Print Page - Yet Another not running CPC464 ^^' (LED doesn't light up)

Title: Yet Another not running CPC464 ^^' (LED doesn't light up)
Post by: GhostLine on 13:49, 14 June 22

Hi guys !

I've collected from a friend of mine a CPC464, who ... don't run.

I've already detected (and corrected) a +5V continuity problem, and I've also dismantled and cleaned the power switch, but still ...

I've no idea what to check in order to continue my diagnosis : when I turn on the CPC, I can catch a fluctuating voltage from the LED connection on the "tape PCB" (from 0.20v to 0.50v) and the voltage measured on the switch go to 0v, but nothing else.

Title: Re: Yet Another not running CPC464 ^^' (LED doesn't light up)
Post by: GhostLine on 14:26, 14 June 22

Addition : I've separately tested the LED, who is ok, and just to be sure, I've connected the CPC to my OSSC : no signal when turned on.

Title: Re: Yet Another not running CPC464 ^^' (LED doesn't light up)
Post by: JupiterJones on 15:35, 14 June 22

Hi!

Most usual culprit is the switch itself. Check its continuity with the multimeter, if no continuity or high resistance, it can be disassembled with pliers and thoroughly clean and re-assemble it again.

Title: Re: Yet Another not running CPC464 ^^' (LED doesn't light up)
Post by: GhostLine on 15:52, 14 June 22

Thanks for your answer !

I've already done this, and even tried to shortcut it, without any success so far.

Title: Re: Yet Another not running CPC464 ^^' (LED doesn't light up)
Post by: JupiterJones on 16:06, 14 June 22

Sorry, just read the message too quickly :picard:

Title: Re: Yet Another not running CPC464 ^^' (LED doesn't light up)
Post by: Audronic on 00:05, 15 June 22

Can you without any thing else connected measure with an Ohm Meter from +5 Volt point on the motherboard to 0 Volt line to check that there is not a short ??

Keep Safe

Ray

Title: Re: Yet Another not running CPC464 ^^' (LED doesn't light up)
Post by: GhostLine on 16:17, 15 June 22

Hey Ray,

Here are the results. Sorry if the measurements are not all logical, I'm a beginner at this ;)

Title: Re: Yet Another not running CPC464 ^^' (LED doesn't light up)
Post by: Audronic on 01:14, 16 June 22

@GhostLine

It Looks like you have a Short on the 5 Volt power line ??
These can be difficult to Trace.

Unplug the Tape deck and repeat test

Good luck

Keep Safe

Ray

Title: Re: Yet Another not running CPC464 ^^' (LED doesn't light up)
Post by: Bryce on 11:18, 16 June 22

Quote from: Audronic on 01:14, 16 June 22@GhostLine

It Looks like you have a Short on the 5 Volt power line ??
These can be difficult to Trace.

Unplug the Tape deck and repeat test

Good luck

Keep Safe

Ray

How do you work that out? 2-3 (which is a visible piece of wire) gives the result .0, meaning the meter gives .0 for a short and 1. for open circuit, so everything is measuring at it should.

Bryce.

Title: Re: Yet Another not running CPC464 ^^' (LED doesn't light up)
Post by: Audronic on 13:41, 16 June 22

@Bryce

Hmmnnn

1 and 2 = 1 which I assume is 1 Ohm

But 4 and 5 = 0 Which is Odd

Keep Safe

Ray

Title: Re: Yet Another not running CPC464 ^^' (LED doesn't light up)
Post by: GhostLine on 13:53, 16 June 22

@Bryce : that was my way of reading it too ... I guess I've to found someone to test the chips (I don't know how to use an oscilloscope ^^').
@Audronic : there's a capacitor on top of that, if I'm not mistaken.

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General Category => Technical support - Hardware related => Topic started by: GhostLine on 13:49, 14 June 22