cviller said:
I prefer not to assume anything before the initial setting has been done. Actually, that is why I use my multimeters, so I don't have to assume there's 0v at the output... Prefer to measure and be sure. Once it's 0 at the input and 0 at the output, we do measure with the input open...
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how will an 500va 2x18v toroide whit 4x33000uf caps in parralel work on 2 channals ?
how will an 500va 2x18v toroide whit 4x33000uf caps in parralel work on 2 channals ?
Use each secondary winding with a full wave bridge to produce the + 24VDC and -24VDC rails. The two amps share each rail. If you want a true dual-mono PSU, you need to double this circuit - 2 transformers, 4 bridges, 4+ filter caps, etc.
Hi,
you could, with a bit of extra work, use a 500VA 35+35Vac toroid.
Split the secondaries to create 17.5Vac times four.
You don not need to unwind the secondaries, just identify the midpoint of each winding and snip it. Add on four extra leadouts and re-wrap the insulation.
The wire used in a 500VA, 35+35 will likely be 1.2mm to 1.3mm diameter. You could add a few turns to each of the four secondaries to get precisely the voltage you want.
That gives isolated power to both channels and some of the benefits of pseudo monoblock are achieved.
you could, with a bit of extra work, use a 500VA 35+35Vac toroid.
Split the secondaries to create 17.5Vac times four.
You don not need to unwind the secondaries, just identify the midpoint of each winding and snip it. Add on four extra leadouts and re-wrap the insulation.
The wire used in a 500VA, 35+35 will likely be 1.2mm to 1.3mm diameter. You could add a few turns to each of the four secondaries to get precisely the voltage you want.
That gives isolated power to both channels and some of the benefits of pseudo monoblock are achieved.
nitpicks
I'm finishing my F5 and have a few questions.
I am using cviller's boads. But my questions are more general so I'm posting here.
1. Is is ok to use a 22 ohm 3W resistor from circuit ground to chassis ground like Zen v.4 instead of the 10 ohm thermister CL-60 in F5? Reason is cause I have a resistor but not a thermister.
2. Can I use a .047 uF AC rated line capacitor likeBOSOZ instead of .0033 uF as in F5? It seems that across all of the Pass Labs projects, these line caps are kind of guesswork, educated gusswork, anyway. Zen v. 4 uses .1 uF, this project is .0033, another is .047, etc.... Again, I have .1uF and .047 uF AC rated line caps but not anything small like .0033 uF.
3. Also I am going to put a fan in using a LM317 variable reg circ tapped off the 1st leg of the CRC power supply, any problem with using the 1st + instead of the 2nd + leg (other than the extra 2V I will have to reduce...but I figure if the fan circ adds noise it will be prior to the final "nice" DC). I underestimated the heat that those two xistors generate.
Thanks.
I'm finishing my F5 and have a few questions.
I am using cviller's boads. But my questions are more general so I'm posting here.
1. Is is ok to use a 22 ohm 3W resistor from circuit ground to chassis ground like Zen v.4 instead of the 10 ohm thermister CL-60 in F5? Reason is cause I have a resistor but not a thermister.
2. Can I use a .047 uF AC rated line capacitor likeBOSOZ instead of .0033 uF as in F5? It seems that across all of the Pass Labs projects, these line caps are kind of guesswork, educated gusswork, anyway. Zen v. 4 uses .1 uF, this project is .0033, another is .047, etc.... Again, I have .1uF and .047 uF AC rated line caps but not anything small like .0033 uF.
3. Also I am going to put a fan in using a LM317 variable reg circ tapped off the 1st leg of the CRC power supply, any problem with using the 1st + instead of the 2nd + leg (other than the extra 2V I will have to reduce...but I figure if the fan circ adds noise it will be prior to the final "nice" DC). I underestimated the heat that those two xistors generate.
Thanks.
labjr said:
I had a 2x37V 500VA toroid initially prepared for a Quad405 replica. Removed the outer layer of insulation, counted the number of windings and tried removing just a small patch of wire insulation at approximately the middle of each winding, after a few attempts it was found, cleaned it up a bit and attached (soldered) two new wires to act as middles for each of the 37V windings. It is working fine (with insulation back where it belongs) The hardest part of the work is removing and returning the insulation because there's only one hand to hold the transformer and a 500VA chunk is not so light... 😉
Re: nitpicks
1. Buy a thermistor, at least that one is not hard to get and not expensive. I used the Thermistor from a ditched PC PSU, there's usually only one NTC there, where the mains wires are inserted into the PCB, marked with TH1
2. Any C value will do ...
lgreen said:
1. Buy a thermistor, at least that one is not hard to get and not expensive. I used the Thermistor from a ditched PC PSU, there's usually only one NTC there, where the mains wires are inserted into the PCB, marked with TH1
2. Any C value will do ...
Re: nitpicks
If you don't use a Power Thermistor, then you must augment the resistor with a high current diode assembly. A 35A bridge rectifier does the job admirably and has been tested to ensure compliance with the survive requirement.
This connection must be capable of passing fault current to Safety Earth and must survive longer than it takes for the fuse to rupture and the arc to extinguish.lgreen said:
If you don't use a Power Thermistor, then you must augment the resistor with a high current diode assembly. A 35A bridge rectifier does the job admirably and has been tested to ensure compliance with the survive requirement.
From Line to Line (Live to Neutral) any X rated capacitor will have some benefit.
Curl and others say use 10uF at the distribution board for best attenuation of the RF and other spiking.
Line to Earth must use Y rated caps and the size determines the earth leakage through the cap. Small is beautiful here. Many use 2n2F. If RCCBs are fitted then the total leakage on the Earth must be limited to 25% of the trigger rating. i.e. for 30mA RCCB the maximum size of Line to Earth cap ~47nF if no other leakage flows. For UK voltages and regulations.
Curl and others say use 10uF at the distribution board for best attenuation of the RF and other spiking.
Line to Earth must use Y rated caps and the size determines the earth leakage through the cap. Small is beautiful here. Many use 2n2F. If RCCBs are fitted then the total leakage on the Earth must be limited to 25% of the trigger rating. i.e. for 30mA RCCB the maximum size of Line to Earth cap ~47nF if no other leakage flows. For UK voltages and regulations.
20V secondarys too much?
I am able to source 2-220VA torrid transformers for a good price. Each have dual 20V secondarys. Is this going to be too much for the F5 using the values listed in the schematic? Any advice on how to implement these if that is the case? Many Thanks in advance.
I am able to source 2-220VA torrid transformers for a good price. Each have dual 20V secondarys. Is this going to be too much for the F5 using the values listed in the schematic? Any advice on how to implement these if that is the case? Many Thanks in advance.
Ryssen said:
Yes, and approximately. It might end up with 0.63V, the 0V at the output is the goal.
F5 Temps
My heat sinks are about 8 inches long by 5 and 1/4 inches tall.
The temp at the hottest part (in center) is about 54C in open air without enclosure after 1 hour with voltage drop across R11/R12 at about 5.68v and all the time playing music into efficient speakers at medium volume.
Does this sound right?
I am going to add a fan at slow speed to keep the temp at 50C or under and set bias to .6 or .59 across R11/R12.
My heat sinks are about 8 inches long by 5 and 1/4 inches tall.
The temp at the hottest part (in center) is about 54C in open air without enclosure after 1 hour with voltage drop across R11/R12 at about 5.68v and all the time playing music into efficient speakers at medium volume.
Does this sound right?
An externally hosted image should be here but it was not working when we last tested it.
I am going to add a fan at slow speed to keep the temp at 50C or under and set bias to .6 or .59 across R11/R12.
f5- blowing fuses
Ok boys-
now we separate the builders from the talkers!~(read the glove is thrown down)
Fired up for the first time- rectification is good-got DC
voltage is good(right around 26 volts +&-
when hooked up to the boards and i get over 50 volts AC(variac) my 1 amp fuse blows- no boards connected no blown fuse/ with amp modules attached blown fuse-
no visual grounding except mosfets to the heatsinks through grease and mica - ie should not be conducting
First thing I thought was to remove the modules from the heat sinks and see if I can power up if for only a short time ie maybe the mica has slipped .
Other thoughts for places to check?I've torques the mosfets down pretty tight to try to get full contact- is this a mistake?
inquiring minds wanna know
tnx
rob
I'm using PD's boards and the GB antek torroid, teck-diy parts
Ok boys-
now we separate the builders from the talkers!~(read the glove is thrown down)
Fired up for the first time- rectification is good-got DC
voltage is good(right around 26 volts +&-
when hooked up to the boards and i get over 50 volts AC(variac) my 1 amp fuse blows- no boards connected no blown fuse/ with amp modules attached blown fuse-
no visual grounding except mosfets to the heatsinks through grease and mica - ie should not be conducting
First thing I thought was to remove the modules from the heat sinks and see if I can power up if for only a short time ie maybe the mica has slipped .
Other thoughts for places to check?I've torques the mosfets down pretty tight to try to get full contact- is this a mistake?
inquiring minds wanna know
tnx
rob
I'm using PD's boards and the GB antek torroid, teck-diy parts
lgreen: all sounds ok, except you should be seeing 0.568V approx across R11 and R12 - maybe a typo? Maybe watch the temp when you have it cased. That will add another bit to the temp.
rob lenk: Both your pots turned down all the way? Have you tried hooking up just one board to see what happens? IIRC, the F5 needs a 3A slow blow fuse for 120VAC operation?
Fran
rob lenk: Both your pots turned down all the way? Have you tried hooking up just one board to see what happens? IIRC, the F5 needs a 3A slow blow fuse for 120VAC operation?
Fran