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PS step 4, 10v across C1
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PS step 4, 10v across C1

by Brandon Daniel on Sat Jun 04, 2005 11:44 pm

I'm a total n00b at kits, so sorry if I end up asking a lot of questions here, I'm hoping I don't run into too much trouble but...

I've started the power supply section, and I've gotten to step 4, and I'm see 10v across C1 instead of 6v, in checking the output of the regulator ic21, it too seems to be spitting out 10v.

All the check-points up until this step came out ok, and continue to read just fine despite the overvoltage out of the regulator. I've double checked that all the joints on and around the regulator are solid and not bridged with anything else, and ic21's orientation is according to the board silk screen.

Anyone have any thoughts or suggestions?
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by Jonnay on Sun Jun 05, 2005 2:39 am

Are you using the proper IC? Are you properly probing it with the multimeter? Have you given it a few seconds to stablize its reading? Not that I really know what I am doing... I had some issues with that step, and my problem was that I reversed the direction of IC21 >8-P Maybe double check your orientations of IC's and Caps?
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by altitude on Sun Jun 05, 2005 8:36 am

check your resistors, orange and red look alike on the pictures

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by Brandon Daniel on Sun Jun 05, 2005 12:20 pm

Jonnay wrote:Are you using the proper IC? Are you properly probing it with the multimeter?


I'm sure I've got the right regulator IC, I took a cue from your pictures (thanks for posting those, btw, I'm sure this step is helping me immensely!) and printed off the assembly guide for the PS before starting, then sorted all my parts, and taped the various parts to their pictures in the assembly guide. Also, I double checked the part before I placed it. I trust that the multimeter reading of the IC out is correct, given that it is the same as what I'm seeing across C1, which is getting the IC's output.

Jonnay wrote: Have you given it a few seconds to stablize its reading? Not that I really know what I am doing... I had some issues with that step, and my problem was that I reversed the direction of IC21 >8-P Maybe double check your orientations of IC's and Caps?


Yeah, before it's stabilized it's jumping around between 13v and some mv readings... I was pretty careful to match the two big polarized caps with the pictures and get the long legs in the positive side. I *know* ic21 is in there right, unless the silk screen is wrong, but I doubt that. IC20 is spitting out the right V, so I'm guessing that's right too.

Maybe I'm just incredibly unlucky and got a bum 6v regulator?

I'll explore that possibility today, I guess. Thanks for the help, guys, I wanted to make sure there wasn't anything going on here that had escaped my grasp, but you're confirming my thoughts that there wasn't a whole lot here yet to go wrong...
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by Brandon Daniel on Sun Jun 05, 2005 12:22 pm

Altitude wrote:check your resistors, orange and red look alike on the pictures


A. at step 4 you haven't placed any resistors yet, according to the instructions.

B. I give my Rs a quick multimeter test before I tape them to the printed assembly guide to make sure they're the right ones and within a decent tolerance, I figure that'll save me a lot of work second-guessing things later.
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by Jonnay on Sun Jun 05, 2005 5:14 pm

I'm sure I've got the right regulator IC, I took a cue from your pictures (thanks for posting those, btw, I'm sure this step is helping me immensely!)


Good stuff. Nice to know they are actually helping people. Just remember, I screwed my voltage regulator at IC21 so your IO board will look different!
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by adafruit on Sun Jun 05, 2005 5:19 pm

Brandon Daniel wrote:Yeah, before it's stabilized it's jumping around between 13v and some mv readings... I was pretty careful to match the two big polarized caps with the pictures and get the long legs in the positive side. I *know* ic21 is in there right, unless the silk screen is wrong, but I doubt that. IC20 is spitting out the right V, so I'm guessing that's right too.

Maybe I'm just incredibly unlucky and got a bum 6v regulator?

I'll explore that possibility today, I guess. Thanks for the help, guys, I wanted to make sure there wasn't anything going on here that had escaped my grasp, but you're confirming my thoughts that there wasn't a whole lot here yet to go wrong...


is your 5V regulator working right? it is possible (although very unlikely) that your 78L06 is busted. posting a high quality picture might make it easier for us to see whats up

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by Brandon Daniel on Sun Jun 05, 2005 9:24 pm

Jonnay wrote:
Good stuff. Nice to know they are actually helping people. Just remember, I screwed my voltage regulator at IC21 so your IO board will look different!


Yeah, I wasn't really using your assembly so much as your process. Taping the parts to the BOM ahead of time removes the part searching from the part placing and soldering, which is just the ticket to keep my easily-distracted mind from screwing this stuff up. As it turns out, I too am using a different IC there at 21 now, but more on this in a minute...
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by Brandon Daniel on Sun Jun 05, 2005 9:28 pm

ladyada wrote:is your 5V regulator working right? it is possible (although very unlikely) that your 78L06 is busted. posting a high quality picture might make it easier for us to see whats up


My 5v was fine, everything was great up to the 6v reg IC, and that was spitting out over 10v. I ran down to the local Fry's today and picked up a pin-compatible NTE 6v reg and once that replacement was in the output was 5.83 solid, within the acceptable range.

So I guess something was funky with that 78L06, either from factory or something I did (though I'm not sure what this would be). No big deal, it's good to know I'm not going insane here ;0)
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by adafruit on Sun Jun 05, 2005 9:36 pm

ok thanks for the heads up on the misbehaving part.

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by Brandon Daniel on Mon Jun 06, 2005 12:02 am

ladyada wrote:ok thanks for the heads up on the misbehaving part.


np, thankfully after that little catch the rest of the PS went together nice and quick-like, works perfect. Now onto other, more interesting sections...
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by Brandon Daniel on Wed Jun 08, 2005 9:55 pm

hm, anyone know anyplace I can order a 78L06 where shipping won't cost me 10x the cost of the part? The regulator I have in there is fine for now, but it looks like it will get in the way of the headphone output once I get to that point, so I'd like to get one in the original form factor on order soon so it will arrive before I need to place the headphone out parts...
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Please be positive and constructive with your questions and comments.