Another speccie restored, yeah. I'm a Commi guy so rest entertained by watching your videos. This barrel plug center pin got broken strangely. Good you had it replaced because the other two pins both would be ground. Enjoy your holiday and the rest of the summer!
This is the first Amstrad made Spectrum but it's not the last Spectrum - there's the +3 which has a built-in 3 inch disc drive, and the black +2A/+2B which have tape players and the PCB is based on the same redesigned board as the +3 .. they have a square gate array chip that provides the glue logic taking place of the ULA.
Checking the supply voltages should always be the first thing you do not something you do way down the time line! Saves a lot of time and possible additional chip damage.
I agree with the other person who said that it's the IORQ signal connected to the ULA at the transistor. A0 can pull up IORQ, but it seems that IORQ is never going low, so you just get a constant high level. (3V is a valid TTL high) Maybe the CPU is not executing the code properly. Maybe due to the odd waveform you found on some data bus pins. Have a nice visit to Hong Kong.
I know you’re not going there for electronics, but I have been there many times and you at least have to go to Apliu street for some electronics, and maybe a visit to the market at Sham Sui Po. And have diner at “good luck Thai food”, this restaurant is in the middle of the Hong Kong nightlife district. There are so many things to see there, the beach, the jungle (with monkeys) and the horse races are great places to visit too. Regarding the speccy, the tea2000 video chip needs 12v, also the databus and address bus are fine, it’s running the diagnostics so no problem there. If you can’t find the ztx650, I have some NOS and can send some to you. Enjoy your holiday!
It is always a good idea to do some homework before opening up a machine... You are wrong in thinking that 12V is not needed, if you check the schematics, you will see that the video encoder IC needs 12V to work. This machine is working, you can see that from the diagnostics, all that blinking and beeping indicates a working machine. All you need is to replace that transistor for the 12V rail to come back up. You should not use an "equivalent" there, especially BC series, ZTX651 will do well. Also BC series transistors have a different pin layout, you can't just solder one in there and expect it to work. And Spectrum +2 Grey is NOT the last Sinclair made machine, it is the first Amstrad made Spectrum, a big clue is all those AMSTRAD logos on the board and the ICs. The last Sinclair made Spectrum is the Toastrack.
Tommy, you and yours stay safe out there and have a wonderful vacation. I'll be here when you get back.
Thanks!
I hope we will see you back after your vacation!!
I will be back :)
Another speccie restored, yeah. I'm a Commi guy so rest entertained by watching your videos. This barrel plug center pin got broken strangely. Good you had it replaced because the other two pins both would be ground. Enjoy your holiday and the rest of the summer!
Excellent! I am building a ZX Max +2A new from PCB.
Have fun!
Enjoy your vacation! Hope you have a wonderful time!
Thank you, I will
That is one rare transistor to find. ZTX650, i've never seen them before. But that replacement ZTX651 is not rare. Very lucky.
Yes indeed
Greetings form Türkiye to Norway. Nice video, thanks ❤
Thanks for watching!
30:56 I think that signal on ULA pin 40, or at least the signal going into the transistor, is IORQ (I/O Request), and it may be an active low signal.
Ok, thanks!
Enjoy your vacation! Hong Kong would be an interesting trip.
Can't wait!
This is the first Amstrad made Spectrum but it's not the last Spectrum - there's the +3 which has a built-in 3 inch disc drive, and the black +2A/+2B which have tape players and the PCB is based on the same redesigned board as the +3 .. they have a square gate array chip that provides the glue logic taking place of the ULA.
Thanks!
Checking the supply voltages should always be the first thing you do not something you do way down the time line! Saves a lot of time and possible additional chip damage.
I use a modern, well known power supply
I agree with the other person who said that it's the IORQ signal connected to the ULA at the transistor. A0 can pull up IORQ, but it seems that IORQ is never going low, so you just get a constant high level. (3V is a valid TTL high) Maybe the CPU is not executing the code properly. Maybe due to the odd waveform you found on some data bus pins. Have a nice visit to Hong Kong.
Thanks!
Enjoy the vacation!
I know you’re not going there for electronics, but I have been there many times and you at least have to go to Apliu street for some electronics, and maybe a visit to the market at Sham Sui Po. And have diner at “good luck Thai food”, this restaurant is in the middle of the Hong Kong nightlife district. There are so many things to see there, the beach, the jungle (with monkeys) and the horse races are great places to visit too.
Regarding the speccy, the tea2000 video chip needs 12v, also the databus and address bus are fine, it’s running the diagnostics so no problem there. If you can’t find the ztx650, I have some NOS and can send some to you.
Enjoy your holiday!
Thanks a lot! I want to visit some electronics markets of course :)
I realized now that the machine needs 12V to run. I have ordered some zxt651's already. Thanks a lot for the help!
Have a good vacation.
Thank you :)
Looking forward to part 2 (possibly part 3 given the state 😂)
Me too. I actually got some (but not all) replacement key-caps now
Have a good holiday!😀
Thanks!
I would love to add one of these computers to my collection but they are very scarce in the US.
I saw a couple on eBay. But quite pricey
Thank you for the video !
My pleasure!
It is always a good idea to do some homework before opening up a machine... You are wrong in thinking that 12V is not needed, if you check the schematics, you will see that the video encoder IC needs 12V to work. This machine is working, you can see that from the diagnostics, all that blinking and beeping indicates a working machine. All you need is to replace that transistor for the 12V rail to come back up. You should not use an "equivalent" there, especially BC series, ZTX651 will do well. Also BC series transistors have a different pin layout, you can't just solder one in there and expect it to work. And Spectrum +2 Grey is NOT the last Sinclair made machine, it is the first Amstrad made Spectrum, a big clue is all those AMSTRAD logos on the board and the ICs. The last Sinclair made Spectrum is the Toastrack.
Ah, thanks. That's might be the fix then :)
The ULA needs to be head sink or you can damage it.
Yes, I did not have it on that long. I checked the temp
❤❤❤❤❤ nice honey❤❤😘