Spectrum Computing

Hey long time i didn't post nothing, this week i'll go to an important flea market for electronic in Modena. I hope to find some spare parts for my ZX (rubber keyboard, capacitors, etc..). Lately i was busy to repair some C64.

I want show you something curious... https://i.postimg.cc/SnKJzW4h/IMG-20190808-235455.jpg In this picture, you can see on my mat a white/beige shadow line pointed by my red probe. That is the result after cleaning the black dirt from the membrane. Seems like that IPA removed with the dirt also the ...

I'm now cleaning the keyboard sheet, I found these black dirty lines on the tracks, with IPA very easy!

I double checked the wires I soldered for Lower ram traces and I discovered a wire not connected! https://i.postimg.cc/gLx0Zp6p/IMG-20190807-WA0020.jpg Hurrah! Really happy to see this mate, I applaud your perseverance. Also big thanks to everyone who helped Hyuma, I knew I could rely on you when t...

I've noticed that with OTLA loading games some are working, some others not, dunno why... and not all keys are responding when i press... maybe the keyboard need some clearing or some other to check?

I double checked the wires I soldered for Lower ram traces and I discovered a wire not connected! https://i.postimg.cc/gLx0Zp6p/IMG-20190807-WA0020.jpg I download OTLA software and try to load some .tap: https://i.postimg.cc/MnJWWNqn/IMG-20190807-193132.jpg https://i.postimg.cc/mzBjBb6m/IMG-20190807...

Ram arrived! Check pictures. There is still issue.



I uploaded also a video, I pressed reset button after a bit.

http://imgur.com/a/0UGyyEQ

As a test, i checked all voltage on upper Ram module on pin 8 and i have all 4.98V.

Hey guys, I've tried the DRAM tester with 3 different faulty 4264 RAM. During the test, the green led is blinking and sometimes also the red blink, but at the end, the green one is on and on Serial monitor I've DRAM OK message. This is strange because RAM is faulty and it must be the Red led On. Any...

I sent an email to the guy of retroleum and he re-stock the item! I just bought 1 lower ram! Let's wait for it!

I just noticed that retroleum website has lower ram module out of stock... damn!

Can i do some tests now? (I still don't have ram) Sure! :D Test the voltages on pins 1,8 and 9 in the position where IC6 was (or any other of the 4116 or equivalent DRAM chip positions). With the negative probe to 0V/GND (e.g. the case of the modulator or the heatsink). Expected voltages: PIN 1: be...

Ast A. Moore wrote: ↑Tue Jul 09, 2019 11:38 am Looks like the CPU can fetch and execute the first few instructions, including a jump, from the ROM, which is great news.

Wow! I'm really, really, really happy today! Next step will be RAM!

I power on without ram for some seconds and the screen is bit better then before. THERE IS STILL LIFE! :D :lol: Now with new ZTX 651 and 7651 (without new RAMS) After some seconds I pressed the reset button and this is result: https://imgur.com/a/Se0bVKu this was before: https://imgur.com/raae8HW

With multimeter in continuity mode i got:

ZTX 651 values:
670, 671, 1, 1

ZTX 751 values:
670, 668, 1497, 1

Time for some updates, 751 and 651 are in place!





Can i do some tests now? (I still don't have ram)

yes, now next step will be buying rams and ZTXs

I think it should be connected to the pin 14 of IC7, but i'm waiting some confirm!

Hey guys, it's been a bit that I didn't update my post. Here some news: https://i.postimg.cc/t12y8gdb/IMG-20190701-172512.jpg https://i.postimg.cc/QBXh67TS/IMG-20190701-172529.jpg I put all the 7 sockets!!!!! And I'm very proud of me guys!!! Now I've a doubt, I dunno where to solder this pin: https:...

Hi guys, a little update. With a software I designed the lower ram pcb scheme to be sure not to make mistakes later when I try to restore the tracks. Did I do everything right? Thanks in advance for every reply.

I use this interesting topic to ask, as a novice that I am, if you know some video tutorials to learn how to use the oscilloscope applied to these vintage computers (zx spectrum, commodre 64, etc.). I would like to buy one, but I would also like to learn how to use it well.

Ok, on the next weeks i'll buy some new equipment to repair this damage. I will keep you informed on how it is proceeding. For now thanks to all!

Thank you mark! As regars schematrics diagram i found this: https://spectrumforeveryone.com/wp-content/uploads/2017/08/ZXSpectrumIssue6a-Schematics.gif But where i can find some schematics to restore the track of RAM that i have broken? i only found this: https://k1.spdns.de/Vintage/Sinclair/82/Sinc...

thank you! I understood your step, next days i'll try to fix the mess! If anyone use discord i'll glad to chat with someone just to have a moral support

Removing ram was a nightmare and there were serious damage: the RAMs hascrumbled when I pulled them out and some of the tracks were broken. http://i.imgur.com/Q4FlNTb.jpg http://i.imgur.com/KZu2W3Y.jpg http://i.imgur.com/BIzzRfO.jpg http://i.imgur.com/Pf5UVdz.jpg http://i.imgur.com/2fAWVy7.jpg what ...

Ok guys, it's been a while since last time I posted something. Today I removed the two ZTX



ZTX 650 and ZTX 213. So I have to buy Ztx651 and Ztx651 right?