GOLDSCAN 5 SCHEMATIC QUESTION

[eclipse]

It's just where the 47nF cap is located and it isn't used in the schematic.

[dbanner]

Yes, and there's a 100nF on shematic that isn't anywhere near the TLC2262 on board.

[eclipse]

Well perhaps the 47nF cap on the PCB is marked as 100nF cap in the schematic, and there are no other caps missing there.
Exact value probably is not that important (47nF-100nF).

[Jose]

It looks like it's 47nf, instead of 100 nf. It was observed along with three 1K resistors, close to the gain control.
Apparently a 1K resistor is missing in the scheme, this would be in series with the TLC2262 output and the audio input on the other missing board.
Something similar to the GS4 scheme, (between GND pot and pin 3 of 1/4 IC3)
Jose

[dbanner]

Yes, I see three 1K resistors, one in series with output, makes perfect sense. Had to use electrodroid app on my android phone to read those pesky 5 band resistors though. I think the schematic is very close to what it's supposed to be. Working through stage by stage is the right approach.

[Idefix]

Hi,

The audio part is on the upper board, if I understand. Have you others pictures than these on this thread? it is hard to make a schematic with only few pictures.

As I saw, the audio uses an AD654 , wich is quite rare today in DIL, more easy in SO8. The price seems about to 8 €.

May be an easy way will be to use an LTC6990. Cheaper , about 2€ , and can make the same job.
http://cds.linear.com/docs/en/datasheet/6990fc.pdf
https://www.digikey.fr/products/fr/i.../689?k=LTC6990

[eclipse]

Looking into the GS4 schematic by Alex J113 drains are connected to GND.
This is not a big deal as these are bidirectional but do you think Drain and Source of the J113 are swapped?

[dbanner]

As I recall, I think there was an issue with that on GS4 schematic and they were swapped. They issue was the orientation of the jfets but can't recall which thread it was discussed. I'll have to do some digging.

[Idefix]

Hi,
When Drain and Source can be swapped , it is indicated in the datasheet. like ther in a fairchild J113 datasheet.
https://www.fairchildsemi.com/datasheets/J1/J111.pdf





But, on a 2005 ONSemi J111, J112 datasheet , it is not indicated.
http://www.onsemi.com/pub/Collateral/J111-D.PDF
so, don't swap in this case.

Today, Fairchild is inside Onsemi.
So ?? in the doubt, don't swap.

[dbanner]

O.K. Good to know this.

[Jose]

On the GS4 line, the issue of the possibility of inverting the source and drainage terminals was discussed, some members said that it would not be advisable.
What I can say is that a few FET can work well in GS4 or GS5, the J113 and the BF245A, also the J112, I can not recommend another.
Jose

[Idefix]

Hi,
To Eclipse :
Would it be possible to you to take 2 pictures of the audio board, with full components, one top side, other bottom side?
And if possible , tell where the colored wires go , on the main board.
The white one , as I see , is the ground.

I will try to give a schematic.
There is the AD654, an thers is a dual opamp TL052. the other part is missing from the pictures .
Thanks

[eclipse]

No one here has the original board. Even if he does, he preffers to remain silent, probably too much hassle to take the device apart. And reverse engineering by photos - not the brightest idea.

About the JFET orientation - I meant on the GS4 JFETS are oriented backwards (G-S are swapped on some schematics).

I'm not too worried about the sound right now, I will maybe try to create PWM based sound.

A bit more info: on the final op amp stage I'm getting 0V (no target) to ~4V (target) right now (geb channel disconnected).

Final op amp on GS4 is -4.2V (no target) to +4.2V (target) - those are the numbers I get

[Idefix]

I have seen your post with pictures 1 to 6, so , I thought that you have a GS5.
So, with good pictures, with only 2 layers it is quite easy. See my PM.

May be you can answer to the question about the wires : (from or to Audio board)
on East side : 3 wires :1 blue / 1 White /1 Yellow . The label on board for blue is Ground. where do they go ?
On south side (the 2 pots are on S.S ), three wires plus 2 wires under the board (label Thresh ) 1/White / 1 Grey /1 Purple / They go to a POT I suppose. ?
and the 2 : 1 black / 1 green : going to main board
On North Side 4 Wires (3 with blue/Brown/orange and one Blue alone)

Are these colors the same as GS4 ?

[dbanner]

I did try to reverse engineer audio from some photos and this is as far as i got. These are the pics i got of the audio board.