A complete schematic would be very helpful. I started one, but really have not had the time to complete it.

 

I would probe at the base then collector of Q1 now. At this point, a signal injector would be more useful.

sorry but I dont have one of those .

 

A complete schematic would be very helpful. I started one, but really have not had the time to complete it.

it would be nice . sorry but cant find one . thank you for starting one at least .

 

sorry but I dont have one of those .

Yes, I know you don't have a schematic, and there doesn't seem to be anything available online. MrChips drew out the power amp section, but the problem seems to lie earlier in the circuitry. Drawing out a full schematic from your pictures is a time consuming process, but can be one.

 

sorry but I dont have one of those .

If you have a smart phone, there is an app for that. All you would need is the plug (3mm stereo) to plug into into the phone’s audio jack. If you have a recent iphone, you would have to get an audio jack converter to plug into the lighting or USB C connector.

Anything that can produce a line level audio signal would work.

 

Can I get a couple new photo's of this area of the board? I need them straight on, all the way to the bottom of the board (many of the previous photo's have the bottom cut off). Try using a moderate light source behind the board so that the runs show through, but not so bright that the component color codes are washed out. Also, a photo of the run side of the board in the same area - again straight on and try to minimize reflections so the runs are clearly seen.

 

so , probing the input we are looking to see if current is getting there so we can track back from there right ?

Well, yes, but since it seems that the first stage is working, AND a source of input signal is available, checking from input toward output would be simpler. It will provide the additional benefit of being able to immediately know the results of a repair.
Also, like I mentioned before, even with no circuit drawing at all, you can check for the signal at the output of each amplifier output. The output pin is well defined. And then, for any IC with no output, you can use a voltmeter to verify power supply voltages are present, and also check the DC voltage on the output terminal.

 

wi

View attachment 307109

Can I get a couple new photo's of this area of the board? I need them straight on, all the way to the bottom of the board (many of the previous photo's have the bottom cut off). Try using a moderate light source behind the board so that the runs show through, but not so bright that the component color codes are washed out. Also, a photo of the run side of the board in the same area - again straight on and try to minimize reflections so the runs are clearly seen.

will do asap.

 

Ok, I am back.
Your bass amp has six front panel controls, GAIN TREBLE BASS VOLUME | 62.5Hz 125Hz BASS EQ |



Each control pot (potentiometer) looks somewhat like this, looking at it from the front view.
There are three terminals 1, 2, and 3.



On the first GAIN pot, turn the knob fully clockwise.
Do the signal probe test on terminals 1, 2 and 3, while inputting signal from the guitar.
We are expecting to get full volume sound at terminals 2 and 3, nothing from terminal 1.

 

welcome back .

no signal from pot terminals .

 

View attachment 307109

Can I get a couple new photo's of this area of the board? I need them straight on, all the way to the bottom of the board (many of the previous photo's have the bottom cut off). Try using a moderate light source behind the board so that the runs show through, but not so bright that the component color codes are washed out. Also, a photo of the run side of the board in the same area - again straight on and try to minimize reflections so the runs are clearly seen.

 

We never came up with a schematic for it, right?

It is possible the other opamps are not in the signal path. Does the amp have reverb? If so, that might be the function of some of the others.

Is the signal after opamp 1 noisy or is it clear?

the signal is good , clear but with some hiss in the background

 

Here is your next signal test point, test point #3.
Turn the guitar volume full, and GAIN full clockwise.

 

Here is your next signal test point, test point #3.
Turn the guitar volume full, and GAIN full clockwise.

View attachment 307167

good, clean loud signal there .

 

The next place to check for signal is at the VOLUME control, terminals 1, 2 and 3.

 

There is a Direct Input jack (D.I.).
You need to exercise that jack by plugging in a 1/4" guitar cable in and out a few times.

 

Here is what I see so far. That tone control arraignment looks odd to me, but it seems correct. Component values listed where I could read them.

 

I need to see a better view of the solder side of this portion of the board, all the way down to the bottom edge of the board.

 

View attachment 307175
Here is what I see so far. That tone control arraignment looks odd to me, but it seems correct. Component values listed where I could read them.

well thank you very much for doing that Ylii. more pieces of the puzzle coming together .

 

I need to see a better view of the solder side of this portion of the board, all the way down to the bottom edge of the board.

View attachment 307177