3.3v GD-ROM and 5v GD-ROM

[LSL]

Hello!

I bought a VA1 at the end of the 2000s, it came without GD-ROM. In 2020, after my VA2.1 had a defect I decided to buy a GD-ROM for my VA1, after research I bought a 3.3v GD-ROM on AliExpress.

I remember that the GD-ROM 3.3v worked when it arrived, but I don't remember if it works with Dreamcast game disc + music CD or just with music CD.

I tested my VA1 in the last few days and it only plays music CDs, it doesn't play original Dreamcast discs or CD-Rs.

In December a VA0 arrived for me from Japan, it had a problem with the GD-ROM, a broken track and I fixed it. So when I looked at the VA0 GD-ROM board I realized that it was the same model as the VA1 GD-ROM.

With an oscilloscope I measured all G1 pins of the GD-ROM connector, in VA0 the GD-ROM works with a 5v signal and in VA1 the GD-ROM works with a 3.3v signal.

I did a recap on the GD-ROM 3.3v card, but it didn't improve, it can even read a Utopia CD-R, but it can't read the original Dreamcast CD.

I took the R48G from the GD-ROM 3.3v and put it in the GD-ROM 5v and it works perfectly, reads CD-R and original discs, but when I go back to the GD-ROM 3.3v it doesn't read the original disc.

So, comparing these 2 GD-ROM boards, they are the same, IC5 has the same label: 313-5691. There is a difference in the sub-label, at 3.3v it is 0038HAI U16212 and at 5v it is 0039HAI U20055.

Does this difference in the sublabel indicate the difference in operating voltage or is it just batch information?

I wanted to test the VA1 GD-ROM board on the VA0, but I'm afraid that the VA1 GD-ROM board (3.3v) is not really compatible.


3.3v board



5v board

So, do I test the 3.3v board in VA0?

[LSL]

I reread my first topic and realized I wasn't very clear. I was very tired from the day at work, today was no different.

The question is the following, there are 2 types of GD-ROM, one that works with 3.3 volts and the other with 5 volts. By Katana board, you can know which type of GD-ROM is used, which can be confirmed by checking the voltages of the GD-ROM connector on the Katana board with the oscilloscope.

How do you know if a GD-ROM card is 3.3 volts or 5 volts if both types use the same SOH R48G optical lens and use the same card (reference 171-8129A) with the same components and the same references? This is my case, if I compare the 2 GD-ROMs the only difference is in the shield metal.


Left: 3.3v - Right: 5v


Board 171-8129A

Is there something on this board (171-8192A) that identifies that one is 3.3v and the other is 5v? From what I saw practically everything is the same and the difference is the IC5 sub-label, today I found a photo of the same 171-8129A board with a third sub-label and this was a board described as 3.3v on the shield metal.


3.3v GD-ROM board


5v GD-ROM board

My question is, with two boards of the same model, with the same components, will it work on both 3.3v and 5v?

Does anyone else have a GD-ROM with this board? And what voltage does it work with?

The 3.3 volts GD-ROM is having difficulty reading, but the SOH-R48G is fine because I put it in the 5 volt GD-ROM and it worked without problems with CD-R and original discs, but when I returned the lens to the 3.3 volts GD-ROM the same SOH-R48G does not read games, only music disc. I changed the capacitors on the 3.3v GD-ROM and the reading difficulty continues. I tried to adjust the trimpot, nothing changed, the remaining test is to connect the 3.3v GD-ROM to the VA0 model, but I'm afraid of damaging it, even though the GD-ROm has the same components as the 5v model.

[truemaster1]

you can try 2 things. first put the 3.3v gdrom in the va1 system. load up utopia and then swap an original disk. 2 take from 5v gdrom board the lens mechanism and put it on the 3.3v gdrom board and test with the va1 system

[LSL]

you can try 2 things. first put the 3.3v gdrom in the va1 system. load up utopia and then swap an original disk. 2 take from 5v gdrom board the lens mechanism and put it on the 3.3v gdrom board and test with the va1 system

Thanks truemaster1!

1- I already tried to do this before writing this topic, but it didn't work;
2- I thought about this option, but I'm afraid of damaging the 5v GD-ROM, even though I know that 3.3v won't damage a 5v device (the VA0 is the only Dreamcast that works perfectly, I don't want to damage it).

* I have a VA2.1 which has no audio and no video and the VMU only beeps and doesn't show anything on the display. I will write a topic just for him.

[truemaster1]

the 2 option is to take the motor-lens only from the 5v gdrom board and put it on the 3.3v gdrom board and test with the va1 mainboard. but if you afraid do so, do this take va2.1 motor-lens and put it on 3.3v gdrom board and test. if i remember correct the pins of motor-lens of the va2.1 can be fitted on 3.3v gdrom board. also on va2.1 the gdrom board is one with mainboard but like va1 is 3.3v

[MoeFoh]

Let us know the results if you decide to test the 3.3v drive system in the VA0 Dreamcast.

[LSL]

the 2 option is to take the motor-lens only from the 5v gdrom board and put it on the 3.3v gdrom board and test with the va1 mainboard. but if you afraid do so, do this take va2.1 motor-lens and put it on 3.3v gdrom board and test. if i remember correct the pins of motor-lens of the va2.1 can be fitted on 3.3v gdrom board. also on va2.1 the gdrom board is one with mainboard but like va1 is 3.3v

I worked in this Dreamcast yesterday (12/31) and today (01/01) and I found the problem, first I will say what did I do:
1- I put the 5v GD-ROM in VA1 and it worked like seem as if it were in VA0. No reading problems. I chose not to perform the inverse test, placing the 3.3v GD-ROm on VA0, but I believe that at least on this model of board that I have, the units are interchangeable, remembering that they are the same board model with the same laser model, but different operating voltage GD-ROMs.
2- Swapped the mechanic block(plastic part with spindle and sleed motors and lens rail) and the R48G from VA1 worked perfectly. This test confirms that the 3.3v GD-ROM board is good.

The point 2 indicates that the problem is in mechanic block from 3.3v GD-ROM, but spindle e sleed motors are good and the problem would be the disc clamp and/or lens rail.

Do you remember that I said that I bought this 3.3v GD-ROM from AliExpress? Problaby they misaligned the entire block because the screw that adjust the lens rail height was glue point dislocated.



The clamp disc height was below if compared with 5v GD-ROM and the measure from R48G trimpot was 432 Ohm.

I adjusted all height comparing from 5v GD-ROM mechanic block and put R48G trimpot to 696 Ohm (same value of R48G from 5v GD-ROM).

After this I got better results but adjusting heights is a time-consuming and tiring job, a millimeter difference and the behavior is different, I already have an operating range for the screw that adjusts the lens rail and at the end I will readjust the trimpot value.

thanks for the tips, truemaster1!

Happy new year!

[LSL]

Let us know the results if you decide to test the 3.3v drive system in the VA0 Dreamcast.

I confess that when the VA0 arrived at the beginning of December, I put the 3.3v GD-ROM in the VA0, but I didn't test it with a disc, I just checked that the motors were rotating and that the lens was moving in focus. Test for a few seconds.This GD-ROM already had a reading problem before testing on VA0

[LSL]

What is the minimum trimpot adjustment value for the R48G?
In this 3.3v GD-ROM it came with 342 Ohm, in VA0 the value is 696 Ohm.
I adjusted it from 342 to 696 Ohm, but I'm not successful, I remember that when I only put the R48G of VA1 in VA0, with the value adjusted to 696 Ohm, it worked without problems, but now in VA1 I can't get an ideal adjustment for original discs and CD-R.

I ended up putting in an old SPU3200, the trimpot was at 609 Ohm and I set it to 509 Ohm and it seems to work better than the R48G and with the same height adjustments.

[MoeFoh]

Cool, have considered a GDEMU for the VA1 Dreamcast?