I did, they all read a forward voltage of 0.45 volt roughly.
But they are not in use anymore, I replaced them with mosfet rectifiers last week, the buzz is exactly the same.
When I used Graetz bridges, I had no "snubber" of any kind.
But they are not in use anymore, I replaced them with mosfet rectifiers last week, the buzz is exactly the same.
When I used Graetz bridges, I had no "snubber" of any kind.
plural, toroids
both buzzing?
care to give more info about rectifier and cap banks arrangement?
and , again - is there buzzing without load ( amp pcbs) connected?
They both buzz, maybe one a bit more than the other.
They are silent with nothing attached to them. I'll check if they are silent with the PSUs connected, but without the amp boards.
I'll post pictures as soon as I can, things will be clearer.
I have 2 secondary per toroid, 1 diode bridge per secondary, then two Firstwatt style PSU PCB, the 2009 revision with thermal switch (used without the resetting fuses) and all CL60 onboard (mains live & audio gnd) https://6moons.com/audioreviews/firstwatt11/board.jpg
They are silent with nothing attached to them. I'll check if they are silent with the PSUs connected, but without the amp boards.
I'll post pictures as soon as I can, things will be clearer.
I have 2 secondary per toroid, 1 diode bridge per secondary, then two Firstwatt style PSU PCB, the 2009 revision with thermal switch (used without the resetting fuses) and all CL60 onboard (mains live & audio gnd) https://6moons.com/audioreviews/firstwatt11/board.jpg
Sorry for the fat images, dunno how to make the forum system to reduce them.
Note that the mosfet rectifiers are in temporary state for testing, they need a PCB for proper use, and I'll be drawing one (my very first).
Interesting finding tonight: I have connected one toroid to the full chain (one psu and one amp board), and it was totally silent during 5 to 10 seconds.
Buzzing then increased fast to normal volume.
Could the equilibrium load be too little for toroid that big?
Is the cold CL60's resistance stopping something from the mains, and releasing it once hot?
I'm sure it's raising some ideas to the good brains
Note that the mosfet rectifiers are in temporary state for testing, they need a PCB for proper use, and I'll be drawing one (my very first).
Interesting finding tonight: I have connected one toroid to the full chain (one psu and one amp board), and it was totally silent during 5 to 10 seconds.
Buzzing then increased fast to normal volume.
Could the equilibrium load be too little for toroid that big?
Is the cold CL60's resistance stopping something from the mains, and releasing it once hot?
I'm sure it's raising some ideas to the good brains
Looking at the PS board at the AC connection to the transformer, there may be an issue there.
1. There is no picture of your transformer so does it have only one primary winding?
2. Your sketch of your power supply wiring shows a thermistor from power supply ground to chassis safety ground. I do not see that in the pictures.
3. I do see a thermistor in the AC out location on the PS board to suppress the start-up current surge. I am not familiar with the FW PS board so I do not know if the AC surge thermistor is in the proper location.
4. I am not familiar with the wiring for the transformer to the AC out location on the FW PS board, and you do not show how you have connected your transformer to that location.
You may have connected the transformer primary or the AC input thermistor or both improperly to the PS board AC out causing a high current to run through the transformer, causing the buzz.
1. There is no picture of your transformer so does it have only one primary winding?
2. Your sketch of your power supply wiring shows a thermistor from power supply ground to chassis safety ground. I do not see that in the pictures.
3. I do see a thermistor in the AC out location on the PS board to suppress the start-up current surge. I am not familiar with the FW PS board so I do not know if the AC surge thermistor is in the proper location.
4. I am not familiar with the wiring for the transformer to the AC out location on the FW PS board, and you do not show how you have connected your transformer to that location.
You may have connected the transformer primary or the AC input thermistor or both improperly to the PS board AC out causing a high current to run through the transformer, causing the buzz.
1- yes, single 240v primary
2- the ground lifting thermistor is a bit hard top locate, it's at the speaker side. You see it in the first pic, right behind the cap
3 & 4- i'm not using the mains lines as written on silkscreen. I may check again under the board if everything is nominal.
I fired one channel again from cold start, the buzz appears after maybe 15 seconds.
The toroid is only happy under a big load, or it's a thermistor bug when hot enough
2- the ground lifting thermistor is a bit hard top locate, it's at the speaker side. You see it in the first pic, right behind the cap
3 & 4- i'm not using the mains lines as written on silkscreen. I may check again under the board if everything is nominal.
I fired one channel again from cold start, the buzz appears after maybe 15 seconds.
The toroid is only happy under a big load, or it's a thermistor bug when hot enough
Transformers generally do not make any noise under low load. They usually buzz when they are overloaded.
As I said previously I am not familiar with the First Watt power supply board. Is your PS board a legitimate First Watt board or a copy? Good pictures of the top and bottom of the PS board and also your transformer connection to the board would be helpful.
Zen Mod is probably familiar with the First Watt power supply board so if you post pictures of your hook-up, he will probably tell you whether it is connected properly or not for single primary 240VAC transformer.
As I said previously I am not familiar with the First Watt power supply board. Is your PS board a legitimate First Watt board or a copy? Good pictures of the top and bottom of the PS board and also your transformer connection to the board would be helpful.
Zen Mod is probably familiar with the First Watt power supply board so if you post pictures of your hook-up, he will probably tell you whether it is connected properly or not for single primary 240VAC transformer.
I believe that these pcbs (Papa's Cap Bank) are in group of those I don't have any info about ( no files, in other words)
Frankly - I'm too much of a Chicken to combine mains and DC in Papa's way, so didn't even tried anything similar, except having Papa's original PSU pcb in DEFiSIT
anyway, it's easy checking with ohmmeter is there proper connection between IEC and xformer primary, situation being simple with single 230Vac primary, as we are usually having on this side of Big Splash
so - measuring at bare primary wires - reading X Ohms, when connected to IEC through Papaclone pcbs, same reading when shorting NTC pins, increased for 10-15R if NTC is included
now, origin of Donuts, declared VA, pics pretty please?
at first - Sissy is not biased at all, so you can count on alt least 30secs of pretty much non existing loading of PSU, then Iq is rising gradually from 0 to full throttle
-if there is no buzz in first 30secs and
-if you decrease Iq to, say, 1A and buzz is decreased vs. buzz in nominal Iq state - it is quite possible that you're having subpar quality Donuts
Frankly - I'm too much of a Chicken to combine mains and DC in Papa's way, so didn't even tried anything similar, except having Papa's original PSU pcb in DEFiSIT
anyway, it's easy checking with ohmmeter is there proper connection between IEC and xformer primary, situation being simple with single 230Vac primary, as we are usually having on this side of Big Splash
so - measuring at bare primary wires - reading X Ohms, when connected to IEC through Papaclone pcbs, same reading when shorting NTC pins, increased for 10-15R if NTC is included
now, origin of Donuts, declared VA, pics pretty please?
at first - Sissy is not biased at all, so you can count on alt least 30secs of pretty much non existing loading of PSU, then Iq is rising gradually from 0 to full throttle
-if there is no buzz in first 30secs and
-if you decrease Iq to, say, 1A and buzz is decreased vs. buzz in nominal Iq state - it is quite possible that you're having subpar quality Donuts
As Zen Mod said, you need to check all connections are correct.
When you are certain all connections are correct, power up the power supply with no amplifier board attached, and check that V+ and V- out are correct. Initial power-up with a dim bulb tester may be prudent in case of a wiring problem. If the power-up passes with the dim bulb tester in place, then remove the dim bulb tester and power up and check that V+ and V- are correct.
With no load on the power supply the transformer should not buzz. Do you have a bleed resistor on the PS board? The bleed resistor should be sized for milliamps of drain so that should not strain the transformer. If you have bleed resistors, what is the value?
Only power up with the amplifier board connected when you are certain that the power supply is working correctly.
You mentioned in post #1998 that you are "reworking" your SissySIT. Was it working before? Was it previously with the same power supply and transformer? What changes did you make? Was it buzzing before?
When you are certain all connections are correct, power up the power supply with no amplifier board attached, and check that V+ and V- out are correct. Initial power-up with a dim bulb tester may be prudent in case of a wiring problem. If the power-up passes with the dim bulb tester in place, then remove the dim bulb tester and power up and check that V+ and V- are correct.
With no load on the power supply the transformer should not buzz. Do you have a bleed resistor on the PS board? The bleed resistor should be sized for milliamps of drain so that should not strain the transformer. If you have bleed resistors, what is the value?
Only power up with the amplifier board connected when you are certain that the power supply is working correctly.
You mentioned in post #1998 that you are "reworking" your SissySIT. Was it working before? Was it previously with the same power supply and transformer? What changes did you make? Was it buzzing before?
I'll try both trimming Iq and offboard mains connection.
There is no bleeder installed. I use a temporary one only for discharging a floating PSU.
And yes, it's my main amp for more than a year. I waz lazy to finish the inside, so I tolerated the buzz until now. I have not changed anything beside the rectifiers, but buzz did not change from Graetz bridges or MOSFET rectifiers (the latter were supposed to be friendlier to the transformer).
There is no bleeder installed. I use a temporary one only for discharging a floating PSU.
And yes, it's my main amp for more than a year. I waz lazy to finish the inside, so I tolerated the buzz until now. I have not changed anything beside the rectifiers, but buzz did not change from Graetz bridges or MOSFET rectifiers (the latter were supposed to be friendlier to the transformer).
Today I have challenged the mains connection, it's correctly wired, and direct connection to mains without cap and thermistor did not change anything.
The buzz was a bit different somehow, and I had an idea: measuring mains.
I had 247v, I'll compare values with moments of different buzz.
Could a too tightly designed toroid buzz? It was designed for 230v, and I cannot recall the tolerance, but this may be the culprit?
I'll try trimming Iq to see if buzz changes.
By the way, I have 25 mv of DC at mains, measured without my DC trap and with a trueRMS meter.
The buzz was a bit different somehow, and I had an idea: measuring mains.
I had 247v, I'll compare values with moments of different buzz.
Could a too tightly designed toroid buzz? It was designed for 230v, and I cannot recall the tolerance, but this may be the culprit?
I'll try trimming Iq to see if buzz changes.
By the way, I have 25 mv of DC at mains, measured without my DC trap and with a trueRMS meter.
well, in time of Yore when we all had 220Vac, +/-10% was normal tolerance and all ( properly made) gadgets really worked in that bracket
however, nowadays, I'm still surprised when Donut is not complaining when given 10% more voltage
so, if you're in area where you have almost 100% higher voltage - either complain to your Electricity Dealer ( slim chances) or do something, at least for your audio gadgets
mains corrector/conditioners - Audio Grade - are somewhat expensive
general use - those you can find cheaper, or look for locally made autoformers, made for shaving mains voltage purpose
now- you have DC trap - so , at least you can exclude that as reason, when having it in chain
however, nowadays, I'm still surprised when Donut is not complaining when given 10% more voltage
so, if you're in area where you have almost 100% higher voltage - either complain to your Electricity Dealer ( slim chances) or do something, at least for your audio gadgets
mains corrector/conditioners - Audio Grade - are somewhat expensive
general use - those you can find cheaper, or look for locally made autoformers, made for shaving mains voltage purpose
now- you have DC trap - so , at least you can exclude that as reason, when having it in chain
If I narrow down the options of mistake to an overvoltaged trannie, the winder is okay for rewinding them.
It's the good part of choosing expensive "local" craftsmnen : they stand behind their products.
Better than trash the iron and make china build another one.
I'm not equipped or bully enough to try a bucking transformer, as described by Rod Elliott.
It's the good part of choosing expensive "local" craftsmnen : they stand behind their products.
Better than trash the iron and make china build another one.
I'm not equipped or bully enough to try a bucking transformer, as described by Rod Elliott.
there is no need to exactly rewind them
he can add some additional turns for primary without butchering everything else, so you will have 230Vac and 250Vac taps
no penalty that way, practically just reworking some isolation and GOSS screen
he can add some additional turns for primary without butchering everything else, so you will have 230Vac and 250Vac taps
no penalty that way, practically just reworking some isolation and GOSS screen
I finally tried a bucking transformer, it was a bit in a rush but it was buzzing again.
And the buzz is the same pitch, but quieter when Iq was reduced from 2A to 1A.
I'm discussing again with the winder, I guess that there cannot be many possibilities left...
And the buzz is the same pitch, but quieter when Iq was reduced from 2A to 1A.
I'm discussing again with the winder, I guess that there cannot be many possibilities left...