Alas, I didn't think about this when I soldered in the TL431. Clearing it would be difficult. I could rework this, but I will most likely mess it up. I'll have the sink face the other way.
You could do that also, easy peasy.
The reason my heatsink is the way it is, is because my fat fingers need room to wiggle the faston connector back and forth without hitting the heatsink and possibly bending the assembly. C10 is also in the way.
The reason my heatsink is the way it is, is because my fat fingers need room to wiggle the faston connector back and forth without hitting the heatsink and possibly bending the assembly. C10 is also in the way.
You forgot washers. Mechanical force is now applied (uneven) so that the transistors casings may crack. It is about spreading mechanical force evenly over the given surface and without washers either the bolt or the nut will have turning forces scratching/cracking the plastic when tightening directly to a plastic casing. The casings are not designed for such forces. Using washers is therefore common practice. The transistor on the right is soldered too low (the resistors too high) and its heatsink is very close to the resistors lead wires. Remove excess solder blobs with solder wick to have E curve solder joints with highest strength. All this for standard quality & reliability purposes.
Possibly those transistors do not need a heatsink.
"Common Q7/Q8 heatsink is required only above 30V output. At 50-60 V output, you can attach token heatsinks to Q5 & Q6 as well."
Possibly those transistors do not need a heatsink.
"Common Q7/Q8 heatsink is required only above 30V output. At 50-60 V output, you can attach token heatsinks to Q5 & Q6 as well."
Last edited:
Yep, no washers, but it’s tight enough.
I put the sinks because I target 58V.
Edit: You clearly don’t know my rework skills; if I touch this, I won’t have a board. It’s good advice, though. Thanks.
Thankfully, I don’t do this for a job or I would get fired every 2 weeks most likely.
I put the sinks because I target 58V.
Edit: You clearly don’t know my rework skills; if I touch this, I won’t have a board. It’s good advice, though. Thanks.
Thankfully, I don’t do this for a job or I would get fired every 2 weeks most likely.
Last edited:
I did not want to comment the expences of the R25, just wanted to get more information of LT4320. I like it a loot, just for my need, two of LT4320 and eigth proper mosfets, and that just for one channel (I have designed mosfet amp combination of Class A and Class B where I need floating low voltage high current power supply) the price is very high. I tried to simulate LT4320 with center tapped transformer hopping it was possible with some tricks, but no.
Common Q7/Q8 heatsink fins are better to be turned toward trimmer. TL431 should be soldered in low position. Also, you can always rotate that small heatsink (around hole) that longer part is facing upwards. It will do its job just fine.
C3 is required only with RF filter. Without RF filter, it is not required but can be left there as it would be in parallel with C2, increasing reservoir capacitance.
You mentioned +/- 5V supply? Minimum operating voltage for LT4320 is 9V, so another obstacle if circuit can’t operate at higher voltage.
I don’t know if member iTiberius is still active, but he has designed active bridges that work with center tapped transformers. It’s his own custom discrete design.: https://evotronix.eu/
@tombo56
First test tonight at 58V / 0.2A.
All is well. Adjusting voltage was easy as pie.
Hottest sink after 10-15 minutes of constant draw was the shared one at maybe 45-50°C. The big sink on the SUP was 35-40°C... warm.
More tests tomorrow with the intended transformer. The one I tested with is 300VA and it over-delivers massively with such a paltry load, so I had to restrain it with the VARIAC.
First test tonight at 58V / 0.2A.
All is well. Adjusting voltage was easy as pie.
Hottest sink after 10-15 minutes of constant draw was the shared one at maybe 45-50°C. The big sink on the SUP was 35-40°C... warm.
More tests tomorrow with the intended transformer. The one I tested with is 300VA and it over-delivers massively with such a paltry load, so I had to restrain it with the VARIAC.
Power supply requires only a fraction of volt higher voltage at input to operate at full performance. However, in practice mains voltage variation and ripple at the first reservoir capacitor lead to 1 – 1.5 V required difference.
How much voltage will be available after rectification depends on transformer properties and load. With very light or no load, there will be about 1.39 x AC voltage. Depending on standard transformer loading, that would drop to 1.2 – 1.27 x AC voltage. So it depends on specific use case.
In general, 22V AC is too much and 17 – 18V could be enough. For what purpose would you like to use this supply and what load current is expected (constant or variable)?
How much voltage will be available after rectification depends on transformer properties and load. With very light or no load, there will be about 1.39 x AC voltage. Depending on standard transformer loading, that would drop to 1.2 – 1.27 x AC voltage. So it depends on specific use case.
In general, 22V AC is too much and 17 – 18V could be enough. For what purpose would you like to use this supply and what load current is expected (constant or variable)?
@rickmcinnis,
Did you post any pics of your R25 with the added capacitance wired externally?
Before I lock in placement and start drilling holes for mounting components inside the chassis, I'm thinking ahead to create space for where I might add the extra capacitance, if needed.
@tombo56,
Twisted, heavy gauge wire as short as possible would be my approach to connect off-board caps. But, what would be too long for "as short as possible"?
Did you post any pics of your R25 with the added capacitance wired externally?
Before I lock in placement and start drilling holes for mounting components inside the chassis, I'm thinking ahead to create space for where I might add the extra capacitance, if needed.
@tombo56,
Twisted, heavy gauge wire as short as possible would be my approach to connect off-board caps. But, what would be too long for "as short as possible"?