Eagle has landed...sort of.... Bad video

[prowler]

https://imgur.com/a/BQNwphY

Hi,

Recently procured an Eagle II computer. The problem it has a strange video issue. As you can see in the video all you see is complete green on all the rows. In the video I held "T" down to enter test mode. Every even numbered pass shows a green screen with inverted color text. The text shows that the CPU ram etc.. is most likely fine. The odd numbered pass go back to the green row look. This alternates forever

As you can imagine I find this quite strange so I took apart it apart and started probing (with screen or drives not attached because it is just about impossible to probe wit the top half connected). Voltages seem generally fine (4.7V for the 5V and 13V for the 12V. I know the 12 is a bit high but the drives aren't connected so it isn't fully loaded). My first thought was to look at the two video chips....CRT8002 and CRT 5037. Here are some of the weird things I've noticed:

• I first probed PIN 21 of the CRT8002 which is also the REVID pin (and apparent VD7?). I figured since things look reverse somewhat this might be a good place. It is always low with barely visible square ripple (like 0.1V)
• CRT 5037 is getting very hot. Almost burn your finger hot. Makes me think it is bad. I removed it and inserted a socket. With it removed the aforementioned VD7/REV pin goes to ground with no ripple. Interestingly the CRT 5037 chip is the only chip to use 12V besides the drives.
• the DCC (dot crawl counter) which i assume is a clock for the 5037 looks unusual. Not too sure what it should look lie but low is at 1v and high is at 3.6V with a 1.95MHz frequency. it goes high then gradually drops to low each cycle. not a square wave at all.
  
  
  Anyways I was wondering if any Eagle II CPM computer owners have had something similar or any suggestions. I ordered some 5037 replacements its in case for $5 each but I figure its 50/50 if they fake or not

 

[Hugo Holden]

From what I can see, it looks like your CRT & VDU is fine, it is being fed with a defective/abnormal video signal, You need to look at that on a scope. I"m doubting if there is anything wrong with the VDU. There could be an issue with the character generator in the computer, but it looks like at least it is outputting rows of character cell blocks from the spaces seen between rows of them. Also I have no idea what the numbers that you have quoted refer to or what they mean.

 

[ldkraemer]

That Video has some text very light on the Screen. If you just get a Photo of that in focus it shows up
as normal text.

Another clue is both Floppy Drive LED's aer on at the same time? WHY?
How are those Tandon TM-100's PHYSICALLY strapped? And is your Floppy
cable a straight through conductor cable or conductors 10 thru 16 twisted?


Larry

 

[elanda]

It looks like you have the brightness turned most of the way up. You didn't mention any effect of manipulating this control, but the REVID behavior does also seem suspicious. The alternating text inversion each test cycle is normal, at least as I remember it. I'd check my Eagle, but its 5037 was also acting up as well. It runs extremely hot and takes about 5 minutes to "warm-up" before it _sometimes_ will show text. Now I have the bug again, so will probably pull it out soon. The DCC is generated by some 7400 logic, so that should be pretty traceable.

Did you have any further progress or success with replacement chips?