The Sinclair QL Forum

Hello Everyone!

It must be about 4 years since I was last on here: a house move from Oxfordshire to the Lake District mean’t that all my computers were boxed up and are only now emerging from their hibernation!

Anyway, I finally have brought my QL out to set up. However, when trying to get my Issue 1 SuperQ board connected, this capacitor (Wima 0.1uf 63V) which was soldered right on the edge of the board came loose. Looking at the few photos online of the board (I’ve not yet tried working through the schematic), I’m not sure what the purpose of this capacitor, or the green ceramic disc one below the board actually is. Can anyone provide some insight, particularly in terms of replacement… does this capacitor have polarity, and what would be the best replacement for it (if needed)?

Many thanks in advance…

Simon

Looking at these pictures https://www.worthpoint.com/worthopedia/ ... 1475679431 it only has the one electrolytic capacitor, so the other two might have been added after the fact. And as there seems to be a voltage regulator below the heatsink it is common practice to have 2 100nF from Pin 1 and 3 towards ground (middle pin). You could get any 100nF foil capacitor (those are non polarized) or even some SMD capacitors and place them directly on the pins.

Thanks for that, it does certainly look pretty home modified, as the soldering is ‘lumpy’ at best. I guess I am curious as to why there are two very different capacitors added on to what look to be the same location, just either side of the board. As long as no-one can think of any critical reasons why these should be so, I’ll see what caps I have in my collection for a replacement.

Cheers,

Simon

Perhaps the previous owner had latch-up problems with regulator ? https://electronics.stackexchange.com/q ... -regulator

Simon_Carr wrote:I am curious as to why there are two very different capacitors added on to what look to be the same location, just either side of the board.

The different types of cap on the same location is because the red unpolarised one has a higher frequency response and the bigger one is for low frequency ripple smoothing. Since the red one was fitted you should solder it back or even replace it with a ceramic disc that is the usual cap for regulator suppression.

Thanks for the answers: I’ve managed to solder the original capacitor back into place, and the board seems to be working okay, so I’ll take that for now!

Thanks for the responses, I’m sure there will be more questions in due course!

This is an official mod at Sandy to make the regulator less noisy. Any small ceramic capacitor will do as long as it has the rated voltage. It can be added either side of the board.