Tech21 Character Series

Post by **mxrmxr** » 02 Aug 2009, 18:17

Some more pics......

JiM · Post by **JiM** » 02 Aug 2009, 21:48

To complement yours, i did a quick&dirty composite image of both sides of the PCB.
The alignment is not perfect, and the colors are not exactly what i expected but anyway i hope it might help in the tracing process.

estragon · Post by **estragon** » 03 Aug 2009, 02:24

I'm tackling the hybrid device (associated with the Character control), as it is the most intriguing part for me.

First, I numbered the components in this part starting from 100, so they can be clearly addressed in further discussions. Also, this will add some order to the final schem. The values of the thick film resistors (R100 to R104) will have to be measured as time permits. Notice that the wider R100 and R103 resistor should be low values, probably around 1K.

Second, I drew what I think are the hidden tracks below U100 and Q100. This should be verified or corrected when possible.

When the underlying tracks are verified I'll to draw a schem for this device.

DimebuGG · Post by **DimebuGG** » 03 Aug 2009, 15:59

mxrmxr,

Can you please desolder those non-SMD caps except in the power supply filter sections?. If that will be OK to you and if possible ID'ing them too. I'm almost done tracing except for capacitor values(both SMD and non-SMD's). By the way, the circuit definitely looks similar to Tri-AC + a new "character" circuit..

The input stage, EQ section, and output stage is similar to Tri-AC.

The stages are:
Input > "Character" > SIP module/"Drive" > Speaker Sim > "Level" > "Mid" > "Low" & "High" > Output

Hopefully, those components values in the SIP module will be identified and the connection too underneath the opamp.

DimebuGG · Post by **DimebuGG** » 03 Aug 2009, 17:21

The speaker sim by the way has the same configuration with those in GT-2 but with different resistor values..

estragon · Post by **estragon** » 03 Aug 2009, 18:12

Yes, the non SMD electrolytic caps difficult following the upper traces.
I've been trying to find a valid P/N for Q100 during all morning here, although I haven't found anything that uses the "V1" legend in SOT-23 package so far. I've checked transistors like 2N5088, 2n5087, 2n3904, 2n4401, mosfets like 2n7002, bs170, bs108, and JFETs like J201, 2n5457/8/9, 2n5458, J305, and others. Most of these parts are identified by something like a number and a letter (for instance "1D" or "6F"). Onother manufacturer has five digits, not two.

It would be great if you could check if there's some logo that would allow to identify the manufacturer of Q100. I can't read clearly the markings on the left, just the "V1" on the center, and something like "8A" or perhabs "BA" on the right, with smaller printing.

I can't make much sense of this part of the circuit yet. It seems there is a resistor from one output of the opamp to VCC. Also, trying to make sense from the usual B-C-E pinout would suggest if the device is a bipolar transistor, it should be of the PNP type, like a 2N5087. Odd. Hopefully some further inspection will give more light.

Post by **mxrmxr** » 03 Aug 2009, 19:43

DimebuGG wrote:mxrmxr,

Can you please desolder those non-SMD caps except in the power supply filter sections?. If that will be OK to you and if possible ID'ing them too. I'm almost done tracing except for capacitor values(both SMD and non-SMD's). By the way, the circuit definitely looks similar to Tri-AC + a new "character" circuit..

The input stage, EQ section, and output stage is similar to Tri-AC.

The stages are:
Input > "Character" > SIP module/"Drive" > Speaker Sim > "Level" > "Mid" > "Low" & "High" > Output

Hopefully, those components values in the SIP module will be identified and the connection too underneath the opamp.

I'll see what I can do for the caps

Have you got a schematic for the Tri-AC you could share ? Don't think I've seen that one.

Any chance you could post what you've traced so far ? That would be cool to see.

Post by **mxrmxr** » 03 Aug 2009, 19:47

estragon wrote:Yes, the non SMD electrolytic caps difficult following the upper traces.
I've been trying to find a valid P/N for Q100 during all morning here, although I haven't found anything that uses the "V1" legend in SOT-23 package so far. I've checked transistors like 2N5088, 2n5087, 2n3904, 2n4401, mosfets like 2n7002, bs170, bs108, and JFETs like J201, 2n5457/8/9, 2n5458, J305, and others. Most of these parts are identified by something like a number and a letter (for instance "1D" or "6F"). Onother manufacturer has five digits, not two.

It would be great if you could check if there's some logo that would allow to identify the manufacturer of Q100. I can't read clearly the markings on the left, just the "V1" on the center, and something like "8A" or perhabs "BA" on the right, with smaller printing.

I can't make much sense of this part of the circuit yet. It seems there is a resistor from one output of the opamp to VCC. Also, trying to make sense from the usual B-C-E pinout would suggest if the device is a bipolar transistor, it should be of the PNP type, like a 2N5087. Odd. Hopefully some further inspection will give more light.

It's V3 on the SOT-23 device not V1. That's the only thing that's readable on it.

Post by **mxrmxr** » 03 Aug 2009, 19:49

Two more resistors under the opamp

JiM · Post by **JiM** » 03 Aug 2009, 21:03

mxrmxr wrote:Two more resistors under the opamp

Darn !

The good thing is, it should be easy now to accurately measure the resistances.
Great work so far, mxrmxr

About the "V3" marking on the SOT-23, i've found some cross-reference : http://www.marsport.org.uk/smd/smdv.htm
It might not be a transistor after all, but maybe a couple of zener diodes !
http://www.datasheetcatalog.org/datashe ... s18002.pdf

Does that make sense with the rest of the circuit ?

estragon · Post by **estragon** » 03 Aug 2009, 21:23

Man, I was looking for a cross reference table to see if I could find a "V3" device in such package (I noticed the V1 mistake after the edit time had expired). Tonight I'll draw the circuit, as I'm at work now. Perhaps the pair of zeners is what makes the most sense so far. At least the 3.3V+0.6V is just as much as you can handle with a rail-to-rail opamp fed from 9Vdc. Nice catch!

For now I have handy the TRI-OD and TRI-AC schems which I found in a russian site.

estragon · Post by **estragon** » 03 Aug 2009, 21:30

mxrmxr wrote:Two more resistors under the opamp

If I don't see it I don't believe it! You've done a superb job here!

This would be the referenced Hybrid in the meantime.

estragon · Post by **estragon** » 03 Aug 2009, 23:02

This would be the hybrid circuit, assuming the V3 device is a pair of zeners (currently the most consistent option).
Someone please verify it.

RnFR · Post by **RnFR** » 04 Aug 2009, 16:03

wow, great work guys!

bajaman · Post by **bajaman** » 04 Aug 2009, 21:24

please DON'T stop

bajaman

DimebuGG · Post by **DimebuGG** » 05 Aug 2009, 01:28

This is the preliminary tracing I did..It may contain errors in the points labeled "?????" as they're the areas blocked/hid by those non SMD caps. FET/flip flop switching is excluded. The "EMPTY" labels are the pads left alone on the BLONDE board.

I'm not really an SMD expert but there's this resistor or whatsoever marked "O", what I thought was this was 0 ohm so I labeled it as "0 ohm?" in the schematic drawing.

flood · Post by **flood** » 05 Aug 2009, 06:29

INCREDIBLE work!

i'd have fried my brains by now!

estragon · Post by **estragon** » 05 Aug 2009, 11:38

DimebuGG wrote:This is the preliminary tracing I did..It may contain errors in the points labeled "?????" as they're the areas blocked/hid by those non SMD caps. FET/flip flop switching is excluded. The "EMPTY" labels are the pads left alone on the BLONDE board.

I'm not really an SMD expert but there's this resistor or whatsoever marked "O", what I thought was this was 0 ohm so I labeled it as "0 ohm?" in the schematic drawing.

Nice job!

Yes, these are 0 ohms resistors. In SMD they are usually placed to set options like jumpers, so you can just label them as "0 ohms" or just "0R" or 0.

DimebuGG · Post by **DimebuGG** » 05 Aug 2009, 16:19

I kinda revised the schem and corrected some minor mistakes in the feedback loop at the input stage. The EMPTY pads on it appears to be a capacitor on VT Bass.

Post by **mxrmxr** » 05 Aug 2009, 19:23

Great work DimebuGG & estragon

Here's a pic of the PCB with the through hole caps removed, and some pics showing the values of the Electrolytic caps.

I also removed the 4013 ic as well. What the hell

Gone this far.

Hopefully this will get us close to the final Schem.

In the mean time, I've got a pedal to rebuild

Tech21 Character Series [schematic]