K8048 assembled, ld8 stays on

Kits Microcontroller Programmer - Experimenting Project
1

Hello forum,

i just assembled a K8048 and everything looks fine. It’s just not working and LD8, the “read/write” LED is always on. The green power LED LD7 goes on and if i switch from Standby to Program or Run, LD9 starts flashing.
Unfortunately im not the best when it’s about electronics, so i could need some help finding the problem. What is the most probable problem? Is one of the transistors broken? I removed the Run/Standby/Program switch just to be sure, that there is nor problem with the switch, but that did not change anything.
Anybody who can make a good guess before i start to desolder everything?

Thanks,

Stefan

2

[quote=“SPucki”]Hello forum,

i just assembled a K8048 and everything looks fine. It’s just not working and LD8, the “read/write” LED is always on. The green power LED LD7 goes on and if i switch from Standby to Program or Run, LD9 starts flashing. [/quote]

I checked the transistor T5 and it looks good: when i connect it between R30 and ZD1 to ground, LD8 goes off. VR1 delivers 12 Volt, VR2 5 Volt. The voltage on ZD1 is unstable and is somewhere between 1.7 Volt and 0.03 Volt.

Any ideas what i could check or what’s wrong here?

Thanks,

Stefan