Aion Electronics Nimbus - no effect

[DIY Bass]

So, a brief explanation is that the point where R20 and R21 join is "half way" between the 9v and Gnd rails.  On the photo of your board above, that would be the right side of R20 or the left side of R21.  In fact, if you measure the resistance from the right side of R20 and the left side of R21 you should get 0 - indicating that they are joined together.  As R20 and R21 are each 10k resistors, you should be measuring approximately 20k between 9V and Gnd (The 2 resistances add up).  A bit lower is to be expected because of the rest of the circuit interfering a bit.  That "half way" point should give 2 readings - one to Gnd and one to 9V.  Those 2 readings should add up to the reading that you get from 9V to GND because of the way that resistances add up.  Getting about 6.6k between the half way point and GND is about right.  Getting 6.6k between the half way point and 9V is also about right.  If both those are 6.6k though, you should be measuring 13.2k between 9V and gnd, but you are measuring 6.7k, which doesn't really make sense.  If 6.7k between 9V and gnd is correct, then that would indicate that one of the measurement to the half way point should be 0 - which would show a lot about where to start looking for your problem.  Can you please take those measurements again.

[ajhuff]

OK I got a helper it help me document.

So here is +9V to GND



Here is +9V to right leg of R20



Here is +9V to left leg of R21



Here is right leg of R20 to GND



Here is left leg of R21 to GND

[willienillie]

IC1 - IC2 JRC4558D      JRC4558D OpAmp

Well there aren't any actual JRC4558Ds in your pictures, so those are fakes.  Some people get working fakes, so that may not be related to your problem, but do buy from reputable vendors like Mouser, Small Bear, DigiKey, or Tayda.  I would avoid Alibaba, AliExpress, or anything on Ebay from China.

[ajhuff]

OK thanks. I did buy them off eBay but not from China. They were labeled as JRC4558D  OpAmp TUBE SCREAMER ,PEAVEY ,Orange replaces LM4558, RC4558. But I didn't know what I was doing.

I will check Mouser.

-AJ

[Marcos - Munky]

It indeed could be a bad ic that are shorting the power supply. Try to do this test:
- remove all the ics. Easy to do, since they're all on sockets.
- power the pedal. I don't know if you used a stereo jack to switch power on, if yes then plug in a cable. Use the dc brick with the metallic jack not touching the enclosure or use a fresh battery, the one that got hot is probably dead.
- measure the voltage between gnd and +9V.

If you get a measurement that's close to 9V, then put IC3 on the socket, put the black probe on gnd and with the red probe measure the voltages on pins 4 and 8 of the sockets of IC1 and IC2.

[Slowpoke101]

Your pictures show that your multimeter is in resistance test mode (Ohms ). To measure voltages turn the meter selector switch to position 20 V DC and redo the R20, R21 voltage measurements (power must be supplied to the effect ).
If you are uncertain that you have the correct voltage range selected on your multimeter then just measure your 9V battery. The meter should display a reading somewhere near 9.00V

Edit: I forgot to ask; You have used some tantalum capacitors in this build. Tantalum capacitors can be difficult to install  with the correct polarity (usually not marked clearly ). Are you certain that they are all installed correctly?

Yet another edit: Now that I have actually managed to read the entire thread  ....Please ignore this post. Sorry everyone  .

[ajhuff]

OK, I took the three IC chips out.
This is what they look like BTW, if I bought the wrong thing.





So, hooked battery up to metal jack hanging freely, not touching the case. Battery read 8.75V. Plugged a guitar cable in. With the red test lead on the +9V and black test lead on GND it read -1.5V. I pressed and depressed the foot switch but that number didn't change. I didn't check the voltage at the socket pins since I didnt  get 8.75V between +9V and GND.

-AJ

[Marcos - Munky]

That test confirms there's indeed a short somewhere on your board. Measure the resistence between +9V and gnd pads, just to be sure. Don't need to power the circuit for this test, as long as the metal jack is not touching the enclosure.

[ajhuff]

OK. Hopefully that's progress. Thanks again for the small steps.
The resistance from +9V to GND is 6.7 on the 20K ohm setting.

-AJ

[Marcos - Munky]

If by 6.7 that means 6.7r, there's indeed a short. To be really sure, put the multimeter on the smaller scale and measure it again. If it's still around 6.7 (or any small value), there's a short between gnd and +9V pads. Or just put the multimeter on continuity mode and check if there's continuity between those pads.

If there's continuity/low resistance, post a few more photos of the solder side of the board. The parts' side seems to be good, maybe there's a very small solder bridge between some pads that isn't supposed to be there.

[willienillie]

OK, I took the three IC chips out.
This is what they look like BTW, if I bought the wrong thing.

There seem to be about a bazillion of those fakes with the 0058T code on them.  Again, some people have pedals that work fine with them, meaning they are actual working dual opamps of some kind, in some cases.

The real JRCs look like this, with the circle indentation at pin 1, "JRC" in bolder font, right-justified:

The earlier (1980s) ones had a 4-digit code on the bottom, later ones have a 5-character alphanumeric code.

Doing a google image search for "jrc 4558" brings back more fakes than real ones, that's how bad it's getting.

[willienillie]

If by 6.7 that means 6.7r, there's indeed a short.

I would assume it's 6.7k, since he's on the 20k range.

[Marcos - Munky]

There seem to be about a bazillion of those fakes with the 0058T code on them.  Again, some people have pedals that work fine with them, meaning they are actual working dual opamps of some kind, in some cases.

I got 50 of those ones from aliexpress, for a very cheap price. Used about 10 of them, all worked. I don't know what exactly they are, since I can't think on a cheaper opamp than a 4558 to be remarked and sold as a 4558. I can't even think on how profitable is to sell fake 4558s. I mean, for a rare IC, like a bbd or something like that, they can get a IC that costs a few cents and remark it as one that can be sold for a dollar or more. But for faking a 4558 they just get a IC that costs a few cents and remark it as one that costs... a few cents! Probably the cost for remarking the IC is bigger than the profile for selling a fake 4558.

I do believe mine are fakes. The same goes for a bag of jfets I got from aliexpress (which I also used a few and they work but I had to use a totally different value for the bias resistor). Just saying I can't really understand why to counterfeit a so cheap part, it makes no sense.

Back to TC's circuit, so far we can't say those 4558s work or not, but there's indeed a short somewhere, because of the voltage measurement even without all ICs.

[DIY Bass]

I am a bit suspicious of C14.  You could remove it and see what happens to those voltages.  It acts as a filter on the power supply, so without it the circuit would still work perfectly well. 

[willienillie]

Just saying I can't really understand why to counterfeit a so cheap part, it makes no sense.

I agree.  Maybe they're not remarking chips, but manufacturing them as fakes from the get-go, figuring they can get 2 cents more each with the brand recognition.  2 cents x a bazillion = real money.

[duck_arse]

like that guy ^ sez. squint at this pic, it could be made a poster of what to look for. note well the difference in shape and method of the pin 1 divots, and the one chip has chamfered all round body, the other doesn't. yet both show the same date code, both show the exact same size shape spacing weight and content of the print printed.

also - never buy before checking the datasheet. if the datasheet sez :

TOSHIBA Field Effect Transistor Silicon N Channel Junction Type 2SK246

and the advert you are looking sez  :

2SK246-Y Original New Toshiba TO-92 MOSFET K246

..... close the page, look elsewhere. it ain't worth the hassle.

[ajhuff]

If by 6.7 that means 6.7r, there's indeed a short.

I would assume it's 6.7k, since he's on the 20k range.

Sorry, I didn't know if you were supposed to halve the number or double it since the  dial setting says 20K so I just reported 6.7 of the 20K setting. I'm inferring then that you just add zeros? I'm learning as we go. I would have figured that out if it said x10K on the scale but the 20 confused me.

-AJ

[ajhuff]

I am a bit suspicious of C14.  You could remove it and see what happens to those voltages.  It acts as a filter on the power supply, so without it the circuit would still work perfectly well.

I can try that. I'm guessing with the tests we are doing I should expect 9V from the +9V to GND and so the 1.5V I got is really off?

I don't see anything labeled continuity on my meter So I don't know what setting that is.


I'll go over the back of the board with a magnifying glass. Back when I soldered in college we used to scrub our joints with a stiff brush and 1,1,1, trichloroethylene. Sometimes we'd use a dunk tank. Made all the joints nice and shiny. Should I be doing this?

I'll check the joints and if I don't find anything I'll remove that C14 capacitor and check the voltage from +9V to GND again.

Thanks!

-AJ

[ajhuff]

I don't see anything to my unpracticed eye under the magnifying glass that look like bridges. I also double checked the tantalum capacitors and all off the + signs printed on the capacitors line up with the + signs printed on the board. This is C14.


Oh, and I checked, all of the diodes have the stripe on the square hole side.

-AJ

[PRR]

> Probably the cost for remarking the IC is bigger....

I think in many Asian factory towns, parts-printers are as common as staplers are in offices. Bring thousands of chips in your lunch-bag, remark them over lunchtime or after quitting time.