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Projects => General Questions => Topic started by: timbo_93631 on March 07, 2012, 02:09:37 AM

Title: What to do with AC187 and AC188 equivalents?
Post by: timbo_93631 on March 07, 2012, 02:09:37 AM
So I finished salvaging parts from my Lowrey organ find today, one of the last things out was a Bell & Howell cassette recorder.  I was about to toss it, but I figured I'd better look inside to see if there was anything good.  I found:
2SB22 AC188K equivalent    3 peices
2SB405 AC188K equivalent   1 piece
2SD30  AC187K equivalent  2 pieces
2SD186 AC187K equivalent  1 piece

I have seen some nice Fuzzface clones with AC188's.  A Ge Fuzz would be a nice addition to my board.  After looking at the Japanese datasheets All have gains in the 100-200 hfe range.  Would be nice to know what the pinout is, but that was in Japanese and a PDF so I couldn't even use a translator program.
What would you guys build if you had found these?
EDIT:  I used google translator and entered emitter base and collector one at a time translated from english to japanese and figued out the pinout!  Normal EBC, hooray!
Title: Re: What to do with AC187 and AC188 equivalents?
Post by: cjkbug on March 07, 2012, 05:38:13 AM
depending on the gains and leakage. I'd build a "Face-Bender" A  MKII tone bender variant that you can switch the first transistor stage out of so you can get Fuzz Face-like tones as well as bender tones. I have a spare Fuzz Face enclosure that I've had sandblasted down to the bare aluminum, for building either one of those, or a "Trem Face" clone.
Title: Re: What to do with AC187 and AC188 equivalents?
Post by: Diamond on March 08, 2012, 10:19:54 AM
NPN Buzzaround! Definitely!
Title: Re: What to do with AC187 and AC188 equivalents?
Post by: timbo_93631 on March 08, 2012, 09:28:11 PM
So I breadboarded a buzzaround but it looks like I gotta mess with the biasing to get that right.  Off the bat changing the 470k on Q1 to 270k helped and dropping the 10k on the emitter to 6k8 helped too.  I am not getting unity gain at the loudest settings yet though.
Title: Re: What to do with AC187 and AC188 equivalents?
Post by: timbo_93631 on March 09, 2012, 06:30:08 PM
Okay, I rebiased the buzzaround and it was better but not, "knock-my-socks-off" great.  So I breadboarded a Fuzz Sound MKIII/IV and I am in love.  Freaking awesome.  The trannies are NPN Sanyo Germainums, 2SD30 for Q1 and Q2, 2SD186 for Q3.  Gotta order a Pastyface PCB now if anyone has one and wants to trade for 3 of the PNP transistors (2SB22 AC188K equivalent, 2SB405 AC188K equivalent) let me know.
Title: Re: What to do with AC187 and AC188 equivalents?
Post by: Diamond on March 09, 2012, 10:11:24 PM
Glad it worked out!  :)
Title: Re: What to do with AC187 and AC188 equivalents?
Post by: Fernando on April 18, 2012, 02:15:06 PM
There is one great application for ac187k and ac188k, a 3W guitar amp!

The original is called "Tengo Na Minchia Tanta" from an italian author. I didn't have time to build one but I will when I can. My idea is to have a nice portable battery germanium transistor guitar amp! :D

http://freestompboxes.org/viewtopic.php?f=2&t=5881 (watch for updated schematic here)

http://topopiccione.atspace.com/PJ21TPCTengoNa.html

http://topopiccione.atspace.com/pjimages/TPCTengoNaMinchia.sch.jpg

http://topopiccione.atspace.com/pjimages/TPCTengoNaMinchiaBuffer.sch.jpg

http://topopiccione.atspace.com/pjimages/TPCTengoNaMinchia.lay.gif

http://topopiccione.atspace.com/pjimages/TPCTengoNaMinchia.PCB.gif

Please report if you try it !!!

Best,

Fernando
(Barcelona, Spain)
Title: Re: What to do with AC187 and AC188 equivalents?
Post by: Bret608 on April 18, 2012, 04:14:50 PM
The Keeley Fuzz Head uses an AC187 apparently. Ian etched me a board to try based on the schematic--not verified, but looks like there shouldn't be any problems. I'll let you know if it works out and you can do one too!

Now I just need to find an AC187 myself!
Title: Re: What to do with AC187 and AC188 equivalents?
Post by: timbo_93631 on April 18, 2012, 08:22:53 PM
Built a NPN Pastyface with the 2SD30's and 2SD186:
http://www.madbeanpedals.com/forum/index.php?topic=4592.msg40501#new
So awesome!