copy of article below incase the link ever breaks.
Troubleshooting Light Print Issues on the Xerox Phaser 6500 / WorkCentre 6505
I haven’t worked on a whole lot of these machines but one problem that I’ve ran into on more than one occasion is light print issues. Before I get started I want to explain that this article is for light print issues associated with a single color. If you have light print issues with the whole page you might want to move on because this article might not contain the answers your looking for.
First, I get a call to check a machine out that has light print. Upon arrival the customer informs me that over the last few days the print kept getting lighter and lighter. Finally, they replaced the cartridge but unfortunately that didn’t solve the problem. Most times I see this in black as that is the most used cartridge but it could happen in any color. Obviously lots of things can cause this problem but more often than not I’ve been finding it to be an issue with third party cartridges. I’m unsure exactly what happens but it would seem the cartridge runs out of toner before the chip tells the machine it is. Therefore the auger system empties out and the developer unit inside the Drum unit does the same thing. The only way to fix the problem is to put the machine into Diagnostic Mode and pump more toner into the auger and developer.
Troubleshooting Tips
1. Probably the easiest way to see if you have a toner issue is to remove the effected toner and one of the other colors.
2. Remove the Drum Unit – You must remove the cassette tray to open the front cover enough to remove. Careful not to damage or scratch the black transfer belt assembly as this will effect image quality.
3. On the right side, inside the print mech, is the end of the four augers that feed toner into the developer. Typically this area is usually dirty.
4. In the picture below you will see the toner motor gear, move the gear in the direction shown a few times. If there is no toner is the auger system the very little or no toner will come out the end in the front of the machine. Now do the same test from the good color cart that you previously removed. you should notice the difference in the amount of spillage between the two.
Note : For step 5 make sure the toner cartridge you are using is new. Recommend Xerox OEM.
5. If you do find that the auger is empty you will need to put the machine into diagnostic mode and run the toner motor for that selected cartridge. The service manual says to run the test with the cartridge out but in this case we will want to leave the cartridge in. Turn on the motor test for about 30 seconds. Then print off 10 to 20 pages. It might take a few pages to get the color fully restored. Now if that doesn’t work then you could try another 30 seconds. If that still doesn’t work then I would start looking some where else or take the cartridge out, cheat the side interlock switch and verify the motor gear is rotating.
Entering Service Diagnostics 1. Turn the printer Off. 2. Press and hold the Up and Down arrows simultaneously and turn the printer On. 3. Release the buttons when Service Mode and ESS Diag appear on the SFP display, or Service Mode, Printer, and Fax/Scanner appear on the MFP display. 4. Run the Toner Motor test: Engine Diag > Motor Test > (C)(M)(Y)(K) Toner Motor.
Exiting Service Diagnostics Scroll to Exit Mode, select Complete, then press OK.
Conclusion on the Light Print Issues
Obviously, this article only touches on specific problem with the light print issues. However, I’ve seen this enough to know it’s a real problem with these Xerox and Dell models. I hope this will help others find solutions to there problems. Not every problem is the same and this might not be the fix for your particular issue. If anything it might help you rule out several parts of the machine.
I have not coded Conway’s life in many years – I thought it would be fun to try on the Z80. First I implemented it in C on the Raspberry Pi. It uses an array to both keep track of prior generations (to determine if the pattern is still evolving) and the same array to figure out the neighbour count.
#include <time.h>
#include <stdlib.h>
#include <stdio.h>
unsigned char *grid;
const int rows=48, cols=160, maxt=3;
int same;
void* calc_grid(int *t) {
int i, j, q;
for (i=rows+rows-*t*rows/maxt-1; i>=rows+rows-(*t+1)*rows/maxt; i--) {
for (j=cols+cols-1; j>=cols; j--) {
if ( (grid[(i-rows)*cols+j-cols] & 64) ) { /* for each cell that is alive, add 1 to all the neighbours in every (8) adjacent cell */
grid[((i-1) % rows)*cols + (j-1) % cols] += 1;
grid[((i-1) % rows)*cols + (j ) % cols] += 1;
grid[((i-1) % rows)*cols + (j+1) % cols] += 1;
grid[((i ) % rows)*cols + (j-1) % cols] += 1;
grid[((i ) % rows)*cols + (j+1) % cols] += 1;
grid[((i+1) % rows)*cols + (j-1) % cols] += 1;
grid[((i+1) % rows)*cols + (j ) % cols] += 1;
grid[((i+1) % rows)*cols + (j+1) % cols] += 1;
}
}
}
}
void* shift_grid(int *t) {
int i, j;
for (i=*t*rows/maxt; i<(*t+1)*rows/maxt; i++) {
for (j=0; j<cols; j++) { /* for every cell take the 7th bit and the lower 4 bits (total) - empty cell =3 - live cell = 64+2 or 64+3 - then mark the 8th bit as live for next gen*/
if ((grid[i*cols+j] & 79) == 3 || (grid[i*cols+j] & 79) == 66 || (grid[i*cols+j] & 79) == 67) grid[i*cols+j] |= 128;
grid[i*cols+j] = (grid[i*cols+j] >> 1) & 240; /* shift to the right one bit, and keep the top 4 bits 128+64+32+16 to see what was going on in prior gens */
if ( same == 1 && ((grid[i*cols+j] & 64)>>2) != (grid[i*cols+j] & 16) ) /* compare the 7th bit to the 5th bit- if those are not the same, then the pattern is changing */
same=0;
}
}
}
int main() {
time_t qt;
srand((unsigned) time(&qt));
pthread_t thr[maxt];
int c, x, y, i, j, gen, t, rc;
grid = malloc(rows*cols*sizeof(char));
for ( c=0; c<1000; c++) {
// printf("Try: %d\n", c);
for (i=0; i<rows; i++)
for (j=0; j<cols; j++)
grid[i*cols+j] = 64 * (rand() % 2); /* initialize the array with random numbers in the 7th bit */
for (gen=0; gen<20000; gen++) {
for (t=0; t<maxt; t++) {
calc_grid(&t);
}
same=1;
for (t=0; t<maxt; t++) {
shift_grid(&t);
}
//if (same==1) break;
printf("Gen: %d\n", gen );
for (i=0; i<rows; i++) {
for (j=0; j<cols; j++)
putc( (grid[i*cols+j] & 64 ) ? '*': ' ', stdout);
putc('\n', stdout);
}
getc(stdin);
}
}
/* print out survivor */
printf("Gen: %d\n", gen );
for (i=0; i<rows; i++) {
for (j=0; j<cols; j++)
putc( (grid[i*cols+j] & 64 ) ? '*': ' ', stdout);
putc('\n', stdout);
}
free(grid);
}
I’ve made it very similar on the z80 in terms of the algorithm that is implemented. The grid it uses is smaller.
org 0100h
; to do a given cell, we need to do IX-1, IX+1, IX-81, IX-80, IX-79, IX+79, IX+80, IX+81
; board is 78x24 with an extra space all around so 80x26 - 2080 elements
ld a,0ffh ; do at most 255 generations
top: push af
ld hl,c_home
call my_write_string
call print_board
call calc_n
call calc_g
pop af
dec a
jr nz,top
ld hl,c_home
call my_write_string
call print_board
ret
calc_g: ; calculate the next generation
ld de, board
calc_g_loop:
ld b, 080h
ld a,(de)
ld c,a
and b
jr z,no_128
ld (de),a
jr end_calc_g
no_128: ; continue with calcs
ld a,c
ld b,79
and b
ld b,3
cp b
jr z, set_128
ld b,66
cp b
jr z, set_128
ld b,67
cp b
jr z, set_128
ld a,c
jr shift_mask
set_128:
ld a,c
ld b,128
or b
shift_mask:
ld b,224
and b
srl a
ld (de), a
end_calc_g:
inc de
ld hl,b_done
sbc hl,de
ret z
jr calc_g_loop
calc_n:
ld ix, board
ld de, board
ld c,040h
ld b,080h
calc_n_loop:
ld a,(ix+0)
and b
jr nz,calc_x ; found a 128 - skip calc
ld a,(ix+0)
and c
jr z,calc_x ; only increment if its currently alive
inc (ix-1)
inc (ix+1)
inc (ix-79)
inc (ix-80)
inc (ix-81)
inc (ix+79)
inc (ix+80)
inc (ix+81)
calc_x: inc ix
inc de
ld hl,b_done
sbc hl,de
ret z
jr calc_n_loop
; print_board: routine to print out board - uses a, bc, de, hl
print_board:
ld de, board
print_nl:
ld c, 00h
print_loop:
ld a,(de)
ld b,040h
and b
jr z,space_char
ld b,'@'
jr end_char
space_char:
ld b,' '
end_char:
call my_write_char
inc de
inc c
ld a,80
sub c
jr nz,print_loop
ld hl,crlf
call my_write_string
ld hl,b_done
sbc hl,de
ret z
jr print_nl
; puts a single char (byte value) on serial output
; call with char to send in B register; also uses A register
my_write_char:
in a,(3)
and 001h
jp z, my_write_char
ld a,b
out (2),a
ret
my_write_string:
in a,(3)
and 001h
jr z,my_write_string
ld a,(hl)
and a
ret z
out (2),a
inc hl
jr my_write_string
crlf: defm 0dh,0ah,0h
c_home: defm 01bh,"[H",0h
b_junk: defm 128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128
defm 128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128
board: defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,00,64,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,64,64,00,00,00,00,00,00,64,64,00,00,00,00,00,00,00,00,00,00,00,00,64,64,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,64,64,00,00,00,64,64,64,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,64,00,00,00,64,00,00,00,00,64,64,00,00,00,00,00,00,00,00,00,00,00,00,64,64,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,64,64,00,00,00,00,00,00,00,00,64,00,00,00,00,00,64,00,00,00,64,64,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,00,00,00,00,64,00,64,00,00,00,00,64,00,00,00,00,00,00,00,00,00,00,128
defm 128,64,64,00,00,00,00,00,00,00,00,64,00,00,00,64,00,64,64,00,00,00,00,64,00,64,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,00,00,00,00,64,00,64,00,00,00,00,64,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,64,00,00,00,00,00,64,00,00,00,00,00,00,00,64,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,00,00,00,00,64,00,64,00,00,00,00,64,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,64,00,00,00,64,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,64,64,00,00,00,64,64,64,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,64,64,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,64,64
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,64,64,00,00,00,64,64,64,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,64,64,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,00,00,00,00,64,00,64,00,00,00,00,64,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,00,00,00,00,64,00,64,00,00,00,00,64,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,00,00,00,00,64,00,64,00,00,00,00,64,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,64,64,00,00,00,64,64,64,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,64,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
defm 128,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
defm 00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,128
b_done: defm 128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128
defm 128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128
end
I’ve been trying to learn z80 assembler, and one of the programs that I typically do for that is writing a version of the Sieve of Eratosthenes. My version runs under CP/M on my CPUVILLE z80 computer.
; this program implements the sieve of eratosthenes on the z80
monitor: equ 046fh
cpm: equ 0fa00h
data_start: equ 1000h
data_end: equ 3000h
current_location: equ 0x3000 ;word variable in RAM
line_count: equ 0x3002 ;byte variable in RAM
byte_count: equ 0x3003 ;byte variable in RAM
value_pointer: equ 0x3004 ;word variable in RAM
current_value: equ 0x3006 ;word variable in RAM
buffer: equ 0x3008 ;buffer in RAM -- up to stack area
var_c: equ 0ffeh
org 0100h ; set origin of execution
ld de,data_start
ld a,00h
zero_loop:
ld (de),a
inc de
ld hl,data_end
sbc hl,de
jp nz,zero_loop
ld de,02 ; start sieve at c=2
main_sieve_loop: ; we are using de for this loop
ld (var_c),de ; store in ram too
ld h,d ; ld hl,de
ld l,e ; use hl to figure out memory location
srl h ; since we can store 8 bits in each memory loc
rr l ; we need to shift left (16 bit) 3 times
srl h ; https://chilliant.com/z80shift.html
rr l ; 2
srl h
rr l ; 3
ld a,10h
add a,h ; add 1000h to hl to get actual location
ld h,a ; here is the data in (hl)
ld a,00000111b
and e ; last 3 bits of de into a - will need srl a times
ld b,(hl) ; load the data into b
cp 0b ; compare a to 0
shift_a_times_1:
jp z,done_shift_1
srl b
dec a
jp shift_a_times_1
done_shift_1: ; a is garbage, b has the bit in the lsb position
ld a,00000001b
and b ; Z flag will be correct here if zero
ld (var_c),de ; store de in memory
jp nz,end_main_sieve_loop ; non zero - just inc loop and get out
; we found a zero, now need to loop and mark composites
ld h,d
ld l,e ; ld hl,de
ld b,d
ld c,e
start_composite_loop: ; de stores the value in this loop
add hl,bc ; start at 2 * de to mark composites
jp c,end_main_sieve_loop ; get out if overflow 16 bit
ld d,h
ld e,l ; ld de,hl
srl h
rr l
srl h
rr l
srl h
rr l
ld a,10h
add a,h
ld h,a ; here is the data in (hl)
ld a,00000111b
and e ; a has which bit to set
ld b,00000001b ; start with lsb
cp 0b ; is a zero?
shift_a_times_2:
jp z,done_shift_2
sla b
dec a
jp shift_a_times_2
done_shift_2:
ld a,(hl) ; retreive what is in memory
or b ; mark the bit
ld (hl),a ; write back to memory
ld h,d
ld l,e ; put hl back to where we were
ld bc,(var_c) ; put step into bc
jp start_composite_loop
end_main_sieve_loop:
ld de,(var_c)
inc de
jp nz,main_sieve_loop
ld hl,data_start
call memory_dump
ld hl,2f00h
call memory_dump
ret
Some time back I built a CPUVILLE Z80 single board computer. I used a USB serial cable to connect it to one of my Raspberry Pi computers. The issue that I faced is that my assembler skills are pretty sus at this point, and I would need to go to the computer to hit the reset switch. I made a simple circuit to allow using a GPIO pin on the Pi to reset the computer.
