about 50mA would be good. From memory, Mr. Mile recommends about min value of 25mA or 30mA.
It would be convenient and straight forward to set bias with output transistors in place, insulated from and mounted on heatsink .
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..I bought the components here Componenti elettronici. Distributore e negozio online - Transfer Multisort Elektronik , I never had any problems
AX14.
Ok my big output transistors mounted. I'm going to relocate Q10 with wire to the heatsink via a 3 pin pcb quick clip connector. And I have some funny looking heatsinks for the MJE 340/350s.
Does anyone have a photo/schematic of the voltages I should roughly see, please.
I will have 35vdc rails from my 25vac secondarys.
Should I have thiel circuit on the outputs?
Thanks lads for all the help. Almost there now!
Ok my big output transistors mounted. I'm going to relocate Q10 with wire to the heatsink via a 3 pin pcb quick clip connector. And I have some funny looking heatsinks for the MJE 340/350s.
Does anyone have a photo/schematic of the voltages I should roughly see, please.
I will have 35vdc rails from my 25vac secondarys.
Should I have thiel circuit on the outputs?
Thanks lads for all the help. Almost there now!
Hello Terry,
Could you also attach the spice file and models used.
So people can work out voltages depending upon their supply voltage levels. It will indeed be very helpful to debug every build on their own.
regards
Prasi
You will be using some mica or silicon insulators on the transistors connected to the heatsink right?
OK, so just theoretically how much damage are you likely to do if you reversed the polarities on the power supply leads to the AX14 board?
Yes, testing my 2nd board I connected the + and - incorrectly, well the marking for the + on the board had gotten a bit hard to see and looked like a - and I rushed things a bit.
Onboard fuses blew straight away then the 2.2uf caps exploded before I could shut the power off. They are before the fuses so not protected.
Obviously fuses and caps need replacing but do you think I likely did any other damage? Everything looks OK, probably try powering up carefully once I replace fuses n caps.
Yes, testing my 2nd board I connected the + and - incorrectly, well the marking for the + on the board had gotten a bit hard to see and looked like a - and I rushed things a bit.
Onboard fuses blew straight away then the 2.2uf caps exploded before I could shut the power off. They are before the fuses so not protected.
Obviously fuses and caps need replacing but do you think I likely did any other damage? Everything looks OK, probably try powering up carefully once I replace fuses n caps.
If the fuses blew quickly, D5 and D5 may have saved you. You may have to replace them though. It's worth trying it out with a light bulb tester in series with the AC input.
Thanks. I googled light bulb tester and what I saw was simply a mains bulb in series with the AC, is that all?
Thinking new build of the blown board will be best, I would never trust the damaged one and I really don't want to blow my expensive speaker drivers.
Darn, was so pleased the first channel came up first time. Should have taken more time over it. Still, of the many amps I have built over the years this is the first failure.