MicroVAX II Console Garbling Characters

[Jon Elson]

On 08/24/2016 09:53 AM, Jerry Weiss wrote:
>> On Aug 24, 2016, at 9:41 AM, Rob Jarratt <robert.jarratt at ntlworld.com> wrote:
>>
>> I have a MicroVAX II which has started garbling and losing characters output
>> to the console. It had seemed that re-seating the processor board would fix
>> it, but that no longer seems to be the case.
>>
>>
>>
>> I was just wondering if anyone else has ever come across this failure mode?
>>
>
> I’ve seen similar  with under two occasions.
>
> 1) Non-compliant USB adaptor - Doesn’t fully support RS232C levels
> 2) Poor grounding, noise in the data lines - long cable runs or devices on different sides of the (US) power main.
>
> I have not dealt with component problems on the KA630 itself.
>
The console interface is a set of 9636, 9643 and 9639 chips 
(8-pin DIP).  I had mine blown out about 1988 or so when a 
power supply failed.  There are a couple capacitors and 
resistors related to that circuitry, too.

Jon