Re: Great Design
- From: Tim Wescott <tim@xxxxxxxxxxxxxxxx>
- Date: Sat, 25 Apr 2009 12:20:55 -0700
alchazz wrote:
I was amazed the other day. At my town's recycling center, I found two variable power supplies made by HP, model 721A. I cleaned them up, plugged them one at a time into a fused extension and turned them on. Voila, they both worked!
The date code on the PCB is 12-15-59. These beauts are ~50 years old and work like a charm. I tested them throughout their operating range, 0-30VDC, 0-225MA.
The pass transistor is a 2N375, with a P(max) of 45W and an Ic(max) of 3A. I wonder if it is germanium? I also wonder what the predicted MTBF was of these guys? I know the current ones are targeted to 3yrs.
How you run a bit of power semiconductor has a huge effect on the MTBF (more properly the MTTF) -- derate it so that it runs cooler, and it'll last a lot longer.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
.
- Follow-Ups:
- Re: Great Design
- From: alchazz
- Re: Great Design
- References:
- Great Design
- From: alchazz
- Great Design
- Prev by Date: Re: flu
- Next by Date: Re: How you can tell someone is a pirate.
- Previous by thread: Re: Great Design
- Next by thread: Re: Great Design
- Index(es):
Relevant Pages
|
