Sinclair QL no Video Fault

[Sme007]

Hi all, I hope someone may be able to help me. I recently dug my Boxed Sinclair QL out from the loft to see if it still works. I have a number of Microdrive’s with my programming and writings on that I would like to recover if possible. The QL is an issue 5 with a serial number of D12-048291 and seems to be in good clean condition.

I am connecting it to a modern Monitor using converters as I have both the RF to HDMI and the digital to HDMI converters and the fault is the same whichever one I use.

Once powered up, the fault I am getting is the Monitor is alternating between 5 seconds of “no signal” onscreen message and then 1 second of a blank white screen, then repeats.

The green power LED is on. If I press F1 or F2, MDV1 lights up momentarily. If I then type “DIR MDV1_”, MDV1 LED lights up. If I type “DIR MDV2_”, MDV2 LED lights up. From this I assume the computer is working, just a problem with the video output. I am reluctant to put an actual Microdrive in yet, as I don’t want to corrupt them not being able to see what’s going on with no screen.

I have changed IC28 – MC1377P to a new one with no improvement. From what I have read, a white screen could mean damaged memory chips, but would the computer still allow me to type stuff if it was that?

I would appreciate anyone’s input on this as I don’t know what to do next. Hopefully point me in the right direction.

Kind Regards
Sme007

[Popopo]

I have changed IC28 – MC1377P to a new one with no improvement. From what I have read, a white screen could mean damaged memory chips, but would the computer still allow me to type stuff if it was that?

I would appreciate anyone’s input on this as I don’t know what to do next. Hopefully point me in the right direction.

Hi!
Yes, that may happen (QL boot up even with a faulty RAM).
In order to find where is the problem and in anyway to protect your QL:
1. Do not use any device connected (at least by now) to your RGB output. Use RF.
2. Open your QL and take photos of your board, in particular elements where we could see the labels (type of RAM IC, board version, ROM versions, etc).
3. Measure the power supply output. There must be about 2 voltages if I remember right. 1 AC, 1 DC.

Re-seat the ICs and clean the sockets (CPU, ROMs, ULAs).
if power supply is OK (voltages in rank), I would try to turn it on and touch with my hand the RAM ICs, paying special attention in those could could be too hot.

That is what I would do, for sure an expert in this system could address you at the exact problem. But this process that I describe usually is the first start to find the most common issues.

Note: you have an speaker in your QL, depending in the ROM it beeps when you push a key. Do you hear something when holding a key pressed? Keep in mind, that QL after long time its original membrane become faulty. Thus no sound it doesn't mean something is wrong, just that keyboard membrane could be broken. Same goes about led MDV activity. QL usually try to boot up from MDV1 when it starts, so you may think it is because you typing when actually it is the normal booting process.

Note2: about led activity from my previous note, forget it. I didn't read your whole description. MDV2 doesn't light automatically so your QL is working.

[Pr0f]

The chip you replaced isn't required for RGB output - though it may affect it. The fact you are getting to the point of a working command line does suggest that the RAM is probably ok, as the computer would normally stop with a 'video pattern' before that point if it wasn't.

Do you have access to any older monitor that's not HDMI and therefore requiring a converter? A scart lead for RGB to SCART would allow you to test the video from the QL without requiring a converter.

The chip that produces the video output is the ZX8301 - next to the processor - they are known to fail if the video is plugged / unplugged whist it's on - as the outputs from this chip are not well protected. If the outputs had failed - that would mean a working QL without any video output.

So you have a few options depending on what's available to you:

1) Find a suitable lead to take you straight from composite video output to composite input on a monitor - the 8 pin connector for video has both composite and RGB signals available. You may also be able to go from RF on the modulator output to an ariel input on a TV.
2) Find an older monitor/telly and a suitable SCART lead and test the video output without a converter
3) If you have access to a spare ZX8301 - replace it and see if you then have video output.

[jobdone]

The modern monitor may not be capable of displaying the QLs output. I would recommend trying the picovga or output to a TV. A good option for this is the composite output. Also look into refelting those mdvs before trying them.

[Sme007]

Hi, Thanks for the quick replys, looks like I have to look deeper into it. At this moment, I do not have access to an old TV, so cant try the RF out properly. The way I am connecting at the moment are as follows:-

1) QL 8pin Out to Scart Connector - A 5V Powered Scart to HDMI converter Box - HDMI lead to HDMI input on the Monitor

2) QL RF out lead to a BNC connector - A 5V Powered BNC to HDMI coverter box - HDMI lead to HDMI input on the Monitor

I have a bad feeling that it is the ZX8301 chip as I have read that connecting and disconnecting the QL while it is powered could blow the chip. In the 80's, I only ever connected through a TV via RF lead so I had never used the 8pin out option. When researching how to connect to a modern monitor, I came up with option 1 above. At first I had a solid white screen, but unplugged it in and out while powered, and now I get the intermittant screen mentioned in my first post. I don't have access to another ZX8301 chip, so can't try swapping it out yet. I will try all the reseating things suggested, and report back if I get any new results.

Thanks again for the replies
Kind Regards
Sme007

[Popopo]

Hi, Thanks for the quick replys, looks like I have to look deeper into it. At this moment, I do not have access to an old TV, so cant try the RF out properly. The way I am connecting at the moment are as follows:-

Hi,
Not many modern TVs has not RF signal. That is a very good reason why nowadays I don't recommend Vid.comp mod, because almost every modern TV has RF signal input. Only very few has not. So I guess yours (by your reply) is one of those.

You have only 1 tv OK... but do you have any other device like DVD player or BlueRay player? they usually have RF and Vid Comp inputs. You could use them.
Well... do not forget to take photos of your Board once you open your QL and touch RAM ICs with your hands to check if one is very hot.

Waiting for your feedback!

[jobdone]

Here are a few ideas. Quite a few 'SCART TO HDMI' are only wired as composite only. The RF would be fairly non-standard too. In your first post you state that the mdv spins up after pressing F1/F2. if you are not running minerva, then yes I would say you are right in thinking the fault is ONLY the video(thus zx8301,broken trace/dirty socket,cable or monitor) and possibly just a case of finding a correct cable.

[tofro]

That would be my question as well: Has the QL ever worked with this converter and cable?

[Martin_Head]

You might also want to check that the +12 volt line is there. I think it's pin 14 of the MC1377.

I can't quite remember that if the 12 volt is missing, You get no composite video, or no colour.

[Sebright]

Just for info, I have a QL Scart cable that I used back in the day on a portable colour TV. When I tried the same cable recently it didn’t work on a more modern tv and that got me worried that I’d blown the video chip. But I got hold of a composite cable and that worked ok, which was a relief. That would be worth doing if you can find any display that has composite input. You can get the cable quite cheaply on eBay.

Cheers,
Alan