Oops Fried my Denon HD2500

[NKR]

Yesterday I rearranged the kit in the boxes and amanged to put the HD2500 decks the wrong way around on the desk.

Realised this when fired up at the gig. As I was tight for time I left everything plugged in and pulled the phonos out of the HD2500 to swap over. Its tight for space in the box so managed to short circuit the outputs by touching a phono across both channels.

Oops broken! outputs now don't work. Well one does in left hand side mono only. Well that was not a cheap gig last night. Happens and reinforces the point never try and do cable changes with stuff turned on. SCHOOL BOY ERROR.

Luckilly I have another HD2500 so could keep going and can keep gigging going forward.

I May be on the look out for another HD2500 at some pont soon.

[DJ Jules]

Realised this when fired up at the gig. As I was tight for time I left everything plugged in and pulled the phonos out of the HD2500 to swap over. Its tight for space in the box so managed to short circuit the outputs by touching a phono across both channels.

So you connected the output from the left deck into the output from the right hand deck?

If so, I'm surprised that was enough to kill an output channel, but I guess it happens?

Julian

[Excalibur]

Yesterday I rearranged the kit in the boxes and managed to put the HD2500 decks the wrong way around on the desk.

I'd have just left it, after all it couldn't make it any less intuitive to use, could it? :p :whistle:


So you connected the output from the left deck into the output from the right hand deck?

If so, I'm surprised that was enough to kill an output channel, but I guess it happens?

Julian
I'm not sure that I understand exactly what Neil did with the cables, but I too am very surprised that it should result in damage. :confused:

[NKR]

I had the left hand deck of hd2500 connected to the to the right hand channel of the desk and the right hand deck of the hd2500 to the left hand channel of the mixer, therefore it was back to front in terms of intuitive use of a cross fader.

Left everything turned on and unplugged the phonos on the hd2500 to swap over. managed to touch a phono across both channels due to lack of space and it sparked and shorted it out.

Now confined to the box of broken stuff in the garage. You live and learn, but not a cheap lesson.

[DJ Jules]

Left everything turned on and unplugged the phonos on the hd2500 to swap over. managed to touch a phono across both channels due to lack of space and it sparked and shorted it out.

That really is surprising, in theory outputs from any kind of audio equipment are via some kind of resistance or capacitance to protect them from these kinds of goings on (and to remove any DC voltage from the line) so it's pretty damn weird that doing this would kill a channel. That's not to say you wouldn't have seen sparks if you touched the phono tips or even the outer to another phono lead or even a grounded chasis on another piece of equipment, but even then it shouldn't have damaged the line.

I know from experience Denon are pretty wacky with the power supplies in their kit. The DN-S1200's I had weren't earthed so whenever you connected them to something else which was earthed, you tended to get a few sparks as you bought the kit "down to earth". If you were holding on to something earthed (e.g. a Mic) and touched any of the exterior metal on the units once they'd been disconnected from the laptop and mixer they could give you a bit of a buzz (not much - probably about 5v-12v or so!)

I'm still surprised about the damage though, I would have thought you would have had to hit a much higher voltage to kill the output stage. At the risk of being patronising, have you tried it again since the gig with different cables, etc?

Julian

[Excalibur]

I'm still surprised about the damage though, I would have thought you would have had to hit a much higher voltage to kill the output stage.
Julian

Me too. :confused:

[NKR]

I have done a full fault find on it. Cables account for 99% of all equipment faults, so that was the first point of call.

Have changed cables, check desk channels, etc, etc, etc. It is broken. I have an engineer friend who is going to strip it and check the output stage on the boards and see if he can use some parts off a couple of HD 2500 bases he has lying in his shed.

[katman]

I'm still surprised about the damage though, I would have thought you would have had to hit a much higher voltage to kill the output stage.

The problem with modern equipment is that to meet energy efficiency regulations almost all equipment comes with double insulated switch mode power supplies. These always leak a small amount of the mains at very low current levels which is why you often feel a tingle if you catch your forearm on something as you are fiddling with connections round the back of a rack.

( Hence the Leakage tests as part of PAT testing )

Once connected everything is at the same potential and you dont get any tingles because at least one piece of equipment will be earthed and holding everything down to ground.

However when connecting equipment whilst powered up, you can have the situation where one item is held down to ground and you are connecting to something which is effectively "floating" at half mains voltage hence the tiny sparks.

As many modern semiconductors can be damaged by as little as 20 volts, seeing 120 volts being connected momentarily is enough to kill stuff if you are unlucky :(

Its probably the output opamps that have failed but these days you will be extremely luck if they are DIL chips in sockets which are easily replaceable, most likely they will be surface mount devices which are a :Censored: to change without the proper rework tools.

Forgot to add, thats one of the reasons pro gear uses balanced signals and XLR.

The balanced signal is immune to interference and becuase ground it not part of the signal chain you dont get ground loops, and also on the design of the XLR connector the first contact to make is the ground which ties the equipment to the same potential.

With Jacks and Phono connectors the tip which is the active part of the circuit is first to make with the ground being connected once the connector is fully inserted hence the pops and buzzes you get when "hot plugging"

[DJ Jules]

The problem with modern equipment is that to meet energy efficiency regulations almost all equipment comes with double insulated switch mode power supplies. These always leak a small amount of the mains at very low current levels which is why you often feel a tingle if you catch your forearm on something as you are fiddling with connections round the back of a rack.

A "not quite floating" 0V rail? :D


( Hence the Leakage tests as part of PAT testing )

Hmm... Leakage is measured from live/neutral to the equipment casing isn't it? Not questioning your experience here, just interested so I can understand more myself, especially when we're talking about double insulated power supplies?


Once connected everything is at the same potential and you dont get any tingles because at least one piece of equipment will be earthed and holding everything down to ground.

Agreed.


However when connecting equipment whilst powered up, you can have the situation where one item is held down to ground and you are connecting to something which is effectively "floating" at half mains voltage hence the tiny sparks.

That'd explain what I used to get with the Denon's then. I've got to admit I haven't found any other equipment as bad as the Denon's for this.

Julian

[katman]

Hmm... Leakage is measured from live/neutral to the equipment casing isn't it? Not questioning your experience here, just interested so I can understand more myself, especially when we're talking about double insulated power supplies?


Leakage is indeed measured to the casing and with items that have connections to the outside world eg CD players, laptops etc that leakage makes its way to the 0v rail of the equipment and thus onto the audio connectors.

HDMI seems to suffer badly from being hot plugged as well. As electronics progresses and components get smaller they also become far more prone to electrical damage and at the same time they are getting more difficult to repair so you end up replacing the whole item :(

[SoundONE]

Katman is pretty much spot here, Having a more than an interest in anything electrical I would like to add some information. From a very young age all I wanted to do was be an electronics engineer, once I left school and studied electronics at college for some years and so have a sound background have sinced worked on various projects until last year I was working as a full time electrican and have for over 6 years.

Something known as a potential difference, this is the difference in voltage between 2 points normally earths or between the main bonding condutor and any equipitential bonding or other cpc's, this can be as high as 50v above 50 volts will usually cause RCD's residual currect devices to trip even though they are specifically designed to trip at 30mA in most instances. It could be you simply had a potential difference or as Katman explains leakage between the different devices and sent anything upto 50v into the final output stage, quite rightly as katman says very likely to be otpo amp or transistor and more likely to be surface mount, probably a relatively easy repair to be honest even without rework tools, but unless like myself you have worked on a lot of smd's best just to take it to a pro. The replacement parts are likely to be a few quid at most with postage costing as much or more than the actual parts.

[katman]

A few years ago I could have repaired surface mount but now I cant even count the legs on the chips. My eyes have really deteriorated over the last decade.

When I have seen some of my mates DJing from CDs and reading the sleeves in near darkness I wonder how the hell they can read them. I find with a lot of CDs that I cant read the tiny text even in good lighting !!! Doesnt help that so many sleeves seem to have been designed from a prettyness aspect with poor contrast on the colours rather than from a practicality point of view with the aim of actually reading the damn thing !!!

[SoundONE]

I know exactly where your comming from katman, thats why I changed direction and moved to electrician plus it pays better, most firms tend to board change nowdays and there is no call for componet level work thats pays well anymore. My failing eye sight ment I could no longer carry on in a professional manor I need magnifiers and microscopes if i work now, I have all this at home, but you cant work like that 8hrs a day. Everyone starts to get long sighted at around 40+ and you and I are both well there mate :) But if you took those shades off it may help for you lol.

[Excalibur]

.

When I have seen some of my mates DJing from CDs and reading the sleeves in near darkness I wonder how the hell they can read them. I find with a lot of CDs that I cant read the tiny text even in good lighting !!! !!!

And now do you understand why the more mature DJ's have uncharacteristically welcomed the new technology, and become Laptop DJ's? An illuminated screen, with big letters and numbers cures a lack of visual acuity. And when you connect them to a 42" monitor..........................:D :D :D :D :D

[katman]

Everyone starts to get long sighted at around 40+ and you and I are both well there mate :)

WHAADYA MEAN ??????

Im not old. Im only 21........








...... with 31 years experience :D

[Excalibur]

Im not old. Im only 21........


Well I'm eighteen. :p Until I look in the mirror, or pick up an active sub. :( :(








( And don't take any notice of anyone who tells you that I'm nearer eight than eighteen in terms of mental age ) ;) ;)

[katman]

And now do you understand why the more mature DJ's have uncharacteristically welcomed the new technology, and become Laptop DJ's? An illuminated screen, with big letters and numbers cures a lack of visual acuity. And when you connect them to a 42" monitor..........................:D :D :D :D :D

:)

Even though I was one of the first Mobile DJ's in Yarmouth to have CD Players ( I had a couple of individual CD players built into my deck ) I only ever used them for oldies that I had got on compilation CDs. I much preferred the accessibility of vinyl.

If I thought of a perfect next record with only 20 seconds to go, I could turn round, put my hand on the record box within an inch of the actual record, slap it on the deck and cue it up in time to start. With the CDs I had to try and remember which disc it was on, load it into the player and select the right track which took way too long.

Digital DJing has solved all the problems, instant access to any song in your collection and you can have it playing within a couple of seconds.....

....then watch the floor clear because you accidently picked some rubbish remix by mistake :lol: