denon mc6000 dj mixer blowing fuse

[benwrong]

Hi, the board keeps blowing the 2.5 amp fuse f700. when I remove the capacitor c773 it doesn't.

I have replaced c773 with a new 2200uf 16v but different package size, thinner and longer, but still blows fuse. I also tested three different capacitors inc. the one I removed and all behave exactly the same removed from circuit on a diode test.

I then removed q700, q701 and ic704.

Replaced and tested r711,c726, c727.

With all these components removed and the three others replaced, I have the exact same behaviour, blows fuse with capacitor and powers to correct area without. I have also checked for short circuits in the traces between points, with diode check, all clear....... Any help greatly appreciated! please find image of schematic attached

[CapLeaker]

Re: denon mc6000 dj mixer blowing fuse

could you upload the whole schematic? what about IC705?

[benwrong]

Re: denon mc6000 dj mixer blowing fuse

sorry for slow response, I didn't think ic705 would be 'in play' so to speak since I had other components disconnected...I had a quick look just now (magnified) and nothing obv. ....thanks for your help, unfortunately pdf schematic is too big for page limit, even compressed is still over so have the link to download... thanks ...... https://www.manualslib.com/manual/10...Dn-Mc6000.html

[madan1]

Re: denon mc6000 dj mixer blowing fuse

By the way, have you checked the power supply?

Also, If I read it right, there is a branch of the power supply line from SW700 ( SW12V ) which I'm not sure where it is going... it could be page 43 near IC101.. anyway, just be sure to know the position of SW700 when testing.

[benwrong]

Re: denon mc6000 dj mixer blowing fuse

yeah power supply all good, been testing in off position and still blowing. Tested without capacitor, power to correct points on board with switch on or off (with the components listed above removed).. thanks

[benwrong]

Re: denon mc6000 dj mixer blowing fuse

cheers madan, do you mean the line going from standby on ic704? can see it on schematic, just checking circuit around d703 and q708, thanks!

[petehall347]

Re: denon mc6000 dj mixer blowing fuse

first make sure the power supply is correctly polarised and correct voltage .
then be sure c773 is correct way round .
then check q701 for being shorted .
it is most likely your power supply is wrong .

theory is c773 seeing reversed voltage will act shorted and blow the fuse .

[benwrong]

Re: denon mc6000 dj mixer blowing fuse

supply is fine, double checked voltage and polarity. As with c773, checked then double checked. q701 and q700 (which i think seperates it from rest of circuit?) are currently removed and still blowing fuse. Also no short to ground on this line

[benwrong]

Re: denon mc6000 dj mixer blowing fuse

ps is it possible a board would rely on earths created from being bolted onto its outer casing?

[madan1]

Re: denon mc6000 dj mixer blowing fuse

Measure the current without the capacitor.
Also if you have scope check the waveform of the power supply.

"ps is it possible a board would rely on earths created from being bolted onto its outer casing?" - yes it is possible. I have an Onkyo receiver which does not want to power up ( just erratically switching the power relay ) without proper ground from the backplate.

[budm]

Re: denon mc6000 dj mixer blowing fuse

Hi, the board keeps blowing the 2.5 amp fuse f700. when I remove the capacitor c773 it doesn't.

I have replaced c773 with a new 2200uf 16v but different package size, thinner and longer, but still blows fuse. I also tested three different capacitors inc. the one I removed and all behave exactly the same removed from circuit on a diode test.

I then removed q700, q701 and ic704.

Replaced and tested r711,c726, c727.

With all these components removed and the three others replaced, I have the exact same behaviour, blows fuse with capacitor and powers to correct area without. I have also checked for short circuits in the traces between points, with diode check, all clear....... Any help greatly appreciated! please find image of schematic attached

When Q700 is removed then any loads on the Drain are no longer present, so the only connection left after the main fuse are the loads after the power switch if the switch is ON, but you said the fuse is still blown even the switch is in the OFF position. Something is not making any sense.

[petehall347]

Re: denon mc6000 dj mixer blowing fuse

does it blow fuse with power switch off ?

[petehall347]

Re: denon mc6000 dj mixer blowing fuse

ok stop wasting fuses .. take your meter and set to low ohms .maybe 200 .. look for the short with it .
also test the power supply using a dc blocking capacitor to see how much ac is passing if any . .01uf or something like that in series with a meter lead . i dont think ac is the problem though so disregard that bit for now . useful to know anyway .

[CapLeaker]

Re: denon mc6000 dj mixer blowing fuse

yeah power supply all good, been testing in off position and still blowing. Tested without capacitor, power to correct points on board with switch on or off (with the components listed above removed).. thanks

The switch is off, Q700 and Q701 are out and it is still blowing fuses, without there being a low resistance reading to GND?

[budm]

Re: denon mc6000 dj mixer blowing fuse

Are you using the original power supply that comes with unit? Switch is off the main switched power MOSFET is removed and still blowing fuse, something is fishy to me.

[benwrong]

Re: denon mc6000 dj mixer blowing fuse

Hi Everyone, thanks for all the advice! Sorry for late reply, I've had a ridiculously busy few days but am now back. It is original power supply, blows with fuse on or off but only when c773 is connected.

I will go over, check all things recommended. will also try another of my 2200 uf 16v c773 replacements, slightly longer and thinner in package. Will also check traces around c773. checked at 200 ohms resistance test and no short to ground. On diode test (to gnd, from power line) w/c773 connected, starts low and charges capacitor.

I have been a mechanic most of my life, started doing boards about two years ago and for about the last nine months have done nothing but study and practice electronics. I'd say I have a decent idea but being self taught does leave you open to missing basic things.

I have also cross ref. my multimeter, which is fine... I seem to be missing
something... thanks again!

[benwrong]

Re: denon mc6000 dj mixer blowing fuse

Also have just discovered that c792 does not make earth whilst board is out of its casing, hopefully that would cause it to behave this way. Poss clutching at straws, think it would be mentioned in service manual if so. will wire it to earth and test ;-)

[CapLeaker]

Re: denon mc6000 dj mixer blowing fuse

Yeah that's another reasons why pictures are important

[benwrong]

Re: denon mc6000 dj mixer blowing fuse

new capacitor, earth trace from c792... same result... the schematic says 2.5a 32V chip fuse. I got 2.5 amp, 32v ac 63v dc??? is this wrong? also it blew the original so was a problem before i started replacing fuses.... still to check with dc blocker and don't have a scope

[petehall347]

Re: denon mc6000 dj mixer blowing fuse

fuse is fine ..voltage is before it might flash-over . so higher the better .
pull that cap out again that seems to stop it blowing fuses then measure the DC and AC voltages right across where the cap came from .
then check voltages at the power supply plug and unloaded .