Need help with PS blowing fuses.

[JimBanville]

I'm an amateur at repairing electronics. I have fixed obvious issues on electronics before, but I could use some help on this fix. I picked up a Pioneer CLD-D504 laserdisc player that won't power on. There is no standby light. I was told it may have gotten wet but I see no obvious water damage. It had a blown fuse. I've downloaded the service manual. Nothing, including the fuse itself, says wether it's fast or slow blow, but I'm guessing it's slow, seeing as its right at the point where the AC power goes to the PS. I'm guessing it's the standby power that's "bad". I put in another fuse and it blew as soon as I plugged the player into the wall. I completely removed the PS from the chassis so it was not connected to anything. I replaced the fuse. As soon as I plugged it into the wall, that fuse blew. I've started measuring components on the primary part of the PS while still "in circuit". I haven't removed anything. The first thing I noticed was that R2 measures 2M ohms. I believe it should be 22.5 ohms. Could that be the "problem"? What should I measure next? I've ordered a pack of new fuses that should be here in a couple of days. Thanks!!!!!!

[stj]

Re: Need help with PS blowing fuses.

can you link or upload the service manual.
it's probably a shorted diode or bridge rectifier.
is this arcade-related??

[stj]

Re: Need help with PS blowing fuses.

btw, check the main transistor on the heatsink too.
leave R2 alone if you want to live - it links the mains neutral to the metal chassis!!!!!

[JimBanville]

Re: Need help with PS blowing fuses.

can you link or upload the service manual.
it's probably a shorted diode or bridge rectifier.
is this arcade-related??

Here you go...
http://manuals.lddb.com/LD_Players/P.../CLD/CLD-D504/

Arcade related? Did I post this in the wrong forum? Sorry

[JimBanville]

Re: Need help with PS blowing fuses.

btw, check the main transistor on the heatsink too.
leave R2 alone if you want to live - it links the mains neutral to the metal chassis!!!!!

Thanks. I'm measuring all this with the PS unplugged. Does that R2 impedance reading of 2M ohms sound right? Does still being in-circuit affect that reading?

[stj]

Re: Need help with PS blowing fuses.

no, just curious - most laserdisk players where used in arcade equipment - very few were privatly owned because of the lack of discs.

[stj]

Re: Need help with PS blowing fuses.

Thanks. I'm measuring all this with the PS unplugged. Does that R2 impedance reading of 2M ohms sound right? Does still being in-circuit affect that reading?

2meg is about right.
to blow a fuse you need a short - so probably a diode or transistor near the fuse.
the fuse should be a "T" or time-delay aka slowblow type - preferanbly ceramic.

[JimBanville]

Re: Need help with PS blowing fuses.

2meg is about right.
to blow a fuse you need a short - so probably a diode or transistor near the fuse.
the fuse should be a "T" or time-delay aka slowblow type - preferanbly ceramic.

The old fuse didn't look ceramic. Not sure if it was original or someone tried to repair this before I got it.
I measured Q1 on the heat sink in diode mode. It's marked ground drain source. When I measured it with + on the S, I get .41v on D and .57v on G. When I reverse leads and measure with - on S, I get 1.9v on D but it drops to 0v within a second. I get 0v on G. When I touch the G D S in continuity mode, I might get a quick tone, but I'm not getting a continuous short.

[JimBanville]

Re: Need help with PS blowing fuses.

2meg is about right.
to blow a fuse you need a short - so probably a diode or transistor near the fuse.
the fuse should be a "T" or time-delay aka slowblow type - preferanbly ceramic.

When I put the leads on D6 in both directions, I get a continuous tone/"short" across it in both diode mode and in continuity mode. I assume that means it "bad"? Again, I'm measuring it in-circuit.

[JimBanville]

Re: Need help with PS blowing fuses.

2meg is about right.
to blow a fuse you need a short - so probably a diode or transistor near the fuse.
the fuse should be a "T" or time-delay aka slowblow type - preferanbly ceramic.

When I measure the 4 leads on D1 (bridge recitifier??) I only get a constant tone/"short" if I touch the two center leads in either direction (+ and -) marked with the ~ symbols. If I touch the other leads I'll either get around .5v or 0v.

[JimBanville]

Re: Need help with PS blowing fuses.

2meg is about right.
to blow a fuse you need a short - so probably a diode or transistor near the fuse.
the fuse should be a "T" or time-delay aka slowblow type - preferanbly ceramic.

When I measure across the big cap (C11) in the primary part of the PS, while still connected in-circuit, I get 1M ohms.

[stj]

Re: Need help with PS blowing fuses.

desolder d6 and see if the recifier d1 loses the short.
d6 sounds fucked.

[JimBanville]

Re: Need help with PS blowing fuses.

desolder d6 and see if the recifier d1 loses the short.
d6 sounds fucked.

Thanks! I'll do that this evening. At work now. So I take it the two center pins on the rectifier should not be showing continuity between themselves? They are the two pins with the ~ symbols as viewed from the bottom of the board. I hope it's just that diode! Seems like a cheap fix.

[stj]

Re: Need help with PS blowing fuses.

none of the rectifier pins should be connected to each other,
but it is soldered parallel to d6 - so you cant tell which is bad without removing one.

[JimBanville]

Re: Need help with PS blowing fuses.

desolder d6 and see if the recifier d1 loses the short.
d6 sounds fucked.

So..Good news...I hope!! I had also posted this question over at the laserdisc archive. Turns out that D6 part is basically a surge/arc suppressor and considered underrated by people over there. Some replace it (the right thing to do IMO) and some just clip it out and use an outboard surge suppressor. I'm going to run by Home Depot tonight and grab a pack of 2A fuses and try clipping that part to see if the unit will power on. Wish me luck!! Haha.

[JimBanville]

Re: Need help with PS blowing fuses.

none of the rectifier pins should be connected to each other,
but it is soldered parallel to d6 - so you cant tell which is bad without removing one.

Haven't made it home yet but couldn't wait to grab a pair of scissors and clip that D6 part. The continuity between the two center pins of that rectifier is gone! I think we may have fixed it. Thanks!!!!!

[stj]

Re: Need help with PS blowing fuses.

good.
btw, the reason for a ceramic fuse is simply that when you have a mains-short like here, it can actually break a glass fuse and create a big mess.

most originals are glass unfortunatly - to save a few penny's

[JimBanville]

Re: Need help with PS blowing fuses.

good.
btw, the reason for a ceramic fuse is simply that when you have a mains-short like here, it can actually break a glass fuse and create a big mess.

most originals are glass unfortunatly - to save a few penny's

Gotcha. Never knew that. Makes sense (cents!). Lol

[sam_sam_sam]

Re: Need help with PS blowing fuses.

I would highly recommend that you use a 100 watt incandescent light bulb instead of the fuse just in case you have issues and blow the fuse again

When doing this the light bulb with glow bright for a couple of seconds and dim down to maybe nothing or very dim depending on how much current you are drawing from the switching power supply

If for some reason the light bulb is bright and does not dim down then there are issues with this power supply

What are the devices that are mount to the heat sinks part numbers