Post Reply 
HP 41C Video interface test. Howto?
07-11-2020, 01:08 PM (This post was last modified: 07-11-2020 01:10 PM by vassilisprevelakis.)
Post: #13
RE: HP 41C Video interface test. Howto?

The Intel 8048 has an internal ROM, so if this is losing bits, then you need a new CPU.
The RAM is the Intel P2114 part which is a 1024x4 static RAM (4 kilobits).

But let's start from the basics. First check that the power supply is giving correct voltages. E.g. the RAM chips have GND on pin 9 (bottom left) and +5V on pin 18 top right. If you have an oscilloscope you may also want to measure the ripple in case the electrolytic capacitors are feeling their age.

I am not sure what's the other big IC. Its an HP part (on my unit it has ILF4 01 and 82241 written on top), but I guess its the video chip, and since you are getting a picture, its probably OK.

So since you can't do anything about either of the big ICs, assuming the voltages are OK, I'd replace the RAM chips and hope for the best.

Find all posts by this user
Quote this message in a reply
Post Reply 

Messages In This Thread
RE: HP 41C Video interface test. Howto? - vassilisprevelakis - 07-11-2020 01:08 PM

User(s) browsing this thread: 1 Guest(s)