What is this stuff on this board?

[Locrian99]

Hey guys,

Recently acquired an rc-300 loop station that is doa, I figured I'd nothing else I could cannibalize the jacks etc.   i confirm it's doa and pop it open to see if the switch is good etc and I see this stuff in these two spots.   Any idea what it is?   And would it be related to the problem? 

Thanks

[DIY Bass]

looks like glue applied to stop the parts moving around

[Locrian99]

Yea it feels glue, weird They just covered that one cap and those diodes. 

[ElectricDruid]

+1 what DIYBass said. I'm not sure *exactly* what that is, but it looks like generally harmless "gloopy stuff" used to stick things down and help prevent damage from vibration or knocks. I very much doubt it is the cause of your problem with the pedal.

Can we see the rest of it, please? Maybe we can spot something else?

[Locrian99]

Sure. 

I literally just got it open when I posted it.  So far I have confirmed the power switch has power at the it.   It's a momentary dpdt without the button pushed it shows
0. 0
0. 0
9.3.  9.3

With everything shorts to ground. 

[Locrian99]

Seems weird that the only place on the board I can see voltage is those two pins on the switch, thinking maybe that is bad.   Can i wire a regular dpdt in its place to confirm that?

[intripped]

Check if that white substance hasn't became slightly conductive.
I once had to repair all of my 3 TV decoders (same brand, same shop) that had a very similar stuff on the rectifier diodes. They all became non functional after almost a year of use.
That stuff was conductive enough to make a short circuit and if I remember well a couple of 1N4007s were fried.
I think It was a kind of a programmed fault, and probably they did it on purpose (at the factory or at the shop), in order to force you to buy new ones or have them repaired.
Weird, I know, and a very rare scam I hope.

... But that stuff really looks like what I found in those TV decoders.

[Locrian99]

Check if that white substance hasn't became slightly conductive.
I once had to repair all of my 3 TV decoders (same brand, same shop) that had a very similar stuff on the rectifier diodes. They all became non functional after almost a year of use.
That stuff was conductive enough to make a short circuit and if I remember well a couple of 1N4007s were fried.
I think It was a kind of a programmed fault, and probably they did it on purpose (at the factory or at the shop), in order to force you to buy new ones or have them repaired.
Weird, I know, and a very rare scam I hope.

... But that stuff really looks like what I found in those TV decoders.

I'll check that out soon as I get some time to dig back into it.   I need to find a replacement switch for it as well haven't seen anything like it with 90 degree pcb pins yet and of course boss won't sell it to Joe Schmo

[diffeq]

Kinda amusing they glued in 2gb microSD card like that. Probably to make programming easy.

[soggybag]

I notice Boss uses the same stuff to stick the DC jack to the PCBs. Removes stress on the solder joints.

[DIY Bass]

Kinda amusing they glued in 2gb microSD card like that. Probably to make programming easy.

I figured it was so it didn't get knocked loose.  Rigours of touring and all that

[anotherjim]

More likely the wrong external PSU used has fried the power input. Could be a simple fix.
I've seen a few goop-related problems over the years, that don't look like a problem one, but you never know. If it was, you'd expect an epidemic of similar failures.
Some I've seen...
RTV used which gives off corrosive acid when it cures.
Contact glue sticking down panel filament lamps to PCB. Lamp heat carbonises glue and shorts out key scan traces.
Heatsink glued with cyano onto ceramic 40pinDIL MCU chip. Heatsink expands and breaks the chip in half.

[ElectricDruid]

.
RTV used which gives off corrosive acid when it cures.

I've seen a similar thing; enclosure sealed against water with silicon sealant. The 'wrong' sealant gives off acetic acid fumes, which eat the copper off the PCB.

Heatsink glued with cyano onto ceramic 40pinDIL MCU chip. Heatsink expands and breaks the chip in half.

Oooh! That's a great one!!

[Locrian99]

More likely the wrong external PSU used has fried the power input. Could be a simple fix.
I've seen a few goop-related problems over the years, that don't look like a problem one, but you never know. If it was, you'd expect an epidemic of similar failures.
Some I've seen...
RTV used which gives off corrosive acid when it cures.
Contact glue sticking down panel filament lamps to PCB. Lamp heat carbonises glue and shorts out key scan traces.
Heatsink glued with cyano onto ceramic 40pinDIL MCU chip. Heatsink expands and breaks the chip in half.

I located and ordered a replacement switch, if it didn't need one before it does now but I did notice when I took it apart one of the slider pins was all bent.    So this is probably some what on hold until that comes (from Spain to the us, couldn't find it in the US guessing because boss/Roland says they won't sell them to the end user).   Do you have a suggestion on what to look for if it was a wrong power supply plugged in.   These surface mount components... there was power at the switch, a couple components located between the switch and dc in (a resistor and cap).   

[Locrian99]

Anyone have any thoughts if this part labeled d15 here is likely the protection diode? 


Oops mislabeled it in my scribbling here.  D15 not d12 as drawn in pic. 




Been searching around for a schematic for it, or more specifically the power section here.   As previously stated there's power between the dc in and the switch.  not surprisingly no luck so far lol.   

Any input appreciated thanks

[Locrian99]

Used my cheap multimeter test function when I had a chance to crack it open and I'm measuring 179 on that diode.   It's an sr24.   





Looks shorted to me... is that correct in that?   I measured it in place in the circuit as well. 

[amptramp]

I'm also on audiokarma and there is a 19-page thread about someone trying to diagnose why his H. H. Scott LT112 FM tuner will not go into stereo and on the 378th post, he finally reported that cleaning the flux off one particular transistor cured the problem.  He had done an alignment to get all the tuned circuits into best tuning and had removed transistors to test them and found them good, but he only solved the problem when he cleaned all the flux off which allowed the base current to flow.

The LT112 was a tuner kit, so the craftsmanship of the buyer who built it is the most contentious issue whenever you pick one up second-hand.

This is in addition to the glue used to hold down large items like electrolytic capacitors.  Tuners sometimes have a problem that regulators and resistors in the power section get hot and scorch the board under them into conductivity.

[Locrian99]

I'm also on audiokarma and there is a 19-page thread about someone trying to diagnose why his H. H. Scott LT112 FM tuner will not go into stereo and on the 378th post, he finally reported that cleaning the flux off one particular transistor cured the problem.  He had done an alignment to get all the tuned circuits into best tuning and had removed transistors to test them and found them good, but he only solved the problem when he cleaned all the flux off which allowed the base current to flow.

The LT112 was a tuner kit, so the craftsmanship of the buyer who built it is the most contentious issue whenever you pick one up second-hand.

This is in addition to the glue used to hold down large items like electrolytic capacitors.  Tuners sometimes have a problem that regulators and resistors in the power section get hot and scorch the board under them into conductivity.

It doesn't look to me like anything was has been soldered resoldered.   Person I got this from said it just stopped working and he set it aside where it sat for a couple years.   I'm just going to remove that diode and test it off the board see if I get the same reading and order one and try it.   Got a little over my head on this I think, would be awesome to get it going but I won't be out much if I don't.   Was just hoping someone might know if I'm looking in the right direction with that diode.   Never messed with smd stuff so I would rather not be soldering/resoldering a ton and cause other issues like you mentioned. 

[duck_arse]

I know nuffink of boss gear, but, looking at the back panel I see it sez use only boss blah blah power adaptor. with this in mind, it makes little sense for boss to then fit supply protection diodes internal, because they've just told you ..... and it's probably in any written manual for the user which may have been supplied. don't need protection if you use the thing we told you, because we know that to be the right thing.

and your found data sez the diode is fast, and it's mounted on the board near a dozen or more inductors, so I'd think it was an invertor diode rather than for protection. if it was short, it wouldn't then voltaage invert, and the system would be cack - perhaps there is even a sense correct volts shutdown circuit.

there may be inductors parallel to the diode making it look short. do you measure any voltage across it when powered, or doesn't the juice reach that far? also, have you metered the power switch for continuity?

[Locrian99]

I know nuffink of boss gear, but, looking at the back panel I see it sez use only boss blah blah power adaptor. with this in mind, it makes little sense for boss to then fit supply protection diodes internal, because they've just told you ..... and it's probably in any written manual for the user which may have been supplied. don't need protection if you use the thing we told you, because we know that to be the right thing.

and your found data sez the diode is fast, and it's mounted on the board near a dozen or more inductors, so I'd think it was an invertor diode rather than for protection. if it was short, it wouldn't then voltaage invert, and the system would be cack - perhaps there is even a sense correct volts shutdown circuit.

there may be inductors parallel to the diode making it look short. do you measure any voltage across it when powered, or doesn't the juice reach that far? also, have you metered the power switch for continuity?

Hey thanks for the response.   The switch I guess would be described as momentary.   The two middle pins appear to be be ground, then back two which are connected to the middle two when the button is pushed have 9.1v to them.  The two "front" pins from what I can see aren't connected to anything (they are soldered in) but I haven't found any points with continuity to them.   There is continuity between the ground pins and other places I would expect to see ground (ie pin 4 of the 4580 ic's on the board, where the board screws in).  There is a resistor and cap appears to be between switch and the dc jack where I show 9.3 on both, I'll have to check that diode for voltage tonight, I don't know why but I didn't check that.   I have a new switch coming found on eBay coming from Spain.   Boss literally tells you they don't sell replacement parts to the end user if the part requires you to open the unit you have to take it do an authorized service center. 

Edit - still trying to dig around but found info that "most" boss pedals have a polarity protection diode.