Hi there - I have just replaced the capacitors in my DCC900 with Tantulum Capacitors - which seemed to go OK.
I have reassembled the deck only to find that it will not power on.
I am in New Zealand and we have 220 - 240V power supply here but I can only measure at JB51 about 135V and the same at JB03.
The transformer outlet pins on the top of the transformer measure all over the place with the earth being ok and everything else below what the diagram says they should read.
Have I somehow killed my transformer do you think?
The odd thing as well is that the heat sink on the output side of the IC’s get warmer and warmer the longer I leave the power switched on - with actually no evidence to suggest that the unit is on at all - no display - no red light above the power button either.
It sounds like you have a short circuit. I’m not very familiar with the DCC 900 so I don’t know if it has Tantalum capacitors but those usually fail by short-circuiting. That would cause the voltage regulators to draw the maximum current (usually 1 A) which gets the heart sinks very hot and drag the supply voltage down.
Make sure you’re using the schematic for the correct variant of the recorder you have. On the back side of the recorder you’ll see a number behind the type, eg DCC900/17 or DCC900/00. The /00 (or whatever) indicates what power supply is in your machine. The service manual has the schematic for all the different power supplies, and you must use the schematic that matches yours. I know it sounds obvious but it’s a possible reason why you’re not seeing the voltages you’re expecting so I figured I should mention it.
Thanks to all whom have replied so quickly - no magic smoke thankfully - found the problem and it was my rookie mistake. Deck is back up and running and the Tantalums all seem good. Wasn’t able to replace all of the electrolytic capacitors though as I misread the 22uF 6.3V one as 2.2uF 6.3V - so wasted a small amount of money unfortunately. Will have to try finding the remaining replacements.
Not always. Failed Tantalums unfortunately can sink a lot of current so they don’t explode. They just blow the fuse but they don’t even look any different when they fail. Failed Tantalums are hard to find, though I think it helps to have an accurate (5 digit) volt meter so you can try to find the spot where the voltage difference between the shorted power rails is the lowest.
Maybe you’re confused with RIFA caps? Those do explode (inevitably) and can release a lot of magic smoke or worse. If you’re lucky, they’re behind the fuse and they take it out before causing too much of a mess. But often they’re right where the AC comes into the device, in front of the fuse.
Only one way. Blue is always “up”. If the cable is not connected the correct way, the player will not start. It has the same effect as the PZ03 mounted the wrong way, I believe.
No, I’m not confusing them with anything. Just based on my experiences with them, that’s all; whenever I’ve had a tantalum go bad on me, they nearly always ended up burning – not “exploding” in the sense of an actual detonation that scatters debris everywhere, just torching themselves into a charred remnant with a fair bit of accompanying smoke.
