• Please review our updated Terms and Rules here

Power Supply

E

Erik

Site Administrator
Staff member
Joined
Apr 27, 2003
Messages
3,588
Location
San Jose, CA
Okay, I'm at wits end (or Witts End if you're into classic text adventures.)

I need a power supply with +5V and -9V and I'm having absolutely no luck finding anything at my local junque places (I've been to HSC and Weird Stuff) or online.

Does anyone have a good source for these types of hobby supplies?

I know I can use a +/-5, +/-12 and "neck down" the 12 to 9, but I'd prefer to get something that doesn't require extra work, if possible.

Ideally I want a linear supply but I'll be happy with a switched supply if that's all I can get. . .

Any ideas?
 
Hi Erik
It sounds like you are doing a 4004 or 8008 project.
For my 4004 system, I bought a closed frame switcher supply
with a 5V and 12V output. To get -9V, I found that it was
within the range of adjustments for the supply. I just
turned the adjustment pot down!
Even if it doesn't quite make it to 9V, one can uaually add
a resistor to bring it to level. In many cases, the 12V is
regulated by a linear regulator so you have to derate the
current output but that usually isn't an issue if the supply
starts with enough current overhead.
Usually on combination switchers, the 5V is regulated by
the switcher power cycle.
Dwight
 
Right you are, Dwight. I'm on an 8008 project at the moment.

I guess I'd be fine with a 5/12 volt switched supply that I could either adjust or run through a regulator (7909, I think) to get to -9.

I'm not even finding a good supply of those (pardon the pun.)

I'll hit up Anchor on Monday (I need switches, LEDs Molex parts and some tools anyway) and if I'm still in the hole after that trip I may have to spring for a bench supply to get started.
 
Hi Erik
Be careful about sequencing. Most parts required the -v to
come up first and go away last or they'd draw a lot of power.
This is usually OK because the filter caps on the +5v are
much slower than the smaller values used on the -v rail.
The -v rail is usally lightly loaded and comes up faster
and then holds longer than the +5v.
I was a weirdstuff about 4 months ago and they had a
number of non-PC type switchers with 2 and 3 outputs.
I guess they've mostly move on. I don't hold out much
hope for Anchor. It is just not their type of product.
HSC or Weirdstuff are still your best bets.
Dwight
 
Dwight Elvey said:
Hi Erik
It sounds like you are doing a 4004 or 8008 project.
For my 4004 system, I bought a closed frame switcher supply
with a 5V and 12V output. To get -9V, I found that it was
within the range of adjustments for the supply. I just
turned the adjustment pot down!
Even if it doesn't quite make it to 9V, one can uaually add
a resistor to bring it to level. In many cases, the 12V is
regulated by a linear regulator so you have to derate the
current output but that usually isn't an issue if the supply
starts with enough current overhead.
Usually on combination switchers, the 5V is regulated by
the switcher power cycle.
Dwight
Click to expand...

On the supplies I use the same trim controls all output voltages. Trying to get 9v from a 12v seems pretty tough. It may work, but maybe not for everyone even on the same supply. Manufactures give a trim specification like -10% to +10%. Anything outside that isn't guaranteed (can generate either under or over voltage faults).

I think Erik's best bet is to get a supply with both +5 and -12, then regulate to -9v.

Erik, I also have -9v regulators. :)
 
Yes, I have the B. But I would probably send you a quad output unit because I think I should keep the one in my Kenbak. I wasn't thinking straight.

The quad has +5/-5/+12/-12. I bought it to try in the Kenbak but I am going to sell the triple one with it.

Grant
 
Well, as per some off-line discussions I'm pretty sure I have the power supply issue figured out.

As it turned out, one of the untagged but brand new supplies I got at Weird Stuff was a +5, +/-12 with what appears to be sufficient amperage to do the job.

The good news is that there was an adjustment pot on the supply that allowed me to trim -12 down to -9. Once I got that figured out I ran back to Weird Stuff to buy some more of the same supplies. I'll use two for the project, one for the -9V and one for the +5V that I need.
 
Dwight Elvey said:
Hi Erik
Be careful about sequencing. Most parts required the -v to
come up first and go away last or they'd draw a lot of power.
This is usually OK because the filter caps on the +5v are
much slower than the smaller values used on the -v rail.
The -v rail is usally lightly loaded and comes up faster
and then holds longer than the +5v.
I was a weirdstuff about 4 months ago and they had a
number of non-PC type switchers with 2 and 3 outputs.
I guess they've mostly move on. I don't hold out much
hope for Anchor. It is just not their type of din rail switching mode PS.
HSC or Weirdstuff are still your best bets.
Dwight
Click to expand...

bet this will help
 
You must log in or register to reply here.
Back
Top