the close rated fuse should be about:
transformer VA / rated Mains voltage.
600VA/230 = 2.61A
Use a T2.5A mains fuse and a soft start with the added resistor = 40r to 50r bypassed by a relay after ~ 100ms to 300ms
The internal Thermal Fuse will never rupture during all normal operation.
The only thing that could seriously overheat the transformer is a massive shorting of the transformer wiring (either internal or after the secondaries). That type of abuse will have blown the close rated fuse long before the transformer got hot.
Do use your Mains Bulb Tester for EVERY power ON while you are building and testing.
Only do direct on line starting AFTER you have completed all changes/modifications etc.
Your profile gives no clue to what mains voltage you have.
transformer VA / rated Mains voltage.
600VA/230 = 2.61A
Use a T2.5A mains fuse and a soft start with the added resistor = 40r to 50r bypassed by a relay after ~ 100ms to 300ms
The internal Thermal Fuse will never rupture during all normal operation.
The only thing that could seriously overheat the transformer is a massive shorting of the transformer wiring (either internal or after the secondaries). That type of abuse will have blown the close rated fuse long before the transformer got hot.
Do use your Mains Bulb Tester for EVERY power ON while you are building and testing.
Only do direct on line starting AFTER you have completed all changes/modifications etc.
Your profile gives no clue to what mains voltage you have.
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Hi Andrew, as usual helping every time 😉, appreciated, my mains voltage is 230V, but fluctuates to maxim 240V, the soft start is the one on the diyaudio store, normally even if I short by accident the secondary that thermal fuse should not blow, but as a precaution I will add fuses on the secondary and primary (slow blow is recommended no?) also just to protect the transformer in case of fault somewhere in the circuit. The transformer looks quite good, big diameter wires, tightly done, I can't complain regarding the construction. I would remove the thermal fuses if these are somewhere reachable but it's not the best thing to do.
Thanks again,
Florin
Thanks again,
Florin
I have picked 35V because I read on the forum that for 4 ohm loads this is recommended, I just hope that I am not on the bottom side regarding power delivered by the transf. , also the extra capacity on the power board would somehow compensate in some harder musical portions.
Thanks,
Florin
Thanks,
Florin
The close rated primary will blow if you abuse the transformer, long before it has a chance to overheat.
It takes sustained overload to overheat a transformer, that cannot happen with a close rated fuse in the primary circuit.
Charging up 100mF to 50V is virtually done in a couple of seconds. The transformer will remain cold during this starting duration.
Secondary fusing adds almost nothing in helping to prevent damage to your transformer and the wiring after it.
dual 35Vac will give you ~+-50Vdc as supply rails for quiescent operation.
That will allow peak output voltages of 39 to 42Vpk into an 8r0 dummy load
You can expect a bit less into a 4r0 dummy load.
expect a well assembled amplifier rated for 4ohms loading to give 180W to 200W into a 4r0 load using a dual 35Vac transformer.
600VA is well above that and will not get hot.
It takes sustained overload to overheat a transformer, that cannot happen with a close rated fuse in the primary circuit.
Charging up 100mF to 50V is virtually done in a couple of seconds. The transformer will remain cold during this starting duration.
Secondary fusing adds almost nothing in helping to prevent damage to your transformer and the wiring after it.
dual 35Vac will give you ~+-50Vdc as supply rails for quiescent operation.
That will allow peak output voltages of 39 to 42Vpk into an 8r0 dummy load
You can expect a bit less into a 4r0 dummy load.
expect a well assembled amplifier rated for 4ohms loading to give 180W to 200W into a 4r0 load using a dual 35Vac transformer.
600VA is well above that and will not get hot.
Thanks for the fast reply Andrew, in that case I will not use fuses in the secondary if you say it adds no major benefit, I wanted that mostly to avoid those thermal fuses to blow in some very unforeseen events.
Can you guys recommend any other model that does not come with those thermal fuses or all manufacturers implement these in their products?
Regards,
Florin
Can you guys recommend any other model that does not come with those thermal fuses or all manufacturers implement these in their products?
Regards,
Florin
I have only come across internal Thermal Fuses in very small transformers. Even then not in many.
I am really enjoying this thread, the posts and comments. If found amp kits and projects such as these are becoming harder to and harder to find. I'm looking for a amp project that offers slightly more power than the standard Honey Badger, (about 200-300W RMS) but am having some difficulty. I can think of no better place than this to dig for clues. Does anyone have any suggestions or give me some better direction? Thanks
200 - 300 Watts RMS into 8 ohms at <0.05% THD I don't really drive lower impedance speakers but about 250 watts RMS would be ideal. Class AB. in fact that's why I've posted here as I think this thread/amp is a very good footprint for what I'm seeking. Hope this helps.
300W into 8ohms is equivalent to 69.3Vpk and 8.66Apk.
That is probably going to require supply rails of near 80Vdc and 100V smoothing capacitors.
That is probably going to require supply rails of near 80Vdc and 100V smoothing capacitors.
Ostripper designed the Slewmaster series as the next step up from the Honeybadger. It can easily deliver that kind of power. http://www.diyaudio.com/forums/solid-state/248105-slewmaster-cfa-vs-vfa-rumble. html#post3753356 Vzaichenko's Non-switching output series are easily able to produce this power level too. Virtual Zero Audio - power amplifier products
Omit the fuses if you can. I used 35 VAC secondaries in my Badgers, works very well. Toroidy make good transformers at reasonable prices.
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