Collosalus...it works? Wha, ok....

[blearyeyes]

I finally got this beast to function...I re flowed and messed around, redid a few components and then slapped a JRC4558 in there and it freaking works...don't ask me how...

This one gave me the most trouble of all.....

[blearyeyes]

Let me know if I need to post any other info....

[blearyeyes]

More Pics

[Scruffie]

Start by getting the right voltages, lift the regulator output leg and make sure the charge pump is actually doing it's job of getting 17.1V on the regulator input and the regulator is providing 15V out, then you know if the circuit is causing an issue or if you need to debug your power section.

[blearyeyes]

Pulled output pin from 7815T

Pin 1 is 16.50v
Pin 3 is 14.80


Looks good so far...

[blearyeyes]

I pulled the v regulator out completely and was getting proper input voltage from pad 1 to ground. When I checked the output PAD 3,  it was showing the 9v from the external power supply from the pad to ground. Is that 9v supposed to be there? Sorry if that is a dumb question...

[Scruffie]

Are you saying you have 9V on ground? If you're saying what I think you are, that you have 9V on the regulator output pin without the regulator in place, then no that's not right and what's causing your issue, you probably have a solder hair or short somewhere round IC7 & 8.

[blearyeyes]

Looking at the schematic and the voltages above, I'm seeing the voltage divider output (VB) after IC5 in the power supply circuit, showing up at various IC pins on the rest of the circuit, but I'm also seeing the 9.22v from the bench supply showing up on other IC pins. So that seems to be a clue. The input voltage of 9.22v isn't supposed to be going anywhere but to the charge pump as far as my meager reading of the schematic goes. Can someone verify that?

Or is that a wrong assumption?

[blearyeyes]

I just verified that and see that the Pins that are reading 9.22v are to ground.. See if I can fix it tonight....

[Scruffie]

Looking at the schematic and the voltages above, I'm seeing the voltage divider output (VB) after IC5 in the power supply circuit, showing up at various IC pins on the rest of the circuit, but I'm also seeing the 9.22v from the bench supply showing up on other IC pins. So that seems to be a clue. The input voltage of 9.22v isn't supposed to be going anywhere but to the charge pump as far as my meager reading of the schematic goes. Can someone verify that?

Or is that a wrong assumption?

No that's a right assumption, so you likely have a short or solder hair somewhere, start searching around the power section of the PCB and 9V & Gnd pads.

[blearyeyes]

Thanks Scruffie... It helps to have someone with experience to point you in the right direction. I've learned a lot from this one. I know just enough to get into trouble. Hope to have it up and running tonight.


Sent from my iPad using Tapatalk

[blearyeyes]

Ok I found where the power is getting to the output of the voltage regulator. It is the 9v pad and the output of the voltage regulators trace that runs around the outside of the board.  I am trying to cut between the trace and the 9v input pad as you can see. They are connected and I wonder if we ever get bad PCBs or did i do something somehow to connect them. I don't see how I could have but then what do I know? I guess it could be connected somewhere else but I'm flummoxed fer sure....

[wgc]

Its rare but you can get bad pcbs.  Usually its not a short but an open trace/thru hole in my experience.  I don't believe you can cause a short under the soldermask in the manner you seem to have.

That is a good catch, hard to see with the silk screen over it and all.

Last time I had an IC get hot (really hot..!) was when I installed a dual opamp in backwards.  Didn't have a notch at the top like many do, and I forgot which side had the bevel before I installed it.

[blearyeyes]

Oh Bean, help me for I am lost and forsaken. Wondering in the wasteland of mediocrity.

[blearyeyes]

OK that was the issue, 9v pad was connected to the 15v trace. cut it with an exacto knife and now will sleep. as I am tired and must try to live another day! Tomorrow I will set bias and try to get this thing to sing.....