Vaxstation 4000/60 Power Supply & Monitor Questions

[Partyn]

I'm looking for some tech advice. I work for a company that is still running an old Vax/Alpha based control system that has been dying for years. Somehow I am now responsible for maintaining it until they approve some upgrades. Our latest failure has been the some power supply issues for the 4000/60 systems. Symptoms include complete power down and no restart after an hour or so of runtime. Some general reboots which I believe are temp. related as our control room hit about 90 degrees when the AC failed. And now I have another system that just seems to not stay running.

Questions....

I've been looking at the power supply requirements and they seem close enough to an modern atx supply, all but the -9v rail. I can re-pin connectors but finding a schematic has been well..... difficult. Is this something I should even entertain trying to fix, or should I just force the company to purchase some refurbished P/S from somewhere?

Final question, Can anyone recommend a monitor that will work with or an adapter, to convert the Sync-on-Green that the DEC systems use? Our current supply for monitors has not been able to make anything for about a year now.

 

[bobaboba]

I don’t think you’ll have any luck finding a circuit diagram - I‘ve looked pretty thoroughly and couldn’t find one. You can get replacement psus on line, not cheap but if it’s a key bit of kit …

FWIW I had similar problems a few years ago and did the time-honoured fix of replacing the electrolytics which fixed things completely so it‘d be a good starting point especially as it’s basically working. The machines likely have a good few operating hours on them by now. Easy job once you’ve found out how to open the psu up .

 

[Partyn]

Yeah I have no problems pulling the power supply apart. I was just hoping for something where I could find some test points maybe a pin out so I could do some basic checks. I ran across something that I'm not too sure of though. The p/s have two 12v fans. Do the older ones control voltage for fan speed? with no motherboard connected and p/s on i get about 8v on the terminals for the fans. I started looking there due to a van not turning and stalled. So any idea if they actually control fan speed or should it be the full 12v power?

 

[cruff]

I use a Viewsonic VP171b with mine normally, but an Extron RGB-HDMI 300A or similar does a good job driving an HDMI monitor from the 4000/60's video signals.

 

[DECtechGuy]

Yeah I have no problems pulling the power supply apart. I was just hoping for something where I could find some test points maybe a pin out so I could do some basic checks. I ran across something that I'm not too sure of though. The p/s have two 12v fans. Do the older ones control voltage for fan speed? with no motherboard connected and p/s on i get about 8v on the terminals for the fans. I started looking there due to a van not turning and stalled. So any idea if they actually control fan speed or should it be the full 12v power?

I'd imagine it's full 12v as I've never heard my 4000 or 3100 systems regulate the fan speed, has just been a constant drone.

 

[Partyn]

I'd imagine it's full 12v as I've never heard my 4000 or 3100 systems regulate the fan speed, has just been a constant drone.

I may not have been clear and thats my fault. The fans are internal to the psu. There are no fans inside of the actual vax4000 box, just internal to the psu.

 

[DECtechGuy]

I may not have been clear and thats my fault. The fans are internal to the psu. There are no fans inside of the actual vax4000 box, just internal to the psu.

No worries, I'm also aware of that, as I've had to do a recap for a variant of the same PSU and found that to be the case. Seems as if that was a standard design at DEC to have the fans internal to the PSU. When I was last in it, the fans didn't seem to have any circuitry that would lead me to believe their speed can be regulated, although I'm a rank amature in that space.

 

[Partyn]

Well for a bit of information if anyone else has some of the same issues. Through multiple power supplies the fan voltage in the Digital Model - 30-34690-01/H7819-AA (zytek P/N: EP 07166) seems to be 8v at the pins.