner cartridge one is wast chamber another is main chamber smaller one is wast cleane it .

open the both side of main chamber by unscrewing 4 screw ond pour the toner power powder in that main hopper and do all the steps in vice versa. your toner is filled TAKE A TEST PAGE.

I can frovide you photos step by step mail me [email protected] if neded

if you are using original hp catridge (not refilled) u got warranty exchange it

else change the drum it costs around 4$

Thank you
Take care
Bye

are you using non refilled genuine HP carts?