New CPC 464 Owner, Tech Support Needed

[Fourdy]

Hi All, just signed up to this forum, looks like a great place with many knowledgeable people willing to lend a hand!


So, I've been collecting retro systems for a while now and just last week was gifted a CPC 464 with colour monitor from a friend who had it stored in his loft for 20 years or so. However when powering up I get a blue/grey screen with black boarder and occasionally a scrambled mess sort of green and red. Also no beeps when pressing DEL key.





I've carried out a bit of fault finding as I have an electrical backround but PCB's/IC's ect.. are not really my thing. Testing carried so far:


Visual check of the all components - Look generally in good condition
Reflowed solder on DC socket as system was only powering when DIN was connected (using ground from DIN rather than DC jack)
Reseated Z80 & 40007


Checked voltages:
Unloaded = 5.2V
Plugged in and measured at back of DC socket = 4.9V
At each IC = 4.65V
I get about 4.8V at the socket on the PCB that supplies the tape deck and 4.6V on it way back, pin 1 & 3 I think.
 
Checked IC temp with thermal imaging but looks ok...I think?









Do these symptoms warrant replacing the CPU/Gate Array?
Is there anything I can try before replacing RAM chips or other through hole IC's because that's above my skill level and will need some advise of where to send for repair if that is the case.



Thanks in advance...

[gerald]

The screen you see is typical of dead RAM and some of the 8 DRAM devices (in the middle of the board) seems hotter than other.

I would start by changing the hottest one.
The gate ARRAY is fine. 40007 will heat and it is supposed to have a heatsink!

[Fourdy]

Hi gerald,


Thanks for the feedback. I took the heatsink off when re seating the 40007 but put it back on after taking the photo.


I suspected it might be RAM. As replacing these chips is not something I'm comfortable doing, could you point me in the direction of someone/somewhere that repairs these boards?




Thanks

[CanonMan]

4.9v at the power socket and 4.65v at each chip sounds a bit too low to me.


I'd replace the power socket first as they have a tendency to tarnish and go high resistance, causing a  voltage drop.

[dragon]

I have these 464, he have a crapp cassette conector, its different from the rest of 464 cpcs.


The mine uses russian memory chips they are indestructible.


I read these guys make repairs in u.k. But really any tecnicall  that repare crt tvs or so should can repare the cpc.


http://www.mutant-caterpillar.co.uk/shop/product_info.php?products_id=3500

[Bryce]

I read these guys make repairs in u.k. But really any tecnicall  that repare crt tvs or so should can repare the cpc.

http://www.mutant-caterpillar.co.uk/shop/product_info.php?products_id=3500

I definitely WOULDN'T recommend these guys. However, there are others in the UK that could fix this for you. The issue is most likely what Gerald said, see red square below. If you can't get someone in the UK, you can send the PCB to me for repair (I'm in Germany).

Bryce.

Problem:

[Fourdy]

I might take you up on the offer, I'll make some calls today to places in the UK but if they don't fill me with confidence I'll send you a PM.


Thanks.

[Bryce]

Ok, let me know how you get on.

Bryce.

[||C|-|E||]

I might take you up on the offer, I'll make some calls today to places in the UK but if they don't fill me with confidence I'll send you a PM.


Thanks.

Bryce is miles better than me and has much more material stocked,  but if you live near Oxford, removing those chips and socketing new ones should be very doable. If you are far away in UK and you need to send the board by post anyway he is the person of choice, imho.

[Fourdy]

Thanks for the offer!


I've been in touch with Bryce and arranged to send him the board for repair.


I'll update this thread with the outcome in due course.


Thanks all...

[Fourdy]

UPDATE!


So, the 464 is in full working order thanks to Bryce, 6 of the 8 RAM chips were replaced and I believe a broken trace was repaired under a RAM IC also. I'm sure he'll be able to give some further detail as to what was done exactly.


I'd like to say thanks to Bryce for taking the time and effort to repair the board and send it back to the UK, top man!


Thanks all...

[Bryce]

Yes, your summary is correct: 6 broken RAMs and due to some strange residue (computer possibly stored in a damp environment), one PCB trace that needed some repair.

Bryce.