TS-808

[Coda]

I’ve had this on a breadboarding for two weeks. Finally decided to box it up. Sounded off; very muffled, and the gain pot does nothing. Found two mistakes: I had two resistors swapped (R6 and R16). Fixed them and now I get nothing, except sometimes I get this roaring sound,
As if the circuit works briefly. I have found that if I press the op amp down and to the left I can replicate my initial sound, but the gain pot still does nothing.

Pics are attached, I’ll grab some voltages now and edit.

JRC4558D:
1: 1.448
2: .568
3: 5.17
4: 0
5: 2.365
6: 2.367
7: 2.365
8: 8.88

 

[Coda]

D2 anode connects to R9 and pin 1. D1 anode connects to R6. You can see in the screenshot I attached above…

 

[steviejr92]

No you see D1 cathode connects to Pin1 and R9 and D1 anode connects to pin 2.

D2 cathode connects to pin 2 and D2 anode connects to Pin1.

I could be wrong though....

 

[Coda]

No you see D1 cathode connects to Pin1 and R9 and D1 anode connects to pin 2.

D2 cathode connects to pin 2 and D2 anode connects to Pin1.

I could be wrong though....


View attachment 43343

I think we are saying the same thing…

 

[steviejr92]

Something is going on in that soft clipping section. That much i know! You should be getting close to 4.5v on Pin2

 

[Coda]

Something is going on in that soft clipping section. That much i know! You should be getting close to 4.5v on Pin2

I’m gonna go through the clipping section piece by piece and see where the issue is…

 

[Coda]

I should be getting continuity between D2 anode/D1 cathode and pin 1, correct?…

 

[Mcknib]

Check what VREF you get on 3 and 5 with the op amp out of socket

With no power to the circuit check resistance between op amp pins 1 and 2 with the drive pot fully CCW and CW

Edit *
With lugs 2 and 3 being connected:
CCW you should get 51K + a few ohms
CW 51K + pot value

Then from pin 1 to R8 side that goes to vref

That should indicate anything funky going on in the feedback loop bad joints, shorts, opens etc

Yes on D1and 2

 

[steviejr92]

I should be getting continuity between D2 anode/D1 cathode and pin 1, correct?…

Correct you should be getting continuity between those points.

 

[Coda]

I am not getting continuity between…those points I mentioned. VREF at pins 3 and 5 is 4.4v. Resistance between pins one and two ccw/cc: 1M/500k

 

[Mcknib]

So we know your VREF set ups OK

Resistance in the loop should go down with the pot CCW

Check resistance between lugs 1 and 3 CCW it should be a few ohms CW pot value

Another wee note you've got C4 as 100n not 47 that's a high pass so will only affect that just in case it's not intentional

 

[steviejr92]

Hmmm thats unusual can it be that your Diodes are not seated all the way in?

 

[KR Sound]

Hmmm thats unusual can it be that your Diodes are not seated all the way in?

I hate sockets for diodes- they never seem to fit tight, so I bend up the lead to make sure it's touching. When I'm happy with what I have, I solder it in. On this board, I don't know a reason to socket them, right?

 

[Coda]

So we know your VREF set ups OK

Resistance in the loop should go down with the pot CCW

Check resistance between lugs 1 and 3 CCW it should be a few ohms CW pot value

Another wee note you've got C4 as 100n not 47 that's a high pass so will only affect that just in case it's not intentional

That was intentional. Its socketed. Am I checking resistance on the gain pot?

 

[Mcknib]

Yes no power to circuit across 1 and 3

 

[Coda]

CCW/CW: 195.3k/2.2 Ohms…

 

[Mcknib]

Strange your earlier suspicion may be correct either the pots dodgy or a solder joint

With it fully CCW you should get continuity on all 3 lugs It being or should be low ohms CW continuity only between 2 and 3 with them being connected

 

[steviejr92]

I hate sockets for diodes- they never seem to fit tight, so I bend up the lead to make sure it's touching. When I'm happy with what I have, I solder it in. On this board, I don't know a reason to socket them, right?

The reason to socket would be to experiment. Lets say he can try germanium diodes or LEDs if he wanted!

 

[KR Sound]

The reason to socket would be to experiment. Lets say he can try germanium diodes or LEDs if he wanted!

Oh, I know. I just hate them with a passion. lol.

 

[steviejr92]

Oh, I know. I just hate them with a passion. lol.

I tend not to use them at all because of connection reasons as you mentioned!

 

[Mcknib]

I'd maybe fix your diode lack of continuity problem first