33941RE: [midatlanticretro] LA120 Destination^Wfaults unknown
- Jan 14, 2014Cory Smelosky <b4@...> writes:
>On Tue, 14 Jan 2014, Brian Schenkenberger, VAXman- wrote:+-----+-----+-----+-----+
>> Cory Smelosky <b4@...> writes:
>>> I have the PSU operational again.
>>> 2 +12, 1 -12, and -5V are all present.
>>> These voltages could be wrong: (pin-wise) on J2.
>>> Pin 6: 4.97VDC
>>> Pin 5: GND
>>> Pin 4: GND
>>> Pin 3: -12.28VDC
>>> Pin 2: about 12VDC
>>> Pin 1: about 12VDC
>>> +/-24VDC are both present on J4 where they should be.
>>> The motors do not run and there is no voltage present at fuse F2 (the fuse
>>> OTHER than the line feed one. There is +24VDC present at the line feed
>>> one.) There is continuity between the -24V pin and the non-line-feed
>>> motor fuse. No fuses blow.
>>> With J2 disconnected, power draw drops from ~65W to ~42W. Several random
>>> resistors checked (in-circuit) that should measure 540Ohms measure about
>>> 588Ohms. No LEDs light up and there is no bell. No components are
>>> particularly warm to the touch with power removed.
>>> Anything with this taste wrong to you? I'm completely stumped. The motor
>>> ran before I started working on the PSU. When I was doing repair work on
>>> the PSU (caused by my own mistakes -- oops) I had it disconnected from
>>> the LA120 entirely save for a couple tests with test resistors. There was
>>> no -12V present when these tests were performed and +5 would've measure
>> Are you aware of and or have copied of these?
>Yup. I have been browsing through them.
>> I have a fully functional LA120 if you need me to check voltages for you.
>> However, I believe you have the appropriate voltages within tolerances.
>Yes please. Do check them in relation to which pin is which.
>> Are both fuses (carriage return and line feed) good? Are you sure that
>> the ribbon cable from the logic board is connected to the keyboard logic
>> board? Make sure pin 1 and pin 1 on each are correct. The cable has a
>> marker to coincide with pin 1 on the main board. Check that whatever
>> color coincides with pin 1 there is closest on the connection on the
>> keyboard logic to the keys themselves. Do you have the carriage return
>> motors sense wires connector properly oriented on the main logic board?
>> The paper out (pins 1 & 4) and cover open (2 & 3) (note I may have them
>> backward but it doesn't matter) won't matter if you connect ti upside
>I'll need to look more closely at those pins. I could have any number of
>them orinted wrong. Both fuses pass a basic continuity test.
(1) | +24 | 0 | -24 | N/C | J4
| +24 | 0 | -24 | N/C |
| +24 | 0 | -24 | N/C |
(1) | 0 | 0 | J2
| +12 | 0 |
| -12 | +5 |
These voltages were measured with the power supply connected to the printer
logic board. The printer was on but not actively outputting any characters.
The +5 measured +5.2 which is within 5%. All other voltages were spot on!
Measurements from common ground with meter's lead connected to the wire of
C48's negative lead.
VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)ORG
Well I speak to machines with the voice of humanity.
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