Here are some pictures of the DEC T11 microprocessor trainer that I have.
It has a power supply fault. With a little luck it will otherwise work OK.
Power supply fault
I have found the problem with the power supply. Mounted on the outside of the wooden box is an LM338K. This is a variable voltage regulator in a T03 package. It is supposed to regulate by maintaining a 1.25V differential between Vadj and Vo. When I have the evaluation module disconnected (so there is no load), the LM338K operates as expected (Vi=12.7V, Vo=5.24V, Vadj=4.03V). But when the evaluation module is connected, the current draw is 0.72A and the voltages are as follows: Vi=11.0V, Vo=3.97V and Vadj=3.03V). Note that with the load connected, there is only 0.94V between Vadj and Vo. So something is broken inside the LM338K – it is unable to ramp up the output voltage to maintain the required 1.25V differential.
So I have ordered a replacement LM338K from China on 3 April 2018.
Manuals
Here are some links to relevant manuals:
DCT11-EM Evaluation Module User’s Guide
