Reddish 500 EQ

[capacitorless]

The only thing I see between the edge connector pad (#12) and pin 8 on the opamp is a diode (D1). Could you measure between pin 8 and either side of the diode?

Edit with a couple of general questions: would the nature of the continuity test depend upon the orientation of the leads, when measuring across a diode? And could the forward voltage drop mess with a continuity measurement, depending on the meter being used? Asking for a friend... (I'm guessing yes on the continuity test across diode - still working on coffee...).

 

[JMan]

Still no connection between pin 8 and +16v pad. Using a fluke 117

Sorry, I need to stop asking you to check things when I'm not actively looking at the circuit. Please check continuity between pin 8 and the cathode of D1.

Possible solder bridge? View attachment 145224

It does look like it. This is one of the gain switches, right? This is worth fixing even if the primary issue is the voltage to the opamp.

 

[Forcemusicgroup]

thats papertowel from cleaning the board. 99% alcohol

 

[Forcemusicgroup]

The only thing I see between the edge connector pad (#12) and pin 8 on the opamp is a diode (D1). Could you measure between pin 8 and either side of the diode?

Edit with a couple of general questions: would the nature of the continuity test depend upon the orientation of the leads, when measuring across a diode? And could the forward voltage drop mess with a continuity measurement, depending on the meter being used? Asking for a friend... (I'm guessing yes on the continuity test across diode - still working on coffee...).

stand by ill check right now

 

[Forcemusicgroup]

stand by ill check right now

I am getting connection with pin 8 and diode d1

 

[capacitorless]

Pro tip (not being snarky): when doing remote debugging like this, especially with people such as the original designer, it's super considerate, helpful, and saves time for everyone if you can be exact. For example, giving the results of testing from pin 8 to *both* sides of D1, what the meter settings are, and indicating the polarity of the test leads for each test. We collectively cannot read each other's minds, and since you're the one in need you should strive to be as specific as possible.

Just IMHO and definitely not trying to be mean here

 

[Forcemusicgroup]

Pro tip (not being snarky): when doing remote debugging like this, especially with people such as the original designer, it's super considerate, helpful, and saves time for everyone if you can be exact. For example, giving the results of testing from pin 8 to *both* sides of D1, what the meter settings are, and indicating the polarity of the test leads for each test. We collectively cannot read each other's minds, and since you're the one in need you should strive to be as specific as possible.

Just IMHO and definitely not trying to be mean here

Hey Iron Sharpens Iron. Not much of an internet talker. However I appreciate it.

 

[JMan]

I am getting connection with pin 8 and diode d1

This is a bit confounding. If you have this connection, can you check again whether or not you are getting the +15v on the IC pin 8 when power is on?

Hey Iron Sharpens Iron. Not much of an internet talker. However I appreciate it.

I get it, and I sure don't fault you for it. That said, "internet talking" is definitely important when asking the internet for this kind of fiddly technical assistance. The more specificity you provide, the more likely we are to find the issue. Similarly, the more zipped up the communication is, the less likely we are to be aware of crucial details.

 

[Forcemusicgroup]

I can confirm that We have voltage on IC pin8 powered, and engaged.

 

[JMan]

Excellent!

Okay, now that that's sorted, just to confirm - is it still not passing audio?

 

[MidnightArrakis]

@MidnightArrakis
This PCB is known to work well - if you read this thread you would know that - in fact - it is one of the nicest designed PCBs I've seen on this forum. @JMan has done an excellent job and has shared something excellent with the DIYers here. No one who has put so much work into developing a project like this wants to give you the Gerbers. Go develop your own project here to understand what it takes - instead of going into threads and criticizing.

[No one...wants to give you the Gerbers] -- There is something that -- YOU -- and so many others on this forum simply -- DO NOT UNDERSTAND -- and that is..........with me being 75-3/4 years old, --- THE LAST FRIGGIN' THING THAT I HAVE ANY INTEREST IN DOING IS > STEALING < SOMEONE ELSE'S GERBER FILES --- for some project of my own!!! My requesting for a set of GERBER and N/C Drill data-files is so I can import them into a -- $4,500 -- "GERBER & N/C Drill -- analysis program that is capable of finding and reporting -- fabrication and manufacturing issues -- within those files that you and nobody else on this forum are even cognizant about!!! In other words.....despite how "lovely" someone's GERBER-files may look and despite how much "care and intention" was used during their design, my "GERBER & N/C Drill" programs can -- STILL -- find things wrong within the GERBER files posted on this forum.

Other GroupDIY members have sent me their GERBER files and my programs have issued error reports about them on items that their creators had no idea about!!! So, since my programs are also "editing" programs, I have gone ahead and corrected these various issues within their GERBER files and then sent back to these members -- updated -- GERBER files that they then sent to their PCB-fabricator. >> FOR FREE!!! <<..... -- Some other GroupDIY members have even sent me their KiCAD schematic and PCB-design files for me to review. WEIRD, HUH??? -- So, after I reviewed their layouts and found that they had far too many component placement issues and routing errors to both commenting on, I just -- wiped-the-slate-clean -- and redesigned their entire PCB from "scratch". After these members received their -- updated -- PCB-designs, they would send me a "THANK YOU!!" message with a comment about how much more "clean" and "efficient" their layouts now looked!!! -- ALL DONE FOR FREE!!! --

[Go develop your own project here to understand what it takes] -- YOU'RE ABSOLUTELY RIGHT!!! I have -- NO IDEA -- of what it takes to design a PCB and create a set of GERBER files!!! In the future, I guess I should be asking YOU whenever I need any PCB design assistance, right??? (See below):







-- TOPSIDE --

-- BACKSIDE --


>> And.....I do fully understand that PCB-designs such as these are all "common-place" on this forum!!!

[@JMan -- The copper pours were placed with care and intention and all of them have a low impedance path to the relevant ground pad (audio or power) on the edge connector] -- Of which I can only see 1 via that connects to the edge-finger.

/

 

[Forcemusicgroup]

Something more going on behind the screens here? Sheesh.

Looking at the other working unit it's the same. Sounds amazing, I am however going to replace c0 at some point when I get this unit working.

 

[Forcemusicgroup]

Excellent!

Okay, now that that's sorted, just to confirm - is it still not passing audio?

Still not passing audio. Used the same channel as the working unit. Using a JLM 2 channel test Jig

 

[JMan]

Something more going on behind the screens here? Sheesh.

MidnightArrakis just checks in periodically to imply that I've slapped together a lazy, auto-routed pcb design and remind us all that he has expensive software. The latter seems to be true, but the former is far from it. That doesn't stop him. He also seems to suffer topic-specific amnesia, each time forgetting what this project is and that he had the chance to assist with the design and was, despite all his bluster on the thread, completely unhelpful.

Still not passing audio. Used the same channel as the working unit.

Okay, now we need to start tracing the audio signal. Are you comfortable with how to follow the signal path in the schematic? We need to ascertain where it is dropping out.

 

[Forcemusicgroup]

MidnightArrakis just checks in periodically to imply that I've slapped together a lazy, auto-routed pcb design and remind us all that he has expensive software. The latter seems to be true, but the former is far from it. That doesn't stop him. He also seems to suffer topic-specific amnesia, each time forgetting what this project is and that he had the chance to assist with the design and was, despite all his bluster on the thread, completely unhelpful.

Okay, now we need to start tracing the audio signal. Are you comfortable with how to follow the signal path in the schematic? We need to ascertain where it is dropping out.

Sure let's do it. Let me know where you want me to start. From the edge connector or is there a specific spot you want me to look at.

 

[andia]

looking at the pictures of your pcb solderside - you should not cut the component legs so close to the pcb. just cut on top of the "volcano" of a good soldejoint, if that makes sense. if you cut that low you could hurt the solderjoints.

 

[JMan]

Okay, let's start broad and narrow it down from there. I am going to ask you to report back in as much detail as you can, please.

Send a 1k test tone to the unit.

With your multimeter in AC mode, confirm that you have a healthy signal between IN+ (red probe) and IN- (black probe) on the edge connector. Actually it does not matter which probe goes to which pin, but you should measure AC voltage here. I would suggest adjusting the level of the test tone until you read something like ~1.228VAC across those pins, or 0VU. The level will drop considerably as we work our way through the passive circuit, then should increase back up to unity gain as we go through the amplifier section. But it should never disappear completely.

Set your front panel controls to twelve o'clock (no gain). With your meter still set to measure AC voltage, place your black probe on the Aud GND pin of the edge connector, then use your red probe to measure the following points relative to Aud GND:

-Both sides of R0
-the bottom leg of R11
-the top leg of R25
-Both sides of R27
-Both sides of R28
-the right leg of R29

Then measure the AC voltage between Out+ and Out- on the edge connector.

Since your unit is not passing signal, you should see it drop out somewhere in that sequence.

Again, please report back with specifics.

 

[JMan]

looking at the pictures of your pcb solderside - you should not cut the component legs so close to the pcb. just cut on top of the "volcano" of a good soldejoint, if that makes sense. if you cut that low you could hurt the solderjoints.

This is good basic soldering technique, so heed this advice. Lord knows I've been guilty of this from time to time.

 

[Forcemusicgroup]

Thanks for the help guys. okay diving in .