Some Faults Are Hard To Diagnose. This Time I Got It WRONG, Let's See IF I Can Do Better!

Рет қаралды 6,552

3 ай бұрын

I have a HK Nano 500 Powered speaker system stuck in protect mode. There are no schematics and the cause of the fault is not obvious. I thought I had daignosed the fault in Part One but....
If you didn't see it first or want a refresher here is part one of this repair
• How to diagnose faults...
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Пікірлер: 35

@thefixer6973 3 ай бұрын

High Richard. I emailed you what I found for a service manual for nano 600. hope it's the right one. here in Wisconsin USA, we just got 80mm of snow and on Sunday have another 120mm of snow and then rain. love spring.

@budgiefish 3 ай бұрын

Weather warning for 50mm of rain hmph... I think up here in the North West of England we get weather warnings if we're due 50 mins of sunshine 😄

@Dutch_off_grid_homesteading 3 ай бұрын

Heya, lets go down the differant rabbit holes and fing the fault, love these diagonese find fault video's, I untherstand the most of it 90% I would say only doning it myself is still difficult

@zakaria0440 3 ай бұрын

I love what you do keep going ❤

@danblankenship5744 3 ай бұрын

The diode/LED bank is an array that is wired in series. Pin 8 (Cathode leg) is the GND connection. Pin 7 (where you measured the diode drop) is the Anode. This connects to the neighboring diode's Anode, etc. Pin #1 is where I would start to see where it originates.

@thefixer6973 3 ай бұрын

Don't eat the yellow snow! 🤣

@avi4828 3 ай бұрын

I think you should try power on the board and use your thermal camera to see if some shorted component is getting hot

@TheHayruss 3 ай бұрын

We had a cyclone watch hit landfall as a cat 3 cyclone luckily no one was injured but masssive flooding occurred.

@jonathanrose456 3 ай бұрын

Had an inbuilt amp that would go into protect if the driver was faulty. Could it be detecting that there’s no driver on the output?

@Dutch-linux 3 ай бұрын

you call that rain !!!!! we got 10 mil of rain steady here ....

@ianhaylock7409 3 ай бұрын

10 mil is only 0.01 inches, hardly anything.

@chrishartley1210 3 ай бұрын

We have yellow snow warnings, Don't eat it!

@tonysheerness2427 3 ай бұрын

Caught a cold going up on the Bar's roof fixing the satellite dish. Only mad dogs and Englishmen go out in the mid day sun.

@GregM 3 ай бұрын

Here this time of year if a weather warning occurred it would because there was 10cm+ of snow coming or freezing rain.

@pault6533 3 ай бұрын

The red light also indicates the mute mode or setup mode is activated. Could it be that either of these modes are stuck on, whether by a switch fault or other input glitches? It might be on the other side of the device? This reminds me of a protection mode glitch with my under-seat powered subwoofer Boss Bass 600. It goes into protect mode sometimes when cold but then after used for a while works just fine. Have not yet found the problem. I can sympathize with your challenge here and understand why mistakes happen in diagnosis.

@LearnElectronicsRepair 3 ай бұрын

Hi Paul, yeah the amplifier ICs are definitely being held in standby by the voltage on the Mute pin, as discovered in part one. The link to that is in the video description.

@bones1225 3 ай бұрын

Thermistor maybe?

@andygardiner6526 3 ай бұрын

We had a yellow snow warning the other week ... :-)

@LearnElectronicsRepair 3 ай бұрын

PMSL 😂😂😂😂

@andymouse 3 ай бұрын

And I hope you listened to Frank Zappers advice !

@Dutch-linux 3 ай бұрын

@ timestamp 34:35 I think there is a resister open somewhere or another diode so the positive voltage can not reach the three diodes may even be a transistor somewhere .. it does not look like a faulty opamp if you got an open resistor that should feed the positive voltage then it can never be pulled positive

@LearnElectronicsRepair 3 ай бұрын

I didn't trace that far yet, but all three diodes have -13.8V on the anodes and these are all 'independent voltages' from each other as the diodes are connected together at the cathodes, if you get what I mean. The voltage at the Cathodes junction will be which ever diode is highest on the anode. That would suggest a combination of one or more of three conditions can take the protection LED off. That seems kind of back to front logic to me, I would expect any one or more of the three signals could put the protection ON. Makes more sense Yeah? We seem to have Protection OFF if either A,B or C is true (high) I expected Protection ON if A, B or C is true.

@Dutch-linux 3 ай бұрын

@@LearnElectronicsRepair why i think there is something open like a resistor or a short like a transistor it can even be a capacitor ... i do not believe a opamp is the problem ... what you could try is to list 1 leg of all three diodes and put a positive voltage on one of them ... if the protection goes off you really have to trace back from there .. i slow process but i am sure it is just something small that is causing it

@gardnecd 3 ай бұрын

Here's a thought. Perhaps the diode "or" is actually an "and" . The diode node only goes high if all three inputs are high. That might make sense if for example it would only enable the amp if all three conditions were "good" . And the capacitor is there to delay the turn on until everything is stable. The fact that the node is low with all three diodes forward biased (ie trying to turn the amp on?) makes me think there is a short at the node. Have you checked the capacitor hasn't failed short?

@Dutch-linux 3 ай бұрын

@@gardnecd best way to find out is to lift on leg of all three diods then put a positive voltage on it ... if the protection goes off then check the cap and measure the outputs for dc or if no dc on the outputs then take out the amp ic's then there is an internal fail in one of the output ic's if it in none of that then you have to trace the protection circuit

@gardnecd 3 ай бұрын

Correction. could still be an or. Got my logic up side down . Anyhoo observation re short somewhere still stands.

@jonathanrose456 3 ай бұрын

❤

@orion310591RS 3 ай бұрын

7:25 - It WILL ALWAYS show which one is faulty, on those simple chips. Most reliable test is to unsolder them both (since they are identical) and test outside of circuit in that way. At given moment we dont know what is connected to first one, what to another one, meaning we cannot draw conclusions what is correct what is not. When they are outside of circuit, we can. It has nothing to do with diodes in IC. In diode mode we test a lot of components.