751 leaking toner and throwing malfunction code.

[copyman]

Blame the Di-7210, Biz750, & Biz751 on Konica, these were Konica designed boxes even after the merge. Konica made the B&W, Minolta the color models. Anyway this is one of the worse machines made. A real toner pig! The main reason these models dumped was from developer contamination from paper dust. What a poor design with the waste toner being recycled! The paper dust, etc would crash the dev around 100k. Only time these worked half decent was if a tech would vac the waste toner every few weeks. And the 250k maint kits were done on time. Even with that this model was horrible!! And what makes it worse is Kon/Min kept this horrible design for more than 10 yrs!

[nullskull]

on the back of the drum there is a 3 digit number usually in the low 700s, this is the voltage you set the grid voltage to.
you measure from ground to the round shaft in the grommeted hole in the center and you run the adjustment in service mode and measure the voltage and + or - it to match whats on the drum.
did you do the developer calibration? the LD adjustment will help it less likely to overtone and spill as well.

look at the adjustment section, its all outlined what adjustment to do and in what order when replacing parts. (for best results of course)

Ok I finally found the chart that shows the processes to run after replacing a part. Got the grid charging manual adj and blade set finished. (Thanks btw for the help folks) Problem is it seems the toner control board (TCSB) is getting dirty as i keep getting 2202 and one 2801 codes. (2202 from malfunction detect and then booting in admin and then the 2801 most recently while trying to run auto max) And I get error 1 codes when I run auto max and auto laser. Is there a trick when i'm installing the drum and knife back in to make sure it doesn't get any setting powder on the sensors? I've opened it once already and found that. Once i get that completed do I need to restart all the processes from start?

[Synthohol]

you are supposed to do the adjustments when parts are brand new, this gives a baseline for the machine to operate. once the machine adds toner to the developer the adjustments are almost useless.
also for setting powder you tap the bag on the drum while its in the machine, roll drum backwards a bit, lift the blade and roll the drum backwards, release the blade and roll forwards to coat the blade. i mean thats how i did it for 20 years, i didnt allow the setting powder to come in contact with the density sensor.

[Albonline]

Yes this machine will be very low volume so I should talk to the boss about selling it. But in the meantime what sort of mods can be done?

The drum grounds through the shaft via a copper tang, it becomes intermittent during rotation, developer bias voltage is also through a bearing, loss of continuity allows drum charge to bleed into developer. magnet angle and h cut adjustments help a lot also. if its already spewed developer into the adu and hv unit inside it you will also need to deal with that mess. spewed developer also makes its way to the fusing unit. importantly the toner misting collection system will need to be cleaned out or it will just happen again.

[Albonline]

search 601 751 spewing on this site there were many posts about this issue.

[nullskull]

Seems like i've gotten the machine mostly working except for the C-2202 codes. I've checked for a flipped blade but i'm not sure if there is one. Inserting a metal ruler underneath the dev roller does go in but not a ton. Is it obvious from the outside if the dev unit has a flipped blade? I don't really want to dismantle the unit. Or could there be any other reasons for the 2202 code?

[Synthohol]

C-2202

An error of the EM signal is detected when a specified period of time elapses after the developing motor (M3) turns ON.

Developing motor (M3) Printer control board (PRCB)

check the coupling of the dv unit and make sure it turns fairly easy but not too tight. also the coupling in the machine that mates up.
if all ok then check m3 motor.
run load check

1. "Service Mode screen"Press [State Confirmation].

2. "State Confirmation screen"Press [Load Check].

3. "State Confirmation screen"Enter the check code and the multi code with the sheet number setting key.

4. Press Start key.The load specified operates.

5. Press Stop key.The operation of the load is completed.

6. When conducting the output check of other loads or signals, repeat Steps 3 to 5.

7. Press [OK].State Confirmation screen appears.

41	0	M2/M3	Drum motor (LS357) and developingmotor	The Developing motor also turns on at the same time
1	M2/M3	Drum motor (LS300) and developingmotor	The Developing motor also turns on at the same time
2	M2/M3	Drum motor (LS178.5) and developingmotor	The Developing motor also turns on at the same time
3	M2	Drum motor(LS357)	Developing motor OFF
4	M2	Drum motor(LS300)	Developing motor OFF
5	M2	Drum motor(LS178.5)	Developing motor OFF
6	M3	Developing motor(2500rpm)
7	M3	Developing motor(1500rpm)

if all passes it may be a PRCB problem.

[Albonline]

Seems like i've gotten the machine mostly working except for the C-2202 codes. I've checked for a flipped blade but i'm not sure if there is one. Inserting a metal ruler underneath the dev roller does go in but not a ton. Is it obvious from the outside if the dev unit has a flipped blade? I don't really want to dismantle the unit. Or could there be any other reasons for the 2202 code?

the h cut blade is visible from the top the aluminum part , there is nothing to flip in the developer unit. the blade edge becomes rounded when i was rebuilding these i would remove the blade and retrue the edge by sanding it down on a glass table. 10 sheets of 20lb paper as gauge between blade and developer roller wear on this blade will cause developer to be crushed past the cut point destroying the superball coating on the developer beads.

[nullskull]

I ran all the load checks. And nothings seems to be the issue. I think you must be right then. PRCB should be replaced? Or can it be repaired?

[nullskull]

the h cut blade is visible from the top the aluminum part , there is nothing to flip in the developer unit. the blade edge becomes rounded when i was rebuilding these i would remove the blade and retrue the edge by sanding it down on a glass table. 10 sheets of 20lb paper as gauge between blade and developer roller wear on this blade will cause developer to be crushed past the cut point destroying the superball coating on the developer beads.

I think I found what you were talking about . It's held down with two screws underneath the lid for the dev unit? I removed it and found that the blade was pretty worn.

Screenshot 2025-02-03 162713.jpg
(PM has no label for this for some reason)

[Synthohol]

can you cheat the door and see if the dv unit is spinning on warmup?
honestly if the bias adjustment was not done at developer change it prolly ran so low on toner it was hard for the auger to turn in all that metal powder.
how hard is it to turn it by hand?

[copyman]

I may have the PCRB, Dev unit, and other parts removed from a low meter Biz 601 if you need them. PM me. Shipping to USA only.

[Albonline]

I think I found what you were talking about . It's held down with two screws underneath the lid for the dev unit? I removed it and found that the blade was pretty worn.

Screenshot 2025-02-03 162713.jpg
(PM has no label for this for some reason)

they intend you buy the whole developer unit. fix the blade, reinstall it put fresh supplies in it run the drum carriage adjustment . the anti misting system must be clear .

[nullskull]

can you cheat the door and see if the dv unit is spinning on warmup?
honestly if the bias adjustment was not done at developer change it prolly ran so low on toner it was hard for the auger to turn in all that metal powder.
how hard is it to turn it by hand?

Yes it's spinning on warmup. It's not too hard to turn. But it is probably harder to turn then it should be. I think you are correct with what happened to the dev unit. I had a suspicion that the dev replacement couldn't be so simple. I only read the replacement procedure under the maintenance section. Guess i really should read the manual more thoroughly. oof

[nullskull]

I may have the PCRB, Dev unit, and other parts removed from a low meter Biz 601 if you need them. PM me. Shipping to USA only.

Thanks I appreciate that but I'm in Mexico and besides I think i got one of those machines back in storage for parts.