Gentlemen a little help please. Here is my situation (i only have one channel now).
--All Chinese Boards
--80mF capacitors/channel
--Biased with input shorted,o/p open
---Steady bias of .48mV across R11/R12, 3.5V across R3/R4, offset bias 2mV
---Heatsink extremely cold (as if there is no heat exchange)
Connected all my sources & i have to literally hold my ear to the speaker (tried 3 types) to listen to sound (it is playing though).
Are my mosfets fried? But if they are, will everything be so honky dory.
Thanking you all
--All Chinese Boards
--80mF capacitors/channel
--Biased with input shorted,o/p open
---Steady bias of .48mV across R11/R12, 3.5V across R3/R4, offset bias 2mV
---Heatsink extremely cold (as if there is no heat exchange)
Connected all my sources & i have to literally hold my ear to the speaker (tried 3 types) to listen to sound (it is playing though).
Are my mosfets fried? But if they are, will everything be so honky dory.
Thanking you all
problems:
- IP stealer's boards
- no pictures , sch with important points tested and written down
- IP stealer's boards
- no pictures , sch with important points tested and written down
Thank you sir...yes not very proud of the boards .
Only one question - Can the o/p mosfets be fried even though the bias is right/steady and i can hear the output although extremely low?
Only one question - Can the o/p mosfets be fried even though the bias is right/steady and i can hear the output although extremely low?
If it's 0.48mV than no wonder that:
----> Heatsink extremely cold (as if there is no heat exchange)
What are the sources? Are you using a preamp? What is the input (into F5) signal voltage ?
No but you wont get a lot of volume unless speakers are fairly (90dB and up) efficient. With 85-86 dB speaks I can get listening levels at full volume with B-1....not real loud but ok.
Russellc
Well I have troel gravessen's nomex..should be 90db (if I have beuilt them right)...the cold heatsinks are bothering me...it did not get even warm after 1 hour
I would check the value of the source resistors. I'll bet they are not .47 ohm. If they are a higher value, like 4.7 ohms then you will have hardly any current flowing.
Goog luck,
Rush
The resistors are around .47 ohms (.9 ohms with DMM). More questions to help me with troubleshooting
With i/p shorted o/p open & mosfets soldered. Bias at .48V
--- Will Vgs of mosfets show values? If yes around how much?
---Will Jfet Ids show values? If yes around how much?
With i/p shorted o/p open & mosfets soldered. Bias at .48V
--- Will Vgs of mosfets show values? If yes around how much?
---Will Jfet Ids show values? If yes around how much?
hum I think that 99.9 % of times mosfets breack as a shorth circuit so I think you don't have a problem there.
I was waiting to post my 2 cents as much beter helpers here but as so far no much came up I would suggest to pop the J fets on simple test rig and find out the current. Ids?
VGS on mosfets shuld be about 4 Volts for N types bit more for poss.
Do you have power limiting transistor installed If so you can take them out for shorth while (one less thing to worry about while testing)
What is the Vdrop across the source resistors?
I was waiting to post my 2 cents as much beter helpers here but as so far no much came up I would suggest to pop the J fets on simple test rig and find out the current. Ids?
VGS on mosfets shuld be about 4 Volts for N types bit more for poss.
Do you have power limiting transistor installed If so you can take them out for shorth while (one less thing to worry about while testing)
What is the Vdrop across the source resistors?
no problem
This means that you have not been able to turn the pots p1 p2 so far from zero that there is enough of gate voltage. Some people needed to series an extra resistor to get it higher, such that the drain current of the input creates enough bias.
Of course. The output stage is still shut off.
no not at all.
Which can be found here - http://www.diyaudio.com/forums/pass-labs/188691-illustrated-guide-building-f5.html
Thank you all...yes I have read the illustrated build thread...I have made a mess of the current board & I ordered 3 🙂...so I'll start from fresh (might harvest some parts)..by the way my Vgs was 3.6v(9240) & 2.9v(240) & I was using 2 2.2k in series for r11& r12...I promise photos if I need to reach out again
Thanks to all once again
Thanks to all once again
