Denon DRA-325R - Replace IC

racer2086

Member
Hey there,

Hope I'm posting this in the right place. I mainly lurk on this forum.

Last weekend I picked up a Denon DRA-325R reciever and CD player. The CL ad said that the CD player was intermittent but the receiver worked when last used (a while ago). It was implied that it should work but buy for parts. I didn't spend much, and figured I'd give it a shot.

Welp, no luck. The receiver is silent. No audio through aux from my phone or the tuner. In fact, my phone doesn't even detect that there is a headphone plugged in when hooked up to the receiver until I unplugged the wire from the back of the unit.

I downloaded the service manual and did some snooping. The IC204 on the board gets really hot. It is slightly melty on the top. This component is obviously bad. It appears to be the main confluence of all the rear inputs and sends signal out from there.

My question is, do you think I can replace the IC204 (Toshiba TD62706P) and have a working unit? Or is there something else that caused that to blow?

Sorry if this is a super basic question. I'm no electrical engineer. I know how to use a meter, solder, etc. I worked on some projects and fixed stuff with my grandfather, who was an electrical engineer. Wish he was still around...

Thanks for the help!
 
Well, not a lot of views, but figured I'd update...

I spent some time looking over the SM. The amp was in protection mode, because I wouldn't get a click from the relay at power on. Couldn't really see anything that would be causing that, as the output transistors all seemed to test ok.

IC204 melted and gets nice and hot when the power is on. I decided to risk my fingers and feel around for any other hot items on the board. R421 was also smokin hot.

Looking at the schematic, it appears that R421 was part of feeding power to the protection circuitry. R421 has a twin R417 that pulls some circuitry to ground that links to IC204.

Both R421 and R417 are labeled in the SM as 1 ohm 1/4watt resistors of important tolerance. Measuring R417, the resistor was open. Measuring R421, it read 188 ohms. Testing IC204, VCC and Sub pins were shorted, while it looks like they should be separated by a diode. What I didn't know is if the resistors cooked because of the IC or the IC cooked because of the resistors.

Either way, I got myself a desoldering bulb and desoldering braid and removed the IC and resistors. It was easy to get 1ohm 1/4 resistors, but the IC is hard to find. I bought some off ebay from Hong Kong.

It appeared to me that the unit should function fine without the IC in place, you just couldn't select an input. I soldered in the resistors and left out the IC. Fired it up and...CLICK! No longer in protection mode!

I hooked up my phone to the Tape Rec jacks in the back (they are hooked up to the final input), and the damn thing started playing music. I'm blown away. I don't have much knowledge in this stuff, but some logic and deductive reasoning has me pretty close to repaired. Just waiting on the IC.

I have to say the unit sounds quite good. Very clear and decent power. It pushes the CR9s quite well.
 
am having a guess the chip is a selector switch for the inputs .. i have seen a few get fried from pulling inputs in and out with unit powered up .
my second guess and maybe more accurate the chip is a op amp in the tone amp/pre-amp . could have been over driven or hit with dc ..
 
Probably over driven as Pete says. got a couple of ic's from asia myself to repair a logic circuit on a TT. A logic chip that didn't shut off because it didn't get a signal to shut off and blew. Probably re flow on the traces helped... might have been the failure in the first place. Just mind the input V on the chip circuit, make sure that is okay.
 
From the schematic, it controls the input switching. The main microprocessor sends voltages to different pins on the chip based on the input selected, and that chip then has output pins going to 3 other ICs that switch the inputs coming in from the back of the unit.

When I look up the datasheet on the Toshiba TD62706P, it is called a 6 channel, high-voltage source-current driver, FWIW.

I already hooked the CD player that is in question up to another receiver, and it not only worked, but sounded good. Didn't fry anything, but I didn't have it on too long either. What would I measure to make sure the CD player isn't outputting high voltage or something?

I did measure the voltage going to the chip, and it is the 15.8v specified in the schematic. The sub pin was supposed to have -15.8, but it instead measured +15.8. I figured this was because the Vcc and sub pins were shorted to each other according to my meter. I bought a few of the chips ($1.99), just in case the first one I put in blows for some other reason that I need to diagnose.
 
The more popular this forum gets? The more the schematics are in error on many brands reported. (freebees..? but many schema's were not updated.. thus procede with caution note that you can read -/+ on the meter and the circuit may read same but next time you check it may read the +/- ... you are energizing and taking a brief reading. if dmm equipped with hold you can see it again or jot it down. don't forget in many a test you are inducing v's so meter maybe reading off another circuit with caps discharging.
 
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