3.6+-0.1 is sized for a 3.5mm diameter bolt or screw.
I have drilled out some ONsemi plastic packaged to allow 4mm bolts to be used. The plastic lined hole was tapered 3.7 to 3.9
A sharp drill did this neatly. The tiny plastic washer on the back sometimes fell out, but this caused no problems.
I have drilled out some ONsemi plastic packaged to allow 4mm bolts to be used. The plastic lined hole was tapered 3.7 to 3.9
A sharp drill did this neatly. The tiny plastic washer on the back sometimes fell out, but this caused no problems.
Hi labjr
The Fairchild and most similar packages are designed for M3 screws and insulating bush
If you like to go extreme you can use heath spreaders or mid way just the top clamp
You can make many variations on this
The Idea is that as the single screw is only on the top the transistor may lift on the opposite side a flat bar of Aluminium or cooper across the to will keep it flat
Main thing is not to over tighten and to go over the top part of the tread 1/2 mm with a slightly larger drill so the metal will not lift and push the transistor up.
Al
The Fairchild and most similar packages are designed for M3 screws and insulating bush
If you like to go extreme you can use heath spreaders or mid way just the top clamp
You can make many variations on this
The Idea is that as the single screw is only on the top the transistor may lift on the opposite side a flat bar of Aluminium or cooper across the to will keep it flat
Main thing is not to over tighten and to go over the top part of the tread 1/2 mm with a slightly larger drill so the metal will not lift and push the transistor up.
Al
Hmm, looks like Fairchild does not follow TO-247 specification. Does it?
According to the spec the hole must be 3.55-3.65mm. I'm always using 3.5mm metric drill bit for 6-32 screws and never had problem with it. I have Vishay FETs and they are perfect with 6-32 screws. Usually for FET mounting I'm using 10mm flat washer plus spring washer. This combination allows to have even and reliable pressure on the transistor case (I can see that the thermal compound evenly goes out along case perimiter).
According to the spec the hole must be 3.55-3.65mm. I'm always using 3.5mm metric drill bit for 6-32 screws and never had problem with it. I have Vishay FETs and they are perfect with 6-32 screws. Usually for FET mounting I'm using 10mm flat washer plus spring washer. This combination allows to have even and reliable pressure on the transistor case (I can see that the thermal compound evenly goes out along case perimiter).
Buddy, can you spare a dime. Mod transformer for my F5
I was able to pick up a couple Stonehenge size toroidal transformers rated at 500VAC but they have 24v+24v windings. Being of little brain, but knowing that once through the bridge rectifiers, I will be over voltage for the F5, I need direction on how to reduce the voltage to the spiffy blue boards I am set on assembling.
My question is, short of buying 18v+18v transformers, what are some straight forward ways that some kind soul would draw out and I would build. I can solder well, am very handy in a shop and I can read schematics. But mostly I love to listen to music. I have read that "voltage regulation" is not critical for the F5 but frying it with too much juice is likely an important consideration none the less.
I have been reading about linear voltage regulators and they seem pretty straight forward. Is this the way to go and if it is what unit would be most appropriate for my F5 power supply?
Thanking you in advance.
I was able to pick up a couple Stonehenge size toroidal transformers rated at 500VAC but they have 24v+24v windings. Being of little brain, but knowing that once through the bridge rectifiers, I will be over voltage for the F5, I need direction on how to reduce the voltage to the spiffy blue boards I am set on assembling.
My question is, short of buying 18v+18v transformers, what are some straight forward ways that some kind soul would draw out and I would build. I can solder well, am very handy in a shop and I can read schematics. But mostly I love to listen to music. I have read that "voltage regulation" is not critical for the F5 but frying it with too much juice is likely an important consideration none the less.
I have been reading about linear voltage regulators and they seem pretty straight forward. Is this the way to go and if it is what unit would be most appropriate for my F5 power supply?
Thanking you in advance.
Yes, quite so.
But that begs the question. What is the next easiest way to reduce the voltage making the boat anchors I have stand in for the right transformers?
Use several RC stages. 0.5 ohm will drop about 1 volt or so. You will need 7-8 of them on each rail. And the resistors will need to be rated 10W or higher. But then all this will probably end up costing the same as a new transformer.
Not easy, nor quick, but here is a voltage solution.
Remove the outer insulation to expose the secondary windings.
Do not at this stage remove any of the existing windings.
Measure the open circuit voltage of the two secondaries.
Move to about 1/3 of the way around the toroid. Scape off a tiny bit of insulating enamel. Measure the opencircuit voltage of that tapping point from the four ends. You will find that two ends give silly readings. The other two will give ~19V and ~9V, ( the total should exactly equal the whole winding voltage).
You may be able to discern a slight colour difference in the two secondary windings. Scrape the enamel off the other other secondary. Measure the open circuit voltage. You need to find two tapping points (one on each winding) that are exactly the same voltage. The original windings had exactly the same number of turns, you need to match this accuracy. One turn error is not good enough.
Go and buy more enameled copper wire of the same diameter as used for the secondaries. Wind on sufficient turns to bring the two ~9V taps up to to the same voltage as the two higher voltage taps.
Connect these extra turns in series with the existing 25Vac windings. You have created a 18-0-18 + 18-0-18Vac transformer.
Connect these centre tapped windings in parallel. You will now have a 550VA 18-0-18Vac transformer.
You now have a choice. Do you need centre tapped or dual secondaries? If you need dual secondaries, allowing dual bridge rectifiers, then you must snip the secondaries at those accurately measured tapping points. But before you do so, bind the secondaries with a few tight turns of insulated sticky tape to prevent the loose (snipped) ends from becoming loose.
Now add on insulated flexible cable to each of the 4 ends you have created. add on flexible cables to the 4 ends of the extra windings you created. You now have twelve ends coming from the transformer. Carefully insulate these soldered tappings and lay the wires so that they all come out from the same (top) corner of the toroid. The soldered joints must not rub through the enamel of adjacent windings, nor puncture the outer insulating layers.They will be spread around the circumference of the toroid and look ugly but that can't be helped.
Re-wrap the saved insulating tape using ~55% overlap to fully cover all the secondaries with at least 2layers of insulating tape. If you have sufficient tape left over add on a second 55% overlap layer over the whole secondary, giving at least 4 layers of tape insulation. If there is insufficient tape make the second layer a 5% overlap and this guarantees 3 layers of tape insulation over the secondaries.
This takes a while to read. Imagine how long it takes to do !
You have added ~45% copper to the secondary winding. This will increase the VA rating of the transformer by about 10% (1/6 to 1/3 of the 45%). Each secondary will be rated at 10.4Aac exactly as the original transformer. The total of all windings cannot exceed the new 550VA rating, set by the primary and the core. The heat load in the secondary has been massively reduced and this allows the transformer to pass slightly more VA without creating extra heat.
Remove the outer insulation to expose the secondary windings.
Do not at this stage remove any of the existing windings.
Measure the open circuit voltage of the two secondaries.
Move to about 1/3 of the way around the toroid. Scape off a tiny bit of insulating enamel. Measure the opencircuit voltage of that tapping point from the four ends. You will find that two ends give silly readings. The other two will give ~19V and ~9V, ( the total should exactly equal the whole winding voltage).
You may be able to discern a slight colour difference in the two secondary windings. Scrape the enamel off the other other secondary. Measure the open circuit voltage. You need to find two tapping points (one on each winding) that are exactly the same voltage. The original windings had exactly the same number of turns, you need to match this accuracy. One turn error is not good enough.
Go and buy more enameled copper wire of the same diameter as used for the secondaries. Wind on sufficient turns to bring the two ~9V taps up to to the same voltage as the two higher voltage taps.
Connect these extra turns in series with the existing 25Vac windings. You have created a 18-0-18 + 18-0-18Vac transformer.
Connect these centre tapped windings in parallel. You will now have a 550VA 18-0-18Vac transformer.
You now have a choice. Do you need centre tapped or dual secondaries? If you need dual secondaries, allowing dual bridge rectifiers, then you must snip the secondaries at those accurately measured tapping points. But before you do so, bind the secondaries with a few tight turns of insulated sticky tape to prevent the loose (snipped) ends from becoming loose.
Now add on insulated flexible cable to each of the 4 ends you have created. add on flexible cables to the 4 ends of the extra windings you created. You now have twelve ends coming from the transformer. Carefully insulate these soldered tappings and lay the wires so that they all come out from the same (top) corner of the toroid. The soldered joints must not rub through the enamel of adjacent windings, nor puncture the outer insulating layers.They will be spread around the circumference of the toroid and look ugly but that can't be helped.
Re-wrap the saved insulating tape using ~55% overlap to fully cover all the secondaries with at least 2layers of insulating tape. If you have sufficient tape left over add on a second 55% overlap layer over the whole secondary, giving at least 4 layers of tape insulation. If there is insufficient tape make the second layer a 5% overlap and this guarantees 3 layers of tape insulation over the secondaries.
This takes a while to read. Imagine how long it takes to do !
You have added ~45% copper to the secondary winding. This will increase the VA rating of the transformer by about 10% (1/6 to 1/3 of the 45%). Each secondary will be rated at 10.4Aac exactly as the original transformer. The total of all windings cannot exceed the new 550VA rating, set by the primary and the core. The heat load in the secondary has been massively reduced and this allows the transformer to pass slightly more VA without creating extra heat.
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If you still want to use the big transformers, gain some rail performance and at the same time, writing off some rail voltage, then an Aleph Amplifier type "C-Multiplier with a zener voltage limiter" is a rather good way of doing it and a very simple proven cct.
Another more recent way would be to use a version of Ikoflexor's double Cap Multipliers (as seen on "keantoken's CFP cap multiplier" thread post #8) but with IRFP devices instead of the D44H11 ones, and this will also drop about 8 - 9 volts off the rails and not contain any of the "so-called" zener noise behaviour (if present)
Your problem of high voltage windings should give you a much better sounding amplifier and is a bonus, although the extra heat (maybe 30W) will require a big change in heatsinks from about 0.35*C/W up to about 0.25*C/W - starting to get a bit big!
There are also quite a number of excellent power rail regulator ccts that you can use, too, but the heat has to also go somewhere ....
Another more recent way would be to use a version of Ikoflexor's double Cap Multipliers (as seen on "keantoken's CFP cap multiplier" thread post #8) but with IRFP devices instead of the D44H11 ones, and this will also drop about 8 - 9 volts off the rails and not contain any of the "so-called" zener noise behaviour (if present)
Your problem of high voltage windings should give you a much better sounding amplifier and is a bonus, although the extra heat (maybe 30W) will require a big change in heatsinks from about 0.35*C/W up to about 0.25*C/W - starting to get a bit big!
There are also quite a number of excellent power rail regulator ccts that you can use, too, but the heat has to also go somewhere ....
I will read more about the construction of toroidal transformers but I am really intrigued and grateful for the description and rationale of surgically modifying these boat anchors. They were Ebay surplus and I think the shipping was more than the items. But having purchased them I would like to make use of them.
The heat involved in the component level mod is not a problem and I will explore the circuits described for the regulated power supplies. But I have been having trouble finding power rail regulator units that can handle more than 2A let alone the continuous 6A and peak 10A described in the F5 manual. I have plenty of room and potential heat sink for new silicon and while lower noise and ripple are important, It is my understanding that the F5 is not especially sensitive to or needful of carefully regulated current or voltage. I just need to reduce the voltage from 34V to 24V and not restrict the amperage or melt the components in the process. What units come to mind. I have found nothing rated over 2A.
The heat involved in the component level mod is not a problem and I will explore the circuits described for the regulated power supplies. But I have been having trouble finding power rail regulator units that can handle more than 2A let alone the continuous 6A and peak 10A described in the F5 manual. I have plenty of room and potential heat sink for new silicon and while lower noise and ripple are important, It is my understanding that the F5 is not especially sensitive to or needful of carefully regulated current or voltage. I just need to reduce the voltage from 34V to 24V and not restrict the amperage or melt the components in the process. What units come to mind. I have found nothing rated over 2A.
While exploring these helpful options I found a discrete regulator that might be appropriate. The LM338 is rated at 5Amps.
LM338 - 5 Amp Adjustable Regulator
Is there any downside to using a simple device like this to regulate the voltage before it goes to the conventional unregulated capacitor PS of the F5 amplifier? Other than reducing the voltage does it introduce problems that a native 18v transformer would not pose to the passive capacitor power supply filter of the F5?
LM338 - 5 Amp Adjustable Regulator
Is there any downside to using a simple device like this to regulate the voltage before it goes to the conventional unregulated capacitor PS of the F5 amplifier? Other than reducing the voltage does it introduce problems that a native 18v transformer would not pose to the passive capacitor power supply filter of the F5?
brucegseidner,
1. You should not place a large capacitor after the regulator. High charge current will not even let it start regulating.
2. With that regulator you need a minimum 3V voltage drop on it. For practical use the voltage drop should be 5V or higher. This will give you (with 6A load current) 30W power dissipation on the regulator. In this case you will need to parallel them using at least 3 devices for TO-220 or 2 devices for TO-3 cases otherwise they will get overheated.
1. You should not place a large capacitor after the regulator. High charge current will not even let it start regulating.
2. With that regulator you need a minimum 3V voltage drop on it. For practical use the voltage drop should be 5V or higher. This will give you (with 6A load current) 30W power dissipation on the regulator. In this case you will need to parallel them using at least 3 devices for TO-220 or 2 devices for TO-3 cases otherwise they will get overheated.
Now I understand the rather short replies I received initially about just getting the right transformer value.
Caveman questions require Caveman answers.
When I read and looked at the power supply you offered I could see clearly how I would build it. But, as a Caveman armed with only a soldering iron, I had no way to understand how to modify the components and spec the values required to take my 24V-24V toroidal boat anchor and get 24VDC on the other end to power my truly blue and languishing F5 boards.
With my 24v-24v transformer in the circuit and needing 24vdc for the F5 what specific substitutions would be made?
If this is a boorish request it is just my ignorance of what is involved in calculating these values. Just tell this cave man to go dumpster diving for an 18v-18v transformer. I have found them for about $60-$120 retail. But if it is not too much of a chore it would be fun to build a circuit and learn about it and keep the boat anchors. They really are impressive beasts.
Caveman questions require Caveman answers.
When I read and looked at the power supply you offered I could see clearly how I would build it. But, as a Caveman armed with only a soldering iron, I had no way to understand how to modify the components and spec the values required to take my 24V-24V toroidal boat anchor and get 24VDC on the other end to power my truly blue and languishing F5 boards.
With my 24v-24v transformer in the circuit and needing 24vdc for the F5 what specific substitutions would be made?
If this is a boorish request it is just my ignorance of what is involved in calculating these values. Just tell this cave man to go dumpster diving for an 18v-18v transformer. I have found them for about $60-$120 retail. But if it is not too much of a chore it would be fun to build a circuit and learn about it and keep the boat anchors. They really are impressive beasts.
Sorry I did not state that it is the voltage regulator from the Zen 4 that I would like to adapt to my 24v-24v transformer to get 24vdc for the F5 boards.