Yo sigo con mis cosas..

haber desde un post de hace mil años de zacky files he dado con este post en un foro aleman:

http://www.forum.electronicwerkstatt.de/phpBB/topic8438_f38_bxtopic_repliesxDESC_by4_bz90_bs0.html

http://foros.zackyfiles.com/showthread.php?p=1338311&mode=linear

No dice mucho en si, tan solo que toco la eprom y que se le quedo que no encendia...

y aqui dice algo sobre las eprom de un receptor portugues:

This text describes the 24C04 EEPROM found in the TVCabo Geneesis set-top box (commonly known as "type 0 box" or "rf box"), made by Exsad, in Holland.

The EEPROM can be read/programmed trough the RJ11 interface available in the back of the box. This interface has 4 pins, let's call them |YGRB|, from left to right (looking into the interface).
Y - +5V
G - DATA
R - GND
B - CLOCK

The EEPROM seems to have 3 distinct zones.
Offsets 00h-21h: Memorized/Locked Channels Mask (1)
Offsets 80h-81h: Lock Code (2)
Offsets 100h-1FFh: Channel Frequencies (3)

(1) Bytes for Memorized (M) and Locked (L) are interleaved:
00h = MM1, 01h = LL1, 02h = MM2, 03h = LL2 ...
Each byte defines a bit mask for 8 channels (count starts at unexistent channel 0):
MM1 = 1111 1101 means channel 1 is memorized
MM1 = 0111 0101 means channels 1, 3 and 7 are memorized
MM2 = 1111 1100 means channels 8 and 9 are memorized
...
LL1 = 0000 0010 means channel 1 is locked
LL1 = 1000 1010 means channels 1, 3 and 7 are locked
LL2 = 0000 0011 means channels 8 and 9 are locked
...

Locked channels are automatically Memorized, independently of the corresponding bit in MM mask.

This gives room for 136 channels (8*34), or 135, taking into account channel 0 is unusable. In practice, only 127 are usable, and 126 should be the maximum used for perfect box behaviour (see (3)).

(2) Lock Code is in BCD (binary coded decimal) It has 4 digits, one for each nibble of the 80h and 81h bytes:
80h = 12h, 81h = 34h means code is 1234
80h = 01h, 81h = 93h means code is 0193
...

If any nibble is programmed with values different of 0-9, locking becomes unusable.

Default code seems to be 0000

UPDATE: below is a web forum post (portuguese only) showing how to override the box password (without eeprom access).

(3) Channel Frequencies take 2 bytes
The first 127 channel frequencies can be programmed (128, but channel 0 is unusable). After that, the channels wrap around to channel 0 (altough there is bad characters on the display). If a "perfect wrap" is required, channel 127 must be programmed with 0000h: this signals the last channel, and this technique can be (and is) used to reduce the available number of channels (and so reduce zap stressing). Only the first 99 channels are directly accessible via the numeric keypad, the remaining must be zapped to.

The channel frequency is encoded rather strangely. The following empirical form can be used to calculate the 2 bytes that correspond to a certain frequency:

IF = Integer part of channel Frequency
VP = Value to Program (must be converted into base16)

VP = ((IF*10 - 1960) * 2) + 4703

For some frequencies, it's possible that subtracting 1960 after multiplication by 10 leads to a negative value: there's no harm in that, and such value should be used as is.

Example for frequency 727.25MHz
VP = ((727*10 - 1960) * 2) + 4703
VP = ((7270 - 1960) * 2) + 4703
VP = (5310 * 2) + 4703
VP = 10620 + 4703
VP = 15323
Convert VP to hexadecimal and you get 3BDBh

Program this value in big endian format, i.e., the most significant value into the lower EEPROM address. For the example above, 3Bh should go in the lower byte of th EEPROM, and DBh into the higher byte.