[Coco] Coco1 repair parts ?? & Results of Repair!!

[Robert Gault]

mmarlett at isd.net wrote:

> Robert,
> 
> NTE is sold by AEI in Minneapolis if that helps you. I **think** Mouser
> also sells them. I'm sure the distrib. list or reseller should be on their
> site. I have used them before, and the specs are there.
> 
> Good luck! No CoCo should ever die! :)
> 
> Mark


I found a local electronic parts retail store locally with a stock of 
NTE parts. The NTE219 was available but the NTE128P was not there, only 
the NTE128 Can form. Since the specs were as good or better than the P 
(plastic), I bought it. The Coco1 is now working like new.

For those with no 5v at test point6 (at least on an F board), here is 
what is likely a common failure mode. The main power transistor (2N6594) 
fails, then the MPSW01 trys to carry the full load (which it can do for 
a short time), then the MPSW01 overheats and fails. This shuts down the 
5v bus. You may see 0.0v to 0.8v at the test point.

The sequence of the repair process was to replace the MPSW01 first and 
test the Coco. 5V was then present at the bus but the NTE128 was HOT. 
Good thing I bought the Can version. Then the NTE219 was installed the 
the Coco tested again. No change in voltage but now the NTE128 was room 
temp. So based of these results I postulated the above failure route.