Interest for potential GB for UDNess PCBs and matched FETs.

[bullittstang]

------------------------------

ItsAllInMyHead 1 set - Option 2 Obviously
Mark Johnson 1 set (+ as many as possible)
AnthonyA 1 set
OtisCampbell 1 set
bullittstang 1 set +(3+ xtra sets, & let me know if you have extra transistors) - Option 2
myl 1 set
yoaudio 1 set
hirscwi 1 set
mordikai 1 set
zchopper 1 set
jens r. 1 set - Option 1
Astromo. 1 set
----------------------------------------------------------------------
mordikai 1 extra set, will take some unmatched transistors
myl 3 extra PCB sets
Touchdown, 1 set
samoloko 1 pcb set
Billyk 1 Set
BuzzLiteYr 1 pcb set (would take 2 extra sets pcbs for a total of 3 sets)

 

[bullittstang]

ItsAllInMyHead 1 set - Option 2 Obviously
Mark Johnson 1 set (+ as many as possible)
AnthonyA 1 set
OtisCampbell 1 set
bullittstang 1 set +(3+ xtra sets, & let me know if you have extra transistors) - Option 2
myl 1 set
yoaudio 1 set
hirscwi 1 set
mordikai 1 set
zchopper 1 set
jens r. 1 set - Option 1
Astromo. 1 set
----------------------------------------------------------------------
mordikai 1 extra set, will take some unmatched transistors
myl 3 extra PCB sets
Touchdown, 1 set
samoloko 1 pcb set
Billyk 1 Set
BuzzLiteYr 1 pcb set (would take 2 extra sets pcbs for a total of 3 sets)[/QUOTE]

 

[astromo]

ItsAllInMyHead 1 set - Option 2 Obviously
Mark Johnson 1 set (+ as many as possible)
AnthonyA 1 set
OtisCampbell 1 set
bullittstang 1 set +(3+ xtra sets, & let me know if you have extra transistors) - Option 2
myl 1 set
yoaudio 1 set
hirscwi 1 set
mordikai 1 set
zchopper 1 set
jens r. 1 set - Option 1
astromo 1 set - Option 2
----------------------------------------------------------------------
mordikai 1 extra set, will take some unmatched transistors
myl 3 extra PCB sets
Touchdown, 1 set
samoloko 1 pcb set
Billyk 1 Set
BuzzLiteYr 1 pcb set (would take 2 extra sets pcbs for a total of 3 sets)

 

[zchopper]

ItsAllInMyHead 1 set - Option 2 Obviously
Mark Johnson 1 set (+ as many as possible)
AnthonyA 1 set
OtisCampbell 1 set
bullittstang 1 set +(3+ xtra sets, & let me know if you have extra transistors) - Option 2
myl 1 set
yoaudio 1 set
hirscwi 1 set
mordikai 1 set
zchopper 1 set - Option 1
jens r. 1 set - Option 1
astromo 1 set - Option 2
----------------------------------------------------------------------
mordikai 1 extra set, will take some unmatched transistors
myl 3 extra PCB sets
Touchdown, 1 set
samoloko 1 pcb set
Billyk 1 Set
BuzzLiteYr 1 pcb set (would take 2 extra sets pcbs for a total of 3 sets)

 

[yoaudio]

ItsAllInMyHead 1 set - Option 2 Obviously
Mark Johnson 1 set (+ as many as possible)
AnthonyA 1 set
OtisCampbell 1 set
bullittstang 1 set +(3+ xtra sets, & let me know if you have extra transistors) - Option 2
myl 1 set
yoaudio 1 set - Option 2
hirscwi 1 set
mordikai 1 set
zchopper 1 set - Option 1
jens r. 1 set - Option 1
astromo 1 set - Option 2
----------------------------------------------------------------------
mordikai 1 extra set, will take some unmatched transistors
myl 3 extra PCB sets
Touchdown, 1 set
samoloko 1 pcb set
Billyk 1 Set
BuzzLiteYr 1 pcb set (would take 2 extra sets pcbs for a total of 3 sets)

 

[OtisCampbell]

ItsAllInMyHead 1 set - Option 2 Obviously
Mark Johnson 1 set (+ as many as possible)
AnthonyA 1 set
OtisCampbell 1 set - Option 2
bullittstang 1 set +(3+ xtra sets, & let me know if you have extra transistors) - Option 2
myl 1 set
yoaudio 1 set - Option 2
hirscwi 1 set
mordikai 1 set
zchopper 1 set - Option 1
jens r. 1 set - Option 1
astromo 1 set - Option 2
----------------------------------------------------------------------
mordikai 1 extra set, will take some unmatched transistors
myl 3 extra PCB sets
Touchdown, 1 set
samoloko 1 pcb set
Billyk 1 Set
BuzzLiteYr 1 pcb set (would take 2 extra sets pcbs for a total of 3 sets)

 

[EUVL]

> how to build a constant current source to match the 2SK209s
A LM317L and a fixed resistor.

> if I need a heatsink for the FETs themselves
Yes, as large as possible at 22°C (or even better at constant 50°C)


Patrick (EUVL)

.

 

[manniraj]

I would be interested to be in the waiting list for the boards + matched FETs till mid of August and shipped within US.

Thanks

 

[myl]

ItsAllInMyHead 1 set - Option 2 Obviously
Mark Johnson 1 set (+ as many as possible)
AnthonyA 1 set
OtisCampbell 1 set - Option 2
bullittstang 1 set +(3+ xtra sets, & let me know if you have extra transistors) - Option 2
myl 1 set - Option 2
yoaudio 1 set - Option 2
hirscwi 1 set
mordikai 1 set
zchopper 1 set - Option 1
jens r. 1 set - Option 1
astromo 1 set - Option 2
----------------------------------------------------------------------
mordikai 1 extra set, will take some unmatched transistors
myl 3 extra PCB sets
Touchdown, 1 set
samoloko 1 pcb set
Billyk 1 Set
BuzzLiteYr 1 pcb set (would take 2 extra sets pcbs for a total of 3 sets)

 

[manniraj]

ItsAllInMyHead 1 set - Option 2 Obviously
Mark Johnson 1 set (+ as many as possible)
AnthonyA 1 set
OtisCampbell 1 set - Option 2
bullittstang 1 set +(3+ xtra sets, & let me know if you have extra transistors) - Option 2
myl 1 set - Option 2
yoaudio 1 set - Option 2
hirscwi 1 set
mordikai 1 set
zchopper 1 set - Option 1
jens r. 1 set - Option 1
astromo 1 set - Option 2
----------------------------------------------------------------------
mordikai 1 extra set, will take some unmatched transistors
myl 3 extra PCB sets
Touchdown, 1 set
samoloko 1 pcb set
Billyk 1 Set
BuzzLiteYr 1 pcb set (would take 2 extra sets pcbs for a total of 3 sets)
manniraj 1 pcb set (Option 2 with matched FETs)

 

[ItsAllInMyHead]

> how to build a constant current source to match the 2SK209s
A LM317L and a fixed resistor.

> if I need a heatsink for the FETs themselves
Yes, as large as possible at 22°C (or even better at constant 50°C)


Patrick (EUVL)

.

Patrick, thank you as always. I'm glad I posted. A few people reached out on the thread and via PM to ask about matching process and advice. I admit I am new to this. What I originally thought was simple, is taking me a bit more effort to not only execute, but to understand. If I were still living in Hong Kong, I'd be pounding on your door.

Since this is your design, I want to do this justice. The worst possible outcome is for your design to get "bad reviews" b/c I did this poorly. Plus, I'd have wasted a tremendous amount of time. Here is what I have planned. I always appreciate input. Clearly I need it.

For those that asked, and those that may be interested, here is where we are - and what I learned.

FQA9P25 Matching

I wasted (OK, I learned a painful lesson) too much time matching the Fairchilds the way I did it for all my First Watt builds.

Below is how I did it:



MOSFET Matching for IRFP240 (N) and IRFP9240(P) for Pass First Watt

• Conditions – 22V vs. 15V @ ~0.36xA where R1 is two 100 Ohm 3W resistors in parallel.
• Timing is after 30s in ambient with no heatsink.

I used a simple three-pin holder for the part.

The way I think I should have done it for UDNeSS is:

MOSFET Matching for Fairchild FQA 9P25 (P) for UDNeSS

• Conditions – 24V vs. 15V @ ~1.30xA where R1 is two 8 Ohm 100W resistors in series.
  uxcell 100W 8 Ohm Screw Tap Mounted Aluminum Housed Wirewound Resistors 2 Pcs: Single Resistors: Amazon.com: Industrial & Scientific
• Timing is TBD – Patrick recommended heatsinks and allowing parts to get to 50C

So obviously, this will take a lot more time if I use a heatsink. Just mounting and unmounting each piece takes time. Also, if the parts need a substantial (30 minutes or more seems likely) amount of time to get to operating temp / reach some sort of equilibrium, the only way to do it efficiently is to do multiple devices at a time. That would require a gynormous heatsink. That's not what I had planned when I wrote about how I'd match the parts earlier. I'm still willing to give it a go, but only if it's efficient and doesn't require me buying a massive heatsink. I did a bit of back of the matchbook math. I'd need to be able to match 10 parts at a time (and have a heatsink or two that would hold at least 5 pieces) for me to be able to dedicate the time. The tricky part is.... I don't know how I'd apply voltage to multiple parts at a time. I can swing buying another 4 sets of resistors, and I think my bench PSUs are up to the task of supplying enough current for 10 devices. Still pondering options. Requiring heatsinks on the parts was a deal-breaker early on, but I'm still willing if I can do it within reason.

Honestly, I'm not sure I'd go to the trouble of matching even two sets this way for my own build, but it's a learning process. Or... and quite likely... there is a much easier way to do this that I'm overlooking.

Anyone know of a "clip" type mount system? I want to come up with something that ensures no shorts and doesn't require mica and goop or sacrificing a ton of Keratherm (or equivalent)? I have a pile of the ceramic pads. I was thinking of using those. I can bolt the parts to the heatsinks if necessary.

J113 Matching

Originally (when I organized the GB) - I thought it was just looking for parts with an Idss over 8.5. I thought I'd just use the "9V Battery" method. I was mistaken.

Apparently I need a CCS for 6mA. Here is the CCS schematic that a kind someone put together for me. I have the parts ordered. Q1 and Q2 are ZTX450 (or "any NPN").



I have not physically done this yet... so, I'll post more details. Again, if this is incorrect (or ill-advised), I'd love to know before I give it a go.

2SK209 Matching

I'll try to digest what Patrick posted and get back to you. It's not what I thought.

I did get the part holder / mounting device that Patrick posted earlier. It's still a PITA to get the parts in and out, but it'll work. It just takes time.

I appreciate the collaboration.



I hope everyone is safe, happy, and healthy out there.

 

[Mark Johnson]

I emailed this to member 6L6 on March 31st

_

 

[ItsAllInMyHead]

HA!

I didn't know you were the benevolent person that designed the circuit. I did not recognize the signature in the lower left, so I removed it just in case to "protect the innocent". I also know Jim's handwriting... so I didn't want to falsely give him credit.

Once again, thank you for everything you've taught and contributed. This is a slow process for me.

 

[EUVL]

If you have a means to keep the heatsink (or a large block of aluminium) cosntant at 50°C, then you can match at temperature.
If not, then you match at room temperature.
But you still need a large block of aluminium to prevent the FET from being heated up.
And you should just take the reading after say 10 seconds for every device.

There is no need to electrically isolate the FET from the aluminium, as long as the latter is isolated from the rest.
But you will still need grease to ensure thermal contact.
Screwing (at controlled torque) and unscewing is unavoidable.


Patrick

 

[ItsAllInMyHead]

If you have a means to keep the heatsink (or a large block of aluminium) cosntant at 50°C, then you can match at temperature.
If not, then you match at room temperature.
But you still need a large block of aluminium to prevent the FET from being heated up.
And you should just take the reading after say 10 seconds for every device.

There is no need to electrically isolate the FET from the aluminium, as long as the latter is isolated from the rest.
But you will still need grease to ensure thermal contact.
Screwing (at controlled torque) and unscewing is unavoidable.

Patrick

Thanks, Patrick!

I'm crystal clear on all but...

There is no need to electrically isolate the FET from the aluminium, as long as the latter is isolated from the rest.

What did you mean by "the rest". Isolating the aluminum from the rest of the circuit? My assumption was that the drains / "back plate" of FETs needed to be isolated from each other if I had multiple devices on the same heatsink. Is that correct?

Also, the trick with doing the "room temperature" method with a large heatsink seems to be that it would be bad practice and for all intents and purposes defeat the purpose to have multiple devices mounted to the same sink. Am I correct that all voltages would need to be applied simultaneously and all readings taken simultaneously? If not, the heat from one device would heat the sink and carry the heat to the next device. The 10th (or last) device would be measured at a different (highest) temperature than the 1st. Or did I not interpret properly?

Taking each device on and off a heatsink individually and allowing that sink to return to room temp and/or having multiple single device heatsinks is not an option due to time (and some amount of expected expense). Or... is the suggested 10s to keep the heatsink from warming to a level where it would need to be returned to equilibrium / room temp after each test?

Sadly, I don't have a temp controlled table - so keeping a sink at 50C is not a viable option. Unless there is a creative way to make one...
​

For all -

I truly appreciate the ideas. I'm learning a lot. I'm trying to do it properly (and within a reasonable time commitment and budget).

If I were willing to donate another $100 USD to the mutual cause for heatsinks / parts etc, and my time constraint for matching all 3 sets of devices is a max of 40 man-hours; what solutions can we come up with?

 

[EUVL]

If I were you, I would have one FET on the aluminium at a time.
Make things simple. It is supposed to be a low cost project.


Patrick

 

[ItsAllInMyHead]

Thanks, Patrick.

I'll do a test run. I have a decent-sized old CPU heatsink somewhere around here I can tap. I'll see how long it takes me to do a few units later in the week. A bit of goop, and the ceramic thermal pads, should work well.


Patrick

Edited to add - I know I don't need the pads, but they'll also help lift the part off the sink high enough to make the legs more accessible to measure.

 

[mordikai]

ItsAllInMyHead 1 set - Option 2 Obviously
Mark Johnson 1 set (+ as many as possible)
AnthonyA 1 set
OtisCampbell 1 set - Option 2
bullittstang 1 set +(3+ xtra sets, & let me know if you have extra transistors) - Option 2
myl 1 set - Option 2
yoaudio 1 set - Option 2
hirscwi 1 set
mordikai 1 set - Option 2
zchopper 1 set - Option 1
jens r. 1 set - Option 1
astromo 1 set - Option 2
----------------------------------------------------------------------
mordikai 1 extra PCB, 1 extra set parts
myl 3 extra PCB sets
Touchdown, 1 set
samoloko 1 pcb set
Billyk 1 Set
BuzzLiteYr 1 pcb set (would take 2 extra sets pcbs for a total of 3 sets)
manniraj 1 pcb set (Option 2 with matched FETs)

 

[astromo]

Thanks, Patrick.

I'll do a test run. I have a decent-sized old CPU heatsink somewhere around here I can tap. I'll see how long it takes me to do a few units later in the week. A bit of goop, and the ceramic thermal pads, should work well.


Patrick

Edited to add - I know I don't need the pads, but they'll also help lift the part off the sink high enough to make the legs more accessible to measure.

Patrick, is that a CPU heatskink with fan? I take it your plan is to run the fan to achieve as much air flow as practicable to ensure that the component is maintained at ambient?

 

[ItsAllInMyHead]

Hmmm - I never considered using a fan. Great idea. I have a few 140mm case fans around and even some battery powered fans that could be suitable. The heatsink I'm recalling is actually from an old server .... It's chunky by today's standards. At a 10s run, I figured it would keep the part from going up in flames. I still have to find it.

The main thing I was trying to ensure is a level of consistency acceptable to everyone (and primarily Patrick) to ensure I don't botch things miserably.