JoaMat Posted April 23, 2020 Report Posted April 23, 2020 There are only a few modern npn alternatives to c3675. One is fjpf2145 which I’ve used since several years. In my modified T2 the fjpf2145 work alright with its batteries. The battery I’m trying now drives c3675 but not fjpf2145 without stn0214 in a Darlington pair. With stn0214 in the battery you can use whatever npn you like c3675, c4686, ksc5026 or fjpf2145. So for time being I don’t consider stp03d200, but it will certainly work.
Kerry Posted April 23, 2020 Report Posted April 23, 2020 I've tested the STP03D200 device and it works well. I don't have any listening tests with it. 1
thuytn Posted April 23, 2020 Report Posted April 23, 2020 5 hours ago, JoaMat said: There are only a few modern npn alternatives to c3675. One is fjpf2145 which I’ve used since several years. In my modified T2 the fjpf2145 work alright with its batteries. The battery I’m trying now drives c3675 but not fjpf2145 without stn0214 in a Darlington pair. With stn0214 in the battery you can use whatever npn you like c3675, c4686, ksc5026 or fjpf2145. So for time being I don’t consider stp03d200, but it will certainly work. Joachim, Is the FJPF2145 a direct replacement for the 2SC3675 in the original T2? My stock on the 2SC3675 has been running low, would love to have some alternatives.
JoaMat Posted April 24, 2020 Report Posted April 24, 2020 (edited) No, fjpf2145 is not a direct replacement for 2sc3675. 2sc3675 is a 900 V device while fjpf2145 is good for 800 V. I’ve used fjpf2145 in all c3675 positions on T2 except for Q8-10 and Q13-15 (output current sources). But if you decrease to +/-400V I guess you can replace c3675 with fjpf2145 here as well. I’ve also replaced c3675 with other transistors than fjpf2145. For instance Q30,31 with 2sc3324, a sot23 smd part. Might pop up in a future mini T2 with active battery... Edited April 24, 2020 by JoaMat 1
Craig Sawyers Posted April 24, 2020 Report Posted April 24, 2020 Another possibility as a 2SC3675 replacement is the BUL216. Vceo of 800V. Since it is a switching part rather than an amplifier part the specs are a bit sparse. Current part and cheap.
JoaMat Posted April 24, 2020 Report Posted April 24, 2020 Thanks, BUL216 added as c3675 substitute candidate. Here is a schematic of latest battery module if interested. R2 sets current through the voltage reference. R2 = 4.7K gives roughly 0.9mA. With 4.7K Q3 is needed if NPN is FJPF2145. If NPN is 2SC3675 Q3 is not needed. If R2 is 2K then roughly 2mA. Then Q3 is not needed for neither 2SC3675 nor FJPF2145. Purpose of R4 and R5 is to determine current through Q9,Q11 and Q10,Q12. With Q3 I measure roughly 0.05mA through both sides. Without Q3 almost all current goes through Q10/Q12 and if not enough the desired voltage can’t be regulated and that is what happens with FJPF2145 while 2SC3675 works but it’s very close…
mwl168 Posted April 24, 2020 Report Posted April 24, 2020 7 hours ago, JoaMat said: No, fjpf2145 is not a direct replacement for 2sc3675. 2sc3675 is a 900 V device while fjpf2145 is good for 800 V. I’ve used fjpf2145 in all c3675 positions on T2 except for Q8-10 and Q13-15 (output current sources). But if you decrease to +/-400V I guess you can replace c3675 with fjpf2145 here as well. I’ve also replaced c3675 with other transistors than fjpf2145. For instance Q30,31 with 2sc3324, a sot23 smd part. Might pop up in a future mini T2 with active battery... I believe that 2SC4686A would be good substitute for Q8-10, Q13-15? 2SC4686A is a 1200V device available at BDent and much less expensive than 2SC3675 but lower hFE. If you are willing to take the risk, 2SC4686A is also available at Utsource and the last batch I bought from Utsource tested similar to the ones I got from BDent. Be warned that Utsource sells mix of genuine and fake parts. Based on suggestions from someone very knowledgeable here, I plan to use 2SC3675 in the active batteries (need high hFE), 2SC4686A in the output current source and FJPF2145 for all other places to substitute for 2SC3675 in the T2.
RudeWolf Posted April 25, 2020 Report Posted April 25, 2020 Might be the fumes talking, but don't try to solder a CFA3 in one sitting. 4 4
JoaMat Posted April 26, 2020 Report Posted April 26, 2020 Kitchen in a terrible mess. The fellow in black is Pepsi and he loved schrimps. RIP. 5
JoaMat Posted April 27, 2020 Report Posted April 27, 2020 Today has been a nice and interesting day. I finished a mini T2 with active battery. The copper color board on right side in picture in previous post. Late afternoon I were ready for the first power on. One DMM to measure one side verses ground and another to measure the other side. High voltage clicked in – no explosion – on side showed a few volts verses ground while the other almost 400 volt verses ground. It took some time for me to realize that the 400 volt reading in fact was the BIAS. I’m getting to old for this. When I found the right measuring points I had very nice readings. Batteries are always interesting. Readings as follow. Left +194V and -443V, right +196and –443V. So they also seem to be alright. (using 640V instead of original 740V) Connecting headphone. Very noticeable hum but the music sounded good. After a while very annoying noise came. The noise almost disappeared when I approached the trimmer with the screwdriver but came back when I pulled back my hand. Turned power off and changed the small tubes, power up again, lower my guard and went for a cup of coffee and… it all exploded… So tomorrow I have to fix the power supply for the second time within a week. On amplifier board visible; burned traces, resistors and one popped transistor. Maybe I should feed ducks. 10
JoaMat Posted April 28, 2020 Report Posted April 28, 2020 Power supply is back. Replaced a number of FQPF8N80C, 30V zeners, 15R power resistors, one 2sa1486 and one 2k resistor. What actually killed the power supple (except the guy that should be feeding ducks) has to be investigated… 3
Fitz Posted April 28, 2020 Report Posted April 28, 2020 I bet it was caused by that 5G stuff. You can't trust it. 1
n_maher Posted May 2, 2020 Report Posted May 2, 2020 Made what is likely simply as aesthetic upgrade to the Menace TC - replaced the naked Antec . Funny to be tinkering with it 11 years after building it. Old Naked Triad (edit, because I can't remember shit) 9 1
EdipisReks1 Posted May 2, 2020 Report Posted May 2, 2020 (edited) 1 hour ago, n_maher said: Made what is likely simply as aesthetic upgrade to the Menace TC - replaced the naked Antec . Funny to be tinkering with it 11 years after building it. Old Antec God, it feels like it wasn't that long ago when this was brand new. We is old, Nate. Edited May 2, 2020 by EdipisReks1 1
n_maher Posted May 2, 2020 Report Posted May 2, 2020 18 minutes ago, EdipisReks1 said: God, it feels like it wasn't that long ago when this was brand new. We is old, Nate. Yes, yes we are, relatively speaking.
EdipisReks1 Posted May 2, 2020 Report Posted May 2, 2020 1 minute ago, Fitz said: Damn yall old. Correct.
Emooze Posted May 3, 2020 Report Posted May 3, 2020 Nicely done Nate, I really need to pick that project back up. I finally got around to adding a proper ground loop breaker and redoing all the grounding in the KGSSHV. I didn't take any pics... 1
n_maher Posted May 3, 2020 Report Posted May 3, 2020 23 hours ago, Kerry said: Enjoy Nate. Nice to see you tinkering again Next project arrives in two boxes tomorrow, not headphone but still audio related. 😁 1
Fitz Posted May 4, 2020 Report Posted May 4, 2020 19 hours ago, n_maher said: Next project arrives in two boxes tomorrow, not headphone but still audio related. 😁 Is it two of these, to annoy people in stereo? https://www.amazon.com/Original-Singing-Sensation-Motion-Activated/dp/B018IS34BW
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