F3 Builders Thread

[Joschl]

Your 10% error in resistance will give you 10% error in current.
For resistors in the one digit Ohm range, I use a constant current source of 1A and measure the voltage drop over the resistor. That gives me a more precise value.
Do you have a bench supply with current limiting function?

 

[lordvader]

Ah! Gotcha.

Well replacement transistors + fets should be trickling in. I'm going to move everything over to some clean PCBs. All this soldering/de-soldering seems to be causing the pads to lift.

Aaaaand ... We're up an running again. Had a close call when I had an electrolytic cap in backwards (20 years - I've NEVER done that!), but had a spare, and all good

 

[2 picoDumbs]

Good job

 

[edwtsui]

More likely your DMM can't measure resistances that low accurately (the test leads will have nearly as much resistance as the resistor).

Did you measure more than one? Are they all the same?

Thanks. I will try to measure with another DMM later

 

[edwtsui]

Your 10% error in resistance will give you 10% error in current.
For resistors in the one digit Ohm range, I use a constant current source of 1A and measure the voltage drop over the resistor. That gives me a more precise value.
Do you have a bench supply with current limiting function?

I can adjust Vd such that Vgs=1V. But I am sure that Vd will be lower than 3V. I forgot the value, maybe 2.x. I don't remember

 

[edwtsui]

Today I bought two LUs from Jim's Audio. I redo the test and found that the Vgs only got 5xx mV, so pretty sure that they are counterfeits.


Everyone, please tell me where can I get the genuine LU1014D? I have been spending few months on building the F3 and now I cannot continue my work due to missing of the most important parts. I am very frustrated, can anyone help?

 

[JeffYoung]

Post a wanted ad. Nelson handed out tons of freebies; there must be someone out there that doesn't really need theirs....

(I already gave my extras away.)

 

[JeffYoung]

Your Jim's Audio ones look a lot like my probable-fakes (bought off of eBay).

The one from Nelson is on the right; note the shorter legs and thicker lettering.

 

[Rush]

Today I bought two LUs from Jim's Audio. I redo the test and found that the Vgs only got 5xx mV, so pretty sure that they are counterfeits.


Everyone, please tell me where can I get the genuine LU1014D? I have been spending few months on building the F3 and now I cannot continue my work due to missing of the most important parts. I am very frustrated, can anyone help?

Found these on eBay in Hong Kong:

6pcs LU1014D N-channel power J-FET 2 pieces for SE amps and Pass F3 | eBay

They look like the real deal.

I have some real ones I don't need also, but shipping will be cheaper to you from Hong Kong.

Rush

 

[edwtsui]

This is the one I measured with 1.34V Vgs. The physical dimensions matched with the datasheet but I cannot get around 1V Vgs. God, I am very confused...

 

[edwtsui]

Found these on eBay in Hong Kong:

6pcs LU1014D N-channel power J-FET 2 pieces for SE amps and Pass F3 | eBay

They look like the real deal.

I have some real ones I don't need also, but shipping will be cheaper to you from Hong Kong.

Rush

Hi Rush,

I prefer not buying from ebay. How many can you offer? I can pay the shipping cost.

Thanks for your help

 

[Rush]

I replied to your message.

Here are some pictures:


Rush

 

[jameshillj]

Hi edwtsui,

I have quite a few of these you can have if you want - these were the last of Grey Rollins' GB some years ago and closely matched for F3 current use. I also have a couple of spare partially assembled boards too if they would be of any use to you.

 

[lordvader]

Found these on eBay in Hong Kong:



6pcs LU1014D N-channel power J-FET 2 pieces for SE amps and Pass F3 | eBay



They look like the real deal.



I have some real ones I don't need also, but shipping will be cheaper to you from Hong Kong.



Rush

I bought some of these. The items don't match the image.
The right one is a genuine part, the ones of the left are what arrived. The legs are really flimsy too - snapped off while bending them to measure.

They seem to measure ok, but don't trust them

 

[2 picoDumbs]

When certain countries are capable of putting melamine into baby formula, how could you trust those countries with anything.

 

[Zen Mod]

When certain countries are capable of putting melamine into baby formula, how could you trust those countries with anything.

wrong context

if you 're going by country, there is no single one,which didn't violate everything humane in recent history

 

[JeffYoung]

I bought some of these. The items don't match the image.

Sigh.

Yeah, I wouldn't trust them either.

 

[2 picoDumbs]

wrong context

if you 're going by country, there is no single one,which didn't violate everything humane in recent history

I won't argue with any of that.

For me personally, I will avoid where ever possible purchasing electronic components from certain countries that are notorious for producing counterfeit parts.

 

[JeffYoung]

For me personally, I will avoid where ever possible purchasing electronic components from certain countries that are notorious for producing counterfeit parts.

I'm not sure where to go with this.

I do the same because it's such a huge time/aggro saver. But that's profiling, and I'm sure a cop in the 1980's would have said the same about stopping black drivers....

So what does one do?

 

[2 picoDumbs]

I don't mind buying from members but not random people on ebay etc.
If it's a chassis or heatsink that's fine but I won't touch electric components.

Same as I wouldn't let my children being taken care of by strangers etc.