Repair of a DEC VAX4000 power supply (PWJ248)

[@rabidbigdog]

Thank you for taking care of these glorious machines. Definitely NOT junk.

[@jimsvideos7201]

Thank you for the guided tour; I don’t know much about enterprise computing but seeing the parts up close is fascinating.

[@SeanBZA]

To be fair to DEC, they never expected this to be still running 30 years later, after all it was supposed to be tossed out and replaced with the new upgraded one after 5 years, when the guarantee expired.

[@GothGuy885]

this power supply has some really neat and innovative features. I like the interlock, that you cant remove or install the PSW without the power cord being removed, and the circuit to sense temperature. all in all an awesome PSW and video. thanks for posting! 😊👍

[@jj74qformerlyjailbreak3]

Learning right along with you, from far away. Happy Thanksgiving from the States.

[@jj74qformerlyjailbreak3]

I'm glad I made it all the way through. Not hard too do BTW. I really needed a BlueSCSI couple years back. Without this video I wouldn't have known still. It's on my shopping list now. Thanks.

[@Petertronic]

Nice repair. I've had similar issues with those tall chocolate-brown capacitors, in Sony professional video machines of the same age. Also, beautiful watch!

[@PlaywithJunk]

After 20+ years, all capacitors will start leaking. The newer even after 4 years or so. Interestingly I have some very old radios, 70+ years old and those caps are still good. That means, it IS POSSIBLE to make long lasting caps.... but nobody wants to. On the other hand, I would say that 30 years in that VAX P.S. is good enough. :-)

[@Vladimir-hq1ne]

What a nostalgic-sounding machine!

[@ChipGuy]

I like that LM35 - ish airflow measuring circuit. There seems to be even two on them for safety.

[@PlaywithJunk]

Fujitsu made it without any electronics. They used a reed switch and a magnet that loses magnetism when hot. So the switch opened and the alarm went off.

[@f.k.b.16]

Your desoldering station is the most manly sounding one on KZbin!

[@PlaywithJunk]

Yeah, it sucks...

[@f.k.b.16]

@ lol that took me a minute but i just got the joke 🤦😂

[@simontay4851]

Yes, it really sucks. Its a proper beefy desoldering gun. It could suck up SMD parts as well as the solder. What model is it?

[@aizunomnom8556]

Probably using big vacuum pump

[@aizunomnom8556]

Yup, I look it up. Pace use really big vacuum pump in their desoldering station

[@2OO_OK]

The cap leads are bent over so the cap does not vibrate out when the populated board goes through the wave solder machine.

[@simontay4851]

I hate wave soldered boards. There is never enough solder applied. When the wave goes past, the solder falls off. Ive reflowed loads of wave soldered boards with cracked/bad solder joints. Large or hot components should be hand soldered.

[@gibonsamuel2365]

Happy new year 2025. Long uife for chips and electronics

[@brianhanson9367]

Nice when you only need your eyes to troubleshoot. In 35 years it only happened to me a couple of times. Cheers

[@JxH]

I've found that the ratio of *visible* faults to be around 50% (very roughly). But that's with VERY close inspection (under magnification, not just eyes), enough to find even tiny cracks in PCB solder joints (often hot components). It's nice to fix something that only requires a few joints to be reflowed with fresh solder. Cheers.

[@DECcomputers]

A well-known problem. I have spent a lot of time trying to find problems with this PSU. I think my PSU needs a little more attention as well.

[@ryczkowsky]

dobre jak zawsze

[@GeoffSeeley]

Yup, if you have something that is 25-30+ years old that might have capacitors in it, you should probably check for leakage. Had to replace caps in an automotive ECU from 1992 and a number of other modules in the car. Had to do the same on a 1993 truck ECU as well.

[@douro20]

I would imagine there are a lot of HMMWVs with bad caps in the injection pump driver.

[@PlaywithJunk]

I had a 1982 Datsun ZX and I opened the injection control unit out of couriosity. Threre were no electrolytic caps inside. Only foil and ceramic caps. seems they knew how to make it reliable.

[@douro20]

Can you still boot from the DSSI drives?

[@PlaywithJunk]

Sure, they are all working.

[@leggysoft]

I've found a lot of old computers have only a few power rails and are easy to power with modern PSUs with 12v-3.3V or 12v-5V step-downs. The 5v and 3.3v rails on modern PSUs not high power.

[@ChipGuy]

What do people run on a 1994 DEC VAX these days?

[@PlaywithJunk]

VAXgames!

[@f.k.b.16]

Is it still a production server or just a for fun server?

[@PlaywithJunk]

@@f.k.b.16 Mostly fun. But sometimes we use it to test old scsi tape drives.

[@TheEmbeddedHobbyist]

​@@PlaywithJunkare you in an it support lab or a museum 😂😢

[@DECcomputers]

Just for fun :)

[@simontay4851]

Apparently chemicon caps are supposed to be one of the best quality brands but ive replaced lots of leaking/bulging chemicon caps. I don't trust them. I always fit new Panasonic caps.

[@PlaywithJunk]

I love Panasonic electrochemical parts. Also lead acid batteries, I guess those guys know what they are doing. I once had a 17 year old battery from an UPS in my car and it worked fine. But to be fair, 30 years of lifetime before they leak is not too bad. Modern caps do that after 3 years...

[@JxH]

I use to play Lunar Lander on a VAX (which had a *HUGE* CRT monitor) while waiting for the test program to compile on the Factron ICT (which took a fair amount of time). I got really good at landing... 🙂

[@Sine1040]

The beginning is the end ;)

[@PlaywithJunk]

Yeah but in reverse 🙂

[@Sven_Dongle]

E4000 CPU boards used to use a funky chip cooler that looked like Avant Gard chess pieces that used to break off when you removed the board.

[@MultipleObjectSelector]

Hey hey. I had to manage an OpenVMS system at my last job. It had run on one of these at some point in its life.