SissySIT

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pras1170

Member
Joined 2018
schultzsch said:
Well both are suitable, the important thing is to place a temperature sensor on the heatsink to do the measurements at the same temperature
Attaching the sensor to the sink you will have to do the measurements at 55-60c(degrees on the heatsink) so maybe the smaller sink is suitable because it gets sooner in temperature.
Click to expand...

Well, that's a bit of a hassle

What kind of temperature sensor do need
 
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pras1170

Member
Joined 2018
Zen Mod said:
pras

use bigger heatsink , keep fan close to it , blowing on heatsink all the time

we don't need absolute precision from your measurements , just relative ones , but steady in conditions

it's easier to maintain "coldness" with fan , than keeping some higher temperature for all DUTs
Click to expand...

Well, the fan is blowing, there is no problem.
This one of the white, is it right?

I think he is big enough.
 
chromenuts

chromenuts

Member
Joined 2008
Paid Member
Dave from Cinemag reached out to me...they’re very busy.

The order is placed and paid for...well, after a slight mishap with the shipping costs being accidentally billed at $999.00...LOL!!! It’s all sorted out now and they should be here sooner or later.

I’m not in a huge rush as I’m still wrestling with my tonearm project and a few other things.

To be honest, I have a slew of things I feel obligated to finish before diving into the Sissy...including my F2J, trying some iron on my DCB1 and setting up my other horns with the Lowthers.

Did I mention I’m trying to renovate an old sunroom on the back of the house to turn it into a actual listening room? Oh, and the cars needed work done on them and the furnace had to be serviced.:headbash::headbash::headbash:
 
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Ben Mah

Member
Joined 2012
Paid Member
Ben Mah said:
I have been in discussions with watanabetomoaki of ebay regarding the Vgs measurements of the THF-51S that I had purchased from him. His test method was different from the one shown by Zen Mod. He has asked me to pass on the following message:

"I have been requested only by SIT of the same characteristics from many members of this forum. Thank you.
I did not include such strict matching fee for my listing, but at first I was receiving favorably.
However, too many people made the same request, and even complaints about the accuracy of screening came.
In this state, in the near future I will not be able to continue similar services.
Anyway, no so much stock anymore ...
However, I also made a mistake. That is, there are several sorted by connecting drain and source in reverse.
That was happend when the buyer directly requested the determined Id value.
In principle, the FET has no polarity at drain and source. Of course, this FET does not have built-in protection diodes like MOS type ones.
So, drain and source may be either. So, why do you specify it? That is because, of course, the value of Id is not symmetrical at all.
Naturally, as a manufacturing company, because typical characteristics are shown, general polarity designation is necessary.
However, there is no necessity for measuring the characteristics data sheet with DIY and using it.
So, in order to get closer to the Id value that the purchaser wished, the person who specified the Id value,I have measured the metal case as GND.
I think that it is my only mistake to have a case where I forget to tell him that.
So, if you received the SITs those characteristics are very different, measure the drain and source by exchanging it and use it."
Click to expand...

SPWONG said:
Will it cause any damage to the SIT by reversing D and S as in the testing by TOMO?
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Zen Mod said:
I believe not

to be sure , just test yours
Click to expand...
.
Well, I tested one THF-51S with source and drain reversed. This device had 2.5 written on its bottom. According to Tomo, he tested at 25V, Vgs=-1V, at 25 degrees C, with V+ applied to source and drain grounded, and the written number is Id (A).

My Results:

V+ to Drain, Source grounded ...........V+ to Source, Drain grounded

V+............Id............Vgs ................V+............Id............Vgs (g to d)

24.0V......1.8A.........-4.46V.............24.0V........1.8V..........-1.79V
24.0V......2.0A.........-4.38V.............24.0V........2.0A..........-1.47V
25.0V......2.5A.........-4.28V.............25.1V........2.45A.........-0.91V
....................................................25.0V........2.27A.........-1.0V

So with the V+ applied to Source my test result is similar to Tomo's result: 2.27A versus his 2.5A. His number is apparently at 25 degrees C whereas I had attached the device to a heat sink and let the temperature rise above 25 C.

Tomo also wrote that the THF-51S can be used with the source and drain reversed. I had asked him for clarification and he said to connect with metal case to Ground and large pin to V+. Assuming that Vgs is in the proper range, will that work in a SissySit as designed, or work but perform below par, or not at all?
 
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