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Philips AZ1005 CD Radio Cassette Recorder
Recently my youngest sister asked me to look at a Philips Portable CD Radio Cassette Recorder Player of her’s. A Portable Philips AZ1005. Because she and her Boyfriend were moving into a new home they probably had used the player to give them energy while being busy around their new Home. And my guess was that the volume most likely was set to a level that it in the end killed the Amplifier chip inside.
I looked on the internet for a Service Manual but the only one I found was about 6 pages or less of the CD Player circuit of this AZ1005. The other pages of the 33 pages or so were sadly missing. So I had no clue about what chip was used for the Amplifier inside. Which meant I had to open the Player to find out more. The Volume Knob didn’t work anymore and now you only could hear it playing on a very soft level. Almost unnoticeable, no matter what source was selected. My sister warned me that the player could be also a bit dusty from the work in their new Home. And after I had checked the obvious first tests I noticed that also the Headphones gave no significant sound either. So I removed the screws on the back to have a look inside this AZ1005 Player.
The front of the Philips AZ1005 CD Radio Cassette Player. With on the left the Volume Knob that didn’t work anymore. Next photo shows the Inside top view of the AZ1005 after opening.
On above photo, the Board with the Amplifier Chip is on the most left Board. I already removed the four screws that kept the Board in place. Also I removed the 3 plugged in connectors at the bottom of this Board, also removed the Antenna on the back, and the Power connector to better be able to remove the Board with the Amplifier on it.
To be sure that both Speakers were not blown earlier also, I measured both Impedances with the well known Blue ESR tester. And both speakers measured 20 Ohm. So that means they are okay and no problem for the Amplifier Speaker Output Impedance. (As everyone knows that any battery or Power Supply also has an internal Resistance that should be at least equal or lower compared to the attached Resistance of the connected Load. Which means that only in that specific situation the Power given to the Load by the Battery will be at its highest possible value. And in this case the Battery is of course the Amplifier, and the Load is the Speaker. A Battery gives its maximum voltage at its Load when its current through its internal Resistance is lower. Because the Voltage loss is higher over its internal Resistance at higher given currents to its attached Load. Or simply said : The Battery Voltage over its Poles is Maximum when no current flows at all!).
In case that the Speaker Resistance would be too Low for the Amplifier Output circuit, it would likely destroy the Amplifier Chip. And in case that the Speaker Resistance is higher than the Output Resistance of the Amplifier, that would mean less Amplifier Power to the Speakers. (Impedance probably would be in this case be a better description, because Resistance only is used for DC circuits whereas we now in fact use AC frequencies here. Although the Impedance of a Speaker doesn’t have much influence on its Resistance or Real Ohmic Value). Next Photo shows a closer view at the Board with the Cooler removed from the bad Amplifier chip. The Amplifier proved to be a 16 pins UTC2025.
Previous 2 photos showed the side view of the Board also showing one of both Speakers and followed by this Board top viewed with the UTC2025 already removed. Next photo finally shows the removed Amplifier chip Cooler.
And removing the UTC2025 only took me about 30 seconds with my new Desolder Gun. Previous Photos showed this recently bought perfect time saving Desolder Gun. After I knew what Amplifier was used, I of course checked the internet to order this UTC2025 16 pins chip.
It was easily found at a low price and Free Shipping. So 5 chips for only $1.67 dollar would mean that my sister could enjoy her Portable Sound System again very soon ! Maybe not a very big repair article this time, but the fact that this Philips AZ1005 CD Radio Cassette information couldn’t be found (at least for free) on the world wide web, hopefully makes this repair nevertheless worth something.
Anyway, what would the World be without Music ! Until another repair.
Albert van Bemmelen, Weert, The Netherlands.
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Note: You can read his previous repair article in the below link: