Thanks for the input guys. I have attached a pic of the two Jfets. It's hard to read numbering but the 2sk370 is on the left. I have limited knowledge and test equipment but have run another crude test which seems to confirm wrong part. Using two volt meters checking continuity across source and drain, can use lead off one meter to turn gate on/off. The 2sk370 reacts as it should....outer pins are source/drain and center pin gate. The 2sj108 it would seem source and drain are beside each other and gate is outer pin. This does jive with the N jfet (wrong part)
I think I have answered my own question/confirmed wrong part, but there is always possibility of user error!
-cheers
I think I have answered my own question/confirmed wrong part, but there is always possibility of user error!
-cheers
Attachments
Thanks Dennis. That boosts my confidence that tests were correct! Frustrating learning experience, but that's part of the fun I suppose. Time to strip burnt components and start over.
IRF9630/IRF630 would be better as it is a 74W device, however its max capacitance is half of the IRFP9240/IRFP240. I'm not sure if it matters.
Thanks
You can assess SOAR after applying a temperature de-rating to the devices.
Bensen's spreadsheet allows one to see the SOA transgressions for the DC rating of the FETs. You can add on the transients SOA curves and see how your devices cope with the transient demands of driving a reactive load.
Bensen's spreadsheet allows one to see the SOA transgressions for the DC rating of the FETs. You can add on the transients SOA curves and see how your devices cope with the transient demands of driving a reactive load.
Can a dual mono F5 be a good choice in terms of value/quality? My F5 is up and running. However, my new speakers (Frugal mk3 with fostex 126en) brought the existent hum to a higher level. I'm ok with it most of the time. At night i can hear it. I saw a user in this thread that made some modifications to the PCB following the D. Joffe paper and it solved the problem. i
i am trying to figure if the investment in a new trafo (400va toroidy2x18=100€) and some iron panels (i will divide the existent chassis into 2 parts, and adapt it to a mono block)is a wise move, or if i should spend the money in another project. So far, i have built a Ba3 preamp, the F5 and a Salas phono stage. I have at the bench, the vfet kit.
i know that the ideal candidate to the dual mono build is the vfet, but for that i have to wait a while (€).
what can i do with two power supplys and two transformers? i think all the firstwatt amps use the 2x18vac secondaries.
i've never built a dual monoblocks. So i dont really know(never heard one) what the benefits are.
thank you.
BR
i am trying to figure if the investment in a new trafo (400va toroidy2x18=100€) and some iron panels (i will divide the existent chassis into 2 parts, and adapt it to a mono block)is a wise move, or if i should spend the money in another project. So far, i have built a Ba3 preamp, the F5 and a Salas phono stage. I have at the bench, the vfet kit.
i know that the ideal candidate to the dual mono build is the vfet, but for that i have to wait a while (€).
what can i do with two power supplys and two transformers? i think all the firstwatt amps use the 2x18vac secondaries.
i've never built a dual monoblocks. So i dont really know(never heard one) what the benefits are.
thank you.
BR
0.5mVac is too high for a normal Power Amplifier.
I expect <0.1mVac from most of my amplifiers, stereo tends to be a little bit higher, but never above 0.3mVac
This points to wiring errors inside the amplifier.
0.5mVac is 66dB below 1W
A speaker that has a sensitivity of 90dB/W @ 1m will have a hum + noise output of 24dB @ 1m
That is not "almost dead silent".
Hi Joca,
You have probably already read my post 15472, but if not have a look. It sums up my experience with my F5's hum. Right now, I'm breaking my amp in with my Exposure 2010s2 as a preamp and I can't hear any hum.
Hi dbis. Thank you for your help. Also, thanks to Andrew and 6L6.
I've decided to do a monoblock amp. I will debug my F5 and then make it a dual mono config. Dual power supply. Want to hear the diferences.
Just to ask. If you would want to build monoblocks from an F5, what would be your concerns regarding the build? Just another PSU and chassis is OK? Or will you change anything else?
Thanks
I've decided to do a monoblock amp. I will debug my F5 and then make it a dual mono config. Dual power supply. Want to hear the diferences.
Just to ask. If you would want to build monoblocks from an F5, what would be your concerns regarding the build? Just another PSU and chassis is OK? Or will you change anything else?
Thanks
