Getting a more 303 sounding box..

[aminoacid]

i once bought 100 peices of 2sa733 from hongkong on ebay.

they also had a g suffix i think. i think "guest" pointed out they were a different transistor. 100 transistors in vain...

this can happen when buying transistors from shops aswell.

i bought 50 or 100 pieces os 2sa1085 from reichelt but they had wrong pinout and the hfe didnt match the hfe classification.

changing from 536 to 945 makes quite big change. that 6-9khz harshness dissapeared when i changed and im not looking back for 536.

however im willing to try out that other npn type... dont recall their name just now.

[rarara]

very interesting - thanks aminoacid

i have 100 733s on the way from HK but suspect they might be a bit duff as you also experienced. not much money i guess...

have reordered some 945's but this time made sure they have the P suffix

just need to perfect my desoldering

[roxxx303]

Hi,

in another thread I posted a link to my YouTube-Comparison-video
of tb-303 and x0xb0x:

http://forums.adafruit.com/viewtopic.php?f=7&t=37205

-roxxx303

[rarara]

OK made an interesting discovery with my meter - C13 would appear to give no reading.

are capacitors often duff or could it be too much heat at build? also, should I check every capacitor in the box?

[antto]

uhm, what reading are you trying to measure?
C13 is connected to ground, and acts as a LPF, it creates the accent "wow"

[rarara]

dang it - i was getting readings on other caps but think you are right. may swap c13 though as no wow

[rarara]

OK, my quest for perfection continues, and still at this stage I am looking for a "wow" sound....

Originally I thought there was a problem with C13 but now think its OK but my voltages for "IC12A thru D24 - R46 - C13" are:

D24 - 0v, 2.76v
R46 - 2.77v, 2.89v
C13 - 2.89v, 0v
IC12A - seems mostly along the lines of the 'analog voltages' posting/eagle file which is on another thread from quango. I can't measure mV's but the only differences are where quango reported 11.73v on a couple of pins, I am getting a bit lower - more in the region of 10.8v

i tried following some traces around these components and VR4 and noticed a few things....

R47 - getting 3.2v one side and 3.79v the other - a bit low?
C15 - 0v and 4.17v (R67 also has the 4.17 - does this feed C15 or vice versa?)
J5 - is this important? it looks like quango gave the voltages for this the wrong way round (?) but ignoring that, where he noted 34mV/0v/5.96v I am seeing 1.91v/0v/5.96v (with J5 on the I/O being the same)
C43 is also showing 2.4v on the negative side and 2.97V on the other

I am fairly positive that with enough effort I can get this thing as I want it now that i am pursuing voltages, but really would appreciate anyones help. (....and have checked that i am getting 5.3v and 11.8v)