I might try a Nebula ULA. I fitted a 1/4 resistor instead of 1/2 watt doing a R60 Mod and blew up the lower RAM and then got 22 volts on the 12 volt rail. Replaced the lower RAM but can only get blue or green screen adjusting the pots. If that does not work then perhaps the video chip.
Hi Damian, thanks for the comment. Sorry to hear of your misfortune there. It's all a learning curve though. I've mad loads of mistakes. Best way to learn IMHO and apart from the ULA, parts are cheap!
@@RetroComputingRebootI can't remember well so long ago. a stuck bit on a memory is a peculiar fix. On the later models you could swap over a link on PCB because there's a redundant half of chip unused. Keyboard membrane. 5 V regulator. The 9V power supply Oh yes I remember the BC9000 or whatever transistor often fail and couldnt use a normal to92 had to be the one sinclair told us
3:13 eutectic solder. nice choice. the contact cleaner reminded me of something i wanted to pass on earlier. there is a product called _"Tri-Flow"_ that is a mechanical lubricant (not for electronics work!) that is WAY better than WD-40. i was a locksmith for many years and we exclusively used Tri-Flow. WD-40 can leave a residue that will slowly gum up over time. so if you have locks, door hinges, or any mechanical device that needs lubrication, i HIGHLY recommend this stuff. it is made by 3M corporation and is a teflon based, drying lubricant. but beware, if any of this stuff gets on cloth or clothing, it WILL NOT come out. *_CAPACITOR TRIVIA :_* the "K" that is stamped on the metal cannister of some electrolytic caps is not there as an identifier of any sort. it is a planned "weak spot" in the can. that way if the cap blows out, it will almost always rupture where the "K" is stamped, rather than build up too much pressure and become a tiny bomb. soldering on a fat groundplane can be difficult, at best. but from what i saw, you were (de)soldering like a boss. it is important to note that when washing a board, you don't want to use "Rubbing Alcohol" that would be used for medical/massage purposes, but use what is being used in this video, which is 99.9% isopropyl. the rubbing alcohol contains oils and additives that can cause issues with electronics. i'm at the point in the video where you've popped in the new ULA replacement. the only thing about this replacement that i would do differently is that considering it is such a crucial part, i would run a Continuity test from the underside of the board, to the pins of the chip, just to be triple sure it was in properly. but, i tend to be a bit paranoid about these sorts of things...
Thanks John. As always I really value and appreciate your comments. I've learned tons just from you! Just in relation to the WD-40. Is there a problem with what I used. It isn't the standard WD-40, but a contact cleaner under the same brand. It doesn't leave that greasy lubricating residue like what WD-40 does
@@RetroComputingReboot _"It doesn't leave that greasy lubricating residue ..."_ yes, i saw. perhaps i need to work on my communications skills. 😀 it was simply that the WD-40 brand name reminded me of the Tri-Flow that i was meaning to mention earlier. i am a Texan and we don't always make sense outside of our own minds.
@brake_4_cake truth. this is why i grit my teeth when people try to use it as such. but it is so embedded in the consciousness that i finally came to the conclusion that it is useless to try an information campaign.
I did some research on this as I've never known myself. Apparently it was extra solder that was fitted to the tracks at the factory. If anyone knows better, please let us all know
@@WelshLad52 I do think it was extra solder, but I don't know how accurate this is. All I can say though is every Speccy board Ive seen, it's the same. Which supports that theory I suppose
They were all like that. All Sinclair pcbs were like that by the factory that did the pcbs. Maybe it's because of their process of hot air solder level. Didn't seem to do any harm. But the plate through holes fragile
Such a wonderful, classic machine!
Nice video.
Thank you
I might try a Nebula ULA. I fitted a 1/4 resistor instead of 1/2 watt doing a R60 Mod and blew up the lower RAM and then got 22 volts on the 12 volt rail. Replaced the lower RAM but can only get blue or green screen adjusting the pots. If that does not work then perhaps the video chip.
Hi Damian, thanks for the comment. Sorry to hear of your misfortune there. It's all a learning curve though. I've mad loads of mistakes. Best way to learn IMHO and apart from the ULA, parts are cheap!
I repaired dozens of these in the early 80s. Maybe 100. Remember a soak testing trick was enter IN BIN 32 (or 31?) to give it exercise
What sort of problems did you have back then?
@@RetroComputingRebootI can't remember well so long ago. a stuck bit on a memory is a peculiar fix. On the later models you could swap over a link on PCB because there's a redundant half of chip unused.
Keyboard membrane. 5 V regulator. The 9V power supply Oh yes I remember the BC9000 or whatever transistor often fail and couldnt use a normal to92 had to be the one sinclair told us
@jagmarc Pretty much same as now then 😂
not the ZTX650 and 550 then :0)
@@jagmarc
Yes that was it ztx650 Ferranti(?), a special strong one but the pnp one you could use a bc212L or just about any pnp @@rover214brian
3:13 eutectic solder. nice choice.
the contact cleaner reminded me of something i wanted to pass on earlier. there is a product called _"Tri-Flow"_ that is a mechanical lubricant (not for electronics work!) that is WAY better than WD-40. i was a locksmith for many years and we exclusively used Tri-Flow. WD-40 can leave a residue that will slowly gum up over time. so if you have locks, door hinges, or any mechanical device that needs lubrication, i HIGHLY recommend this stuff. it is made by 3M corporation and is a teflon based, drying lubricant. but beware, if any of this stuff gets on cloth or clothing, it WILL NOT come out.
*_CAPACITOR TRIVIA :_* the "K" that is stamped on the metal cannister of some electrolytic caps is not there as an identifier of any sort. it is a planned "weak spot" in the can. that way if the cap blows out, it will almost always rupture where the "K" is stamped, rather than build up too much pressure and become a tiny bomb.
soldering on a fat groundplane can be difficult, at best. but from what i saw, you were (de)soldering like a boss.
it is important to note that when washing a board, you don't want to use "Rubbing Alcohol" that would be used for medical/massage purposes, but use what is being used in this video, which is 99.9% isopropyl. the rubbing alcohol contains oils and additives that can cause issues with electronics.
i'm at the point in the video where you've popped in the new ULA replacement. the only thing about this replacement that i would do differently is that considering it is such a crucial part, i would run a Continuity test from the underside of the board, to the pins of the chip, just to be triple sure it was in properly. but, i tend to be a bit paranoid about these sorts of things...
Thanks John. As always I really value and appreciate your comments. I've learned tons just from you!
Just in relation to the WD-40. Is there a problem with what I used. It isn't the standard WD-40, but a contact cleaner under the same brand. It doesn't leave that greasy lubricating residue like what WD-40 does
A very good point you make with checking the ULA socket before fitting. In retrospect it would have been time well spent
@@RetroComputingReboot _"It doesn't leave that greasy lubricating residue ..."_
yes, i saw. perhaps i need to work on my communications skills. 😀 it was simply that the WD-40 brand name reminded me of the Tri-Flow that i was meaning to mention earlier. i am a Texan and we don't always make sense outside of our own minds.
@brake_4_cake truth. this is why i grit my teeth when people try to use it as such. but it is so embedded in the consciousness that i finally came to the conclusion that it is useless to try an information campaign.
@brake_4_cake evey day is a school day for me
Question: Why does the back of the board the tracks look Crinkly.
I did some research on this as I've never known myself. Apparently it was extra solder that was fitted to the tracks at the factory. If anyone knows better, please let us all know
@@RetroComputingReboot Yes if anyone knows it would be interesting.
@@WelshLad52 I do think it was extra solder, but I don't know how accurate this is. All I can say though is every Speccy board Ive seen, it's the same. Which supports that theory I suppose
They were all like that. All Sinclair pcbs were like that by the factory that did the pcbs. Maybe it's because of their process of hot air solder level. Didn't seem to do any harm. But the plate through holes fragile
@@jagmarc Agreed. The through holes are very fragile
How to restore a dodgy power pack connection would've been super useful 40 years ago!
40 years ago I'd have hoped I wouldn't have to 😁