^ 
Let's say the 5V6 zener didn't have the super-helpful marking on the strip... or that somehow two different zeners got separated from their buddies in the packaging... and you didn't have a wonderful way to read that silly itsy bitsy teeny tiny print...
You could use the same value resistor as in the video (it's just a current limiting resistor) with your variable supply. You need a voltage on your variable supply over the highest breakdown voltage of the two "mystery" zeners you are trying to separate. So, your 15V supply would be just fine.
Give it a try... if they're not already installed, you have a resistor in the kit that will work well. Even if it's not required for this build (hopefully), it's a nice thing to have in your "toolbox of tricks".
Let's say the 5V6 zener didn't have the super-helpful marking on the strip... or that somehow two different zeners got separated from their buddies in the packaging... and you didn't have a wonderful way to read that silly itsy bitsy teeny tiny print...
You could use the same value resistor as in the video (it's just a current limiting resistor) with your variable supply. You need a voltage on your variable supply over the highest breakdown voltage of the two "mystery" zeners you are trying to separate. So, your 15V supply would be just fine.
Give it a try... if they're not already installed, you have a resistor in the kit that will work well. Even if it's not required for this build (hopefully), it's a nice thing to have in your "toolbox of tricks".
I understand the principles and good practice to try and test components I am just being careful this is a big step up from my first project the AMP MINI and KORG pre amp. I have limited knowledge of electronics I am a retired Electrician, it is great to have all this help. You answered a question I raised after I won a Thatcher PSB I believe you recommended a 400VA toroid rather than a 300VA I am yet to source a Toroid.
Best Wishes
Best Wishes
^ I am not sure I recommended 400VA "over" 300VA. They're both wonderful choices depending on availability. i.e. if the 400VA weren't immediately available, I'd grab a 300VA without hesitation and not wait for the 400VA to get back in stock. In a narrow margin, I might choose a 400VA over a 300VA within the Antek family of the AS transformers if stock / cost / weight / space were not part of the consideration. As an example, I personally would not grab the 500VA AN over the 400VA AS. The AS have the shield which to some (including me) may provide benefit.
But... this thread isn't about PSUs. So, I'll stick to my own rules.
Enjoy your build, and enjoy the tunes!
But... this thread isn't about PSUs. So, I'll stick to my own rules.
Enjoy your build, and enjoy the tunes!
The 400 is available with shield if that concerns anyone. 300 adequate, as commercial First Watt units use this.
My F6, M2 and Aleph J builds used 500 VA, still very quiet, despite no shield. Those three in Deluxe 4U chassis from store. It is unneeded overkill, but at time I thought it was needed I guess. Doing over, I would use 300 without concern.
Russellc
My F6, M2 and Aleph J builds used 500 VA, still very quiet, despite no shield. Those three in Deluxe 4U chassis from store. It is unneeded overkill, but at time I thought it was needed I guess. Doing over, I would use 300 without concern.
Russellc
I have a question about the resistance between the two screws mounting the MOSFETs. This is from step 50 in the builders guide. One board measures 0 Ohms but other board measures 1 with the resistance set to the maximum. According to the DMM manual that is equivalent to O.L. I'm assuming this is a critical issue and shouldn't proceed until it is fixed. The MOSFETs are correctly mounted and soldered and the Keratherm is not damaged. One thing I did wrong was to bend the pins on one MOSFET the wrong way before bending them into the correct orientation. Could this damage it? Should I replace it MOSFET or are there other steps I should take to fix this?
screw is bolted to heatsink, so it is shorted to chassis
what needs to read OL (while pcb not being in any way wired/connected to chassis, meaning - there is no NTC nor any other connection to chassis from audio GND) is middle pin of mosfet - that being Drain/back tab of mosfet itself
everything means that isolator in between mosfet back tab and heatsink is doing its job and mosfet is electrically isolated from (any sort of) GND
what needs to read OL (while pcb not being in any way wired/connected to chassis, meaning - there is no NTC nor any other connection to chassis from audio GND) is middle pin of mosfet - that being Drain/back tab of mosfet itself
everything means that isolator in between mosfet back tab and heatsink is doing its job and mosfet is electrically isolated from (any sort of) GND
if there is no visible crack in bending area, you're good
it really depends how tight bend was, in both instances
been there, done that, got both possible outcomes
@mpbrog61 - ZM is correct (as always) re: when you should have an Open Loop / Over Limit reading.
What you are asking about is when you should have the very low resistance reading as demonstrated in step 50. You are correct that the mounting bolts for the MOSFETs should have a very low resistance between them, b/c for all intents and purposes, they should be at the same potential (chassis). You have one channel measuring properly. For the channel in question, your MOSFETs should not affect it.
My guess is that everything is totally fine, but you may have a little glitch in measurement.
Try this. Take a measurement from the top of each of the bolts to any open threaded hole on the heatsinks. If either or both are not reading a very low resistance, please let us know.
What you are asking about is when you should have the very low resistance reading as demonstrated in step 50. You are correct that the mounting bolts for the MOSFETs should have a very low resistance between them, b/c for all intents and purposes, they should be at the same potential (chassis). You have one channel measuring properly. For the channel in question, your MOSFETs should not affect it.
My guess is that everything is totally fine, but you may have a little glitch in measurement.
Try this. Take a measurement from the top of each of the bolts to any open threaded hole on the heatsinks. If either or both are not reading a very low resistance, please let us know.
that "bolt" reading is irrelevant
I mean - by definition and nature of the beast, each bolt must be in contact with own thread, which is physically part of heatsink
I'm always doing measurement bolt head to bolt head, just to be sure that probe I'm leaving at one bolt head is actually in electrical contact with bolt head
practically confirmation that I actually reached reference point
I mean - by definition and nature of the beast, each bolt must be in contact with own thread, which is physically part of heatsink
I'm always doing measurement bolt head to bolt head, just to be sure that probe I'm leaving at one bolt head is actually in electrical contact with bolt head
practically confirmation that I actually reached reference point
^ Exactly - That's precisely what's described in the guide. Check the photos in Step 50. However, for some reason... on one channel, the reading is showing Open Loop / Over Limit vs. a low resistance from bolt head to bolt head. So, it would be interesting to know why, no?
oxidation layer on bolt head, sometimes preventing proper contact with probe
jab it harder, here's contact
after few years in job, it becomes fact and second nature to double check that you did reach reference, in other words - that you actually gripped chassis either with probe pin or crocs
jab it harder, here's contact
after few years in job, it becomes fact and second nature to double check that you did reach reference, in other words - that you actually gripped chassis either with probe pin or crocs
^ I think we're saying the exact same thing... that is why I suggested that they check from the bolt heads to an open hole. If they were measuring (the important measurement) each of the three pins of each MOSFET with the drain pin being most likely a potential (HA!) issue, to a bolt head that was not actually at the same potential as the heatsink, then it would be a false reading. Takes 30s or less to check... and I'd do it just for better sleep, but I understand if you don't think it's important.
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no, I agree with you totally, I was just (maybe clumsy) explaining why "bolt measurement" is irrelevant per se and puzzling about non-conduction is ........ waste of time - just jab it harder
all in effort to establish proper reference, to be sure that bolt to drain measurement is really correct
all in effort to establish proper reference, to be sure that bolt to drain measurement is really correct
^ Yep... Jab harder... and/or check each bolt head to a hole... 🙂 Both tell a story. You never told mpbrog61 to jab it harder or provided any instruction on how to know if they had it correct. I did. 🙂
So - @mpbrog61 - please jab the probes / double check... and/or check the resistance from each bolt head to an open hole in the heatsink as suggested in post #30. Report back.
So - @mpbrog61 - please jab the probes / double check... and/or check the resistance from each bolt head to an open hole in the heatsink as suggested in post #30. Report back.
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just jab probe in open hole, confirm contact of same, jabbing other probe in other hole
or whatever/wherever - entire chassis is there to jab on
or whatever/wherever - entire chassis is there to jab on
besides working on substantial logistic of kit itself, you manage to produce extraordinary Build Guide, not just on par with, but certainly even better than best ones from Hafler of Yore; their guides were great in realm of "do this", but your is giving all they had while giving much more of "why" insight
so, we are going to answer to any additional question, but in reality - nothing lacking in your build guide ....... every Greedy Boy lacking some chupsa besides what's explained there, really need to work on that chupsa ....... be it with our help here or in some other way
O Tempora O Mores .......... books are so passé .........
^ OK ... last comment on this one until we get perfect readings back from our builder friend.
That's very, very kind. A wise person sent some excellent build guides to me as references/inspiration. No way I could have done that without you. It wasn't just me that did the guide.
More importantly, I use this thread to see where I may need to make some small updates / add clarity. Also, even though I truly hope that every build comes out perfectly every time, it's nice to have a dedicated thread to have just clear / concise answers for very specific build questions vs. conversation and theory.
That's very, very kind. A wise person sent some excellent build guides to me as references/inspiration. No way I could have done that without you. It wasn't just me that did the guide.
More importantly, I use this thread to see where I may need to make some small updates / add clarity. Also, even though I truly hope that every build comes out perfectly every time, it's nice to have a dedicated thread to have just clear / concise answers for very specific build questions vs. conversation and theory.
