Yep, found the Ohmite WND non-inductive power resistors and just for fun substituted RN60 50ppm parts for the Beyschlags. Already had some matched 10.6mA 2SK170/2SJ74 in my stash. Case and PS ready to go. Just waiting on the shielded input cable.
BK
BK
An externally hosted image should be here but it was not working when we last tested it.
I was thinking the same thing. Tea's boards will make you look like a Jedi soldering master! I'm using plain vanilla Kester 44 eutectic and a nice hot iron. Nothing exotic.
The nice thing about the Pass circuits is that there are relatively few parts, so you can really take your time and enjoy the process and just get into the zone with your technique...
BK
Thanks for the compliment! Means a lot coming from someone with your credentials. I do appreciate a good solder joint.
BK
I only adjust after 2 hrs, and even with less offset than that, maybe half that, it will float a little bit, but not much.
It took a few days, at most a weak, before I really started respecting what was going on. It's now my office amp, so gets the most use of any amp I have made so far.
What is working voltage on C3? Just look at my drawer,I find lonely Elna silmic ii 1000uF 50V (fit nicely on the board) and nichicon superthru 4700uF 16V (body is too big). If I remember correctly,C3 will set charge up period, higher will be longer,smaller will be faster. Any advice which one that I should use?
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Having had the boards assembled for a few weeks now I finally/reluctantly stripped out the F6 boards
and have fitted in one channel of the M2.
I was surprised at how long it took to show any voltage across the source resistors before having to remove the bulb tester and checking the voltages. The p/s sits at +- 24V with the source resistors having 597mv across them give or take a couple of mv and the offset was adjustable down to below 10mv after an hours warm up.
Hopefully I get the same results with the right channel tomorrow and that I can listen to music by the evening
and have fitted in one channel of the M2.I was surprised at how long it took to show any voltage across the source resistors before having to remove the bulb tester and checking the voltages. The p/s sits at +- 24V with the source resistors having 597mv across them give or take a couple of mv and the offset was adjustable down to below 10mv after an hours warm up.
Hopefully I get the same results with the right channel tomorrow and that I can listen to music by the evening
I finished connecting the right channel board but have a problem. Unlike the left channel which steadied out at 597mv across R13 after a couple of minutes the right one has taken nearly an hour to reach 445mv across R13.
Both channels the offset is adjustable to a low value and no magic smoke has been released.
Any advice on where I have gone wrong much appreciated.
TIA
Both channels the offset is adjustable to a low value and no magic smoke has been released.
Any advice on where I have gone wrong much appreciated.
TIA
The active components would be the first thing I would question. Post in the Pass section for more technical members to give their opinions. I did not even check the bias on my build. The optocoupler is what bias's the board from what little I know about the circuit. If you used correct parts positioned correctly I would first take my iron and go over all the pins again. It could be just a cold solder joint.
A dry joint was my first thought so I reflowed everything and replaced the 4N35 thinking that might be the problem. Both boards were assemled side by side so shouldn't be a wrong placed part but it certainly won't hurt to check again just in case. I will ask over on the Pass forum.
Elfishi it is going to be awkward to check across C3. I guess I will have to pull the board away from the standoffs and bend the mosfet pins.
Thanks both.
The optocoupler placement was my biggest head mystery for me in the build, so I did as much as I could on the blog to sort that out. That being said, it's hard to say what is at play here.
When the optocoupler was put in backwards in my build, the bias continued to rise up to 1.5v before I pulled the plug (not certain this is what your experiencing). I then replaced both the optocoupler and the LM385 semi's, assuming I may have blown them up as a result.
When the optocoupler was put in backwards in my build, the bias continued to rise up to 1.5v before I pulled the plug (not certain this is what your experiencing). I then replaced both the optocoupler and the LM385 semi's, assuming I may have blown them up as a result.
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