Qume 119 plus terminal repair - Page 1
Forum section: electronics / repair

author: poot36
author_rank: Frequent Contributor
timestamp: July 13, 2017, 12:42:00 am
content: Does anyone have a schematic for the CPU board of this terminal? Got one in the shop that the monitor works but the CPU section does not fully boot.

author: poot36
author_rank: Frequent Contributor
timestamp: August 02, 2017, 02:35:32 am
content: Well I dumped the 3 EPROMs and found one of them is blank! The one I am missing is marked 96442-02. Does anyone know where I could find a copy of this chip? I have attached the dumps of the chips that have data on them (marked 96443-02 and 96444-02). If you can not open them try changing the extension to .bin (I changed it to .hex to upload it here). I am presuming that the 96442-02 is the bios boot chip. EDIT: the 96444-02 file attached to this post is corrupted (bad eprom) do not use it. See post 7 for the non corrupted version.

author: CJay
author_rank: Super Contributor
timestamp: August 02, 2017, 01:09:04 pm
content: Can't help with the EPROM contents or schematic but it could be useful to try cooling the chip and varying the VCC as you read it.Is it one of the Qume Paperwhite models?

author: poot36
author_rank: Frequent Contributor
timestamp: August 02, 2017, 01:19:08 pm
content: It has a green colored screen when running so I don't think it is a paperwhite model. You may be thinking of the QVT-52 model which has a white colored screen? This unit is from 1988 or 89.

author: drussell
author_rank: Super Contributor
timestamp: August 02, 2017, 03:02:28 pm
content: I have at least one Qume terminal hanging about but I'm not sure what model it is...I'll try to dig it up the next time I'm up where they are stored....

author: poot36
author_rank: Frequent Contributor
timestamp: August 05, 2017, 12:24:01 am
content: Well I just tried opening the blank eprom file in another program (was using notepad++) and there is data in it! So I am uploading it here as well. So I guess that there is another issue with the terminal that is causing it to not fully power on. Does anyone want to try these files with a z80 decompiler to tell me if they are corrupted or not?

author: poot36
author_rank: Frequent Contributor
timestamp: November 30, 2017, 03:01:45 am
content: Well an identical terminal with a video issue came into shop so I was able to dump its eproms and found out that the 96444-02 rom was the corrupted one. Also found out that one of the chips in the working terminal was labeled 96442-18 is identical to the chip in the originally dead terminal labeled 96442-02. I have attached the noncorrupted eeprom dump to this post.

author: james_s
author_rank: Super Contributor
timestamp: December 02, 2017, 12:35:42 am
content: I fixed a C-Itoh terminal that stopped working due to ROM issues. In that case I found the data had faded but I was able to read it with my EPROM burner and then simply write it back to the chip and that fixed it. I know there are some projects around to archive ROM images for various equipment, MAME has expanded beyond arcade games but I don't know if they cover terminals as well.

author: poot36
author_rank: Frequent Contributor
timestamp: December 02, 2017, 05:35:04 am
content: I have confirmed the eprom chip is self corrupting. It would erase fine but when I programmed it, it did not program correctly. Even though it did not correctly program it still allowed the terminal to boot but I left if on for around 5 mins and literally watched as the eprom corrupted itself even more causing graphics glitches on the screen and eventually crashing the terminal. It may be thermally sensitive but I did not investigate this very far.

author: james_s
author_rank: Super Contributor
timestamp: December 05, 2017, 12:07:17 am
content: I ran into an issue like this repairing an arcade game board several years back. It turned out the EPROM was not fast enough and I could program it and it would work fine at first but then gradually start to fade. I could still read it at lower speed and it verified ok but in the actual circuit it resulted in noise in the picture. They may get slower as they age in some cases, I don't know.

author: CJay
author_rank: Super Contributor
timestamp: December 05, 2017, 09:00:05 am
content: Knackered chips probably, but I've had success programming old, 'difficult' chips using a slower algorithm.However I'd much rather just replace the chips if they won't program using a 'proper' fast algorithm.

author: james_s
author_rank: Super Contributor
timestamp: December 05, 2017, 08:19:04 pm
content: In my case the original EPROMs were missing so I tried using whatever I had around which happened to be slow 450ns parts. They would work right off the bat but gradually degrade until at around an hour of operation the screen was all noise. They still read fine in the programmer though.I've also damaged a few EPROMs by leaving them in the eraser too long when I had one without a timer I got distracted and let them cook for a couple hours and after that they would not program reliably.