Re: fault on 48k spectrum, help needed
- From: Mentore <mentore.siesto@xxxxxxxxx>
- Date: Fri, 22 May 2009 01:04:24 -0700 (PDT)
On 19 Mag, 15:29, "Rich" <toc...@xxxxxxxxxxxx> wrote:
Hi, Ive got a 48k spectrum here that doesnt want to boot, Ive checked the
power supply and I got 10.5volts
I took the key off, and the heat sink on the right over speaker does get
warm, I only have a multimeter to check stuff where a good place to start or
a check list I see some circuit diagrams on the net but I assume there must
be the most comon faults work checking first? any help would be appreciated
?
will it still boot if I start it with the keybord ribbon cables unplugged ?
Thanks Richard
As Brian already pointed out, you can powerup the ZX Spectrum without
its keyboard connected.
The cold heatsink makes me think the 7805 chip is broken. You should
check for +5V between the rightmost pin and the center pin of the IC
connected to the heatsink, just to make sure.
Also, check if there's some noise coming from the power supply section
of the ZX Spectrum mainboard, near to the heatsink. This should tell
you that some section of the power circuit is actually on and working.
Check also the voltage between the leftmost and center pin of the 7805
IC. there should be a voltage between 8 and 15 V, which is the working
range for the chip itself.
This might be enough just as a starter.
Mentore
.
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