FX repair help after flooding - Darkglass microtubes Q

Winny_Pooh

So my house got flooded a few weeks back, managed to scrub and fix/replace, part out some gear but one last thing isnt working.

I have a Darkglass microtubes for bass and while it lights up it acts as if it's in bypass. The switch fizzles a tiny bit when switched and there is no change, just as if the signal is straight through. Its SMD so I cant quite go into checking signal flow, however I'm wondering if perhaps the relay is the likely culprit? (relatively easily replaced)

Cookiemonster

@ICBM ; any ideas on this ?

ICBM

The switch is far more likely than the relay - the relay will normally be a fully sealed unit, whereas the switch is probably not watertight around the button. I have no idea of how the switching on these works, but if it's a latching DPDT or 3PDT switch with one half for the LED and one for the relay, it could easily be operating one but not the other.

ecc83

NEVER turn water damaged gear on. Even weeks after the event there can be damp crap lurking under chips and in switches.

I have taken full TV PCBs that have had allsorts in them, coffee,tea,milk beer and the process was, rinse under running water for a good five minutes turning the board as you go. Then the board was hung up for a week in front of a gas powered blower that heated the factory unit. Was about 75% successful.

And all because we could not get manfctr's service replacement PCBs.

Dave.

meltedbuzzbox

ecc83 said:

NEVER turn water damaged gear on. Even weeks after the event there can be damp crap lurking under chips and in switches.

I have taken full TV PCBs that have had allsorts in them, coffee,tea,milk beer and the process was, rinse under running water for a good five minutes turning the board as you go. Then the board was hung up for a week in front of a gas powered blower that heated the factory unit. Was about 75% successful.

And all because we could not get manfctr's service replacement PCBs.

Dave.

You might find not running them under water for minutes will help 

Danny1969

Any board that's had any liquid on it needs to go into an ultrasonic cleaner really. That will get out all the crap you can't see under the chips and other places. 
The SM components on that board are massive so buzzing through won't be any harder than through hole components. You can check the switch with a meter, likewise the relay. 

WiresDreamDisasters

Does the bag of rice thing still work?

Winny_Pooh

@ICBM said:

The switch is far more likely than the relay - the relay will normally be a fully sealed unit, whereas the switch is probably not watertight around the button. I have no idea of how the switching on these works, but if it's a latching DPDT or 3PDT switch with one half for the LED and one for the relay, it could easily be operating one but not the other.

It's a momentary switch, tested with a multimeter and when depressed the two poles read open to each other. So I assume the switching is done on the board. 

Cookiemonster

WiresDreamDisasters said:

Does the bag of rice thing still work?

I read somewhere recently that it never did interestingly. 

Winny_Pooh

WiresDreamDisasters said:

Does the bag of rice thing still work?

I disassembled and scrubbed Everything with 99% alchohol. A reverb pedal never came back, and I lost a pc motherboard, most other stuff fine but still have to test my two Overstayer compressors and have a replacement capsule waiting for my  SE Gemini II. 

Cookiemonster

Winny_Pooh said:

WiresDreamDisasters said:

Does the bag of rice thing still work?

I disassembled and scrubbed Everything with 99% alchohol. A reverb pedal never came back, and I lost a pc motherboard, most other stuff fine but still have to test my two Overstayer compressors and have a replacement capsule waiting for my  SE Gemini II. 

What a shame.

 are you insured ?

ICBM

Winny_Pooh said:

It's a momentary switch, tested with a multimeter and when depressed the two poles read open to each other. So I assume the switching is done on the board.

Do you mean they read closed when the switch is pressed?

If they stay open, it's the switch.

ecc83 said:

NEVER turn water damaged gear on. Even weeks after the event there can be damp crap lurking under chips and in switches.

I have taken full TV PCBs that have had allsorts in them, coffee,tea,milk beer and the process was, rinse under running water for a good five minutes turning the board as you go. Then the board was hung up for a week in front of a gas powered blower that heated the factory unit. Was about 75% successful.

This is where I have a huge advantage living in Scotland - the tap water here is so soft it's more or less de-ionised. When I've had water-damaged gear in that definitely hasn't been turned on yet 'just to see', I've washed it all very thoroughly with the ordinary shower, then left it in the hot water tank cupboard for at least a week, and I have a near 100% success rate - I actually can't think of any that have failed, off the top of my head (I don't want to tempt fate by not saying 'near'!).

But if the owner has already powered it up, all bets are off...

Winny_Pooh

@Cookiemonster not insured no (freak occurrence with rain) although landlord has helped with reducing last rent.

@icbm poles are unconnected when at rest, when pushed they are connected. I assume this is correct(?)

ICBM

Winny_Pooh said:

@icbm poles are unconnected when at rest, when pushed they are connected. I assume this is correct(?)

Yes. Unfortunately that means it’s not the switch.

Danny1969

It's really hard to see the chip numbers on the board so difficult to work out whats whats. I can see a CD4049 though, that's a chip used to invert and buffer logic signals like cmos to ttl so I suspect that's used to switch the relay from something with a low source current. You can check that switches with the footswitch
The other chips I can't see the numbers but guessing a quad opamp and maybe a dual .... there's also what looks look 4 FET's .. Q1 to 4

So when checking through first identify the chips and make sure each chip has volts on it's VCC + supply pin so pin 1 on the 4049. 
If that other large DIL is a quad opamp then pin 4 is V+ 

Generally when something fails it's because a semiconductor has been reverse biased, caps and resistors and passive components are either unaffected or in the case of polarised caps reasonably tolerant. Normal clean water isn't actually that conductive but something with high input impedance like a FET or the JFET input of an opamp could be reverse biased by a path created by water reacting with the PCB 

I don't know if that pedals expensive but looks fixable for less than £80

Winny_Pooh

I think the chips may be near impossible for me to solder out/in. I did test continuity on the relay from the hot input on the jacks and it does change from bypass to non bypass (does this mean anything?)but I can't hear a click.

http://imgur.com/a/EyJRY91

Also contacted DG support but they dont supply these boards anymore. 

Edit, thanks @Danny1969 cant find voltage on relay coil but connections definitely not as you describe, new one ordered. 

Danny1969

That relay looks like a telecoms type, normally 5V on the coil switchs 2 poles a double pole double throw . The coil is always one end and will have 5V on it when operating. Then the common poles are generally the middle pins switching from and to the pins either side of them. 
You would expect signal straight through in bypass mode and nothing at all in effect in mode if the main circuit was faulty in terms of opamp or FET's but I'm not familiar with it's switching. 

If the relay has volts and is switching then I would google the IC numbers and make sure they have volts on their VCC rail  ... then  put audio into the pedal and make up a probe cable connected to an amp so you can detect the audio as it travels through the stages. 

Sometimes you've better off cutting the legs of an SM chip close to the body of the chip with a sharp knife. Then once the chip body is out the way it's easy to heat the dismembered leg and remove it from the pad quickly with minimum damage to the pad from heat. 
Soldering another in is actually pretty easy with a long conical tip. Line it and solder 2 opposing corner legs so it can't move off square then carefully solder each leg and check for solder bridges with magnification before powering on. 

ecc83

Good stuff Danny. Once I had the 'bits' out of the holes I would clean up with solder wick not a sucker but I know a lot of people like them. I would then always fit a low profile DIL socket. You can then power up and check that voltages are where they are supposed to be and not where not! Once checked, fit chip.

Dave.

CarbonCopy

Winny_Pooh said:

@Cookiemonster not insured no (freak occurrence with rain) although landlord has helped with reducing last rent.

Do you mean you don't have insurance or that you do, but it's not covered? If the latter, most policies should cover storm damage.