1 minute ago, swt61 said:

I seem to remember some guy laughing at me trying to read resistors when I built Colin's amp. 🙂

Now I have one bionic eye, and can read them fine.

😂

8 hours ago, luvdunhill said:

Can anyone recommend a nice portable HD microscope to go with my new far-sightedness for soldering?

I purchased a cheap rebranded scope from amazon one a few years back for smd and pcb inspection It looks identical to this one:

https://amscope.com/collections/student-microscopes-low-power-stereo/products/se420xyz-2l

it works. My only complaints are

1. it does not have a zoom

2. its not trinocular so you can't add a camera look through it at the same time

3. there is no real X and Y adjustment. instead it pivots around which makes moving around a pcb a bit of a pain.

4. because the objective lenses are housed in a rectangular box you cant fit a ring light easily.

5. the objective lenses are not a "standard" mount and that limits you options for different lenses

 

Edited August 30, 20241 yr by jamesmking

14 hours ago, jamesmking said:

I purchased a cheap rebranded scope from amazon one a few years back for smd and pcb inspection It looks identical to this one:

https://amscope.com/collections/student-microscopes-low-power-stereo/products/se420xyz-2l

it works. My only complaints are

1. it does not have a zoom

2. its not trinocular so you can't add a camera look through it at the same time

3. there is no real X and Y adjustment. instead it pivots around which makes moving around a pcb a bit of a pain.

4. because the objective lenses are housed in a rectangular box you cant fit a ring light easily.

5. the objective lenses are not a "standard" mount and that limits you options for different lenses

 

Do you use it for inspection or for assembly?

1 hour ago, luvdunhill said:

Do you use it for inspection or for assembly?

bit of both. working distance is ok for either a hot air handle or a soldering iron.

It takes some getting used to since you have a fixed defined viewing circle, you can't move your head and have to organise everything around that. 

I personally found that exact head positioning was very critical to get a good 3d perspective view and this meant I wanted to minimise the number of times I looked up away from the microscope.

Edited August 30, 20241 yr by jamesmking

Hello all!

Now FJPF2145 obsolete on Mouser. But I need to finish my T2. Where it is possible to get or how to replace them?

What you think?

3 hours ago, bbest said:

Hello all!

Now FJPF2145 obsolete on Mouser. But I need to finish my T2. Where it is possible to get or how to replace them?

What you think?

FJPF5027OTU seems to be a possibility, seems to have similar specs except lower current rating and the same pinout. 
Hfe of FJPF2145 is 20 - 40 which is the same as the O variant of the 5027

 

2 hours ago, jamesmking said:

FJPF5027OTU seems to be a possibility, seems to have similar specs except lower current rating and the same pinout. 
Hfe of FJPF2145 is 20 - 40 which is the same as the O variant of the 5027

 

all good, but output capasitance 60pF vs 11pF.

Edited October 13, 20241 yr by bbest

Not sure where you are at, but Octopart shows this:

https://octopart.com/search?q=FJPF2145&currency=USD&specs=0

 

2 hours ago, bbest said:

all good, but output capasitance 60pF vs 11pF.

farnell in the uk has plenty of stock of the FJPF2145 

https://uk.farnell.com/onsemi/fjpf2145tu/trans-npn-800v-5a-125deg-c-40w/dp/3368628

Looks like you have to buy 250 of them though...

On 10/13/2024 at 4:06 PM, bbest said:

On 10/13/2024 at 1:44 PM, jamesmking said:

 

all good, but output capasitance 60pF vs 11pF

Noted that and am wondering for this application; how much does it matter when used as a current source? I don't know enough of the theory to figure that one out. Help...  ?

On 8/2/2023 at 10:36 AM, jokerman777 said:

Wanted to buy some FQPF8N80C seems uk rs-online only let me enter UK address, is there a way to get them ship worldwide?

Hello all!

Same question - how to replace it or where to buy?

May be something from this:

* FQP8N80C

* STP8NK80Z

* STP7NK80Z

?

Edited March 16, 20251 yr by bbest

9 hours ago, bbest said:

Hello all!

Same question - how to replace it or where to buy?

May be something from this:

* FQP8N80C

* STP8NK80Z

* STP7NK80Z

?

I ended up using STP8NK80Z(FP) in place of those FQP ones and they work all good if that's what you asking? Should be available from major vendors still. 

I've discovered that the C2M1000170D is now obsolete and currently out of stock on Mouser as well as several other distributor sites. 

Has anyone found a good alternative for output transistor for the Carbon?

Thanks in advance.

C2M1000170D  produced by SUPSIC and Inchange Semiconductor. But don't know if they are reliable or not.

PS: Is it possible to replace costly LT1021DIN8-10, something with Negative Shunt Reference (only 2 active pins)?

Edited May 21, 20251 yr by bbest

43 minutes ago, bbest said:

C2M1000170D  produced by SUPSIC and Inchange Semiconductor. But don't know if they are reliable or not.

 

7 hours ago, joehpj said:

Has anyone found a good alternative for output transistor for the Carbon

C3M0350120D can be a substitution. 1200V instead of 1700V. Should be good in this role. Otherwise, the new 1700V next generation Sicfet will be released soon as Wolfspeed said will be in stock Q3 2025.

Edited May 21, 20251 yr by Shawn

There are plenty of suitable candidates for the SiCFET. I count 9 different parts just by running a simple search on Digikey. Look for 1700V rated Vdss, IDmax less than 10A, Ciss less than 240pf, TO-247-3 package. I would prefer ones that are DC-SoA rated, with a moderate transconductance, low and stable Crss across the entire VDS range. Avoid those that are not characterized for linear operation. The vendor doesn’t want to guarantee those use case, and you will be on your own.
 

I would try the onsemi NVHL1000N170M1 if I were to build another KGSSHV Carbon, although there are cheaper options that may be as good. 

The closest sub for LT1021 is the LT1236. As far as I know they only differ in long-term drift specs. There are other shunt mode 10V references but none come close to the noise performance of LT1021/LT1236.

Of course you can also use second-hand, recycled ones. Those are cheap and already aged to perfection (in terms of long term drift).

7 hours ago, simmconn said:

The closest sub for LT1021 is the LT1236. As far as I know they only differ in long-term drift specs. There are other shunt mode 10V references but none come close to the noise performance of LT1021/LT1236.

Unfortunately LT1236 has also insane price.

SUPSIC produces GC2M1000170D  100% the same specs as C2M1000170D, costs 1.5$.

On 5/21/2025 at 2:21 PM, Shawn said:

 

C3M0350120D can be a substitution. 1200V instead of 1700V. Should be good in this role. Otherwise, the new 1700V next generation Sicfet will be released soon as Wolfspeed said will be in stock Q3 2025.

Digikey recommended C3M0900170D as a replacement. Specs are mostly quite similar but Vgs(th) is slightly different, and the gate-source voltage curves look different from C2M1000170D. I believe this graph tells us about the gain and linearity? I am not at all well versed in transistors so don't take my word at face value.

I looked at Wolfspeed's C3M lineup for 1.2-1.7kV, and basically everything had huge input and output capacitance or gate-source curves that didn't look as linear as the C2M1000170D. But again, I don't completely understand what I'm looking at, and will happily be corrected to learn.

Edit: The domain and range of the graph is different. The 175C curve definitely seems droopier than C2M’s, so it’s hard to know what it’s like at 40-60C or whatever we operate it at.

C3M0900170D

https://assets.wolfspeed.com/uploads/2025/02/Wolfspeed_C3M0900170D_data_sheet.pdf

Wolfspeed C3M, 1200 & 1700V, TO-247

https://www.wolfspeed.com/products/power/sic-mosfets/?blockingVoltage=1200 V|1700 V&package=TO-247-3

Edited June 27, 20251 yr by Pubert Peepis
Typing errors, reading graph improperly

On 6/26/2025 at 9:18 PM, Pubert Peepis said:

I looked at Wolfspeed's C3M lineup for 1.2-1.7kV, and basically everything had huge input and output capacitance or gate-source curves that didn't look as linear as the C2M1000170D. But again, I don't completely understand what I'm looking at, and will happily be corrected to learn.

I took a look at the datasheets, and their Vgs vs. Id transfer curves actually seem fairly similar in the linear region, so I think they should be directly swappable. But it's probably best to measure the Vgs your circuit runs the C2M at, and then check if that voltage still lands in the linear/controllable region for the C3M.

That's my understanding for using them in something like the GRHV, though I haven't factored in the overall feedback loop behavior here. So not sure if I'm missing anything on that front.

I have ordered a pair of C3M and have a Carbon on hand, A straight swapped can be easy. Will report it later.

If you need 2SC4686a – check this link. German company claiming they have 4000 pieces available. I bought a couple of hundreds 10 years ago and they were genuine.

Edited September 26, 2025Sep 26 by JoaMat