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jonheal
2006-01-12, 18:02
I bought a couple of alledgedly linear power supplies on eBay for cheap. They're big suckahs. They weigh about 3 lbs:

http://cgi.ebay.com/5-VDC-linear-brick-power-supply-lot-of-2_W0QQitemZ7571275306QQcategoryZ36323QQssPageNameZ WD1VQQrdZ1QQcmdZViewItem

I put the old multi-meter on them and got 5.22V DC. The label says they deliver 2300mA.

Do you reckon they're safe for the SB3?

seanadams
2006-01-12, 18:10
I bought a couple of alledgedly linear power supplies on eBay for cheap. They're big suckahs. They weigh about 3 lbs:

http://cgi.ebay.com/5-VDC-linear-brick-power-supply-lot-of-2_W0QQitemZ7571275306QQcategoryZ36323QQssPageNameZ WD1VQQrdZ1QQcmdZViewItem

I put the old multi-meter on them and got 5.22V DC. The label says they deliver 2300mA.

Do you reckon they're safe for the SB3?

You need to look for an adjustment knob (usually a small pot you turn with a screwdriver). Dial it in to 5.0V and you should be good.

jonheal
2006-01-12, 19:58
You need to look for an adjustment knob (usually a small pot you turn with a screwdriver). Dial it in to 5.0V and you should be good.

Unfortunately, these babies are glued shut.

seanadams
2006-01-12, 20:40
It'll work at 5.2V but I would not recommend running it like that for an extended time. Although SB3 does have over-voltage protection it won't kick in until 5.5 or so.

The thing is the internal VFD supply depends on the 5V supply being accurate in order to generate its filament voltage. If the filament voltage is too high you may decrease lifetime/brightness of the display - I can't say for sure what to expect.

Anyway I would not have much confidence in a 5V supply which is off by such a margin.

nelamvr6
2006-01-12, 20:54
It'll work at 5.2V but I would not recommend running it like that for an extended time. Although SB3 does have over-voltage protection it won't kick in until 5.5 or so.

The thing is the internal VFD supply depends on the 5V supply being accurate in order to generate its filament voltage. If the filament voltage is too high you may decrease lifetime/brightness of the display - I can't say for sure what to expect.

Anyway I would not have much confidence in a 5V supply which is off by such a margin.


That's really only 4% off. And unloaded too. Hard to say just how bad it is without loading it.

Bill Burns
2006-01-12, 21:10
nelamvr6 wrote:
> seanadams Wrote:
>
>>It'll work at 5.2V but I would not recommend running it like that for an
>>extended time. Although SB3 does have over-voltage protection it won't
>>kick in until 5.5 or so.
>>
>>The thing is the internal VFD supply depends on the 5V supply being
>>accurate in order to generate its filament voltage. If the filament
>>voltage is too high you may decrease lifetime/brightness of the display
>>- I can't say for sure what to expect.
>>
>>Anyway I would not have much confidence in a 5V supply which is off by
>>such a margin.
>
>
>
> That's really only 4% off. And unloaded too. Hard to say just how bad
> it is without loading it.

I just measured the no-load voltage on the power supply for my SB1 at
5.3 V. That seems well within tolerance for a low-cost supply. Is the
SB2/3 power supply really so much better?

--
Bill Burns
Long Island NY USA
http://ftldesign.com

seanadams
2006-01-12, 21:37
Actually you're right I just checked our supply and it runs 5.25 with no load (5.0 when connected).

Realize I'm erring on the side of caution here - we spent a great deal of time testing our own power supply but I have no idea how any other particular one is going to perform - I'm just suggesting what *might* go wrong.

If you want to be safe open up the sb3 and check the voltage at the input when it's connected.

Bill Burns
2006-01-13, 08:53
seanadams wrote:
> Actually you're right I just checked our supply and it runs 5.25 with no
> load (5.0 when connected).
>
> Realize I'm erring on the side of caution here - we spent a great deal
> of time testing our own power supply but I have no idea how any other
> particular one is going to perform - I'm just suggesting what *might*
> go wrong.
>
> If you want to be safe open up the sb3 and check the voltage at the
> input when it's connected.

Good advice, and I understand your need for caution, but what's the
manufacturer's voltage tolerance in the specs for the display? Do they
assume it will always be run on a tightly-regulated supply, or is there
some room for normal voltage variations?

--
Bill Burns
Long Island NY USA
http://ftldesign.com