Troubleshooting Shein Fuzz Companion

[Rob Strand]

I'm not sure how this happened, but I have editted willienillie's post.  Weird.

You probably hit the Modify button instead of the Quote button.   I did that once to rankot's post.

Willie quoted something like,

2SC536 datasheet (WEJ datasheet)
https://datasheetspdf.com/datasheet/2SC536.html

2SC536F
F has gain 160-320

Willie had a few more suffix digits on the part.

[willienillie]

I have an original FY-2 and will confirm that the transistors are indeed 2SC536.

I'm not sure how this happened, but I have editted willienillie's post.  Weird.

Whiskey Tango Foxtrot, over?

Shame too, I had typed out the meaning of life and all the secrets of the universe, now I don't remember any of it. 

[willienillie]

I'm not sure how this happened, but I have editted willienillie's post.  Weird.

You probably hit the Modify button instead of the Quote button.   I did that once to rankot's post.

Willie quoted something like,

2SC536 datasheet (WEJ datasheet)
https://datasheetspdf.com/datasheet/2SC536.html

2SC536F
F has gain 160-320

Willie had a few more suffix digits on the part.

I was quoting the GGG schematic, which mentioned the original transistors being C536F7G.  I'm not sure, but I think the F there is the gain bucket, and 7G just a batch number or something like that.  So if the originals ran hFEs in that 160-320 range, then 10-50 is probably way too low.

[Rob Strand]

I was quoting the GGG schematic, which mentioned the original transistors being C536F7G.  I'm not sure, but I think the F there is the gain bucket, and 7G just a batch number or something like that.  So if the originals ran hFEs in that 160-320 range, then 10-50 is probably way too low.

I actually thought you pulled those extra digits from a some secret stash of info 

(A few of the schematics (and there's quite a few on the web)  for the ge units have the low gains marked.   I compiled some info on the ge and si units but it's on another machine).

[Rob Strand]

2SC536F
F has gain 160-320

FWIW, that gain range will put the collector of Q1 around 4.5V.   At the extremes of the gain range the voltage will be quite a way off from 4.5V - that's more of a design issue.

Whatever the gain,  Q2 is biased with a very low collector voltage.

[duck_arse]

there is a purple wire connects to the led - looks to be VERY close to a jack-tip. both legs of the led need to be insulated, or you, may, get trouble every time you button it up.

but to more important matters - when can we see the topside/coverings? how did you fluff the case without seams? so many questions .......

[Rob Strand]

Shin EI FY-2 Silicon

FWIW, here's a few voltages (from the web),


GGG
http://www.generalguitargadgets.com/pdf/ggg_secf_instruct.pdf
6.6V Q1 collector
2.0V Q2 collector     - with the spec'd transistors I don't believe it.

[EDIT both 6.6V and 2.0V imply a transistor gain of about 40 for both Q1 and Q2;  way off the original.]


Mark Hammer on July 10, 2009,
https://www.diystompboxes.com/smfforum/index.php?topic=77729
"I have an original. With a fresh battery that gives a V+ of 9.78VDC, I measured the following:

Q1: E - 0v, B - .59v, C - 3.40v
Q2: E - 0v, B - .55v, C - 0.9v"

LucifersTrip  03 Aug 2014, 08:12
Q1C 3V, Q2C 1.2V


See also, reply #4
https://www.diystompboxes.com/smfforum/index.php?topic=96572

jpiddy118, March 20, 2012
"i reverted back to the original R2 & R4 values, and popped a lower gain 3904 in Q1 (was 250, now 200)... my voltage readings are near identical with MH's original unit readings (Q1 B= .61v, C=3.55v, Q2 B= .55, C= .9v), and most importantly, it sounds good. Can't wait to bring it to rehearsal this week and compare with last week's adjusted bias settings (Q1 C was up to 7v, and it sounded great, but maybe not vintage-accurate)."

Conclusions:
Q1 collector voltage of 3V to 7.0V looks reasonable or the spec'd 2SC536F transistors. 
      Low values like 3.1V to 3.4V seem more likely for typical transistor gains.
      What sounds "best" is up for grabs.
Q2 at 0.9V to 1.2V it seems very reasonable.   I've got doubts about GGG's 2V.
       Perhaps 0.9V is more a typical value.

For Q1, play with the collector resistor value to tweak the collector  voltage (or do by ear).
For Q2 it's probably easier to play with the collector-base resistor; by ear probably best here as you could make large changes to the sound with small changes to the collector voltage.

The hFE's on Mark's unit are probably around 200.  While the spec is 160 to 320, averaging at 240, the spec is at 1mA but the circuit is operating at Q1=260uA and Q2=60uA.  Since transistor gains can drop-off at low currents (no info in datasheet) the 200 seems OK.   It's only a sample of 1 or 2 so we can only make humble estimations.  The Sanyo datasheet shows a fairly flat hFE with IC,
https://pdf1.alldatasheet.com/datasheet-pdf/view/38691/SANYO/2SC536N.html

[Mark Hammer]

I had loaned my original FY-2 to a friend, and forgotten I'd done so.  He returned it today, so I opened it up.  The transistors are 2SC536FDA.