exxos's Atari, Amiga & retro forum

stephen_usher wrote: 28 May 2021 11:49 What happens if you change to a non-teletext mode, e.g. Mode 1?

If the Teletext chip has blown then you would get no display in Mode 7 (default) but would in the other modes.

Good tip, I will try.

Nice, I knew I could trust in you for some Burning Rifa action @rubber_jonnie :lol:

PhilC wrote: 28 May 2021 13:45 Nice, I knew I could trust in you for some Burning Rifa action @rubber_jonnie :lol:

Always!

:girldance: :girldance: :girldance:

stephen_usher wrote: 28 May 2021 11:49 What happens if you change to a non-teletext mode, e.g. Mode 1?

If the Teletext chip has blown then you would get no display in Mode 7 (default) but would in the other modes.

Interesting, the Teletext chip is from Mullard, a name that rings a bell as my uncle used to be a TV repairman.

Indeed, Mullard designed the Teletext system in the first place in the early 70s. I think the business was bought out by Thorn at one point.

stephen_usher wrote: 28 May 2021 14:42 Indeed, Mullard designed the Teletext system in the first place in the early 70s. I think the business was bought out by Thorn at one point.

Ahh, Thorn, there's another blast from the past!!

Interestingly, one of the places I go to get older components, Cricklewood Electronics, has them in stock, which is good. eBay also has them branded as Philips.

Oh, it might have been Philips who bought them then. I know that they got gobbled up.

stephen_usher wrote: 28 May 2021 15:05 Oh, it might have been Philips who bought them then. I know that they got gobbled up.

Bought one to have as a spare, in the middle of rebuilding the keyboard ATM on the replacement PCB.

Ok, status as of now is that the keyboard is almost rebuilt, bar 4 Fn keys that I've left off as I tested all the switches prior to reassembly for continuity and they all failed.

I've given them a squirt with contact cleaner, but no joy, so I'll just have to get some replacements.

I get a BooBip on boot, and the caps & shift lock work just fine as does the cassette LED.

The new problem is that I have no video output. Blind typed commands are clearly working but attempting to change screen mode makes no difference so potentially rules out a problem with the SA5050 Teletext chip, though I have ordered a replacement anyway.

I know the composite works fine on No3, and I can see a 15Khz signal on the composite output of No2, but I suspect it's not something the TV understands. I need to compare the signals so I can try and figure out whats wrong, so good vs bad.

I'll also see if I can get anything on the UHF modulator, but not that hopeful with the TV we have here.

Faults found so far? Dead CPU and bad keyboard. Let's see what's next.

Congrats & cheers! Whisky o'clock here, been diagnosing an A600 PLCC RGBtoHDMI adapter for the last 2 hours. It's giving everything a blue tinge, including the standard RGB out - anyhow looks like the flip flop might be duff as I'm getting a partial short on the red high bit. It worked when it arrived, replugged it and it's gone bad, bah.

So in short, I have some sympathy with you at the moment.

Have you tested those roms I sent in no3? No rush, just my OCD worrying that I may not have burnt them correctly :D