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Re: Useful inspections (capacitors a. o. things) before using a QL?

Posted: Fri Feb 23, 2018 12:01 pm
by 1024MAK
The difference between the environment for electrolytic capacitors in a QL and a ZX Spectrum is what makes the difference.
In a QL, they are in a case that is cooler inside compared to a rubber key ZX Spectrum 16k/48k. The ZX Spectrum+ is not as bad but still rather warm.

The electrolytic capacitors in the DC/DC converter section of the ZX Spectrum are worked hard and operate in a hot environment. The loss of the -5V supply generated by this DC/DC converter means that the 4116 DRAM chips loose their bias supply. They don't like this, and can die as a result... Hence it's best to replace them before failure ;-)

In a QL, with it's design of power supply, the electrolytic capacitors get an easier life (they therefore last longer). Plus, it's safe to run the machine until failure.

Most electrolytic capacitors are rated for 1000 to 2000 hours at 85 degrees C. So if run at 25 degrees C, especially if use is time limited, they can last for many, many years.

With regards to the electrolytic capacitors that were available after the 1980s, a lot of that problem was the drive to reduce size and cost while improving performance, and an alleged stolen but defective "new" electrolyte formula... With far too many companies jumping on the bandwagon...

Now that the manufacturers know about the problem, current production and recently made electrolytic capacitors should be fine ;)

Mark

Re: Useful inspections (capacitors a. o. things) before using a QL?

Posted: Fri Feb 23, 2018 3:01 pm
by YuT666
Thanks to all for your answers ...

I'll check some of the things when the QL arrives ...

Re: Useful inspections (capacitors a. o. things) before using a QL?

Posted: Fri Mar 02, 2018 3:18 pm
by YuT666
Well, it arrived. The QL is in a good optical condition, but the membrane is broken (offered as working). I ordered a new membrane anyway.

Re: Useful inspections (capacitors a. o. things) before using a QL?

Posted: Fri Mar 02, 2018 3:45 pm
by Dave
The new membranes sold by RWAP are of infinitely superior quality and durability. They will not expire during your lifetime.

Highly recommended.

Re: Useful inspections (capacitors a. o. things) before using a QL?

Posted: Fri Mar 02, 2018 4:20 pm
by YuT666
Bought mine from Sintech, 'cause the other seller is not my cup of tea (only my own opinion, so who cares).

I'll take a closer look, when I open the QL. I hope, that the membrane is the only faulty part (except the microdrives).

Re: Useful inspections (capacitors a. o. things) before using a QL?

Posted: Fri Mar 02, 2018 6:01 pm
by Dave
It's the same membrane. I haven't heard of Sintech before. Good to know there's a second source.

Re: Useful inspections (capacitors a. o. things) before using a QL?

Posted: Fri Mar 02, 2018 6:54 pm
by YuT666
Exactly ...

Re: Useful inspections (capacitors a. o. things) before using a QL? Update 24.03. - changed the membrane

Posted: Sat Mar 24, 2018 3:43 pm
by YuT666
Well, here we go ...

The new membrane finally arrived. The guys from Sintech wrote, that these are from 2015. I only heared of older ones (2010) before.

The QL (german) is in a very good condition, but the keys are not responding.

QL-1.jpg


QL-4.jpg


This is the new membrane from Sintech UK.

QL-5.jpg


And here is the old one. It doesn't seem to be broken and i can't see any damage. Very strange, 'cause it is in a good shape and very flexible. But it must be the original one ... the QL was sealed.

QL-6.jpg


... but anyway. Time for the new membrane. And it works . My new RGB cable is on the way and i'll get a Qubide soon.

QL-8.jpg