I'm stuck powering up the F5 (2.0 from cviller)....
I get no heat, and zero volts across R11/R12. Turning the pots has no effect on anything.
If I had to guess, Q1 and Q2 are doing nothing. I see about 30-40 mV across R1/R2.
I have replaced them (Q1/Q2), but from the same stock (yes, I bought crap from China via Ebay).
Any thoughts? Thanks. ~Dave
I get no heat, and zero volts across R11/R12. Turning the pots has no effect on anything.
If I had to guess, Q1 and Q2 are doing nothing. I see about 30-40 mV across R1/R2.
I have replaced them (Q1/Q2), but from the same stock (yes, I bought crap from China via Ebay).
Any thoughts? Thanks. ~Dave
Measure the Idss of your current Jfets (as Andrew suggested) if you have a chance to take them out - if they are genuine, they are pretty durable.
Make the changes to your existing board -- save yourself a bit of work. You will probably be able to get this one working.
Edit - One last question, what schematic are you using? The version with P3? If so, is it on one side of it's range or approximately centered?
Check your PMs.
Make the changes to your existing board -- save yourself a bit of work. You will probably be able to get this one working.
Edit - One last question, what schematic are you using? The version with P3? If so, is it on one side of it's range or approximately centered?
Check your PMs.
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Measure the Idss of your current Jfets (as Andrew suggested) if you have a chance to take them out - if they are genuine, they are pretty durable.
I have a couple new ones from the Chinese source... I can measure those.
I see that 2sk170s are still available in quantity for Mouser (and I assume they are the original Toshiba). Is there a source for the 2sj74?
Edit - One last question, what schematic are you using? The version with P3? If so, is it on one side of it's range or approximately centered?
Check your PMs.
This is the latest version of the PCB that I can find, but it contains components for other versions: http://www.diyaudio.com/forums/blogs/cviller/attachments/x98d1265162390t-gb-f5-guide-pcb-version-2-f5_cascode_forguide.png
Is there a better one? The boards are v2.0 2010-10-23 (standard F5).
Thanks!
Off the top of my head I know that you can get 2SJ74s (and K170s) from member " h_a ", and also from the AMB.org site in his store. There are probably other sources as well, I just can't think of any right now.
Your schematic link is really small... and I wonder if the schematic has different part numbers than the original schematic... Do you have a bigger image of it?
Your schematic link is really small... and I wonder if the schematic has different part numbers than the original schematic... Do you have a bigger image of it?
h_a don't sell only J-fets. but spencer doesOff the top of my head I know that you can get 2SJ74s (and K170s) from member " h_a ", and also from the AMB.org site in his store. There are probably other sources as well, I just can't think of any right now.
Your schematic link is really small... and I wonder if the schematic has different part numbers than the original schematic... Do you have a bigger image of it?
Well, it looks like it was a wrong value for R21/22. By putting the correct 22K resistor in there, it is working more like "normal".
I am only getting about 0.35 - 0.38V across R11 and R12, despite cranking the pots to the limit. I think I got them installed correctly, but as long as they are both in correct or reversed, that shouldn't be a problem?
Again, I don't know what damage I might have done to other components, and I should probably complete the rest of the boards before spending too much time on this prototype...
Thanks all. Dave
I am only getting about 0.35 - 0.38V across R11 and R12, despite cranking the pots to the limit. I think I got them installed correctly, but as long as they are both in correct or reversed, that shouldn't be a problem?
An externally hosted image should be here but it was not working when we last tested it.
Again, I don't know what damage I might have done to other components, and I should probably complete the rest of the boards before spending too much time on this prototype...
Thanks all. Dave
Have you measured the Idss of the jFETs?
Just did....
Out of the roll I got (from eBay/China) one measured 5.5 mA, the other 6.0 mA at 9.00v.
Looks to be in spec...
No, the offset was around 0.6v (no load attached). I didn't try to zero it, as I thought it would be best to get the R11/R12 voltage to the recommended 0.59v
I'll try adding some resistance. I see there is a thread on that...
You need to work the pots in tandem to get 0.6v across R11 and R12 while also monitoring the DC on the outputs.
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