And "Fast Eddie" the technician got his name by welding a Craftsman screwdriver to the terminals of a big blue capacitor the size of a Budweiser can.

I saw a tech short a 100A supply with his metal watch band. It wasn't a pretty sight and he probably took notice of the "no jewelry" requirement we had after that.

 

My only claim to fame in the lab was accepting some "engineering samples" of those big blue jobs, putting them in my 8V 25A supply and having one of them blow it's pressure relief plug. Everybody gave me the "hairy eyeball" as if I had done something wrong. Replaced the bad one under the watchful eyes of the chief tech; I was vindicated and happiness was restored.

 

My only claim to fame in the lab was [snip]

I was working on a power supply line once and the assemblers were having problems installing these big diodes backwards (even though they were color coded on one end). It was causing all kinds of caps to explode. I was cleaning up the electrolyte that leaked on the floor, and was eating the linoleum, when one of the QA engineers walked by. He walked me and the blown supply to the assembly supervisor so she could see what her people were doing. We never were required to wear safety goggles at that station, but we got into the habit of bring up the supply on a variac when testing.

 

300MHz logic was considered fast and computers had 5V supplies you could weld with.

Aye! Gen1 ECL and 'straight' TTL? --- That's a bit before my time -- 'Tho I do recall the 'day' when a CPU occupied an entire rack, the ALU of which filled several boards...

Nostalgically
HP

 

Aye! Gen1 ECL and 'straight' TTL? --- That's a bit before my time -- 'Tho I do recall the 'day' when a CPU occupied an entire rack, the ALU of which filled several boards...

I worked as a tech assembling HP3000 computers; they were the size of refrigerators. The NIR/CIR (Next/Current Instruction Registers) were one board each and the boards were around a square foot. IIRC, memory controller was 2 boards. Each board was around 5 E sized schematics. It ran at 5.5MHz. We did troubleshooting to the component level; though many of the less competent techs were nothing more than board swappers...

 

I worked as a tech assembling HP3000 computers; they were the size of refrigerators. The NIR/CIR (Next/Current Instruction Registers) were one board each. IIRC, memory controller was 2 boards. Each board was around 5 E sized schematics. It ran at 5.5MHz. We did troubleshooting to the component level; though many of the less competent techs were nothing more than board swappers...

Hey! Believe it or not the HP-3000 series III (running MPE V) was the first *real* system I used!!! Additionally I recall the HDD units --- nearly the size of top-loading laundry washers! And when the heads crashed -- Ewwwwww... To this day, I run an MPE emulator on a dedicated Dell Optiplex (as a 'toy') --- An entire 'machine-room' of 1970's functionally (with much to spare) in a 'shoebox'! Times have indeed changed...

With best regards
HP

 

Okay, system appears to be up and running. I went ahead and took out the PTC re-settable fuse for now. After I took it out, I measured the resistance of it...1.1 ohms. Granted that is after it has been off all day and likely had I checked the resistance of it after running and while having the issues, I would have seen a higher resistance. I guess even 1.1 ohms can cause an issue though.

At any rate, this definitely appeared to be my issue. Agree with everybody here that either I don't need any fuse or if I do use one, just use a regular fuse. I know the switching regulator has some built in protection but I guess I was worried about what would happen if the load suddenly started drawing more than my 1 amp rating of the regulator.

A question that I can't seem to wrap my head around, how can the regulator do short circuit protection and NOT have over current protection? Don't they sort of go hand in hand? I would think that a way to do short circuit protection is if the current rises above some threshold (which can either be a really high threshold or just a little above the rating of the regulator). That way the system would shut down whether shorted or over current. Am I way off on this?

Any other final comments or suggestions on my issue before I put this one to bed with no fuse for now?

Thanks for the help from everybody!

Mike

 

Before you ask anymore power supply questions, please read: http://www.google.com/url?sa=t&rct=...=hlZrh_E6fndLN9znqhCBwA&bvm=bv.89947451,d.b2w

It's a really good reference.

I have this wierd 10 Amp HP/Harrison Labs power supply that is "selectable between 0 and 32 V/. Shorting the leads causes a minor spark and nearly zero voltage.

 

Okay, system appears to be up and running. I went ahead and took out the PTC re-settable fuse for now. After I took it out, I measured the resistance of it...1.1 ohms. Granted that is after it has been off all day and likely had I checked the resistance of it after running and while having the issues, I would have seen a higher resistance. I guess even 1.1 ohms can cause an issue though.

At any rate, this definitely appeared to be my issue. Agree with everybody here that either I don't need any fuse or if I do use one, just use a regular fuse. I know the switching regulator has some built in protection but I guess I was worried about what would happen if the load suddenly started drawing more than my 1 amp rating of the regulator.

A question that I can't seem to wrap my head around, how can the regulator do short circuit protection and NOT have over current protection? Don't they sort of go hand in hand? I would think that a way to do short circuit protection is if the current rises above some threshold (which can either be a really high threshold or just a little above the rating of the regulator). That way the system would shut down whether shorted or over current. Am I way off on this?

Any other final comments or suggestions on my issue before I put this one to bed with no fuse for now?

Thanks for the help from everybody!

Mike

Electronic over-current protection is intended to protect functional PS circuitry only and cannot be relied upon from a safety standpoint --- Please use a standard fuse, it'll probably never require replacement, if it does you need to be aware of the over-current condition anyway...

Best regards
HP