Don't snub the PSU of a class-A amp. Without a way to measure and compute the proper values, it's quite easy to do more harm than good.
The .0033uF you see in most Firstwatt PSU schematic is to stop arcing on the switch. Make sure that cap is X1 or X2 rated.
If you want to buy Nichicon Audio Grade caps, feel free. However I'm not sure they are available in values bigger than 15,000uF.
Then again, 15,000uF is more than sufficient - its what Papa uses in the factory-built FirstWatt amps.
UFW1V153MRD Nichicon | Mouser
Jamesblond -- the circled components are NTC thermistors, used for inrush suppression in one position, and the other (near the edge of the PSU board) is to lift signal ground off the chassis by about 10 ohms.
The .0033uF you see in most Firstwatt PSU schematic is to stop arcing on the switch. Make sure that cap is X1 or X2 rated.
If you want to buy Nichicon Audio Grade caps, feel free. However I'm not sure they are available in values bigger than 15,000uF.
Then again, 15,000uF is more than sufficient - its what Papa uses in the factory-built FirstWatt amps.
UFW1V153MRD Nichicon | Mouser
Jamesblond -- the circled components are NTC thermistors, used for inrush suppression in one position, and the other (near the edge of the PSU board) is to lift signal ground off the chassis by about 10 ohms.
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Don't add low esr capacitors to an amplifier PSU. Without a way to measure and compute the proper values, it's quite easy to do more harm than good.
If you use low esr smoothing capacitors you are MORE LIKELY to increase the risk of ringing in the PSU. It does not matter that the PSU is supplying a ClassA amp or a ClassAB amplifier.
Adding an appropriate snubber to a secondary of the mains transformer is a sure way to minimise the ringing of a PSU.
Follow the Quasimodo threads. They show you the sure fire way to avoid the pitfalls of low esr capacitors in the PSU.
Thanks for the info and taking the time to respond. I know it is written to be clear but being a relative newbie it often gets to be more than I understand.
Read some Quasimodo thread and eventually decided I needed to pay someone to do that part for me, as I am lacking a scope but not low on lack of understanding.
Keeping it short, I have misplaced my disk capable of running 8-16 bit Windows programs and no longer have the power supply design tool - and even if I did I would ask if my numbers were correct.
So here is another question.
What value and type resistors should I be using with the setup I mentioned in #257 with 15Kuf capacitors?
Any other add-on's to the Mouser order? Any resistors which are exactly what I would be using on F4 boards so as to get discounts for lager numbers? I can look at the values to determine that, just type of resistor if that matters (and I'm sure it does to some, but not everyone.
DOH! The order I had been building for a couple of weeks disappeared from cart.... 🙁
Read some Quasimodo thread and eventually decided I needed to pay someone to do that part for me, as I am lacking a scope but not low on lack of understanding.
Keeping it short, I have misplaced my disk capable of running 8-16 bit Windows programs and no longer have the power supply design tool - and even if I did I would ask if my numbers were correct.
So here is another question.
What value and type resistors should I be using with the setup I mentioned in #257 with 15Kuf capacitors?
Any other add-on's to the Mouser order? Any resistors which are exactly what I would be using on F4 boards so as to get discounts for lager numbers? I can look at the values to determine that, just type of resistor if that matters (and I'm sure it does to some, but not everyone.
DOH! The order I had been building for a couple of weeks disappeared from cart.... 🙁
Use Panasonic ERG 3W resistors. Easily available from mouser, and have a good price break at 10pc.
So just standard capacitors will do?
By the way: what value classifies as "low" ESR? Or, put differently: what value(s) ESR would be safe to use?
For example: For the Cornell Dubilier 380LX103M100A082 (100V 10mF) the data sheet reads 33mOhm @ 120Hz and 25mOhm at 20kHz (ESR). Ripple current is specified as 8.7A at 120Hz and 9.6A at 20kHz.
Are these typical values, and usable in an ampifier PSU?
(If "yes", then I'll need to find me a vendor who'll sell me 16 of these in stead of 100 minimum...)
I bought epcos a while back and then ordered up more.
I guess I like them.
b41231 b5229 m 25V
b41231 c7109 m 35V
the 50V are all inside amplifiers.
I guess I like them.
b41231 b5229 m 25V
b41231 c7109 m 35V
the 50V are all inside amplifiers.
Thanks, Andrew.
When using a DC output voltage of 56.5V, I guess I would need at the very least 63V caps, right? Better go one stage higher, at 80V?
Could you please take a look at my redrawing of the PSU? It's an interpretation of the PSU v3 schematic, trying to see if I understand the part with the discrete diodes correctly. I'm not sure about the grounding. Can I or should I connect the secondary transformer windings in the middle? In my drawing I've kept them seperated.
Thanks!
When using a DC output voltage of 56.5V, I guess I would need at the very least 63V caps, right? Better go one stage higher, at 80V?
Could you please take a look at my redrawing of the PSU? It's an interpretation of the PSU v3 schematic, trying to see if I understand the part with the discrete diodes correctly. I'm not sure about the grounding. Can I or should I connect the secondary transformer windings in the middle? In my drawing I've kept them seperated.
Thanks!
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Measure your transformer voltages and calculate (predict) the worst case voltage on your smoothing caps.
There is absolutely no point in guessing at the wrong answer.
Be informed and then buy the correct capacitor rating.
Hi i think it is better use 71V or 80 V
higher voltage will not ham you.
Also u must think of the stress peak current & voltage to the Cap.
i think the price not much expensive, for longer terms it is good using the higher voltage. (beside u must think the tolerance 5% to 10%, generally comes in lower value than nominal)
cheers.
led orientation
Question - the board traces are asymmetrical per side so wouldn't one of the two LED's + / - orientation be backwards?
One fairly obvious answer would be they are correct with one side +, the other -, but I would rather ask a stupid question than rework or worse.
Question - the board traces are asymmetrical per side so wouldn't one of the two LED's + / - orientation be backwards?
One fairly obvious answer would be they are correct with one side +, the other -, but I would rather ask a stupid question than rework or worse.
Mount as shown in the photo.
The LED are pointing with their + sides (long leg) towards the more positive part of the PCB.
The LED are pointing with their + sides (long leg) towards the more positive part of the PCB.
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Hello,
I am building my 1st 1stWatt; a dual mono F5.
Do I have to make the PSU <-> Chassis grounding connection with a separate CL60 for each of the two PSU boards to a single chassis screw (so use 2 CL60's and one screw), or is there a better way?
Albert
I am building my 1st 1stWatt; a dual mono F5.
Do I have to make the PSU <-> Chassis grounding connection with a separate CL60 for each of the two PSU boards to a single chassis screw (so use 2 CL60's and one screw), or is there a better way?
Albert
Im wiring a transformer for 230v. Its a sedlbauer 2x115 to 2x18 500VA.
It seems that most tranformers have 4 different coloured wires for the primaries.
My primaries both have a blue and a brown wire.
How do i tell which is the primary 1 and primary 2? Or doesnt that matter. I think that where they pop out the top it would be pri 1, pri 2 then sec 1 and sec 2.
It clearly says on this data sheet for series connect brown with blue, but then why would other transformers have 4 different colours on the primary.
http://www.sedlbauer.de/files/ringkerntrafo_datenblatt_825059_e.pdf
Thanks.
Dave
It seems that most tranformers have 4 different coloured wires for the primaries.
My primaries both have a blue and a brown wire.
How do i tell which is the primary 1 and primary 2? Or doesnt that matter. I think that where they pop out the top it would be pri 1, pri 2 then sec 1 and sec 2.
It clearly says on this data sheet for series connect brown with blue, but then why would other transformers have 4 different colours on the primary.
http://www.sedlbauer.de/files/ringkerntrafo_datenblatt_825059_e.pdf
Thanks.
Dave
The two primary windings are identical. Connect them in series. If each primary has a blue and a brown wire
(you can check this first with an ohm meter), then connect one of the blues to one of the browns and isolate this connection.
Then use the other blue and brown for the input.
Thats great, thanks Rayma,
A quick note about the square pads. On my speaker protection board and soft start circuit the square pad is on the cathode for the diodes (I hope Im correct in saying that its the end of a diode with the line painted on it ). But its the anode for the caps. I think what alerted me to this was that there wasn't any polarity marked other than the pad so i thought id better check. Traced the circuit several times against the schematics etc.
Haven't tested the soft start yet but the speaker protection board works correctly without the caps blowing up so I think I must be right.
Dave
A quick note about the square pads. On my speaker protection board and soft start circuit the square pad is on the cathode for the diodes (I hope Im correct in saying that its the end of a diode with the line painted on it ). But its the anode for the caps. I think what alerted me to this was that there wasn't any polarity marked other than the pad so i thought id better check. Traced the circuit several times against the schematics etc.
Haven't tested the soft start yet but the speaker protection board works correctly without the caps blowing up so I think I must be right.
Dave
The point being is I would double check as they probably are all meant to be the same, but I would double check.
Dual primaries with 4 colours of which one primary has a BLUE and the other primary has a BROWN are designed for use in EUROPE, where BROWN is LIVE and BLUE is NEUTRAL.
The other two primaries get connected together for use @ 220Vac to 240Vac.
Fuse the LIVE feed with a T rated fuse.
Fuse size for a transformer is 3times VA divided by Mains Vac.
If you use a soft start then the close rated fuse is VA/Vac (i.e. one third of the rating compared to the normal direct online starting).
BUT !!!!!!!
I still recommend you build and use a Mains Bulb Tester to Power ON any Mains powered project to check for wiring errors.
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Hi andrew, thanks
I'm still fairly sure that the smaller transformers I have which do have the different colour primaries are still 2x115 but I will check that as the 220 plus a bit extra for 240 makes more sense. I was repairing an Eden bass head and that had loads of taps on the primary for international use but at least there was a label clearly stating what to put where.
The psu I'm building is for an f4. I was going to put a 1.25 amp time delay fuse in like the build guide suggests. The transformer is maybe slightly bigger than it needs to be but I am intending (if it sounds as good as I'm hoping) to build a second and run them with a balanced/diff input, actually I'm not opening that can of worms again, im going to call it bridged!
Nelson said that the f4 draws about 160w when idle.
The way you're rating fuses suggests that regardless what is drawn on the secondaries the primary will still be drawing it's full rating. I have often wondered about that and I figured that the draw on the output would affect the fields around then primary and affect the inductive reactance of the coil.
So in short, are you saying that I should use a 2amp time delay if using a soft start circuit?
I have built a light bulb limiter. But can't find old school incandescent bulbs only these halogen within bulb type affairs. I guess there's still a tungsten coil in them so they will work in the same way. Bought an "electrically rated" 70w and 100w bulbs
Thanks
I'm still fairly sure that the smaller transformers I have which do have the different colour primaries are still 2x115 but I will check that as the 220 plus a bit extra for 240 makes more sense. I was repairing an Eden bass head and that had loads of taps on the primary for international use but at least there was a label clearly stating what to put where.
The psu I'm building is for an f4. I was going to put a 1.25 amp time delay fuse in like the build guide suggests. The transformer is maybe slightly bigger than it needs to be but I am intending (if it sounds as good as I'm hoping) to build a second and run them with a balanced/diff input, actually I'm not opening that can of worms again, im going to call it bridged!
Nelson said that the f4 draws about 160w when idle.
The way you're rating fuses suggests that regardless what is drawn on the secondaries the primary will still be drawing it's full rating. I have often wondered about that and I figured that the draw on the output would affect the fields around then primary and affect the inductive reactance of the coil.
So in short, are you saying that I should use a 2amp time delay if using a soft start circuit?
I have built a light bulb limiter. But can't find old school incandescent bulbs only these halogen within bulb type affairs. I guess there's still a tungsten coil in them so they will work in the same way. Bought an "electrically rated" 70w and 100w bulbs
Thanks