Jump to content

What Are You Building Today


Recommended Posts

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.

Link to post
Share on other sites
  • Replies 668
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

So Tice removed a deck at his job site, which is Armistead Maupin's former home. In his genius he recognized it to be Brazilian Ipe that was only screwed down from one side. The new owner eventually a

The Cherry is lighter than the speakers, but will darken quickly next to the window. I have a vented front plate coming for the top space. The cooling fan sits in that space, and is really quiet.

Second coat of finish. I still have rack rails to install, to hold the gear. The holes are vents, which will get black mesh behind them.

Posted Images

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.

Link to post
Share on other sites

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 by JoaMat
  • Thanks 1
Link to post
Share on other sites

Thanks, BUL216 added as c3675 substitute candidate.

 

Here is a schematic of latest battery module if interested.

 959923696_Skrmklipp.thumb.JPG.0eafcea0c9e8253bef359d0544b45fc8.JPG

R2 sets current through the voltage reference.

  1. 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.
  2. 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…

Link to post
Share on other sites
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. 

 

Link to post
Share on other sites

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.

  • Sad 10
Link to post
Share on other sites

Power supply is back. :D  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…

  • Like 3
Link to post
Share on other sites

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. 

uDpK3Jr2TH6V2zyUa9mqzA.thumb.jpg.8dd1c4aab7ae7f80b99070e1e7042525.jpggo6uaPM1QsWRf7NgJ7BxKw.thumb.jpg.ec2cf165462896db37df5f1b2459e110.jpg
 

Old Naked Triad (edit, because I can't remember shit)

spacer.png

  • Like 9
  • Thanks 1
Link to post
Share on other sites
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 by EdipisReks1
  • Like 1
Link to post
Share on other sites
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.  

Link to post
Share on other sites

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...

  • Like 1
Link to post
Share on other sites
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. 😁

  • Like 1
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...