My cd-player died, I need help with faultfinding.

[Tor M]

Hi!

Yesterday I experienced the tweaker nightmare. After fouling around in my cd-player (testing a clock I built for a future cd-rom project.) suddenly my Pioneer PDS 707 died.

I`ve probably had it open and modyfied it a houndred times before and it has always worked afterwards.

So I started looking for the main fuse, but it seems like it is located inside the powertrafo, soldered between two of the legs on the pcb trafo. My two year old daughter is home with me today, insisting on helping her dad, so I haven`t tried shorting these two pins or done to much measuring. 230 V mainpower and 250 degree soldering iron do not match a two year old hanging around.

I know I have 230 v after the main swich.
I measured the resistance between the two pins where I belive the main fuse to be located, to 0,5 ohm. This I belive idicates that the fuse probably is not blown?

I have also found two fusable resistors, and theese measured 8,2 ohm like they were supposed to, but I haven`t measured them with power on ( I don`t know how theese are supposed to work, high resistance when they act like a fuse?).

When I get some time alone I`m gonna measure to se if there is any voltage over the powersupply caps to see if the trafo works.

Anybody have any Idea what usually is wrong when things like this happens? I haven`t much experience in foult finding.

If anybody have any idea, I would appriciate you shearing it.

Thanks

Tor Martin

[Netlist]

I haven`t much experience in foult finding.

Your intentions are good so far.

/Hugo

[Elso Kwak]

Hi Tor,
I was reading fast and for one second I was understanding your 2-year old was connected to the 230V leads. Sorry, I am bit confused today. See my other post.
To give you some good advice from a experienced repairguy:
Just measure all supply voltages to see if these are OK. These cement resistors act as fuses and are a repairmans nightmare as it is very difficult to see if they are blown or not. But of course you can measure voltage before and after the resistor. 8.2 Ohm is not blown, that would give a 8 turned 90degrees, overload.
If you have a scope check for oscillation of clocks. [You did not specify which one]. Without oscillation the player won't work. Put the probe at 10x.
If voltages and oscillation are OK check the laser for burning and going up and down. Don't look straight into to beam.
If I remember right, it is a very long time ago, Japanese players first try to find focus on a stationary disc, then signal Focus OK to the µP, then start spinning to read TOC (Table of Content) etc.
If it fails on TOC reading it won't work!
Hope this helps.

[carlosfm]

You look very flashy today, Elso.

Tor, try to put the original clock on the player.
Are you shure your clock is fine?

[Tor M]

Hi!
Thanks for advice.

My problem is that the player is completley dead. No light, nothing...
The only thing I know is that I have 230v after the switch. Haven`t had time to look any more in to it yet. All though I`m by education is an engineer I have to work at the postalservice (no engineering jobs around at the moment...) and now this close to christmas they would liked me to be at work around the clock!

I fear that the power transformer somehow have broken. I don`t know why though....

I know that my original clock works, but the player should power up even without a clock.

I had hoped that it was the main fuse that were broken, but measuring between thoose two pins at the trafo showed only 0,5 ohm resistanse. It should be more than that if it was broken.?.
But why do they place the fuse such a stupid place as inside the transformer? Just to force us to buy new orginal parts?

I hope I get some time to look deeper in to this tomorrow.

Thanks

Tor Martin

[Elso Kwak]

Originally posted by Tor M
Hi!
Thanks for advice.

My problem is that the player is completley dead. No light, nothing...
The only thing I know is that I have 230v after the switch. Haven`t had time to look any more in to it yet. All though I`m by education is an engineer I have to work at the postalservice (no engineering jobs around at the moment...) and now this close to christmas they would liked me to be at work around the clock!

I fear that the power transformer somehow have broken. I don`t know why though....

I know that my original clock works, but the player should power up even without a clock.

I had hoped that it was the main fuse that were broken, but measuring between thoose two pins at the trafo showed only 0,5 ohm resistanse. It should be more than that if it was broken.?.
But why do they place the fuse such a stupid place as inside the transformer? Just to force us to buy new orginal parts?

I hope I get some time to look deeper in to this tomorrow.

Thanks

Tor Martin

Hello Tor,
Some transformers have hidden non-replacable fuses. Others have built in fuses that can be bypassed. I remember an Audio Alchemy supply. Can be a non resettable overtemperature fuse or a high current limiting one.
Quite simple if you have AC on the primaries you also should have AC on the secondaries. If not transformer dead/ Kaput.
It is all for for fire precaution I suppose.
Still remember that guy that had a defective fuse in his CD Player. He replaced the fuse by a bigger one, again and again and finally put in a 15A(!) car fuse. Then he blew the houses mainsfuse and I was called in because the player was causing problems....

[Tor M]

Hi Elso and everybody helping me out.

I finally got time to do some measuring.

I have voltage after the trafo. I measured about 9 v ac over the bridges. But here is the strange thing. All the - supplys seems to be fine, from the output of the bridge all the way through the player, but all the + supplys seems to give only 1-2V dc, starting at the bridge.

Does this means the diodes in the bridge used for + rectifying is gone? Or does the transformer put out some kind of werid ac.

I`m gonna measure the diodes now, and I`ll change them anyway to see if it helps.

I`ll let you know where the journey leads.

Thanks

Tor Martin

[Tor M]

Ok changing the diodes didn`t help.

Also this time i noticed that the trafo gets very hot when powered on for a while. It`s probably broken just giving me negative pulses of the ac to rectify.

I guess I`ll have to get a local repair shop to order me a new one. Probably costs ten times a trafo thats not special made for Pioneer.

Tor Martin

[li_gangyi]

check ur trafo out of circuit (not connected to anything) if it has got the correct volatges it's probably ur bridge rectifiers, caps shorting out or regulators not working...should be a simple fix...and since u were messing with the clock...I would uess the regulator got shot somehow while u were fiddling around...

[Tor M]

Hi!

Thanks, I`ll measure the trafo unconnected before I order a new one. But I think it`s probably the trafo where the main problem is.

There is two bridges in my player, one seperate for analog and one for the rest, and they are in paralell from the same secondarys on the trafo. They both show the same.
My guess is since it usen one bridge to make + and - dc probably only one of the secondarys are broken. I just measured over the bridge, not between the bridge "inputs" and the centretap (ground) so I`ll have to measure this But I`m off to work and tomorrow I`m going to London. So I don`t know when I get the time to do it.

Thanks

Tor Martin