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Products => Test Equipment => Topic started by: djsb on May 27, 2023, 10:34:35 am

Title: Thandar LA4800 32 Channel Logic Analyser-Screen replacement/upgrade?
Post by: djsb on May 27, 2023, 10:34:35 am
I've dug out an old TTI Thurlby thandar LA4800 logic analyser out of storage.

https://www.brltest.com/pdf/pdf_analyzers/687.pdf (https://www.brltest.com/pdf/pdf_analyzers/687.pdf)

It fires up OK (battery needs replacing-no problem). However, the screen is very tired and worn out. Now I'm wondering if new life could be breathed into it if I could somehow fit a 9 inch Raspberry Pi screen to it?

https://www.ebay.co.uk/itm/271635467596?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&_trkparms=ispr=1&amdata=enc:16HsFN4UoSRqgsyHwgU5DUg82&customid=2aa923b7-4e1e-457d-a325-e95b6a970cf9 (https://www.ebay.co.uk/itm/271635467596?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&_trkparms=ispr=1&amdata=enc:16HsFN4UoSRqgsyHwgU5DUg82&customid=2aa923b7-4e1e-457d-a325-e95b6a970cf9)

Am I being crazy? Here is a brief description from the linked service manual

http://w.ko4bb.com/getsimple/index.php?id=download&file=06_Misc_Test_Equipment/Thurlby_TTi/Thurlby_Thandar__LA3200_LA4800_Logic_Analyzer_Service_Manual.pdf (http://w.ko4bb.com/getsimple/index.php?id=download&file=06_Misc_Test_Equipment/Thurlby_TTi/Thurlby_Thandar__LA3200_LA4800_Logic_Analyzer_Service_Manual.pdf)

Quote
The CPU board is a single board computer using a 6303X CPU running at
8MHz. The board contains 64K of non-volatile RAM, 32K of system RAM and
64K of system EPROM. The LCD screen generation is based on the M6255
LCD controller, which is programmed to produce 24 lines by 80 characters
of 7 by 7 pixels in text mode and 640 by 200 pixels in graphics mode.
The CPU board also contains the circuitry for the keyboard and RS-423
interfaces. The CPU board interfaces with the MAIN board via a 16-way
connection.

I've not done any physical measurements yet as it's early days. Any thoughts? If you need any further info, please let me know.

Thanks.

Title: Re: Thandar LA4800 32 Channel Logic Analyser-Screen replacement/upgrade?
Post by: djsb on May 27, 2023, 02:15:29 pm
Just found this that gives more insight into the CPU

http://musictechnologiesgroup.com/blog/?p=293 (http://musictechnologiesgroup.com/blog/?p=293)
Title: Re: Thandar LA4800 32 Channel Logic Analyser-Screen replacement/upgrade?
Post by: djsb on May 28, 2023, 08:01:53 pm
Some more info on hacking into a MSM6255 LCD controller.

http://dorkbotpdx.org/blog/paul/large_lcd_reverse_engineering/ (http://dorkbotpdx.org/blog/paul/large_lcd_reverse_engineering/)

I'm just gathering information that MIGHT be useful for now. The PJRC website may have additional information as well.
Title: Re: Thandar LA4800 32 Channel Logic Analyser-Screen replacement/upgrade?
Post by: nctnico on May 29, 2023, 09:14:10 am
I have done DSTN to TFT replacements but it is not easy. You'll need a CPLD (or small FPGA) with an SRAM to sample the exisiting display data (likely a 4 bit or 8 bit parallel bus with clock, hsync and vsync signals) and then convert this to signals that can drive a regular TFT screen. Sometimes the display data is PWM modulated to achieve various pixel intensities which means you need to capture several frames (2, 4, 8...) to make 1 TFT output frame. You'll only need 3 bit for the colors towards the TFT screen though. It all starts with capturing a few frames worth of display data and analyse the contents.

I'd look into how the backlight is working first and if that isn't fixable or OK, I'd look for a direct replacement of the display. Maybe you can find a cheap one that is better.