> On Jun 3, 2016, at 10:33 AM, Rod Smallwood <rodsmallwoo...@btinternet.com>
> wrote:
>
>
> On 03/06/2016 14:58, Jerry Weiss wrote:
>> On Jun 1, 2016, at 8:39 AM, Jerry Weiss <j...@ieee.org> wrote
>>> …..
>>> Have you checked the Unibus supply voltages?
>>> …
>>>
>> As a rule-out make sure the Unibus cards are getting power correctly. The
>> Power Supply sounds like is fine and powering the QBus side of things, but
>> if the connections to the Unibus backplane are wonky it might create symptom
>> that the cards don’t exist. Note: I’m not referring to the AC and DC LOW
>> that Paul K mentioned earlier (which also are good items to check), but
>> just the raw power to the backplane.
>>
> Measured at the MLM -14.8v and +4.98
That's probably close enough. But I remember from DEC that some Unibus cards
don't obey the power tolerance specs. The spec is +/- 5% which is common. But
some, the DMC11 is an example if I remember right, will not function reliably
unless the voltage at the connector is at least equal to the nominal value. In
other words, they want -0% to +5%. We had a machine that wouldn't work right,
and the FS engineer went around with a voltmeter tweaking all the supplies
until they were set a hair above nominal. At that point the machine was fine.
paul
