Did I just blow up my Effectrode Blackbird...?

Mr. Body

Silver Supporting Member
Messages
56
Hi everyone... .

I rearranged my pedal board, and in the process ran my Blackbird at 15v for a few minutes before wising up and dropping it back to 12v. I'm using the Ciocks DC7. I'm noticing now that the blue/ red channel is running a little weak, however the green/ clean channel is running just fine. Additionally, the entire system has a high pitched hum that wasnt there before. I'm going to look at the whole chain to see if a bad cable or other pedal is contributing to the high pitched hum, but I'm worried about the blackbird. Did I just destroy my blackbird by running it at 15v? Also, given that the clean is going fine and the distortion channels are weak, could the issue be better explained by a busted tube in the higher voltage process?

So, am I an idiot thats about to pay stupid tax in a repair? I messaged Effectrode to get their take on the situation, but thought the hive mind could also help here. Thanks everyone.
 

Jim Hagerman

Vendor
Messages
71
Possible, but you'd need a rather high current 15V supply to do so. You may just have overheated a tube. Check to see if they all still get hot (at 12V). I'm guessing the high voltage boost is fine, or you would not have one good channel. You can also look for the orange glow of a heater.
 

Mr. Body

Silver Supporting Member
Messages
56
Possible, but you'd need a rather high current 15V supply to do so. You may just have overheated a tube. Check to see if they all still get hot (at 12V). I'm guessing the high voltage boost is fine, or you would not have one good channel. You can also look for the orange glow of a heater.
Thanks for the follow up. I'll check the tubes and see what happened.
 

lefort_1

Nuzzled Firmly Betwixt
Platinum Supporting Member
Messages
14,936
As the pedal runs on 12V, a good engineering principle would be to ensure that 'safe' conditions would exist if the pedal was plugged into up to 18 (maybe 24) volts for an extended time, since those are commonly found on pedalboard PSUs. The very last thing a good engineer wants to be responsible for is a fire due to an excessive voltage condition.

Since you have one good channel, the internal switcher is likely functioning, tho it is also the most likely source of any high-pitched noise you are hearing. It is possible that a small-value filter-cap has been degraded by the higher-than-expected voltage... even tho a 25% tolerance 'buffer' would be pretty darned skimpy in a power supply. I'd also look into any pre-switcher OVP circuitry that is in the design..protection diodes can 'fatigue in mysterious ways'** and, post damage, can become a significant noise source (if they didn't burn up completely).

The Gain channel tends to be 'hot-biased' (Effectrodes words) and therefore it may have been operating closer to a tube's limits. If that bias voltage is derived from the Vin without benefit of an OVP circuit, the the bias may have been set 25% high in a circuit in which the voltage is already running 'hot'. This may not have good outcomes for either the tube or perhaps other components in the area (e.g. maybe a cathode bypass cap).

Designing a pedal to handle any and all possible OVP-situations might seem like a necessary thing, but when we're talking about running a 12ax7 at max plate voltage around 330, THEN increasing it to a possible 400 volts...well, that may have eaten the safety margin in the filter caps, etc. I don't know Effectrode's philosophy on this, but the cost of spec'ing in a 700V cap where 330 is the max-expected (the case where a 24 v supply is accidentally hooked up) may make the Bill in the BOM a smidge onerous. Same with the breakdown voltage in the switcher's transformer, etc. In my mind, it's best to have a protection device crowbar the input and simply not operate at all.

...ah, this is turning into a schematic-less critique, and I shouldn't do that.

It could be they designed in a good crowbar, but the device didn't fully shut the pedal down.

Maybe try swapping a tube first.
If that doesn't do it, then send it into Effectrode and be very honest with the setup and duration that the unit was playing under improper voltage conditions.

**this is a non-technical manner of describing failure modes that include breakdown in internal resistive layers, junction tunneling, or the formation of heat-caused conductive paths.
 




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