CPC 464 weird problem with rewind (haunted cpc?)

[willow3411]

Hello everyone,
so here I am facing a problem that I have never had with a CPC 464.
when I rewind the tape, reached the end, the screen becomes weird, then black.
then I press stop and there the screen does anything !! ( see photos).
the problem comes from the card of the K7 reader.
I tried with another motherboard, same thing.
when I plug another drive into the original motherboard it works.
So: I cleaned everything with IPA, I changed all the capacitors on the reader card except one which is not polarized (in the middle of the card).
If you have a lead or an idea I'm a taker.
Thanks in advance
Willow3411

[Bryce]

Hi Willow,
       this is most likely a power supply issue coupled with a worn tapedeck. When the tape gets to the end, the motor is in a stall for a second or two. The stall causes a higher current, the voltage drops (if the PSU can't handle it) and some chips don't function correctly causing a crash. Try the same with a better PSU.

Bryce.

[willow3411]

hello bryce!
Thank you for your answer
I use my lab power supply.
It's not good ?
the second image is the black screen with the problem

[Bryce]

Hi Willow,
        what current limit have you set on the PSU? As you can see in the picture on the right, the PSU has gone from CV into constant current mode and the voltage has dropped to under 4V meaning that most IC's will have reset or gone into an unknown state. But it has gone into CC at only 700mA which means you've set the current way too low.

Bryce.

[willow3411]

hi bryce
Thank you for all those informations.
I understood everything !!
you are a boss!
I tested this morning with another power supply (external hard drive power supply in 5v 2a) and it works very well.
Regarding my lab food, I admit that I do not master it perfectly yet 
I retested with my lab power supply by increasing the amperage.
Everything is OK !!!
So to summarize:
When the engine gets old can there be problems like this?
Thank you once again for your clear and precise answers.
beautiful day
willow

Donc SOLVED !!!

[Bryce]

Well congratulations on sorting it out first.

I don't know that particular PSU, but usually on those types, you need to short the PSU outputs and set the max current level (it will be displayed). Then remove the short and connect it to your device.

As for the old tape drive, the brushes are most likely worn down so much that they can cause shorts across commutator contacts when the motor stalls. I don't think anyone at Amstrad ever imagined that the tape deck would be used as long as they are being used.

Bryce.