Hello everyone. I have posted in the past regarding some new parts to use in a build. Things however changed in my professional life so I set the project aside for some time.
In the last 2 weeks I have however got back to it and here is the basic characteristics of it all:
3x500va toroids 36 -18 -0 -18 -36v
900 000uf cpacitors in series (small/medium and huge 40000uf caps).
secondary transformer for Softstart (QUASI design).
2 searate containers. In th first the power system, in the second the 6 nmos200 channels each with a DC protect circuit.
For now I have built only 2 channels and the common cd protect circuit.
Here are the pics
and
problems so far:
I keep blowing fuses. Th softstart works apparently but obviously the capacitors are a huge load on the transformers.
I would like to ask a couple of questions:
a) is there a a ready to print pcb, layout and all to get a slow start in order to avoid the problem I mentioned?
b) Are thermistors good enough? If yes, given my current setup, how would you guys go about installing them?
The resistor of quasi's softstart is hidden because it is bolted on the frame to guarantee best thermal contact and dissipation.
Please help. I Believe the project can work quite well but I have to resolve this mess with the transformers...
Thanks
Alessandro
In the last 2 weeks I have however got back to it and here is the basic characteristics of it all:
3x500va toroids 36 -18 -0 -18 -36v
900 000uf cpacitors in series (small/medium and huge 40000uf caps).
secondary transformer for Softstart (QUASI design).
2 searate containers. In th first the power system, in the second the 6 nmos200 channels each with a DC protect circuit.
For now I have built only 2 channels and the common cd protect circuit.
Here are the pics
An externally hosted image should be here but it was not working when we last tested it.
and
An externally hosted image should be here but it was not working when we last tested it.
problems so far:
I keep blowing fuses. Th softstart works apparently but obviously the capacitors are a huge load on the transformers.
I would like to ask a couple of questions:
a) is there a a ready to print pcb, layout and all to get a slow start in order to avoid the problem I mentioned?
b) Are thermistors good enough? If yes, given my current setup, how would you guys go about installing them?
The resistor of quasi's softstart is hidden because it is bolted on the frame to guarantee best thermal contact and dissipation.
Please help. I Believe the project can work quite well but I have to resolve this mess with the transformers...
Thanks
Alessandro
three 500VA transformers.
Fuse each one separately. With a master fuse at the mains input (IEC) socket.
Soft start with delayed bypass.
A single Power Thermistor soft start can be used to start up all three transformers.
A CL60 is OK for a single 110/120V primary. Two primaries in parallel require a CL60 in each primary circuit. Do not parallel the CL60s.
A CL60 for a 240Vac primary does not provide sufficient resistance to significantly reduce the start up current. Use two CL60 in series for 220/240Vac supplies.
Disconnect all three transformers from the mains. Check with a bulb tester to help find wiring errors before direct powering from the mains. Then test each one in turn after you have proved the wiring is OK.
Next try two transformers on your two CL60 current limiters. Finally try three transformers on your two CL60 current limiters.
Fuse each one separately. With a master fuse at the mains input (IEC) socket.
Soft start with delayed bypass.
A single Power Thermistor soft start can be used to start up all three transformers.
A CL60 is OK for a single 110/120V primary. Two primaries in parallel require a CL60 in each primary circuit. Do not parallel the CL60s.
A CL60 for a 240Vac primary does not provide sufficient resistance to significantly reduce the start up current. Use two CL60 in series for 220/240Vac supplies.
Disconnect all three transformers from the mains. Check with a bulb tester to help find wiring errors before direct powering from the mains. Then test each one in turn after you have proved the wiring is OK.
Next try two transformers on your two CL60 current limiters. Finally try three transformers on your two CL60 current limiters.
Thanks Andrew. Wiring should be okay but I will check.
The cpacitors act as a true shortcircuit. I was unfamiliar with this sort of behaviour. I have never used so many and witch such high values.
Stupid question. The thermistors should be positioned in series after the sofstart?
Thanks!
The cpacitors act as a true shortcircuit. I was unfamiliar with this sort of behaviour. I have never used so many and witch such high values.
Stupid question. The thermistors should be positioned in series after the sofstart?
Thanks!
ehhh, no outer isolation on supply caps, it appears
and looks like some are touching each other
if so, that might be a major problem
anyway, you amp boards looks like relative small output power, thus doesnt need a 1500watt supply
unless you want to use for low impedance load
but with highish 36Vac, they are probably not fit for anything lower than 4ohm
so, you have no use of that much power
I would rather consider double mono, each channel with one of those trafos
and use the third for something else
some times(often) simplification is the winner
and looks like some are touching each other
if so, that might be a major problem
anyway, you amp boards looks like relative small output power, thus doesnt need a 1500watt supply
unless you want to use for low impedance load
but with highish 36Vac, they are probably not fit for anything lower than 4ohm
so, you have no use of that much power
I would rather consider double mono, each channel with one of those trafos
and use the third for something else
some times(often) simplification is the winner
Hi ,
if you connect the capacitors with different voltage range and different values in series it will blow the fuse as huge current will flow and act as short circuit.
i one experienced this issue in one PC smps one of the 2 220 mfd 250v capacitor was bulged and leak i replaced with 150 mfd 220v volt and powered on imedieately it busted with huge flash
vijay
if you connect the capacitors with different voltage range and different values in series it will blow the fuse as huge current will flow and act as short circuit.
i one experienced this issue in one PC smps one of the 2 220 mfd 250v capacitor was bulged and leak i replaced with 150 mfd 220v volt and powered on imedieately it busted with huge flash
vijay
I have drilled holes and connections and have space for 8 modules for a 7.1 system. Each can drive 200w in 4 ohm speakers (theroretically)
Anyway I will insulate the cans. I purchased them used but were in working order.
Is the solution described by Andrew good enough to avoid any caps bursting?
Cheers
Anyway I will insulate the cans. I purchased them used but were in working order.
Is the solution described by Andrew good enough to avoid any caps bursting?
Cheers
Well, the question is: how old are they? You should do intensive testings for each one, separetely. Every time I try to reuse old electrolytics I find lots of unusable ones, for small or large defects.
All the best.
Max.
not sure but they charge and discharge correctly and each passes (by not showing) the continuity test. I am unable to test for capacitance.
I really hope I can get this power unit working because the rest is fairly straight forward.
All the bodywork and cabling has been done and looks very very neat.
So far I understand the only viable solution is to insert 2 Cl-60 in series after the sofstart circuit.
Basically a slow start after the softstart. Correct?
I really hope I can get this power unit working because the rest is fairly straight forward.
All the bodywork and cabling has been done and looks very very neat.
So far I understand the only viable solution is to insert 2 Cl-60 in series after the sofstart circuit.
Basically a slow start after the softstart. Correct?
Well several reasons
1) I got all those caps for very little over several months (100 euros max for all)
2) I would like to power 6 to 8 nmos200 modules in order to have a definitive system for a 5.1 to 7.1 system
3) I like the challenge. 😀
Pure class A amplifiers do have a lot of capacitance ....I would think more than I have. I have a thing for huge/inefficient machines...this seemed a good way to go around building one.
1) I got all those caps for very little over several months (100 euros max for all)
2) I would like to power 6 to 8 nmos200 modules in order to have a definitive system for a 5.1 to 7.1 system
3) I like the challenge. 😀
Pure class A amplifiers do have a lot of capacitance ....I would think more than I have. I have a thing for huge/inefficient machines...this seemed a good way to go around building one.
do the cap cans touch each other anywhere, from positive to negative rail
if they do you have trouble with that
anyway, you have plenty good toroids to build 3 stereo amps, or triple amp, if you like
rip it apart and rebuild
use smallest caps in one amp, bigger ones in another, and so forth
Or maybe just rearrange what you have into a seperate supply box, with different seperated supply, as pr above
Im sure you will get a much better result
if they do you have trouble with that
anyway, you have plenty good toroids to build 3 stereo amps, or triple amp, if you like
rip it apart and rebuild
use smallest caps in one amp, bigger ones in another, and so forth
Or maybe just rearrange what you have into a seperate supply box, with different seperated supply, as pr above
Im sure you will get a much better result
Thanks for the suggestion Tinitus. Simple plicarbonate "fences" will avoid contact between the caps. It should be a 4 euro job to resolve that.
The only amp I want (or need) is a unified 6 channel (or 8) assembly with multiple inputs (I have drilled for 10 channels input and 10 channels output). Once positioned in the living room it should remain there. A friend is willing to sell and install 6 speakers to achieve a sorround effect. He is very competent in these matters but I have to solve the amplifier problem first. I really do not have a need for aything else in terms of units or positioning.
I may sound stubborn (please forgive me if this is the case) but I really conceived this project for a 6 channel amplifiers. If you suggest splitting the toroids and caps within the casing I will have to look into that.
I have ordered the thermistors to try and solve the problems encountered in the current setup. I believe it should do it. I want to walk down this path because everything from component positioning to cabling was conceived to allow for a single power unit to supply an array of channels (I have also created a custom connection cable dividing impedance across the boards as suggeste by another user).
------------------------
One more question:
I have a problem with choosing a preamplifier. My needs are simple: I need some kind of volume control (attenuation) and a way to correctly connect the source to the amplfiier. The source should be either the satellite decoder and/or the blue ray/dvd player. I believe these are already preamplified sources thus making a preamplifier not needed. I also believe these are not fixed outputs so I should be able to vary output by ordinry volume control but I also believe some kind of volume control is always necessary. therefore I created 2 pcb for 6 linear pots with 6 resistive dividers (to achieve log. behaviour). can I connect the source directly to these boards?
Do I need anything in between?
If this is the case could you direct me to a ready to print pcb schematic? (I make my own boards).
Thanks a lot for your help.
P.s. forgive me if sometimes it seems that I may appear insensitive to some opinions. I value each and every comment but I started this "adventure" with a specific goal based on a real need. Anything different simply does not collimate with my actual needs.
The only amp I want (or need) is a unified 6 channel (or 8) assembly with multiple inputs (I have drilled for 10 channels input and 10 channels output). Once positioned in the living room it should remain there. A friend is willing to sell and install 6 speakers to achieve a sorround effect. He is very competent in these matters but I have to solve the amplifier problem first. I really do not have a need for aything else in terms of units or positioning.
I may sound stubborn (please forgive me if this is the case) but I really conceived this project for a 6 channel amplifiers. If you suggest splitting the toroids and caps within the casing I will have to look into that.
I have ordered the thermistors to try and solve the problems encountered in the current setup. I believe it should do it. I want to walk down this path because everything from component positioning to cabling was conceived to allow for a single power unit to supply an array of channels (I have also created a custom connection cable dividing impedance across the boards as suggeste by another user).
------------------------
One more question:
I have a problem with choosing a preamplifier. My needs are simple: I need some kind of volume control (attenuation) and a way to correctly connect the source to the amplfiier. The source should be either the satellite decoder and/or the blue ray/dvd player. I believe these are already preamplified sources thus making a preamplifier not needed. I also believe these are not fixed outputs so I should be able to vary output by ordinry volume control but I also believe some kind of volume control is always necessary. therefore I created 2 pcb for 6 linear pots with 6 resistive dividers (to achieve log. behaviour). can I connect the source directly to these boards?
Do I need anything in between?
If this is the case could you direct me to a ready to print pcb schematic? (I make my own boards).
Thanks a lot for your help.
P.s. forgive me if sometimes it seems that I may appear insensitive to some opinions. I value each and every comment but I started this "adventure" with a specific goal based on a real need. Anything different simply does not collimate with my actual needs.
no.
The twin CL60 arrangement I discussed is the soft start to allow the transformer to start up and become an operating transformer.
The CL60s are in the primary line at start up and after a short period they are bypassed so that the transformer is connected directly on line.
If you were using Power Resistors instead of Power Thermistors then the short time delay must be short enough to get the transformer started and also do so without significant heating of the Power Resistors.
Using Power Thermistors allow two modes of operation. A short delay just as described above or a longer delay that begins to perform as a slow charge.
I am currenty using a 25w 220ohm resistor bypassed by a relay (the basic QUASI design available on his website).
What I understood is that basically there are 2 issues on startup: an initial charging of the trasformer which is typically assoociated with a surge current. I bypassed the surge by using a power resistor bypassed by a timed relay.
A second problem is associated with large capacitance as it behaves like a shortcircuit on the transformers.
Would you suggest eliminating the power resistor and replacing the resistor assembly with the CL60s?
If so how would you modify this circuit? (resistor wise I guess)
http://3779347675151086879-a-180274...BgI2cp8E8cV7c9wXOfyQv66kClIHQ=&attredirects=0
to allow for a suitable "charging time"?
I never used thermistors so I really do not know what is considered a correct time interval for large toroidals in combination with 2 cl60s in series.
Thanks!
What I understood is that basically there are 2 issues on startup: an initial charging of the trasformer which is typically assoociated with a surge current. I bypassed the surge by using a power resistor bypassed by a timed relay.
A second problem is associated with large capacitance as it behaves like a shortcircuit on the transformers.
Would you suggest eliminating the power resistor and replacing the resistor assembly with the CL60s?
If so how would you modify this circuit? (resistor wise I guess)
http://3779347675151086879-a-180274...BgI2cp8E8cV7c9wXOfyQv66kClIHQ=&attredirects=0
to allow for a suitable "charging time"?
I never used thermistors so I really do not know what is considered a correct time interval for large toroidals in combination with 2 cl60s in series.
Thanks!
that 220r on 220Vac mains is not suitable for anything bigger than 200VA.
If the transformer were equivalent to a short circuit then the resistor would limit the current to ~1Aac. This would be equivalent to passing a short term peak power of ~ 440Wpk through the resistor.
I cannot believe that a 25W resistor can survive that power surge (+1660%) repeatedly, when powering up a big transformer.
A series combination of 5off 10r 5W resistors will be much more reliable for starting up bigger transformers. But they must still be bypassed quickly to prevent significant heating.
Changing to Power Thermistors reduces the need to bypass quickly.
But for the current needs of your transformer you need big thermistors and you need a lot of them if you are to reduce the start up current to ~1Aac.
Ok. I ordered (for future needs also) 5 Cl-60
How long after srartup should the relay bypass the thermistors?
Thanks.
How long after srartup should the relay bypass the thermistors?
Thanks.
Hi,
if you intend using primary circuit Thermistors to do the dual purpose duty of soft start and slow charge, then it is trial and error (experimentation).
What you should try to avoid is having a high current pulse, that is larger than the original start up pulse, pass through the mains fuse due to shorting out the thermistors.
Since the fuse is already warm from start up and charging it is closer to it's rupture temperature than it was when cold.
Staged/progressive bypassing of the thermistors may be successful at achieving this gradual transition to direct on line.
It may be very possible to avoid this complication.
if you intend using primary circuit Thermistors to do the dual purpose duty of soft start and slow charge, then it is trial and error (experimentation).
What you should try to avoid is having a high current pulse, that is larger than the original start up pulse, pass through the mains fuse due to shorting out the thermistors.
Since the fuse is already warm from start up and charging it is closer to it's rupture temperature than it was when cold.
Staged/progressive bypassing of the thermistors may be successful at achieving this gradual transition to direct on line.
It may be very possible to avoid this complication.
You suggest the complication may be avoided....how?
In regards to the preamplifier and volume attenuation problem....do you have any suggestions?
I would like to avoid preamps and really use the minimum required circuitry for volume control but I am open to suggestions.
I can have any board printed, painted, drilled and soldered in 24/ 36 hours 😀
In regards to the preamplifier and volume attenuation problem....do you have any suggestions?
I would like to avoid preamps and really use the minimum required circuitry for volume control but I am open to suggestions.
I can have any board printed, painted, drilled and soldered in 24/ 36 hours 😀
Last edited:
absolutely yes, when looking at caps, and by the fact that you actually have 3 nice 500VA toriods
- Status
- Not open for further replies.