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The Iss2 trace, on re-measuring, now looks the same as the Mk II one. Most likely an error on my part. The fault on the PSU turned out to be a lack of -5V owing to a blown fuse. That fuse had already been uprated to 125mA (from 100mA) as per a recent recommendation. It hadn't died a violent death an...

Thanks for that Steve. That's what I'd assumed but, as the waveforms were significantly different, I thought it wise to ask this expert forum. The attachment shows an Issue 2 IC14 pin 3 and a MkII IC14 pin 6. Sync.zip Pin 6 wasn't working as the sync input to the RGBtoHDMI (no amount of adjusting RV...

Thanks for that Steve. Yes, I tread warily with mains PSUs, restricting myself to like-for-like repairs. Very useful info wrt the board DC/DC converters, thanks. Incidentally, the EMI filter I'd used with only partial reduction of the speckles was https://www.ebay.co.uk/itm/155933304852 . I had trie...

The RGB2HDMI cable documentation specifies that the sync should be picked up from IC14 (74LS86) pin 3. That works nicely for Issue 2 boards. I'd be grateful if someone would tell me the equivalent pin for Mk II boards. There are rather substantial changes in the schematics of those two boards.

I've got a few Dragon 32s, one with the original internal PSU PCB and two with the internal SMPS supplied by dragonplus (thanks John). The first is powered by the original transformer, the other two by a 12V wall wart. All three use an external RGBtoHDMI (analog) to produce a colour display. The fac...

How is the converter powered? That could be a source of noise. Have you tried going direct to the composite input of a TV? Do you have more than one Dragon transformer to try? The converter is powered by a 5V DC wall wart. The original wart failed mechanically rather than electronically but its rep...

All my Dragons, before a couple were modified to accept an external RGBTOHDMI, suffered from vertical jail bars and something resembling horizontal hum bars on the display. My original display setup was: Original Dragon PSU->Dragon->SCART to HDMI converter->LCD display. The vertical jail bars were n...

Thanks all.

It seems that's time enough for all to reply who might do so. However, if you happen to remember what the problems were in adapting the Hoglet board to the Dragon my curiosity is still piqued (but isn't itching quite as much now that the RGBTOHDMI is hooked up).

Alan

Thanks Stew. It's so easy at the moment to slip back into a 6502 style of thinking. I remember doing a 64bit multiply on the 68000 using mulu. At some stage I may dig that method out, convert it to 6809 and possibly add it to the library.

Alan

Thanks Mike for the detailed reply. Much appreciated. I prefer quiet and considered to loud and frequent so it looks like I've joined the right group. People can rest assured that this degree of posting is unusual for me.

Alan