F5 power amplifier

If you have counterfeit versions of a discontinued product that outperform the authentic part, I for one would be interested in trying them.

How would you know their performance?

Are you going to buy 1000 of them and test them for 10 years under various environmental conditions etc? What exactly would you be testing for and what is your tolerance for whatever dimension you were testing?
 
You can actually avoid using them

Sure, but your money is already gone ;)

Before getting too excited, I would be inclined to see how
they performed.

Hi Nelson,

The parts I have on hand show an IDSS of around 20mA; I haven't found time to test for transconductance. Noise performance will stay unknown as I don't have the equipment.

I'm not aware of any p-channel jfet that comes reasonably close to the J74 in terms of transconductance (there are a few Sanyos and I think a NXP for the n-channel counterparts), so I would expect a lower performing part. However, it could easily be that you know more than me on alternatives.

Hannes
 
Do you think these are genuine or counterfeits? Thanks.
 

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Ex-Moderator R.I.P.
Joined 2005
Do you think these are genuine or counterfeits? Thanks.

hey, please mark my words

I do not know

but what I see in your picture looks slightly cheap and 'dodgy'

or in other words
doesnt look carefully made like we see other Toshiba's
writiing looks a bit quer
Jfets arent sitting straight
legs arent paralel, or nicely seated in the tape
and tape looks, ehh, cheap
as said, I do not know
 

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Hi everyone,

I received what I supposed to be the case I purchased. Unfortunaly, I a Hifi2000 3U 400mm whereas I ordered a 4U 300mm...

I don't know if I have to send it back or use it. Actually, the 4U 300mm thermal resistance of each sink is 0.31°/W which is what is required according to Nelson Pass' F5 use guide. Unfortunally, I can't find the thermal resistance for the 3U 400mm.

I can read this from Cviller a "few" posts ago ^^

I'm currently using the 40cm 3u version for my f5 and it does not get too hot at all. In fact I think the 30cm would be sufficient.

If someone has more specifications to communicate about this case, feel free to post them please.
 
Can't believe I wrote 3u back then... but I am using 4u 400mm and I can keep my hands on them for as long as I live.

But you can calculate what you need using the specs of the heatsink. The channels are dissipating roughly 60W, so a 0.31 sink would see a temperature increase of 60*0.31=18.6 degrees. You add that to your living room temperature and try to stay below 55 deg C.
 
Can't believe I wrote 3u back then... but I am using 4u 400mm and I can keep my hands on them for as long as I live.

That makes more sense :)

But you can calculate what you need using the specs of the heatsink. The channels are dissipating roughly 60W, so a 0.31 sink would see a temperature increase of 60*0.31=18.6 degrees. You add that to your living room temperature and try to stay below 55 deg C.

Of course, the only problem is I can't find the thermal resistance for the 3U 400mm.
I think I'll ask the vendor for a trade.

Thank you very much for your answer.