My Transistors, original or copy? - Page 22 - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 3rd May 2009, 09:26 PM   #211
diyAudio Member
 
Join Date: Aug 2008
Hello friend,i have some issue like yours,everybody point in oscillation direction,after check that,
i go hard and open an original device (bad one) and compare with the ones i bought,of course i was disappointed, the new ones look smaler the leads are thin and have less dissipation area, and dont work ,fail as soon as i test hard...
Do the "open test"and compare (size area of the chip,leads etc) before go crazy...
  Reply With Quote
Old 3rd May 2009, 11:19 PM   #212
diyAudio Member
 
Join Date: Mar 2003
Location: Amsterdam
Powerflux, where did you buy that batch ?

Here: http://www.baco-army-goods.nl/product_987.html ?
  Reply With Quote
Old 4th May 2009, 01:43 AM   #213
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
unfortunately ST almost invites counterfeiting, since they use silver paint on the top of their TO-3 cans and then prints their logo on top of it. the only real good way to check the transistors non-destructively is the C-E and B-C capacitance, and compare against known good ones (like the RCA devices you have). capacitance is somewhat proportional to die size.
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 4th May 2009, 03:07 PM   #214
diyAudio Member
 
Join Date: Apr 2008
hi,

i have a blown RCA somewhere from some time ago, i'll try to clean it up as good as i can and do some size comparisons.

oscillation is a very good point, but since they've blown so far in the very milisecond i connect vsupply i don't suspect that's the problem. circuit layout is exactly the same betwee channels, as is dc supply. i've switched supplys to double check and the RCA channel keeps working.

i'll try and build a low-voltage (<12v), medium current lamp switch or something like that with one ST :P, i sadly don't have a capacitance meter.

i've bought them from thaishopetc @ ebay, not baco army goods.
  Reply With Quote
Old 4th May 2009, 11:23 PM   #215
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
also, i've never seen 3055's with the large diameter pins.... 3055's always seem to have the standard pins. can you get MJ15024's? same beta range, better Ft (3 or 4Mhz) and 250V.

i've learned to buy my semis from reputable distributors. they may cost a little more up front, but i know what i'm getting. it's actually cheaper, considering that by the time you figure out the 3 or 4 transistors you blew up are fakes, they cost you as much as the 1 good one you wanted. then you have to find one from a better source and pay for the part and shipping all over again. when i'm doing a repair, discovering a fake also costs in client satisfaction, since it's extra time to get the right part.
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 5th May 2009, 09:06 AM   #216
diyAudio Member
 
Join Date: Apr 2008
hi all,

i've sent the ebayshop owner an email explaining the situation. he assured me that they were from ST.

so as a final test i took out all RCA's from the working channel and replaced them with ST's. result: 4 blown ST's, driver transistors (BD140/139) also blown.

put back the original RCA's, new drivers and the channel works perfectly again.

interresting detail: the blown ST's all measure shorted between E-C/E-C but OK (~0.5V - ~0.6V in diode test) between B-E, B-C.
i'm not sure what it means, but normally everything's totally shorted or open, not normal diode values..

i'll order new ones (or no 3055's, but i wanted that for vintage's sake ) somewhere else. i've recieved a PM with advice to sample them at OnSemi.

thank you all very much for your help. i'll check this topic on regular base
  Reply With Quote
Old 17th May 2009, 04:50 AM   #217
PM650 is offline PM650  United States
diyAudio Member
 
Join Date: Jul 2005
Location: Tennessee
I just bought some B1647's, they look a bit fishy to me. A real one is shown (bent leads):
Click the image to open in full size.
back
crack?
real one
The suspects:
http://www.mustangmods.com/ims/u/1363/13725/284881.jpg
http://www.mustangmods.com/ims/u/1363/13725/284882.jpg
http://www.mustangmods.com/ims/u/1363/13725/284883.jpg

Any comments?
  Reply With Quote
Old 17th May 2009, 07:15 AM   #218
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
the one you have labeled real is a real one. two of the fakes show signs of the face being sandpapered, as well as the SK in the dimple above the collector lead. and are definitely fakes. the other one has the same date code and beta code as the fakes, and it;s printed exactly the same way. notice the spacing and centering of the code groups. this makes the third one a fake as well, but the base device used to make this fake came from a different source than the other two fakes, it's possibly even a genuine sanken device, but the printing has been altered and printed exactly like the other fakes. the best test is to test the C-E and C-B capacitances and compare them to the good one.

the sandpaper evidence is the rounded edges of the dimples (sandpaper, wire wheel, buffing wheel, sandblasting box, there are several ways to remove the original numbers)
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 31st May 2009, 06:28 PM   #219
lineup is offline lineup  Sweden
diyAudio Member
 
lineup's Avatar
 
Join Date: Dec 2005
Location: the north
Quote:
Originally posted by unclejed613
the one you have labeled real is a real one. two of the fakes show signs of the face being sandpapered,
---
the sandpaper evidence is the rounded edges of the dimples (sandpaper, wire wheel, buffing wheel, sandblasting box, there are several ways to remove the original numbers)
Very interesting, uncleJed
So this is how they do it .. sandpaper or simlar to remove original label first
... then add the faked print
__________________
lineup
  Reply With Quote
Old 11th September 2009, 12:46 PM   #220
pdul is offline pdul  Denmark
diyAudio Member
 
Join Date: Jan 2009
Location: Copenhagen
Is there anybody who knows where to buy REAL Toshiba transistors in Europe in small quntities. I am soooo tired of that Chinese junk sneaking in everywhere
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
NTE transistors-->> Backwards from original case layout!! What the heck! 777funk Solid State 1 10th May 2009 02:49 AM
Need DVD copy software! Kyte_08 The Lounge 7 16th February 2008 01:48 PM
how to backup original cd as the same sound quality as original cd ctrn Music 3 16th May 2006 04:21 PM
Copy of Kore-Eda pre ? sinski Chip Amps 2 4th May 2006 12:03 PM


New To Site? Need Help?

All times are GMT. The time now is 02:08 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2