CPC 664 won't boot

[anyweb]

hi,I got a 'new' cpc 664 that is DOA. When I connect it to a known good CTM 644 monitor, it makes a buzzing sound (the FDD motor is on i guess). I then disconnected the 12v line and powered it on again. The power LED does light up and the monitor displays a blue rectangle (doesn't fill the screen/borders) which then becomes greyish, there is no Amstrad text, so it appears like there's some hardware problem. I haven't opened it up yet, but any pointers ?

I do have access to a soldering iron, de-solderer and have replaced drive belts on FDD's before so I'm used to dealing with the insides, but identifying possible dead chips is not something i've done before.

below is roughly what the square looks like (on the sellers advertisement)

https://www.amstrad-noob.com/wp-content/uploads/2021/01/monitor.jpg

cheers

niall

[Bryce]

Not much diagnosis required. If you have a square (of any colour) in the middle of the screen, then 99.9% of the time you've a dead RAM chip.

Bryce.

[anyweb]

awesome thanks Bryce,how can i determine which of them is dead and how can I get them replaced ? are they for sale on ebay ?

[anyweb]

i've got a cpc 464 which i could sacrifice for ram chips, are they the same chips ?

[Bryce]

I wouldn't break a 464 to fix it. The part No. is 4164 (with TMS/HM/MC/KM or whatever manufacturer code before the number). They are cheap and easy to find on fleabay: https://www.ebay.de/itm/8x-RAM-IC-KM4164B-15-4164-150ns-passt-C64-ZX-Spectrum-u-A/233656983680

It's probably only one that's failed and the failed chip will often be hotter than the others.

Bryce.

[anyweb]

thanks for your advice, much appreciated, i'll pop it open and see if i can determine the faulty one(s). If i order new ram from fleabay should i order the socket also, if so do you recommend any ?

[llopis]

thanks for your advice, much appreciated, i'll pop it open and see if i can determine the faulty one(s). If i order new ram from fleabay should i order the socket also, if so do you recommend any ?

If you have a Dandanator or some kind of low ROM box, put the RAM test on it to find out which chip is faulty http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/quick-and-dirty-ram-test-for-cpc/


If you don't you can also burn it to an EPROM and replace the ROM, but the 664 ROM probably isn't socketed.


Definitely get DIP 16 sockets for the new RAM. Just about any will work (these days they're all double-sided), so I usually go with the cheapest ones from Ali.

[anyweb]

thanks Noel, small world eh ? I don't have any dandanator (ram tester), but would consider getting one if they are cheap enough
would the following dip socket be ok ?

https://www.ebay.co.uk/itm/50PCS-16-Pin-16pins-DIL-DIP-IC-Socket-PCB-Mount-Connector-NEW-GOOD-QUALITY/351492891857

cheers

niall

[Bryce]

Definitely socket the new RAMs, they are all old IC's and they can fail at any time. Sockets save you a lot of time later.

Bryce.

[anyweb]

ok great, so if i order those 8 rams' and some DIP sockets i should be good to go hopefully, I've already ordered some new drive belts, would be great to see this CPC alive again

[Bryce]

Remove the RAMs like this: http://www.cpcwiki.eu/index.php/IC_Repair
Otherwise you'll end up lifting tracks, the CPC boards are thoroughly flooded on the top layer.

Bryce.

[anyweb]

thanks SO much for the advice Bryce i really appreciate it.

can you please expand on 'thoroughly flooded in the top layer' for someone who hasn't a clue what you mean ?

[Bryce]

Thoroughly flooded = They weren't great at setting up the wave soldering machine, so there's often way too much solder on the top of the PCB on the IC pins.

Bryce.

[GUNHED]

The better deal...
https://www.ebay.de/itm/50pcs-KM4164B-15-64K-X-1-BIT-DYNAMIC-RAM-WITH-PAGE-MODE-DIP-16-/173485198058


But doesn't the CPC contain the 4264 anyway?

[Bryce]

The better deal...
https://www.ebay.de/itm/50pcs-KM4164B-15-64K-X-1-BIT-DYNAMIC-RAM-WITH-PAGE-MODE-DIP-16-/173485198058

With the added suprise of not knowing whether they are genuine RAM or just some random IC that has been relabelled!

Bryce.

[GUNHED]

With the added suprise of not knowing whether they are genuine RAM or just some random IC that has been relabelled!

Bryce.

Same with your chips. I don't care - therefore ebay has a buyers protection.

[Bryce]

Same with your chips. I don't care - therefore ebay has a buyers protection.

No it's not the same. I know you're not a hardware person, but here's a quick lesson in spotting obvious fakes (other than the fact that 4164 IC's are unlikely to exist in big numbers in China):

Here's a real KM chip: Note that the notch only goes half way through the IC, that the KM logo is symetrical as it should be (and printed) and the pins are oxidised as you would expect from a 30+ year old chip.

Now look at the chip that the Chinese site is claiming to be a 4164. Through notch (something that was extremely rare at the time), pins that are way too shiny for old stock and a logo that isn't even close to what it should be and is laser etched, something that wasn't possible in the 80's. In fact the logo looks like a mess that someone threw together in mspaint.

I don't give links to sellers if I am not sure that the chips are highly likely to be genuine.

Bryce.

[GUNHED]

Well, maybe it's just a newly produced chip. I rather use a new one instead of an 30 years old one.


The seller got 857 positive comments this month, and only 4 negative comments. I don't see him to be a person selling fake ICs. Maybe because he got one "fake IC" comment? Oh, well.

[anyweb]

thanks again for the advice guys
here's the motherboard in question.

https://www.amstrad-noob.com/wp-content/uploads/2021/01/inside.jpg

i tried adding an attachment but it wouldn't let me..

Which ones are the ram chips exactly ?

[llopis]

It should say 4164 on them with 16 pins. The ones towards the bottom right. There's a row of 5 and a row of 3 above.

[anyweb]

thanks Noel,hopefully i'll figure this all out

[anyweb]

so while I'm still waiting on the ram sockets (I have everything else), I tried to test RAM on the cpc 664 today using a Dandanator, but this one normally needs you to press R to run the ram test (at least that's what happened on my cpc 6128)
so, as R did nothing either this means i've more problems or the keyboard membrane is screwed, any other way of getting the ram test to run on this Dandanator ?
here's a reference including pics https://www.amstrad-noob.com/2021/02/04/dandanator-cpc-from-hobby-retro/

[llopis]

On the Dandanator you can hold the leftmost button while starting up the Amstrad to launch the extra test ROM.


I don't know which one comes by default, but I recommend you use Gerald's one:
http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/quick-and-dirty-ram-test-for-cpc/


(You'll need to pad the ROM to exactly 16KB to load it in the Dananator).

[Bryce]

so while I'm still waiting on the ram sockets (I have everything else), I tried to test RAM on the cpc 664 today using a Dandanator, but this one normally needs you to press R to run the ram test (at least that's what happened on my cpc 6128)
so, as R did nothing either this means i've more problems or the keyboard membrane is screwed, any other way of getting the ram test to run on this Dandanator ?
here's a reference including pics https://www.amstrad-noob.com/2021/02/04/dandanator-cpc-from-hobby-retro/

How are you testing the RAM if it's not installed?

Bryce.

[anyweb]

I'm just waiting on the sockets, so when i remove the faulty ram i can insert new sockets+ram
i haven't removed anything from the cpc yet.... was kindof hoping that the Dandanator would make life really easy for me and show me which ram was duff