*** M E M O R U M ***

Another simple fix worth trying is cleaning the edge connector. On the last photo there's clear line of dirty marks on the solder "fingers" of the edge connector.

Even a small amount of dirt/oxidation is enough to interrupt the signals between the main PCB and the RS232 board.

Delivering a blow to the case in the area under the keypad and "Thump starting" the MTX/FTX was quite common in our household back in the late 80's

Thank you Mark

At that time My MTX is disassembled ...

When my supply upgrade and retrofit are completed and the MTX in one piece again I will post the result.
I just hope it's for the better.

Best regards

Thank Martin

I will also clean the edge connectors.

I saw also that some ceramic capacitors have a rather old exterior appearance, what's happen inside ?
New ones are just for some cents.

Best regards

SchmitS wrote: ↑23 Mar 2021 16:18 I saw also that some ceramic capacitors have a rather old exterior appearance, what's happen inside ?

In what way? Can you post a photo showing what you mean / see?

Some ceramic capacitors have a wax like coating, this can make it look like they have been damaged if the coating has been disturbed. Ceramic capacitors are generally reliable, so unless they actually have physical damage like a chunk or bit missing or a crack, it’s normally considered that they don’t need replacing. Any that are physically damaged should be replaced.

Electrolytic capacitors are of course rather different, in that they age and degrade over time.

The worst capacitors, are the encapsulated paper type such as Rifa X2 types, often found in switch mode power supply units, or in electric motor powered appliances.

The second worst, are underrated (for the application they are being used in) tantalum bead capacitors. These can, and do go short circuit...

Mark