QL freezing after an hour

[Popopo]

No. This is how I got the machine. I think the mod may have been there in the past but was removed by the previous owner. What does the mod do? It doesn't prevent freezing by any chance does it?

You must place them.
It is for MDVs (if I am not wrong) but may affect other parts.

Is it common practice to replace the capacitors on a QL?

No.
Unless the visual could make suspect on them. By now, the most part of them are working, but Capacitors have a life that may be longer depending on the use, materials, building process and THE HEAT they may suffer. The heat is always the enemy of plastics and electronic components like Capacitors, logic ICs and transistors.

I do although I must admit I don't really know how to use it properly. I can probably measure a clock signal though. Is the idea to measure it when the freeze occurs?

I will try to guide you if the time comes. Now little busy to record a video.

IIRC the replacement voltage regulator is an MuRata OKI Switch Mode 5v rated up to 1.5amps. I bought it originally for a 128k Toastrack but never got around to fitting it to the Spectrum in the end. The freeze was happening before I replaced the voltage regulator but if this regulator isn't recommended, I'll swap it out. Thanks for the heads up.

Are they Murata?... I think the chip could be (I don't know the brand I'm afraid), but I buy those DCDC very low cost to China. They seem the same general DCDC as mine.
Well... I would recommend to use original one when something like your case, is hard to track. Better to be sure than to have another factor that may influence the tests.
I got with those like snow on the screen, I don't use them longer because the quality of image and just need few second for a comparative that I was writing to publish here month ago (I didn't finished it).

When time comes, if it were necessary I would measure with the Oscilloscope some power points and give them to you. That way you can check for noise in your power lines (if it were the case) through the time.

You can check photos of QLs boards on Internet and will see almost all of them have placed the resistors on Z8302. It is also mandatory in the Service Manual. Even if it is not related with the problem... do it (please).

Edit: checking about your Murata... it doesn't seem the same at all by Digikey nor even Mouser sites.
https://www.digikey.es/es/products/deta ... -C/2259781
So... by now, I still think it is the same Chinese DCDC that I use.

[tofro]

No. This is how I got the machine. I think the mod may have been there in the past but was removed by the previous owner. What does the mod do? It doesn't prevent freezing by any chance does it?

You must place them.
It is for MDVs (if I am not wrong) but may affect other parts.

Well, you should put them back if you want reliable micro drive operations. They are not related to your problem, though.

Is it common practice to replace the capacitors on a QL?

No.
Unless the visual could make suspect on them. By now, the most part of them are working, but Capacitors have a life that may be longer depending on the use, materials, building process and THE HEAT they may suffer. The heat is always the enemy of plastics and electronic components like Capacitors, logic ICs and transistors.

Agree. I have four QLs. None of them ever had problems with capacitors. The "leaky caps era" started like 5 years after the end of QL production.

I do although I must admit I don't really know how to use it properly. I can probably measure a clock signal though. Is the idea to measure it when the freeze occurs?

I will try to guide you if the time comes. Now little busy to record a video.

IIRC the replacement voltage regulator is an MuRata OKI Switch Mode 5v rated up to 1.5amps. I bought it originally for a 128k Toastrack but never got around to fitting it to the Spectrum in the end. The freeze was happening before I replaced the voltage regulator but if this regulator isn't recommended, I'll swap it out. Thanks for the heads up.

Are they Murata?... I think the chip could be (I don't know the brand I'm afraid), but I buy those DCDC very low cost to China. They seem the same general DCDC as mine.
Well... I would recommend to use original one when something like your case, is hard to track. Better to be sure than to have another factor that may influence the tests.
I got with those like snow on the screen, I don't use them longer because the quality of image and just need few second for a comparative that I was writing to publish here month ago (I didn't finished it).

If the regulator is rated for 1.5 amps, it should be fine and not related to your problem.

When time comes, if it were necessary I would measure with the Oscilloscope some power points and give them to you. That way you can check for noise in your power lines (if it were the case) through the time.

You can check photos of QLs boards on Internet and will see almost all of them have placed the resistors on Z8302. It is also mandatory in the Service Manual. Even if it is not related with the problem... do it (please)

[markdryan]

I bought the Voltage Regulator from Retroleum in the UK. If you search in this page for "MuRata OKI Switch Mode 5v Regulator for Spectrum 128 "Toast Rack"" you'll see it. Note, you're seeing the back of the regulator in the pictures of the QL I posted. I haven't noticed any new issues, e.g., snow, with the regulator fitted.

mdv_1 seems to work okay, mdv_2 is very temperamental but can be persuaded to work if the microdrive is inserted at just the right angle. I almost never use them, but I will reapply the mod if I can get to the bottom of the freezing issue.

Thanks so much everyone for your replies. I think my next steps will be to get some deoxit and some freeze spray and to wait for another hot day. I'll report back with my findings.

[Popopo]

Well, you should put them back if you want reliable micro drive operations. They are not related to your problem, though.

You are right 100%.
But, since it is a problem that appears only after some minutes (very difficult one to find out), I prefer to set everything as it should.
I don't know as well the machine to assert what affect directly or indirectly, but I know you knows much better than me the QL hardware.
It is more a my policy with equipment than another thing. Bad is not going to be

If the regulator is rated for 1.5 amps, it should be fine and not related to your problem.

About it... I have doubts.
The noise could affect a lot to the machine. How? many ways. Probably not this one, but I don't trust it. I have experience many issue after a while with some devices (in QL).
For example, screen noise, even doesn't boot the QL...
Those switching DCDC maybe start to fail after a while if the load is too big or surpass the operation rank (nominal... or what they say is nominal, cause I don't trust them too much). So, noise in the power lines that feeds the ICs of the QL, with enough time could introduce 1's or 0s when not and get freeze some components.

I was testing some and few introduce a lot of problems. In fact, there was somebody that asked me some help due to MDP and his SGC that didn't work all together. The problem was the DCDC that was replaced from a switching one. After changing it, the QL was working again fine.

Also I wanted to check the clock signal cause it is another common problem that may produce issues with time with a var of the main freq. I've never seen it, but I am aware of it thanks some radio techs that shares their experience.

[Popopo]

I bought the Voltage Regulator from Retroleum in the UK. If you search in this page for "MuRata OKI Switch Mode 5v Regulator for Spectrum 128 "Toast Rack"" you'll see it. Note, you're seeing the back of the regulator in the pictures of the QL I posted. I haven't noticed any new issues, e.g., snow, with the regulator fitted.

mdv_1 seems to work okay, mdv_2 is very temperamental but can be persuaded to work if the microdrive is inserted at just the right angle. I almost never use them, but I will reapply the mod if I can get to the bottom of the freezing issue.

Thanks so much everyone for your replies. I think my next steps will be to get some deoxit and some freeze spray and to wait for another hot day. I'll report back with my findings.

Ah, so that is the back of the DCDC?
About the shop... THIS IS ONE OF MY FAVORITES! very professional and good one. Very trustful one.

Later I will check again some facts.

[Pr0f]

The modification introduces a small amout of negative bias (-12v through 100K resistors) to the RAW inputs on the ZX8302. It is supposed to help with conditioning the signal from the Microdrive units.

It's one of a number of 'required modifications' that are listed in the service manual

[markdryan]

I think it's the CPU socket. I was using the QL last night, and true to form, it froze after 30 minutes or so of use. I hadn't completely put the machine back together after opening it up to take the pictures, and so I rebooted it, and with it running, I applied some gentle pressure to each of the socketed chips. The machine hung immediately when I pressed down on the CPU. I was able to reboot it and get it to hang multiple times just by pressing on the CPU. What's interesting is that I then let the machine cool down and tried to force the hang again by pressing on the CPU. This time it did not freeze. It continued to work without issue. I kept the machine running to give the CPU a chance to heat up and, after a while, I was able to reproduce the hang by pressing on the CPU.

Since I've already reflowed the CPU socket I guess it must be the socket itself, rather than a dry solder joint. Presumably, it stops making a good connection with the CPU when it warms up. Unfortunately, I don't have any sockets that size, so I'll have to order some. I'll report back when I've replaced the socket. Hopefully, replacing the socket will fix the QL.

I'll also put the resistor mod back while I'm working on the board. Is there a description of the resistor mod somewhere?

And I'm inclined to replace the connector on the motherboard for the LED wires. It's very flimsy and barely grips the wires leading to LED flickering. Is it normal to replace this connector? Is there a recommended mod?

[Pr0f]

The service manual mod list is here:

https://www.sinclairql.net/srv/qlsm4.html#s4c

I replaced that keyboard connector on a couple of QL's with a JST connector - it just makes life easier if you have to get inside the machne...

[Tesla]

Hi Mark.
Many years ago I had the same identical problem.
It was that one of the two JM rom was faulty.
I see that you mount a minerva.
Try another rom if you have it.
Best regards.
Marco