What is the exact model of this transistor?

[daisizhou]

Shell reads "MSPF 179 752"

Does anyone know its exact model?
If you know please tell me, thanks

[wasedadoc]

That 'M' is the Motorola logo.  Probably not the first letter of the model number.

SPF179 is a N-channel FET.

[daisizhou]

SPF 179 152？But there is no such model

[bdunham7]

It is a Motorola/Freescale SPF179 aka Fluke 261388, identified as NSN 5961-00-402-1979.  I've no idea what exact type of device it actually is and at least one source says that it is ITAR controlled.  I found no cross-reference to any jelly bean parts as you're probably hoping.  It might be a special or select version of the BF179, but I'd have to know what device it is in and how it is used to say whether that's even a possibility.

[bdunham7]

SPF179 is a N-channel FET.

I didn't find it for some reason.  Where did you look that up?

[wasedadoc]

SPF179 is a N-channel FET.

I didn't find it for some reason.  Where did you look that up?

Occurs in some parts lists for old Fluke equipment.  E.g. bottom of page 5-20 of https://usermanual.wiki/m/3f0ec0ba0fdff036e359a258d61212986186bc5daca87076268a318ead250057.pdf and Q17, Q26 on page 5-13 of https://manualzz.com/doc/22683395/515a---fluke

[bdunham7]

Occurs in some parts lists for old Fluke equipment. 
[/quote]

I didn't try looking in any of my manuals as I'm somewhat familiar with the N-J-Fets in the stuff I have.  I think one could write a whole book just on the custom/select N-J-Fets of Fluke.

Fortunately Central Semiconductor still makes J-FETs, the PN4391/4392/4393 series work in a lot of Fluke applications.

[BrokenYugo]

SPF 179 152？But there is no such model

152 is probably the date code.

[wasedadoc]

SPF 179 152？But there is no such model

152 is probably the date code.

It is 752, not 152.  Date code or some other  batch, factory or other code.

[fzabkar]

Also here:

https://www.bitsavers.org/test_equipment/fluke/314716_8400A_Digital_Voltmeter_Instruction_Manual_w_upd_198907.pdf

[daisizhou]

Thanks.It comes from Fluke 8920a. Please see Q208, Q209 on page 117 of the accessory manual.(https://www.elso.sk/media/download/pdf/fluke/man/Fluke_8920A_8921A_Manual.pdf)

I removed the influence of S202, S203 and U205 on the circuit,Measure the resistance of Q209 and Q208 to be 68.4 ohms.
Q209 and Q208 are the transistors above,I don’t know if Q208 and Q209 are faulty or normal.

[daisizhou]

Q208、Q209，Rds Is the resistance value 68.5-68.4 ohms normal?

[bdunham7]

Q208、Q209，Rds Is the resistance value 68.5-68.4 ohms normal?

Probably normal, the J-FET conducts until it is turned off but is only intended for small power levels.  Without a datasheet it's hard to know precisely what a good value is but I'd expect something like that.  The PN4392 that I commonly use to replace some Fluke J-FETS has a max R_DS(ON) of 60 ohms and the lower-leakage more sensitive PN4393 is 100 ohms.  You should check the gate leakage as well.  What is the issue you're having and what leads you to those transistors as being the cause? 

[daisizhou]

My FLUKE 8920a encountered a strange failure, please watch the video---


This is what I posted a few days ago, but no one can help me --https://www.eevblog.com/forum/repair/fluke-8920a-multimeter-repair-needs-some-help/

If 8920a is not powered on for a long time (power on),The first time you turn it on, it will definitely have the above fault.
If it is normal, turn on the 8920a every day and it will return to normal.So I spent a lot of time testing it,I've never been able to pinpoint the fault point

The fault phenomenon is that when you turn on the computer, you will see "700" flashing all the time.
Sometimes the "mv" gear and "V" gear keep jumping automatically, just like what was captured in the video
I don't know how to find the fault point correctly

[daisizhou]

This is the latest video. It seems that the fault is related to the gear, especially the low range enable.

[daisizhou]

Q209 and Q208 seem to be like this, but my fault still exists.