Oh! Would you recommend another forum? ZX Spectrum was much more common than ZX81 and I would expect it to have a larger community.
Now, suppose I have to do (I guess) 40 diagnostic steps to fix it, and one step takes a week, then we are not talking days, we are talking months.
No, I can't recommend another spectrum forum nor do I want to scare off spectrum users
1024mak is definitely our most active user and his expertise is great.
As you can easily spot I'm more into ZX80 and help there in the unlikely event of problems with a ZX80.
My personal impression is that the issue 2 is prone to problems. Late issues are far better regarding hardware reliability and colour.
If I had a broken issue 2 I'd leave it as it is and get my hands on a later model.
Just my 10 cents.
Probably true. But it's the Issue 2 from my childhood and the only ZX Spectrum I have at home, so I just do not have an alternative.
I don't understand what is the real problem? Sentimental attachment? In your opinion, would it be better if I just threw it away? Please answer honestly so I don't lose my time repairing.
Yes sentimental attachment is why we all are here.
I fully understand that you want to get it repaired.
It also bugs me if I have a machine that doesn't work when I know it could be working.
I don't own a issue two so it's easy for me.
I'd just think it's best to get it running and then keep it as it is. Any effort to get decent colour from it is wasted.
In my honest opinion get yourself a lower ram board and forget about internal power supply issues.
Maybe an upper ram board as well.
Yes I know it's possible to get a good picture out of it. But if you manage to do so you will have spent a bloody hell of time.
Get it running, give it a special place on a shelf and use your time playing with a newer machine.
In my case it's a spectrum next.
You must have mistaken me for someone else. I am not concerned by colour at all, well, at least not now. I just want to make it working first and then spend very limited time to tweak the details.
And after that, as you said, give it a special place on a shelf. I don't intend to get or repair another one but go back to Raspberry Pi and model railroads, which are my permanent hobbies.
Too late for this alley, I've already ordered 10 4116s and 10 4164s from AliExpress for about $10 (total, shipping included) with extremely low effort. And I would prefer to keep everything as close to original as possible.
Also, those boards are difficult to obtain and pretty expensive if you count in shipping and custom duties. I might create the board myself, but I would need a PCB. I have access to reflow oven and even did some SMD soldering manually.
I already did other stuff, but if I report too many things without getting the answers first, this thread will become a mess. In short terms, after I cleaned contacts, I get almost completely black box with no vertical lines, which is I believe a step forward. I also realised that when I change positions of two particular 4116s, the result changes slightly. So they are on my suspicion list despite they passed the DRAM tester test.