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Recapped 3DO FZ-1 has no sound

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I recently bought a dead 3DO back to life by replacing the transformer. I'm in a 240v region but since it's a US model, someone plugged it in just using a travel adapter and fried it.

 

It now boots up fine and the comet screensaver plays, but it's completely mute. I just finished a recap using a kit from Console5 but the issue remains.

 

I'm trying to follow the Audio Check flowcharts in the technical guide that's floating around, but I'm struggling to make heads and tails of it. My knowledge of transistors is limited and I think the guide might be for the UK and Canadian variant - I can't locate Q240 and Q260, for instance.

 

As a side note, I plugged headphones into the controller and can sort of hear the ghost of loud sounds (like when a comet flies past the screen), but it's very low and distorted. I'm testing using composite and have also tried RF - but I can only hear static.

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Looking at the troubleshooter, it says to check Q270 first. The audio transistor network is found here

7C290615-B315-4102-B3DE-F40D75C0EA7B.thumb.jpeg.fd8c34a2937e44c078469edc6bda8c46.jpeg
 

Base should be high and collector should be low

 

6727194E-6E20-46CD-A200-985E407B7C29.thumb.jpeg.da33079adc0e543bc3ae61861170bded.jpeg
 

 

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Yep, testing with my logic probe and the base and collector are high and low respectively. Side note: How do you determine what's the emitter, the base and the collector? I found a few conflicting diagrams that swap the base and collector around (Q270 is PNP, right?).

 

With those testing okay, the next section of the troubleshooting chart says to replace Q220 and check Q240 and Q260. What constitutes as "checking" them? Sorry if this sounds basic, but if anything this is a good learning project for transistors for me ha.

 

As for replacing Q220, the parts list in the Service Manual lists a parts number of DETC114TKT97 (transistor, resistor built-in) and is the same as Q240 and Q260. Any clues for a suitable, modern replacement? DETC114TKT97 appears to be a Panasonic only parts number and I'm struggling to find a specs sheet. 

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An update: I borrowed a working CD-ROM drive and the audio plays, but distorted. It turns out the screensaver was mute because pressing the A button toggles the audio on/off (which I discovered by accident). Any clues on the distortion? Would the transistors still be a focus point? I haven't figured out how to test them yet as per the troubleshooting guide. I also spent all afternoon checking the continuity of the caps I just replaced, so I'm happy they're not the problem.  

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It could still be the transistors causing the problem. There’s a way of testing them with a multimeter but it doesn’t confirm they are fully functional. If you have an ‘o’ scope, you could check the wave forms on the audio circuit at the op amp and the rca outputs. It might be worth just replacing Q270, 260, 240 and 220. 
 

After a bit of searching I found some modern drop ins. The code refers to TA(pnp)144(47k embedded resistor) and TC(npn)114(10k embedded resistor). The last part refers to the package type (not sure if SOT-23 or SOT-323). 
 

Here’s some possible substitutes

 

https://www.mouser.co.uk/datasheet/2/115/ds30335-71381.pdf

 

https://www.mouser.co.uk/datasheet/2/115/ds30331-71353.pdf

 

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I have a very basic oscilloscope that cost something like $30 from China haha - so for now, I think I might just be easier to replace them and see what happens.

 

Thank you for finding those modern equivalents. I spent ages yesterday researching how to read transistor codes and never figured it out. I'm a bit confused by the TA and TC codes, however. In the datasheets you linked TC is PNP while TA is NPN, which is backwards to your explanation of the codes and the original parts list:

 

304987482_transistorpartslist.thumb.jpg.aeb6b1632fbd5efe81f707c7bd0d821f.jpg

 

Just to clarify, Q270 is PNP and Q220/240/260 is NPN right?

 

With that in mind, I found these in stock that ship to down-chunder (with $24 shipping 🙄 ). Can you please double-check they're the same thing:

 

PNP Q270: https://www.digikey.com.au/product-detail/en/diodes-incorporated/DDTA144TCA-7-F/DDTA144TCA-FDICT-ND/815546

 

NPN Q220/240/260: https://www.digikey.com.au/product-detail/en/diodes-incorporated/DDTC114TCA-7-F/DDTC114TCA-FDICT-ND/815570

 

I noticed that when you check the datasheets in those Digikey links (which are the same) it's the opposite again to what's on the sale page. Maybe the datasheets are incorrect? Confusing. 

 

Also, I do believe the original transistors are SOT-23. I measured them yesterday with callipers and crossed checked them with a chart.

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The datasheets and web page are correct. It mentions a complementary component in ‘features’ in the data sheet which is what you probably read. At the top it states PNP or NPN.

 

$24 ouch. We’ve been hit by added VAT now in the UK after Brexit 😞 

 

I thought it might be SOT-23, thanks for measuring. Searching the Panasonic suffixes it points towards SOT323. Ah the mysteries of legacy hardware.

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I bought some other stuff and got free shipping haha. I see what they did there...

 

Anyway, the transistors have been ordered. I'll let you know how it goes.

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Replaced the transistors today. While it didn't break anything (thank the gods) the sound is still distorted. Any other ideas? Any tips on troubleshooting IC200?

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The good news is you can rule out the transistors and continue the troubleshooting algorithm. Check the signals reach IC200. I would also double check the cap replacements, specifically C35, C36. These have been known to affect the sound when bad, check for corrosion or the copper traces. There are also some SMD caps near C35 and C36 that might be worth checking. Have you tried scoping the 5V power rail for stability?

 

Also scope all the clock signals to check they are stable and in spec. Good luck.

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C36 and 36 are definitely good. They've been replaced and I beeped them both out.

 

I'm pretty new to oscilloscopes but when I test pin 19 of IC200 (as per the troubleshooting guide) I get absolutely nothing, close to 0v (and no waveform). It actually seems to short-circuit as the audio cuts out completely when I test the pin.

 

Do you think this indicates that the crystal is bad? I've been trying to suss a replacement but all my local electronics store has is a 16Mhz with an ESR of 25ohms. I can't figure out the ESR of the original and it's been rated at 16.9-something MHz instead. Would it still work?

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Have you checked the waveform directly at the crystal? Double check the soldering at pin 19 and also check the signal gets to pin 129 of the CLIO. Check C201 and C202. If the crystal is dead, you’ll want to replace with a 16.9344Mhz crystal. 

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I just want to take a second to thank you for your patience and ongoing help, Taijigamer. Evidentially, this repair is challenging me quite a bit so I appreciate the ongoing assistance. 

 

I measured the crystal directly and even though I got a fairly erratic signal (which I think is down to my cheap-o oscilloscope) it seems to range close to 16 KHz instead of MHz. Could be to do with the scope itself or the way I'm using it. This is my first time using a scope for a repair.

 

PXL_20210406_122800278.thumb.jpg.837add93b58438a277fe2b26269a4b90.jpg

 

I gave pin 19 a splash of fresh solder but I still get the same result - it shorts when I try to test it (and the audio cuts out). I beeped out where it's supposed to go and everything checked out. Just to clarify, I can attach the ground probe to any ground on the board? And then touch pin 19 with the positive probe to get a reading? As I said, it could be user error on my behalf since I'm so new to using a scope. I'm using the same settings to do this as the image above when I directly test the crystal (although in that case I'm touching each probe to each side of the crystal).

 

As for the XACLK line, a waveform does measure between pin 19 and 129 of the CLEO (again, one scope probe on each end). Whether it's the right one, I'm not sure. The pins on the CLEO are so tiny, it's hard to just get a reading on the one pin lol. I also checked the continuity along XACLK and everything seems cherry.

 

Following on from that, I read further into the troubleshooting diagram and (I think) I successfully measured between the AUDBCK, AUDWS and AUDDAT lines back to IC200.

 

As for C201 and 202, I was unable to find a way online to test ceramic SMD caps. What I do know is that they have continuity going to the right places and using the diode test on my multimeter I know they're not shorting to ground. I desoldered one to test out of circuit but my meter measured nothing in capacitance mode. I don't think it goes down as far as picofarads. 

 

 

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