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Buzzing RL02 - Need Help Troubleshooting

Jameco doesn't have them either. So far, the only places that do have a $200 minimum order. Who would have thought in the 21st century things would still be so backward and underdeveloped? The internet is truly worthless for many things yet...
 
Jon,

I've had two thoughts on this so far today. One, if the load is only 1A, than maybe a TO-220 case 7908 is worth a try. However, if you need the full 1.5A that the TO-3 version gave, you could use an LM337 in a TO-3 case and program it for 8V. But, you cannot just plug the 337 in where the 7908 was, you will need to mount it remotely and wire it back.

For the heck of it, I looked and was not able to locate any 7908s in TO-3 cases anywhere either.

I just looked at my notes scrawled on the top of the RL01 with broken power supply, and it was the 7908 (-8V supply) that is toast. So, with two data points, I would now definitely suggest the LM337 route.

Lou
 
Hey Lou,
So, it sounds like these 7908s are a fairly common failure point on the RL0X's. As far as a 337, I don't know what that is, or how to "program" it.

I was really hoping for something pretty straightforward- replacing with a like unit, but I'm not sure if that will be possible.

-Jon
 
Jon,

The LM337 is the negative voltage cousin of the common LM317 positive voltage regulator. It is an adjustable device, with the output voltage "programmed" with two external resistors. See here: http://www.fairchildsemi.com/ds/LM/LM337.pdf .

Drop in replacements are nice, but on one out of ten projects I run into failed "unobtanium" devices that I have to work out some kind of replacement for. It's part of the fun of working on "vintage" equipment.

Lou
 
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