QL Case Heat Warp

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Derek_Stewart
QL Wafer Drive
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Re: QL Case Heat Warp

Postby Derek_Stewart » Mon May 27, 2019 9:58 pm

Dave wrote:Does replacing the 7805 with a switching regulator to eliminate heat fix the problem?

With the QL sat in front of you, looked at from below, the screws are:

1---2---3---4
KKKKKKKKK MM
5---6---7---8

K is behind Keyboard, M is behind Microdrives.

Order was supposed to be:

5-8-1-4-7-2-6-3.

With this order and a bent lower, you never see stripped threads unless they're over-tightened.


Hi,

Should the screws not be tightened in balanced an oposite direction i.e.

1-8-4-5-2-7-3-6

Is a torque wrench required to get the equal torque on each screw.


Regards,

Derek
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Dave
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Re: QL Case Heat Warp

Postby Dave » Mon May 27, 2019 11:24 pm

Derek_Stewart wrote:Should the screws not be tightened in balanced an oposite direction i.e.

1-8-4-5-2-7-3-6

Is a torque wrench required to get the equal torque on each screw.


5 and 8 then 1 and 4, because the back row screws have 4x the thread area than the front row screws. The back end screws snug the case down first then the front screws make it square. 5 and 1 came before 8 and 4 because the long metal backing plate behind the keyboard has less give and more weight than the microdrive end, so again is less liekly to strip out.

The middle four screws are just done as an X, bottom right, top left, bottom left, top right.

When we had this discussion at Sandy, it wasn't decided due to my stripping out that thread but when I did strip that thread, Arnie explained Sinclair's order used at the factory. Arnie had designed plastic moldings before (he designed the Pot Noodle pot) so he was something the expert.

Honestly, I only think I remember it because his pot noodle design was something real world I could relate to. :)

Or he was totally winding me up. But I thought he was winding me up on racing motorbikes, and it turned out he wasn't.


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bwinkel67
ROM Dongle
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Re: QL Case Heat Warp

Postby bwinkel67 » Wed Jan 22, 2020 4:32 am

Interesting, I had never paid mind to the bend. I think I noticed it two decades ago and ignored it but just now, when coming across this thread, I looked at it and yup, major warp at the microdrive area. What maybe makes this worse is that the US QL's only have 4 feet so there's a lot of hanging surface area causing weight to drag it down on the weak spot. Everything fits tightly on mine though -- i.e. the top and the bottom match perfectly and don't require over tightening and the microdrives are square with that part (because I guess they are mounted independently).

Luckily I don't think this impacts the motherboard because it's only secured by three mounts on the bottom of the case (if I recall correctly). It does mean buying a new bottom doesn't quite work well for these QL's since both upper and lower cases wouldn't match. Wonder if I should put some sort of feet in the middle to help it out. The UK version had 6 feet, right?


tcat
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Re: QL Case Heat Warp

Postby tcat » Wed Jan 22, 2020 10:26 am

Wonder if I should put some sort of feet in the middle to help it out. The UK version had 6 feet, right?


Hey, sharp eye observation!

Only UK early models, latter Iss#6 and Samsung makes, all 4 feeters. Mine is UK and 4 feet as well, I have put two small plastic feet, self adhesive, IKEA style, they fit small circular marks on the bottom.

Currently looking for original plastic feet (flat no inside rim), as mine are degrading,..

Tom


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Outsoft
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Re: QL Case Heat Warp

Postby Outsoft » Wed Jan 22, 2020 3:36 pm

tcat wrote:Hi,

This topic I have wished to bring up for quite some time. Has anyone observed slight distortion of the case as QL warms up? I did. I was thinking what could cause such distortion. I tried to capture in the picture.

QL.png
The warp is apparent on the right, in the worst case, causing top lid touching down on MDV2 head board. Sinclair rectified with a stand off spacer (plastic collar).

Has it not to do with two distinct materials (PCB, case), being firmly fastened with screws, due to some thermal dilation, leading to sort of `bimetallic effect'?

Provided above correct, which really is only my assumption, could it be rectified by making mounting PCB holes oval rather than strictly circular allowing for thermal dilation to compensate?

Tomas


Oh no :-(



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