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Dim Bulb Tester Saves My Dupa

c.coyle

c.coyle

Fighting the Dunning-Kruger effect.
Fixing up a friend's Marantz 2252B. I pulled and tested the output transistors, then re-installed them with fresh mica and grease. Before pulling them, I had carefully noted their position - NPN PNP PNP NPN - and even made a diagram on my bench. Embarrassingly, I completely forgot the diagram and put them back in NPN PNP NPN PNP.

I came this close to saying "bleep it, just plug into the wall", but a little voice said "do it right." So, I plugged into the DBT and that sucker stayed bright as the sun, and no relay click. Figured it out, switched them around, and all is OK. The diagram was right under my nose the whole time.

God protects infants and idiots.

dbt.jpeg
 
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I was trying to remember who made the Dupa brand of audio equipment ... :idea:

And yes, sometimes a bit of forethought goes a long way. :thumbsup:
 
I thought Dupa was an audio company ... don't Dupa make Schiit? <G>
 
My DBT saved me at work, I had to troubleshoot an expensive piece of test equipment that was blowing fuses and the trouble was a pair of blown MOV's at the AC input, but because of construction and location, they almost could not be seen (I only had a block diagram and it did not show them).

Mark T. :music:
 
I can't see the phrase Dim Bulb Tester without thinking of a parody of Awake! magazine. Instead of Awake!, it read: Wise Up!

And the question below was "Is God a Dim-Bulb?"

So, your thread title along with your avatar tickled, and even motivated me to look up dupa! :D
 
I thought everyone knew what dupa meant.

Anyway, worked on a QSC the other week or whatever and its outputs are not arranged how one would think, all for one channel on one side and the other channel over on the other side. One of the four outputs for one channel is with the other three of the other channel.

I have tried to wrap my head around some reason an engineer would do that but the only possible reason I can come up with is to confuse a tech and make for a failed repair, or more costly once they figured it out. This increases the likelihood of selling a new amp. Well they didn't fool me. And they aren't getting the benefit of the doubt either, they were trying to trip up anyone trying to fix it so they might sell another one.

So that company goes into the same category as TV manufacturers, which do everything possible can to make their product unservicable. I know their game.

What's more, this thing includes a crossover for biamping. Now I could see mixing up the outputs to keep the heat even, but that is not what they did. If they wanted to do that they would have interspersed the transistors, but no, they took ONE out of the four and put it over on the other side.

Anyway, about your experience here, umm, on that QSC I marked on the board which transistor went where because there was no easy way to do them one at a time. They are all held down by one big clamp.

In your case, with something like that, you should just do them one at a time. Then there are no such mistakes.
 
JURB said:
I thought everyone knew what dupa meant.
Click to expand...

Depends on the language. In Romanian "dupa" means "later"/"after", and it's a word they actually use a lot, apparently they like to postpone. Hard to keep a straight face when you're a Polish guy at a Romanian party, or sitting next to a Romanian who's on the phone with his wife.
 
... and here I thought Dupa was a French comic artist ...

01edb180-3edf-0130-5fc6-005056945a4e.jpg


Often wondered why my Polish Babcia kept calling me a French comic artist ...
 
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