It's lovely that you go back to the roots and keep the basic Tests in now and again so that new viewers can get a graap. Also, i like when you do a deep dive and do t blindly go for what the diagnostic tools say! :-) Well done, mate!
i've had a difficult to find ram issue in a timex sinclair ts1016 rampack(for ts1000 or zx81), i usually test these behind a memotech 16k set to master so the test ram is out of the normal address space, so not(hopefully) affecting booting, it tested ok poking 170 then 85 in each location, but wouldnt work on its own on a machine, it'd boot but quickly crash when entering program lines, or even trying to read ramtop system variable, when doing random value pokes then read, there was occasional failures all on bit 2, so one 4116 a bit suspect
Sounds quite similar to this case. I built my own ram tester breadboard once but it only wrote values to each and read them back, it certainly wouldn't have found this issue
@@HappyLittleDiodes the 'usual' easy BASIC test of 85 then 170 showed no problems, but random value pokes to locations in turn then reading (using RAND 1 before each pass to ensure same lot of random numbers) resulted in odd failures of bit 2, sometimes high when should be low, sometimes opposite!
@@Doombrain tr4 and 5 generate the +12 and -5v bear in mind a shorted tr4 can damage the coil, not blowing it open but causing shorted turns due to overheating, this cant be tested by resistance checks, only way to know for sure is replacing, or remove and rewind using 30swg enamelled copper wire
Update!
The machine has now had a full service and is good to go 🎉
😊
It's lovely that you go back to the roots and keep the basic Tests in now and again so that new viewers can get a graap.
Also, i like when you do a deep dive and do t blindly go for what the diagnostic tools say! :-)
Well done, mate!
That shirt & tache combo? Click like right away.
I stand by it
That is a very good book. I remember reading front to back in the 80’s. I can’t find my copy anymore though.
Awesome explanation, magnificent moustache. 10/10
That is indeed, a great book. I still frequently refer to it, as well as Rodney Zaks' masterpiece.
Super-informative. Even I could follow this 👍
Is that Lee's old desoldering tool?
Yes it is! Super handy for jobs like this
Lovely diction and flow throughout the video. I bought a pair of ceramic tweezers from Retroleum which are a great replacement for the screwdriver :)
2:00 wow this is one sick scheme. c1 to c4 is shorted, and -5 is shorted to ground, all by design
😂 the schematics have their issues, they should have represented the decoupling caps a bit better
Yeah you're right - it shows the 0V and -5V shorted together at 2:10. I think that 22nf cap at the bottom needs to move to the left.
First time seeing a bit deeper checking on the diagnosing on the memory
Cher! Lovey video, nice little repair
Спасибо, отличный контент.
Спасибо
good job
Cheers!
i've had a difficult to find ram issue in a timex sinclair ts1016 rampack(for ts1000 or zx81), i usually test these behind a memotech 16k set to master so the test ram is out of the normal address space, so not(hopefully) affecting booting, it tested ok poking 170 then 85 in each location, but wouldnt work on its own on a machine, it'd boot but quickly crash when entering program lines, or even trying to read ramtop system variable, when doing random value pokes then read, there was occasional failures all on bit 2, so one 4116 a bit suspect
Sounds quite similar to this case.
I built my own ram tester breadboard once but it only wrote values to each and read them back, it certainly wouldn't have found this issue
@@HappyLittleDiodes the 'usual' easy BASIC test of 85 then 170 showed no problems, but random value pokes to locations in turn then reading (using RAND 1 before each pass to ensure same lot of random numbers) resulted in odd failures of bit 2, sometimes high when should be low, sometimes opposite!
"Trump's turn" - I laughed my head off 😅
Political battles happen in the background from time to time here 😂
👕
🌵
The issue 2 I repaired two years ago has lost its 9v 😢
9V? That's the PSU then right?
@ from the psu is fine. Diag board shows no 9v and won’t boot. Think it’s tr4&5
@@Doombrain tr4 and 5 generate the +12 and -5v bear in mind a shorted tr4 can damage the coil, not blowing it open but causing shorted turns due to overheating, this cant be tested by resistance checks, only way to know for sure is replacing, or remove and rewind using 30swg enamelled copper wire
@ it’s got a tracko in now
Check the schematic, see the path from 9V to the edge connector, something along that path must be open circuit or pulling 9V out of tolerance
Why don't you go deeper and fix the internal leakage between the memory cells? 😂
My wedge iron tip is a bit clumsy in the micron range