CPCWiki forum

Afternoon All

So I powered up my 464 that had been stored away for a while and get the blue screen, great I thought.  Plugged in an old memory expansion, power back on and poof some smoke started coming out of the rear of the 464 where the speaker is.  So switch everything off, remove expansion and power back on ....... dead, no led , no more smoke.  I unplug and try a few magic puffs of air in the back cpc but unfortunately it does not come back to life.

I have several  464s so it's not the end of the world but would like to get it back working if at all possible.

Is there a set by step guide on what to check to try and identify the cause of what went up in smoke and try to get it working again.   I've check the monitor and still getting 5v so know its after this point.

Appreciate any pointers

Cheers

G

PS Just realised it's in the wrong area - can someone move it to "technical-support"

In absence of better advice, I would suggest to open up the CPC and look for capacitors blown up near the vent the smoke got out of.


Did it smell particularly bad? That would point to a capacitor as the culprit.


The capacitor may still be working somewhat, but you should be able to see if its bumped or open by the seams.


Just a quick look wouldn't hurt if you're used to open up electronics.

Visual inspection first. Find out what burnt.

Bryce.

Did it smell funky as well? Most likely a bust cap, but open 'er up and go through them yourself.

Yeah, it didn't smell too good.


Main board - nothing looks burnt/popped, although these look to have flaked

On Tape deck board there's some gunk, but not sure if this some type of glue

Badass title for a video game

Have some capacitors bulged or leaked?These could have shorted between tracks and maybe destroyed Z80 as shorting +5V to ground will do untold damage.

This yellowish slime is just some innocent glue.

When the LED is not lit when you turn on the power, I would expect that you could find a burn on the PCB of the cassette board on the soldering side, near to the connector that goes to the main board. And I would also check the main board for the same on the soldering side.

Quote from: abalore on 20:34, 03 February 22
Badass title for a video game

I saw what you did there!  ;) ;D

Thanks for all the advice so far

Can't find any scorch marks on the boards but did find this on the tape board-  Could this be the cause or a casualty ?

Thanks

Think this is some left over glue as I was able to scrape it off :(

.... But this looks ..... not right compared to other ones

All of those capacitors (and that inductor) look fine. Try bypassing the power switch by shorting the two wires going to the switch and see if the CPC powers up.

Bryce.

Thanks Bryce - I'll give that a go when I'm back home from work

Afternoon

Shorting the switch results in nothing.  I'll have more time this weekend to start checking other bits.  Anywhere in particular I should start looking ?

Thanks

G

I'd start by powering the CPC with a current limited PSU to see how much current the device is actually pulling. Then I'd start looking for components with no voltage or that are pulling too much current. Unfortunately to do this, you are going to need quite a bit of test equipment that you probably don't own.

Bryce.

Thanks Bryce, I only have a multi-meter :(
An update

There is life .....
I disconnected the tape board and shorted pin 1 & 3 where the tape ribbon goes, it lives ....... The CPC powers up. I've checked the switch and that is working, so the issue has to be somewhere on the tape board.

Is there anyway to narrow down which of the components is knackered on the tape board ?

The tapedeck has a grounded metal frame, so it may just be a wire pinced against the frame. Check all the wires for damage and then do a visual check on the tapedeck components.

Bryce.

I've pretty much checked everything and it looks ok, no obvious shorts :(

Looking at the schematic there doesn't appear to be very much that can go wrong from CP001 C-> A just the switch SW302.  I think I'll get another 464 that I know works and connect tape board  then I know it's definitely on that side - or would you advise against this?

Are there any points on the board I can using a multi-meter to narrow down the problem ?

Thanks in advance

G

I initially recommended to provide a picture of the solder side of the cassette board, but it could also be a shortcut somewhere, which you can identify with the multimeter that you have.

Quote from: chilli_taff on 17:01, 15 February 22
I've pretty much checked everything and it looks ok, no obvious shorts :(

Looking at the schematic there doesn't appear to be very much that can go wrong from CP001 C-> A just the switch SW302.  I think I'll get another 464 that I know works and connect tape board  then I know it's definitely on that side - or would you advise against this?

Are there any points on the board I can using a multi-meter to narrow down the problem ?

Thanks in advance

G

There's no problem trying the tapedeck from another 464.

Bryce.

Quote from: Bryce on 10:42, 16 February 22
There's no problem trying the tapedeck from another 464.

Bryce.

Warning! Don't take ir from a advance manufacture year. In PT NO Z70375, MC0044D  amstrad change the  cassette connector, and you can't swap it witouth solder all wires with a old board.

Sorry guys, RL and the kids swimming club have left me with very little time over the past few weeks.  I'll get the 464 out of the cupboard this weekend and get some photos.

In the meantime can someone move this to Technical support - Hardware related.

Thanks

G

Did you ever get an answer to this problem? My cpc has the exact same issue. Thanks