Thompson is probably right. You can see the cathode looking at the legs of the LED. Compare with schematic. Both LEDs should have the same leg towards pos and neg.
You have to close the circuit to ground (via a properly oriented LED) and let some current through. Then you'll see a different story.
Hi, I'm a pretty big noob when it comes to this stuff but I'm attempting to build an F6 clone and I'm in the beginning stages working on the power supply. I have everything I need except for the blue safety cap. I have three Cl 60s. Is the blue cap absolutely necessary? I'm trying to avoid paying the money for the shipping just to order one or two parts.
Hi, Will. You can make a PSU without that capacitor and it will work. However, this capacitor eliminates arching (sparking) of the power switch contacts (making the switch last longer) and somewhat reduces the high frequency noise ever present in the power line, so I would recommend to install it as soon as you have an opportunity to obtain it without high shipping costs.
Interesting. I am just about to order som extra PSU parts in an attempt to improve the performance wrt noise. Just added a bit of R in the CRC and the noise floor dropped. Havent measured yet, but audible.
In 240v mains powered supply, should/can I use the safety cap still, and where to mount it? Across primaries?
Nelson omitted that cap from the 240v supplies as far as I can tell, but I might have gotten it wrong. If he did omit, it is of course for a reason. Such as short circuit or fire. My BA allready burned once. Best not repeat.
Cheers,
Andreas
In 240v mains powered supply, should/can I use the safety cap still, and where to mount it? Across primaries?
Nelson omitted that cap from the 240v supplies as far as I can tell, but I might have gotten it wrong. If he did omit, it is of course for a reason. Such as short circuit or fire. My BA allready burned once. Best not repeat.
Cheers,
Andreas
No problem with 240V, Andy. The same capacitor is there. See the schematics attached.
You cannot use just any capacitor on the power line, it has to be X1 or Y1 rated (fail-safe, safety capacitor, for power line usage). Like this one, for example:
https://eu.mouser.com/ProductDetail/81-DE2E3KY332MN2AM1F/
It's 250V rated. You can search for higher voltage rating if you would like to have even higher margin (but not necessary).
You cannot use just any capacitor on the power line, it has to be X1 or Y1 rated (fail-safe, safety capacitor, for power line usage). Like this one, for example:
https://eu.mouser.com/ProductDetail/81-DE2E3KY332MN2AM1F/
It's 250V rated. You can search for higher voltage rating if you would like to have even higher margin (but not necessary).
Attachments
Thanks, man!
Perfect answers deserves follow up questions.
What anout R9? Can i put that in too on the stores uniPSU?
And on the BA-2 supply (I use the BA-2 output stage), there av 10uf film caps across the supply lines. I have omitted that, thinking the psu dont accomodate them. Can I put those in too? Just solder on to the bord across supplies? I do use the 0,1 uf output snubber cap, but guess The 10uf doesnt replace that, or does it?
Cheers,
Andreas
Perfect answers deserves follow up questions.
What anout R9? Can i put that in too on the stores uniPSU?
And on the BA-2 supply (I use the BA-2 output stage), there av 10uf film caps across the supply lines. I have omitted that, thinking the psu dont accomodate them. Can I put those in too? Just solder on to the bord across supplies? I do use the 0,1 uf output snubber cap, but guess The 10uf doesnt replace that, or does it?
Cheers,
Andreas
Andy, if you talk about the R9 and R10 on the PSU board, then these are called bleeder resistors - they are used to discharge the big PSU capacitors after you switch off the power and have no load connected to the PSU. Without these bleeders, the charge would stay in the capacitors and it would be very danegerous to touch the circuit even when the power is off (that's also why there are LEDs on the board - to show you that the circuit still has active electricity while the LEDs are glowing). So, consider R9 and R10 as a must have!
These resistors have to be at least 3W rated and can be anything from 4.7K to 22K according to the BOM. But I used 2.4K in my PSU. The smaller the resistor, the quicker the capacitors will discharge (it can take a few minutes with the higher values). Perhaps I went too low and perhaps I am loosing a bit too much power on this bleeder resistor during the normal operation. Make your own choice 🙂
Bleeder resistor - Wikipedia
I do not know about BA-2, so I cannot comment on that.
Cheers,
Alvydas
These resistors have to be at least 3W rated and can be anything from 4.7K to 22K according to the BOM. But I used 2.4K in my PSU. The smaller the resistor, the quicker the capacitors will discharge (it can take a few minutes with the higher values). Perhaps I went too low and perhaps I am loosing a bit too much power on this bleeder resistor during the normal operation. Make your own choice 🙂
Bleeder resistor - Wikipedia
I do not know about BA-2, so I cannot comment on that.
Cheers,
Alvydas
Of course. My bad, shoulda guessed that. Btw I use 4,7k and works perfectly. Thanks for the help! I’ll ask around about those film caps.
Hello all,
I have built Aleph J with this PSU.
Everything is working as expected with the only issue: when turned off, one PSU channel (V+) bleeds quite fast, in ~30 s, but all LEDs in other (V-) stays on much longer, for about 2 minutes. What could be the issue? Voltages on PSU outputs are OK, stable. Transformer 400VA, caps EPCOS/TDK 35VDC 18000uF, R9-R10 22K OHM 3W.
I have built Aleph J with this PSU.
Everything is working as expected with the only issue: when turned off, one PSU channel (V+) bleeds quite fast, in ~30 s, but all LEDs in other (V-) stays on much longer, for about 2 minutes. What could be the issue? Voltages on PSU outputs are OK, stable. Transformer 400VA, caps EPCOS/TDK 35VDC 18000uF, R9-R10 22K OHM 3W.
How do I decide whether to populate "optional" resistors?
After several searches relating to "pi" resistors and CRC filtering, I get the feeling that the "pi" resistors smooth the output AND adjust the final output voltage.
Is that right?
If so, or not, how should I decide whether I need to populate these positions with resistors? R1-R8 have a note in the BOM "Replace with jumper if CRC filtering not required", which makes them appear optional, while R_Optional1 through R_Optional6 are, apparently, even more optional. Furthermore, the BOM lists all of these as 0.47R-1R.
Based on what I've read, I feel favorable to CRC filtering. So now, how many do I populate and with what resistances? The construction guides around here are really useful, but this is one place where I have 14 apparently optional resistors with guidance "0.47R-1R" and I feel like a deer in the headlights.
Thanks for pointers to hints or simple guidelines.
After several searches relating to "pi" resistors and CRC filtering, I get the feeling that the "pi" resistors smooth the output AND adjust the final output voltage.
Is that right?
If so, or not, how should I decide whether I need to populate these positions with resistors? R1-R8 have a note in the BOM "Replace with jumper if CRC filtering not required", which makes them appear optional, while R_Optional1 through R_Optional6 are, apparently, even more optional. Furthermore, the BOM lists all of these as 0.47R-1R.
Based on what I've read, I feel favorable to CRC filtering. So now, how many do I populate and with what resistances? The construction guides around here are really useful, but this is one place where I have 14 apparently optional resistors with guidance "0.47R-1R" and I feel like a deer in the headlights.
Thanks for pointers to hints or simple guidelines.
re: purpose - Yes, their purpose is for ripple reduction/filtering along with the caps, but they do have a minor effect on the final voltage (within the range you mention from the BoM).
re: optional positions, you can use more resistors in parallel to get the final value you want for filtering based on parts availability and power rating. So, the board allows for that.
tl;dr - I would go with whatever the amplifier designer recommends unless you feel comfortable otherwise.
What amp are you going to use it with? Based on the BoM, it may be a First Watt amp.
A popular implementation for First Watt amps is R1-8 as 0R47 3W resistors like in the link below. Leave the rest unpopulated / no jumpers. It's likely that you can use the same resistors for the amp boards also, if you're building a FW amp. I think all of them I've built use at least one.
https://www.digikey.com/en/products/detail/panasonic-electronic-components/ERX-3SJR47A/91677
re: optional positions, you can use more resistors in parallel to get the final value you want for filtering based on parts availability and power rating. So, the board allows for that.
tl;dr - I would go with whatever the amplifier designer recommends unless you feel comfortable otherwise.
What amp are you going to use it with? Based on the BoM, it may be a First Watt amp.
A popular implementation for First Watt amps is R1-8 as 0R47 3W resistors like in the link below. Leave the rest unpopulated / no jumpers. It's likely that you can use the same resistors for the amp boards also, if you're building a FW amp. I think all of them I've built use at least one.
https://www.digikey.com/en/products/detail/panasonic-electronic-components/ERX-3SJR47A/91677
I had to digest that stuff too.
Those resistors do what already has been said: the filter ripple and reduce the voltage.
I don‘t know how to calculate it though (or why to go with this or that value), and thus went with the recommendation.
What you have to keep in mind is that parallel resistors become smaller in resistance _and_ higher in „wattage“— 2 resistors of 1r 1W equal 0.5r 2 W...
So,
4 x 0.47r 3W = 0.1175r 12W
Or
8 x 1r 3W = 0.125W 24W
Could be important when operating with higher voltages...
calculator
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@mcaronas - are you sure your R9 and R10 are of the same denominations? Perhaps you mistakengly put 2K2 instead of 22K on one of the channels? Also, 22K is on a maximum side (longest discharge time), so I suppose your V- side could be as you planned it and the V+ side could have lover bleeding resistance. I usually go with 4K7 or 6K8 with these, and the PSU schematics actualy states 2K2 (though the BOM recommendations are from 4K7 to 22K). Not that it matters much.
Also, is any load connected to both PSU sides? Without a load it takes longer to discharge the capasitors.
Also, is any load connected to both PSU sides? Without a load it takes longer to discharge the capasitors.
Andreas
This got me wondering, so I looked it up, here
Nelson says: «You will also note 10 uF film capacitors across the supply lines. You can delete these, remembering that the prototype used them.»
Furthermore, If you search the thread for "output snubbers", 6L6 and others say that you'd better omit these. Otoh, the input snubber seems to be if not important, than at least very beneficial. (The better the snubber is matched with your transformer's characteristics, the more good it does. See Quasimodo for this, and if you're lucky, your tranny is mentioned here)...
Mcaronas - That is normal behavior for the Aleph on power-down.
Blubugeye - although R filtering is helpful and should be used in these projects, it is also lossy. For a standard configuration firstwatt design the (4) 0.47ohm resistors are effectively a 0.12ohm 12W resistor, and you could use the extra slots to, for instance, use a larger quantity of bigger-value resistors to make the 0.12ohms.
As voltages and currents go up, you might need to do this in general, as shown in the F5T PSU.
More filtering (more resistance) works a tiny teeny bit better, but this is a case where more is not actually better, as you’ll lose power because your rail voltage will decrease, and the rule of diminishing returns kicks in very quickly.
So, use (4) 0.47R 3W resistors Per rail as shown on the schematic.
As others have mentioned, the input snubber is helpful if you can determine the proper values for your transformer, and yes, omit the ‘output snubber’.
Blubugeye - although R filtering is helpful and should be used in these projects, it is also lossy. For a standard configuration firstwatt design the (4) 0.47ohm resistors are effectively a 0.12ohm 12W resistor, and you could use the extra slots to, for instance, use a larger quantity of bigger-value resistors to make the 0.12ohms.
As voltages and currents go up, you might need to do this in general, as shown in the F5T PSU.
More filtering (more resistance) works a tiny teeny bit better, but this is a case where more is not actually better, as you’ll lose power because your rail voltage will decrease, and the rule of diminishing returns kicks in very quickly.
So, use (4) 0.47R 3W resistors Per rail as shown on the schematic.
As others have mentioned, the input snubber is helpful if you can determine the proper values for your transformer, and yes, omit the ‘output snubber’.
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ItsAllInMyHead, 6L6, myleftear, thanks for the tips.
I'm looking to build the FirstWatt F-4.
I'm looking to build the FirstWatt F-4.