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Posted: Fri Oct 20, 2006 8:55 am
by andywilks
I thought I would post here details of the common problem affecting these sets.
Basically they are not a JVC set, but made by Akura in Turkey for them as a cheapie.
EEprom memory corruption is the biggest problem, this can give many symptoms, since all settings from tuning to picture width are stored as numbers in the memory.
There is a mod which changes the main microprocessor, the EEprom and 3 resistors to stop memory corruption/failure. Its not a DIY option, as once changed there are 155 different settings to set back up!!!- JVC don't supply the EEprom ready stored with even close to the correct values, but give a photocopy of a sample data set of all 155 from which is a starting point!!
My apologies to you if you have one of these, they are not worthy to have the JVC badge on them in my opinion. I know from other trade repairers the same chassis is used in quite a few other brands- and suffers the same faults there too.

Posted: Fri Dec 22, 2006 11:21 pm
by -pix
hi Andy,
is there any way to re-programe the EEprom when it has corupted?
i have a AV-28GT1BUF, that has been working just fine for 2 years or more. then suddently when changing picture-mode by pressing "ZOOM" button it got stuck in switching-mode, and keep going in standby an powering on (red - green - red - green light in power LED)

any info on how i may solve this problem :? ?


Posted: Sat Dec 23, 2006 1:00 pm
by andywilks
If you can't get the set out of standby then you'll need to fit another EEprom at least to get it to come on.

press I (info) and Mute keys together on remote to get into the service mode, but I suspect your set won't read remote commands until it has actually come out of standby... you can but try.

If you can get it to stay on and show you service mode then I'll send you the pdf setup data to go through and reset the Eeprom.

You can just replace the EEprom... but The micro causes the corruption, at random, and thus if you don't change that for the new type then corruption can continue to occur occasionally.

A BIN/HEX file of the correct data set may be available if you want to remove the 8 pin EEprom and reprogram it on a PC for example. (We have the EK version set here in the UK, your BUF version will of course vary slightly in some of the options, so I would suggest getting a BUF EEprom, and getting the data read before you fit it & after resetting the data values, so you have sample BIN files to reuse).

If all the above sounds foreign, then you need a techie to help you out.


Posted: Sat Dec 23, 2006 3:53 pm
by -pix
Well - it is not completly forgin, but my english is maby not state of the art..
I have not ben able to get it out of standby mode and access the service menu.. ( kepp pressing the menu I can get it to iluminate but no on-screen menu apears, when stop "tapping" the Menu button it goe's continue standby/on toggle ).
Guess that it is the IC502 you refere to as the EEprom.. and as I understand you sugest that I just replace it whit a new data empty one, right ?.

I will have access to a Prom burner ( after X-mas ). same case to get hands on a new EEprom.

Where do I get a BUF vertion of the EEprom ? - Is it a sparepart ?


Posted: Sat Dec 23, 2006 4:07 pm
by andywilks
A JVC dealer in Denmark will be able to order one from JVC... if you can't get one easily, I may be able to order & supply one for you, since all Europe spares come from the same point.

The EEprom they supply isn't blank, its just got a rough working set of data in there for whatever version of set its for. Then you need to go through service menu and set up (fine adjust) all 155 adjustments... the service manual has a list of sample values...why they don't supply the EEprom somewhere near those I don't know.

Someone with good programmer knowledge may be able to read the eeprom you have and experiment with some values to find some which work.

Good luck

I've experienced this problem too

Posted: Wed Apr 18, 2007 1:09 pm
by twid
I've come across one of this model with the EEPROM severely corrupted effecting the geometry of some screen modes. I spent some time "playing" with the service menu and have managed to get some aspects sorted but still have some problems with it. Do you have a list of the sample values for the settings for me to try and then tweak or will I need to purchase the service manual?

Posted: Thu Oct 01, 2009 10:12 am
by vulcan59
andywilks wrote: If you can get it to stay on and show you service mode then I'll send you the pdf setup data to go through and reset the Eeprom.
I know this is a really old discussion and I'm not sure if anyone is here anymore but I'll ask anyway.
I have one of these sets and the picture geometry has suddenly gone all over the place. Vertical lines are now at an angle and the left side and bottom of the picture has disappeared off the screen.
It's probably not worth spending a lot of time or money on this but I'm prepared to have a poke around in the service menu.
Andy, you mentioned a PDF of setup data above. Do you still have it? Would you be prepared to send me a copy if it would help me?
Many thanks for any help / suggestions.