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DTL-H1002 with corrupt bios

Landlord

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Original poster
Jun 5, 2019
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What are my options here? Is the bios swap-able? I'd like to save this unit. It's for a good friend.

We could just swap the board but that defeats the purpose of having a dev PS1. It's basically just a shell now.

Has this bios been dumped and available online? Does the same bios chip model exist for purchase and is flashing it possible? Is there any Sony trickery that prevents any of this from being done.

Symptoms: Freeze on glitched SCEI boot screen. Runs no games.

Thank you
 

Landlord

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Original poster
Jun 5, 2019
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How do you know its a corrupt bios and not something else?

All I have for now are Whats app pics and the symptoms described by my friend as mentioned in the OP.

Might be able to check it in person next week.

I'd like to open it up and touch a few chips while powered on to see if it has any affects. Will also inspect the board for anything that stands out.

A glitching SCEI screen, from what I've seen before, is most likely a bad bios issue. Correct? I was told now that he was able to get past this screen once and the game loaded for a few seconds then it went to black screen. All other attempts ended up with a stuck SCEI boot screen.
 

l_oliveira

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May 31, 2019
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I repaired such a unit (Blue debug) once and it was the CD drive that was faulty not the BIOS. I replaced the CXD1199BQ chip. I took one from a matching retail scrap board.
 
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Trimesh

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May 30, 2019
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If you are talking about the second screen with a black background, most of the data on that is read from the CD. It's also read in Mode 2 by the boot ROM, so it only has the basic CIRC error checking and not the additional EDC/ECC that a data CD would normally have and is hence very susceptible to data corruption.

So corruption of this screen can easily be caused by bad media, bad CD drive mechanics or faulty CD electronics.
 
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dickibow

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Jun 6, 2019
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Yes, I’d try a known good working laser unit first judging by the symptoms you’re describing.
 
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Landlord

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Original poster
Jun 5, 2019
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I repaired such a unit (Blue debug) once and it was the CD drive that was faulty not the BIOS. I replaced the CXD1199BQ chip. I took one from a matching retail scrap board.
If you are talking about the second screen with a black background, most of the data on that is read from the CD. It's also read in Mode 2 by the boot ROM, so it only has the basic CIRC error checking and not the additional EDC/ECC that a data CD would normally have and is hence very susceptible to data corruption.

So corruption of this screen can easily be caused by bad media, bad CD drive mechanics or faulty CD electronics.
Yes, I’d try a known good working laser unit first judging by the symptoms you’re describing.


The first thing I recommended for him to try is a different laser unit to rule the obvious out. The same laser has worked fine on another console. And from that same console he used that laser on the DTL-H1002 and again got a glitching second screen and no games would start up.

He's using multiple different original CDs from different regions but still got the same results.

I will try to see it in person and mess around with it soon and post results.

Thank you
 

Trimesh

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One thing that it's important to bear in mind with these old (PU-7/PU-8 based) machines is that they are way more sensitive to optical pickup quality than the newer ones are. So you could, for example, have a KSM-440BAM out of a PSone that works with no problems in the PSone, but won't work on the older machines - simply because the new chipsets have more gain margin and much better servos.

I have a test pickup assembly that works correctly in machines that have the old boards for exactly this reason - if the machine won't boot using that pickup then it really does sound like an electronics fault.

If you have definitely verified that the pickup is good, then see if the machine can correctly display the TOC and play audio CDs without dropouts. This is admittedly something of a softball test because it runs the drive at 1x, but it's a good indication that the CD-DSP + RF-AMP/SERVO + BTL driver are basically working and that the fault is probably downstream.

If the CD playback is good, then the thing to suspect is the CD interface chip and it's associated RAM - this will be either a CXD1199 or a CXD1815 depending on the board version, and the RAM is a 256Kb (32K*8) chip that's on the back of the board where the CD interface chip is.

I have also seen cases were a noisy power supply will interfere with the CD operation (especially in x2) - so if you have a spare it's worth swapping just to see if it makes a difference.
 
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l_oliveira

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May 31, 2019
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Newer pickups have more tolerance on them at the ceramic chip binning and because of that it's prone to oscillating. That's why the mechanism has a prong which touches a sponge pad at the back corner. If it oscillates the eye pattern will get disrupted and read quality will drop.