SHORTS, voltage across resistor converts to current

[danny davis]

Do you guys know that method how to find shorts by using a Lab power supply set at 0.1 volt and the current limit set to 1amp

The current should be large enough to see voltage drops

So you will see voltage drops except where the short is?

I'm just not sure what to do after you hook up the lab power supply to 0.1 volt and current limit to 1Amp '

You hook up the lab powers supply to the "input" of the regulator of the circuits powers supply?

Then you probe each stage of the circuit measuring voltage drops?

How does that lead you to the SHORT?

 

[(*steve*)]

Nothing leads you to a short.

We've all been kidding you.

There is no solution.

None of the methods we've suggested work.

Technicians can never find shorts.

I think you'd be better off asking this elsewhere.

Alternatively you could read through the advice already given on this thread.

If you can't do something sensible I'll close this thread too.

 

[CocaCola]

The big question I have is that you have been told multiple times how to narrow down your search for the short, and it appears you continue to look for the golden egg that doesn't exist...

Anyway why are you so focused on shorts? In my years of professional repair shorts were the easy ones they where almost easily identifiable with my EYES, faulty components and erratically behaving components were the ones that made your brain ache to no end... I'm not saying a faulty or erratic component can't be a short or appear to be one but that is part of the game...

And I'm not saying components are never defective but lets face it, a vast majority are not unless they are physically damaged as some point...

Are you keeping records of your measurements and what eventually you found causing them? I'm not talking about hap-hazzard guesses where you simply replace every component and it all the sudden works, I'm talking about narrowing it down to the actual failure point... If you have these records are you seeing a pattern develop? Like one type of component causing the issue or one location on the board being troublesome for the chip placers or what not?

 

[Mongrel Shark]

I can't offer the lever of expertise that *steve* and Cocacola can on this.

But in the time it took me to read down this far, I could have replaced close to 30 resistors and capacitors. These seem to be the main components that you ask about, apart from an IC you removed already.

How expensive are the suspect parts, and what are your stocks of spares like? If you start with the parts most likely to fail (again understanding the circuit is important here), and test them as they come out, you can be sure to find the problem. get lucky and you'll do it before removing too many bits...

If you do do this, make sure you know where everything goes back!

Although I can see the benifit of learning to fault find the "smart" way. Your disclosure problem is limiting with this circuit. I assume being paid work, you can't take forever to fix it.

Just sayin.

Good luck whatever you do.

 

[danny davis]

Test Fixture Pins and intermittent problems

when building a Test fixture that has multiple pins sticking up to test for test points and vias

What are the best pins to use?

Because the pins are causing intermittent problems because they aren't thick enough to be touching the copper through hole plating, or the plating is not that great on the PCB boards that are made

What can I do to fix this problem please?

There is about 20 gold pins sticking up out of this test fixture, but only 6 to 10 work the others you have to move the PCB board around and tilt it

When I was looking at the Gold pins, they are not thick enough to make good contract with the through hole test points or the through hole test points aren't plated well?

 

[CocaCola]

There is no 'best pin' the one that suits any particular application is the best for that particular application, but it might be horrible in another application...

Search Ebay for 'Pogo Pins' lots of different sizes and tip configurations, complete with lots of detailed diagrams! Even some assortment packs...

 

[shrtrnd]

Buy the spring-loaded type pins. When you push down on the test board, all the
pins make contact because the spring-loaded contacts push up into the board.
Look on the Newark or Allied sites to see what I mean.

 

[CocaCola]

Buy the spring-loaded type pins. When you push down on the test board, all the
pins make contact because the spring-loaded contacts push up into the board.
Look on the Newark or Allied sites to see what I mean.

AKA Pogo Pins just like a pogo stick

 

[danny davis]

What should i use to push down on the PCB board?

Because there is components on the PCB board so where do u find room to have something push down on the PCB board?

 

[CocaCola]

What should i use to push down on the PCB board?

Your hand (gloved) would be the obvious choice, if not a pad/board with dense non-conductive foam so it better conforms to the irregular surface... Or even pins spaced out where component are not...

OR

You can Google (are you reading this?) click on the image search and do a search for 'electronic test fixture' for ideas...

 

[danny davis]

What desoldering tool is this guy using at PACE, its a desoldering vacuum but I don't know the name of it

I just sucks the solder up like a vacuum

Take a look at this please:

 

[CocaCola]

What desoldering tool is this guy using at PACE, its a desoldering vacuum but I don't know the name of it

I just sucks the solder up like a vacuum

Take a look at this please:

OK before Steve wrings your neck, did you listen to lets say the first 20-50 words out of the guys mouth, in that video? Pay close attention at the 13 second mark, there is a BIG hint that follows! And there is also a BIG hint if you bothered to read the title of the video... I won't give it away, you will have to find the *hints* yourself...

If you are REALLY stuck, maybe the link in the first line of the video description will give it away?

Look familiar?

 

[danny davis]

wait hold on

What is the model and brand and do they still make that?

PACE is the brand right? but what is it called and where do you buy that?

 

[CocaCola]

 

[danny davis]

PACE is not around anymore and you can only get it on Ebay

Is there anything like it that i can buy now that is like the PACE PRC 2000 machine?

I like the desoldering vacuum tool

I don't like desoldering GUNs you find on rework machines

Is there anything else?

 

[CocaCola]

PACE is not around anymore

Dude, let the smoke clear so you can see in front of you before you post again... OK?

 

[danny davis]

what desoldering tools u use?

 

[(*steve*)]

Danny, do you have some form of learning disability? If you do, that's fine. At the moment your posting style is infuriating and it appears that you don't listen and are wilfully ignorant.

If you do have a problem, let us know. We'll be a lot more understanding.

Whilst I would like to think that we can be nice to people all the time, there comes a point when we have been around this mulberry bush a few times already and we begin to wonder why you're not "getting it"

 

[danny davis]

yes i do have a learning disability plus i'm not familiar with desoldering tools

The only ones i have used have been desoldering guns which i don't like much

I like the desoldering tool that the PACE PRC 2000 has, but i don't know who makes one this is like that please?

 

[CocaCola]

I like the desoldering tool that the PACE PRC 2000 has, but i don't know who makes one this is like that please?

If you like the PACE one why are you looking for one like it, just get the PACE one... If you want to spend more money get the Weller (and likely other brand name) tools that it's a knock off of...

Remember when I said...

If you are REALLY stuck, maybe the link in the first line of the video description will give it away?

It's just a few post up, did you follow that lead I gave you?

Can you copy and paste the first line of the video description in your next post so I know you are reading?

And just so there is no confusion, I have attached a picture of what I would like you to copy and paste for me... I outlined it in a red with a glowing orange background...