Stop the press! I hate to be that guy, but I might be about to drop a deuce on this fine parade
I always feel for people who have to buy something from across the pond and have the snot taxed out of it after the snot has been taxed out of it here, plus shipping.
Also, I want to be clear, I am not disrespectful of anyone's technical skills. I'm sure OP and those who have responded are above average with tech stuff, and may or may not have developed that talent into schematic/component level troubleshooting.
As much as
@fdeck has not only graciously offered up his design work for free, and even gone as far as testing alternate parts and shows how to solder SMT FETs by hand, I would advise to make sure you can get the FETs shown in that layout before spending any money on other parts. If you cannot get the correct FETs, it would be advisable to read all three documents on his updated google site located under
Technical & DIY Stuff - hpftechllc ! It's been 5 careers and up to a zillion years ago since I've done any design or repair work with FETs, and even then it was using them as switches for DC motor control. So, I don't know if you need to fiddle with component values to get the alternate parts to work. This could be a show stopper if the builder can not troubleshoot by schematic. I fear building by layout may not be an option if the FETs are not available and in the same package type. SMT can probably be done by study of Fdeck's process and making an adapter board or extending the current board to accept the FETs. Of course a friend lending a hand at some of the details could work as well.
No friends? (OK that was a jab/insult
) I've taken a few brush up classes at the local 2 year tech school, and they always love having something that ties into the real world to work on in labs, including the instructors, of of which were engineering staff or instructors at the local engineering university during the day. I've also found university staff to be helpful. Beer bribes work
If the FET's are still available in the US, perhaps ordering and asking the seller to ship as a gift under $5 value or something. Or ship to one of us to reship if they won't do that. At least you can hide from the VAT man. If I am called upon to reship and it's under maybe $20 (depending on my girly mood swing at the time
), I would probably just ask you do a similar favor for someone else. Maybe give a wino a cheap bottle and a pack of smokes or something.
For SMT, I think this:
plus this:
Then jump G, D, S to the corresponding locations on the perf board layout. See
Quick and Dirty JFET Buffer, Rev. 2 - hpftechllc for instructions and details.
Finally, beware of static electricity (ESD). I mention this as an awareness and not full go paranoia. FETs are generally very sensitive to ESD, some more than others. Presumably these are not super-sensitive since Fdeck does not mention it, but with obsoleted components, they can become pre-damaged, or one can damage the parts handling them without ESD protection. Unfortunately, the result is not always a dead part on the spot. Typically I saw noisy FET input op-amps, or the walking wounded/walking dead that come back to haunt you with noise of failure. If that does not apply to JFETs, that would be good to know, but as a general minimal precaution, it's a good idea to discharge static from yourself and work on a sheet of foil placed on the bench. If you choose to ground yourself or the foil, be sure to use a 1 to 10M OHM resistor in the path to ground for safety. Even then, the foil is only safe to use for soldering unpowered circuts. You only get to die once, so don't make it be from any of my BadExample advice! Most components are pretty safe from ESD once in circuit. GFCI.
I am sorry if any of this puts an end to this plan.
