Sony HCD-300S problem²

[jarl]

Problem squared, that is...

Smart me, I got a home theater from craigslist without thinking too much about it. It's a Sony HCD-S300 (same as the DAV-S300, DVD player + 5.1 amplifier in the same device). Upon testing this thing using the built-in "tone" function, one of the channels (front-right) was dead, so I checked for cold solders at the speaker connectors and redid all of them, with no change in symptoms.

No problem, I thought... got the service manual and my old oscilloscope and started measuring the voltage at the relevant TA2020-020 (there are three: one for the left channels, one for center+subwoofer and one for right channels). Everything went well until I got to pin #26 or #28 -can't recall at this point-, when I turned to look at the scope and the [BIP] tip of the probe slipped from the pin I was testing . I think I shorted out two consecutive numbered pins in the 26-29 range (i.e. 26 and 27).

Nothing tripped nor the essential smoke escaped from any of the components I can see, but now none of the speakers respond to the built-in tone test, and there's a fast-paced "thud" coming from the LEFT REAR channel. As mentioned before, this is on a separate TA2020-020, so I'm positively puzzled by this.

There are some shields that won't allow me to get decent pictures of this thing at this time, but I'm attaching the PCB and diagram for the power/amp PCB. The IC I was probing when I screwed up is IC301 (the one on the left of the PCB).

Suggestions? (other than taking another hobby, that is )

Forgot to mention: the "thud" repeats at ~2Hz, and doesn't change when changing the volume. Other than that there is no sound coming through from any of the inputs, and the video output looks normal (i.e. "insert disc")

[jarl]

Re: Sony HCD-300S - No sound

Update: I was able to solve one part of the riddle...

Turned out the signal causing the "thud" was present in all the channels not related with IC301. The only reason I was able to hear it on the rear-left channel was that a capacitor (6800pf) between that speaker's (+) terminal and ground had failed. It probably has been bad for a while, but that wasn't highlighted until I screwed up with the scope probe.

So... now I have two working and one (apparently) dead TA2020. The protection circuit seems to be triggered, preventing the relays that connect the speakers to the amps from operating. There's something weird with the signals at the ICs in the protection circuit (IC401 and IC403) and I still have to find out what is it and how I caused it (to make sure nothing else is bad).

In the meantime, can anyone suggest a reliable source for the TA2020-020? Is there any modern amp. that can be used as a replacement?

TIA...

[Scenic]

Re: Sony HCD-300S problem²

there are a few on ebay. No other way to get them AFAIK, as Tripath is long gone.

http://www.ebay.com/sch/i.html?_nkw=....c0.m270.l1313

Substitutes are not available.. these are proprietary digital amp ICs..

[jarl]

Re: Sony HCD-300S problem²

Yuck... buying discontinued ICs from someone in China doesn't sound too reliable...
"Surface was removed with sandpaper and new characters engraved" is one of the feedback left for one of the sellers...

[b700029]

Re: Sony HCD-300S problem²

Since the original manufacturer is no more, only used or Chinese clones are the alternatives.

[lcdman]

Re: Sony HCD-300S problem²

Hello,

I found this on Ebay. Maybe you could buy some from this listing. Good luck either way.

http://www.ebay.com/itm/2PCS-Tripath...ht_3203wt_1139


Happy Holidays To You & All BCN Members,
lcdman

[Scenic]

Re: Sony HCD-300S problem²

^ Item location: 深圳市, 广东省, China

[jarl]

Re: Sony HCD-300S problem²

Thank you people...
Yep... the link by Lcdman is for an item located in China. I'm aware this IC has been discontinued, and I wouldn't mind buying a used part from a reputable seller, even if on eBay. Even a counterfeit would be an option, as long as the performance was comparable to the original. However I don't have such expectations from sellers who offer discontinued proprietary ICs by the hundreds...

An option would be to buy an old amp at a thrift store and gut it, as long as I knew it had the TA2020-020... but I don't think that's realistic, is it?

[Scenic]

Re: Sony HCD-300S problem²

http://www.electronix.com/semiconduc...0-p-12950.html
https://p4.secure.hostingprod.com/@p...tno=TA2020-020

The 2nd one seems to be cheaper, but they list it as a Toshiba (mistake?)

[Longbow]

Re: Sony HCD-300S problem²

Your attachment is of the power supply. The TA2020 is an output IC. If this IC were easily available I'd say go ahead and shotgun it. But since it is not, I think a bit more troubleshooting is in order to make certain you actually need one. I'm including the data sheet for this IC. Perhaps you could include the schematic of the output stage, and indicate the critical voltages on your suspected bad output IC?

[jarl]

Re: Sony HCD-300S problem²

Thank you Scenic, Longbow,

The amplifiers share the same PCB-and are on the same schematic- as the power supply. On the PCB the amplifier section is on the left, and the ICs are IC301, IC331 and IC361. The one that wasn't working originally was IC301, but after the probe "issue" while measuring the pins of IC301 the other channels stopped working as well. It looks like either IC361 or some of the associated components got messed up (nothing looks blown/burned though).

The voltages on each of the pins are shown on the attached chart. On the output pins of IC361 there's a square wave with an amplitude of 15V (indicated as 7.5±7.5V). DCAP seems to be Ok for 331 and 361 (indicated as 10-20 and 0-15), but messed up for 301. The OVERLOAD output for IC361 shows a square pulse with a period of ~0.5 seconds, but the inputs look fine.

If you look at the MUTE signal, you'll see that all of them are at 1V... There's a protection circuit that seems to be triggered, either because it's detecting an abnormal output from the amps or because some of the associated components got fried. I can't find the paper where I wrote things down, but I remember the signal seems to die after some of the capacitors at the top-left of the Protect PCB (specifically C139), like R139 is pulling down the signal to ground. Whatever knowledge is left about analog circuits is so rusty I'm not really sure how this part of the circuit is supposed to behave ... is C139 fried? (those three capacitors, and the three on the right of the schematic, receive the signals from OUTM1/2 from the three amps)

[Longbow]

Re: Sony HCD-300S problem²

This chip is definitely a handful. Since you say that none are currently putting out signal, I would focus on the obvious mute problem, and on the suspicious pin 4. All pin 4's should be 1 volt.

Thanks for adding the protect board. Pin 4, mute, should be either 0v or +5v. The power supply schematic shows a +5v mute circuit near IC802. Also, follow what is called "amp-mute" that appears on power board 2/4, and goes off to connector 5 on the dvd board. Don't know if a faulty output IC is causing the 1 volt problem, or if it comes from a previous stage at this point.

Power board 3/4 shows 3 diodes (d304, d334, d364) which perform an OR function for the mute line. The condition of MUTE may also depend on the voltages at FAULT on any of the output IC's. I'd proceed with along these lines for a bit and see if one output IC looks more suspicious than the others.

Pins 10 and 13 of the output IC's are audio input pins. Should be pretty easy to see if audio is getting to the ic. The dcap lines are associated with the internal 300KHz charge pump. The data sheet says you should see a 300KHz square wave. For now, if you see anything that looks even close, I'd give it a pass. If nothing, then I would worry about that particular IC.

Pin 6 overload on IC361 is strange. It should also show either logic high or logic low, to show an audio input overload situation. Square wave output - are you feeding a square wave input to the audio input pins?

You should have the 22 volts indicated on pin 29 CHARGE PUMP. It will probably not be smooth d.c. None of the IC's look good on this pin. Have a look with a scope on pin 29.

Thanks

[Longbow]

Re: Sony HCD-300S problem²

A couple of corrections after looking through the data sheet. The MUTE pin (11) determines that 1 volt is the crossover voltage between MUTE ON (low input) and MUTE OFF (high input). In other words all 3 mute pins are right on the edge, which indicates a faulty or leaking part somewhere else. According to the d.s., you would expect below 1 volt (near ground) to be in the MUTE state, and 3.5 volts (or higher) to be in NOT MUTE. Sounds like TTL levels, which may be coming from the protect board.

This chip has a basket of fault and overload protection and is supposed to tell you where to look if it doesn't work. FAULT outputs, pin 18, are all low indicating no output short circuits or thermal failure. No info from that one.

Test conditions should be to feed -20 dB sine wave into the audio inputs via the rear panel input jacks. Use 8 ohm loads on the speaker outputs that have no common connections, and no connection to ground. Use an isolation transformer on the amplifier before using the scope (or use a differential input scope). Note that the negative speaker output (-) is NOT at ground, so measure across the speaker output terminals (or load resistor) and not from speaker (+) to ground!!!

[jarl]

Re: Sony HCD-300S problem²

Thank you Longbow,

That's a truckload of good leads I'll go over the testing later on... I'm catching up with stuff that got behind because of Christmas, so there's not as much time available as I would like...

[djpc47]

Re: Sony HCD-300S problem²

Jari, what was the actual solution for fixing the right front speaker.... I've the same issue on my dav-s300, was it just a matter of replace the TA2020-020 for the right channels + maybe caps or what? or did you end up fixing it?