Balanced F5 question

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#566
Isn't buying chassis from China risky, they could be fakes.


Howcome i have the feeling, Vladimir and I shop at the same street sign corner ? :scratch1:
 

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#567
since i bought them myself in guangzhou, so i can choose which one to buy.

the raw aluminum market price there between 15-20,000rmb or 2200-3000usd/ton depends on the time of the market.

china have many things to choose from, u can buy the cheapest available, but u can also buy things that really have good value.

cheers
henry
 
#570
Should one worry about thermal expansion problems?

EUVL said:
The idea is good, but if you would read posts #326, 327, (339) and 341, you might also agree that it brings very little.
At most 2~3°C, at the expense of larger PCB and long signal path for the X.


Patrick
Click to expand...


What about differences in the coefficients of thermal expansion of the pc board vs. the heatsinks? Also, between the opposite sides (ie. the opposite polarity halves) of the amplifier? Could this pose problems of mechanical stress on the terminals of the output MOSFETs?
 
#572
The coefficient of thermal expansion for aluminum is 12.3 x 10^-6 inches per degree Fahrenheit. So if you have a difference of 20 to 65 Celsius, thats roughly a difference of 70 degrees Fahrenheit. Over a PCB that is say 6 inches long, that means the aluminum would expand roughly 0.005 inches (assuming I didn't mess up on the crappy windows calculator).

I wouldn't think that's going to pose any problems.
 
#574
> alot of agressiveness here

Was not intending to be. My apologies.

If you know manufacturing in China, then you know that you can get from junk to top quality, with vastly different prices.

Just take the front panel. You can use US imported 6061, or Chinese 6061.
If you black anodise, then you would probably not notice any difference.
If you do matt silver anodise, you can tell which is which immediately.
And we have thrown away a thousand USD's worth of front panels (for our own use) just for that reason.


Patrick
 
#575
EUVL said:
> alot of agressiveness here

Was not intending to be. My apologies.

If you know manufacturing in China, then you know that you can get from junk to top quality, with vastly different prices.

Just take the front panel. You can use US imported 6061, or Chinese 6061.
If you black anodise, then you would probably not notice any difference.
If you do matt silver anodise, you can tell which is which immediately.
And we have thrown away a thousand USD's worth of front panels (for our own use) just for that reason.


Patrick
Click to expand...

Perhaps next time you might consider offering them for sale here on DIYA.
 
#576
hi patrick,

im kind of curious what would be the difference is? the chassis i bought wast machine milled from a alum profiles extrusions.

i dont know for sure the grades they are using, but it does look less pleasing as PASS XA AMPS.

cheers
henry
 
#577
Another update :

Variac is now up to speed and we had our first team meeting by email.

I received the draft of 3 of the PCBs today and shall check them in the next day or so.

We agreed who would be doing the prototype builds, etc., and we also agreed that all PCBs will be prototyped and tested first before volume production.

We also had the first discussion with the case production people.
Apart from a few things that need finalising, we think we'll be able to keep to the promised production costs.

So things are moving at pace, at last.


😉


Patrick
 
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