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Re: General Stuff(tm)
Posted: 02 Feb 2022 23:40
by rubber_jonnie
Very well done sir!
Looks very cool and super useful.
Re: General Stuff(tm)
Posted: 03 Feb 2022 08:50
by JezC
rubber_jonnie wrote: 02 Feb 2022 23:40
Very well done sir!
Looks very cool and super useful.
@stephen_usher @rubber_jonnie Yes, definitely a great addition. I'm trying to save up for a decent scope but it's going to be a long time before I can get anything like that...very envious!
Re: General Stuff(tm)
Posted: 03 Feb 2022 10:09
by BennehBoy
want one :D
Re: General Stuff(tm)
Posted: 03 Feb 2022 10:36
by stephen_usher
Hehe... it was a random, "I rescued this dead oscilloscope from work. I've seen that you fix things, do you want it? I'll bring it around."
It's a nice 'scope but too big for every day stuff. If I were doing a fixing YouTube channel it would be very useful as it has VGA out, so it could be streamed via a capture device. But I don't make such videos, so... :-)
Re: General Stuff(tm)
Posted: 03 Feb 2022 10:40
by BennehBoy
Swap you a Hantek DSO for it :D
Re: General Stuff(tm)
Posted: 03 Feb 2022 10:42
by stephen_usher
hehehe... got one of those already. ;-)
Re: General Stuff(tm)
Posted: 07 Feb 2022 17:46
by stephen_usher
Having got back from my Dad's place (our birthday weekend) and put the 486PC and oscilloscope into storage I looked around for a quick project.
Somewhere I have an Issue 7 ZX Spectrum motherboard with a dead ULA and wondered if I could diagnose it, so went into the loft. I couldn't find that one but there was another spectrum which I'd been donated a while back which didn't work. This was a 6A in a Spectrum+ case.
Looks like this one has the TR4/TR5 fault as it's not generating the +12V and -5V required by the 4116 RAM etc. Otherwise it looks to be trying to boot.
I'll have to see if I can get a supply of those transistors.
I wish I could find that Issue 7 though as that could be more interesting.
Re: General Stuff(tm)
Posted: 07 Feb 2022 18:39
by rubber_jonnie
stephen_usher wrote: 07 Feb 2022 17:46
Having got back from my Dad's place (our birthday weekend) and put the 486PC and oscilloscope into storage I looked around for a quick project.
Somewhere I have an Issue 7 ZX Spectrum motherboard with a dead ULA and wondered if I could diagnose it, so went into the loft. I couldn't find that one but there was another spectrum which I'd been donated a while back which didn't work. This was a 6A in a Spectrum+ case.
Looks like this one has the TR4/TR5 fault as it's not generating the +12V and -5V required by the 4116 RAM etc. Otherwise it looks to be trying to boot.
I'll have to see if I can get a supply of those transistors.
I wish I could find that Issue 7 though as that could be more interesting.
Nice, always good to see a Speccy up for some TLC :)
Re: General Stuff(tm)
Posted: 07 Feb 2022 19:46
by stephen_usher
Definitely TR4. With not quite the right NPN transistor, the +12V is close to 12V but the -5V is bouncing between -1.4V and -2V so it's not woring correctly, but it's close...
IMG_2563.jpg
One of the correct transistors is now on order.
Re: General Stuff(tm)
Posted: 07 Feb 2022 20:18
by stephen_usher
Found a broken (cut?!) 2K2 resistor, which feeds the -5V line.
Even with the wrong transistor and holding the said transistor in the holes I managed to get to a "© Sinclair Research 1982" screen. So, once the proper transistor arrives it'll be a working machine again. (I couldn't take a picture for obvious reasons.)