Turbo Duo CD-ROM drive having trouble reading discs when using RGB Amp!?

[RGB32E]

I finally got around to building the RGB amp for my Turbo systems! (2SC1815 based)  

Unfortunately, for some reason, when I play CD based games in my Turbo Duo, the CD-ROM drive starts making more noise, and cannot read discs!  It will try - disc spins, and optical pickup moves to attempt reading, but it just doesn't work (doesn't appear to load data)!  When I connect the standard composite cable, everything works fine!    Very ODD!  HuCard games work without any issues...

So, I'm planning on making a better cable (one that includes audio) and see if my results are different.  During the RGB mod for the Turbo, I replaced the 5 pin din with an 8 pin din.  I cut the length of the 3 additional pins (top left/right, and center) so that they had 3 mm or so of space from the PCB.  I did the same for the leg that would normally carry +5VDC so that I would have a pin to output CSYNC.  For me, +5VDC is useless to have on the connector, as I'm not connecting the system to a SCART input, and I'd like to retain the composite functionality and didn't want to install a switch on the side of the system - swaping the 5 pin din for and 8 pin version is all the more modified like to make my system appear...

Anyways, I'm tapping +5VDC from the din connector (DIN connector pin not attached) to power the RGBS amp circuit.  Would there be a better place to obtain the +5VDC from?

Please let me know if any of you have had issues with your CD-ROM when using amped RGB.  Thanks!

[Hamburglar]

You can get 5V off any nearby dip IC or a 7805 regulator,  If it was your circuit you'd think that the problem would show up if your cable is connected or not...

Where's Viletim?

The Duo is a strange beast, I remember I had one that would refuse to load discs if I had it on the floor, but played fine on a table, another one where my hand getting close to the cd lid would cause the audio to "crackle" ultimately going out.

Right now I am doing a Super CD ROM2 RGB mod, whenever a CD game is loading data, I get interference, it does not appear to be a ground problem, since I have connected to many ground points on the board with varying gauges of wire with no difference.

[RGB32E]

Where's Viletim?

... He's probably on the outback chasing dingos!

[RGB32E]

Well.... I built another RGB cable for my Duo and... viola... issue resolved!  The cable I was having difficulties with was one I built quickly to test out the amp and mod on my PVM-2030.

Now, it is my understanding that some games on this platform use some sort of dithering pattern to combat the composite video encoding???  I've always heard that the NEC systems have some special sauce when it comes to composite video, but in the end, it is still composite video...  Basically, I'm noticing a grid like pattern on the RGBS output from my system.

Also, after amplifying the RGB, I noticed some of the same issues as my Genesis 2 (caused by sync)... where the left hand side of the image has a slightly higher brightness than the rest of the image.  I'm dreading opening the system again, but I think that if I add the redmond cable sync separator and amp in addition to the RGBS amp, that I will improve the output of the Turbo Duo's RGB section...  Hmm... there's always something to improve upon...

[NFG]

Basically, I'm noticing a grid like pattern on the RGBS output from my system.

I get this too.  I think someone mentioned it was 'cause of the amp itself?  Doesn't bother me much in any case...

[RGB32E]

Basically, I'm noticing a grid like pattern on the RGBS output from my system.

I get this too.  I think someone mentioned it was 'cause of the amp itself?  Doesn't bother me much in any case...

This is what I was referring to:

The PC-Engine's composite output is generally pretty good, but colours still blur together a bit, especially visible in the reds of Dracula X. One thing that should be noted is that the PCE has the ability (a feature?) to have its dot-pattern averaging turned on or off. Most games by Taito and NEC Avenue usually have it turned off, making the composite display much worse looking. The composite shot from OutRun above shows this -- indistinct pixels, and an unsightly dithering pattern on bright reds and greens. Needless to say, RGB video looks almost perfect.

from
http://www.disgruntleddesigner.com/chrisc/gotRGB/screenshots.html#pce

[Endymion]

I dunno man, that just looks like 16-bit artwork to me.

[RGB32E]

Hmmm....

What ever happened to the thead containing a more extensive RGB amp for the DUO?  I recall it was posted by someone in Japan?  It had a section using standard transistors followed by a video amp IC?

Also, has anyone used a Sony CXA1145 to amplify Turbo/PC Engine RGB?

So, it seems that there are 4 routes for amplifying RGB from an NEC system:
-Simple 2SC1815 single transistor route (mmmonkey)
-NFG 2SC1815 full circuit
-??? Multi stage amp (posted on this forum somewhere)
-CXA1145 RGBS outputs

[Endymion]

Is this the one? I guess I can kinda see a fine grain to some of the images but it looks entirely altogether more pleasant to me than the typical overbrightness, bleeding and other general issues of the standard signal. I'd just chalk it up to seeing it as it actually should be drawn for a change.

[RGB32E]

Yup, that's the thread I was referring to!  Thanks!

I'm tempted to build this amp as well.

[Hamburglar]

I'm amplifying with a CXA1145, I've done it before on stand alone systems with amazing results, (i've tried about 3 different amp circuits and nothing looks as good) but on a Super CD Rom2 with PC Engine I get some sort of interference/lines moving across the image- on certain screens, and when the CD drive is accessing data.

[RGB32E]

I'm amplifying with a CXA1145, I've done it before on stand alone systems with amazing results, (i've tried about 3 different amp circuits and nothing looks as good) but on a Super CD Rom2 with PC Engine I get some sort of interference/lines moving across the image- on certain screens, and when the CD drive is accessing data.

Please add detailed pictures of your amp!!  Also, what connections to the CXA did you make?  What additional parts?  DETAILS please!

Also, where did you get your CXAs?  Did you harvest them from Genesis 1s or SMSs?

[Hamburglar]

Please add detailed pictures of your amp!!  Also, what connections to the CXA did you make?  What additional parts?  DETAILS please!

Also, where did you get your CXAs?  Did you harvest them from Genesis 1s or SMSs?

I followed the cxa1145 schematic, you need to connect sync in, add caps on the RGB inputs and outputs, 27K 1% resistor on pin 13 and gnd/vcc of course.

I took the first cxa1145 off of a Amiga CDTV video module, it had RGB out, S-Video all hooked up.. I have since got them off dead Genesis consoles.

I'd rather get CXA1165 DIP parts since you can add S-video so easily, but haven't found a decent source for them.

[RGB32E]

I followed the cxa1145 schematic, you need to connect sync in, add caps on the RGB inputs and outputs, 27K 1% resistor on pin 13 and gnd/vcc of course.

I took the first cxa1145 off of a Amiga CDTV video module, it had RGB out, S-Video all hooked up.. I have since got them off dead Genesis consoles.

Does the attached image describe your circuit to a t?

Connections:
Pin
1. GND
2. Pin 49 from HU6260 through a 0.1uf cap
3. Pin 47 from HU6260 through a 0.1uf cap
4. Pin 51 from HU6260 through a 0.1uf cap
5. NC
6. NC
7. +5VDC
8. NC
9. NC
10. Pin 44 from HU6260
11. CSYNC OUTPUT (cap and resistor)
12. +5VDC with 100uf cap to ground
13. 27Kohm resistor to ground
14. NC
15. NC
16. NC
17. NC
18. NC
19. +5VDC
20. NC
21. BLUE VIDEO OUTPUT (cap and resistor)
22. GREEN VIDEO OUTPUT (cap and resistor)
23. RED VIDEO OUTPUT (cap and resistor)
24. GND

My main concern is whether or not the subcarrier circuit needs to be implemented for the use of a RGB amp?  Do pins 5 and 6 ONLY need to be used if generating a COMPOSITE VIDEO signal?

[Moosmann]

I also have some Problems with the "black" PCE DUO & RGB. The reason is noise in the 5V Voltage or similar (I don`t have an Oscilloscope at the moment, but get them in 3 Weeks, however no old DUO here) in the old PCE DUO (not R and RX).

If you connect a 47uF Capacitor between GND and 5V from HU C6260 Pin 41 & 25, take 5V for the Amp directly from the 5-Din Connector-Pin and hold the 5V wires for the Amp as short as possible (maybe you still need a 10uF Capacitor between GND and the 5V Directly on the Amp) the picture is fine. However, it doesn`t work on all DUOs with the same values and/or types from capacitors.

Greetings Markus

[Hamburglar]

If you are using RGB only, then you can get away by not connecting pins 5 and 6, before you try it though, It seems the RGB levels are too weak coming from the hu6260, there's some sort of interference on certain screens, I can see it well on the Super CD Rom bootup screen, Street Fighter 2 does not show it, last night I found that by connecting a small simple transistor amp circuit I had laying around before the CXA1145 the "interference" was gone...

However, now the image lacks some detail because it seems the image is too bright, like on a Genesis 2 without the 75ohm resistors in series on the RGB lines.
I'm going at this the wrong way, I need an oscilloscope to see what's going on.

What I intend to do is create that "buffer" circuit off of that Japanese DUO RX RGB mod site and fit it before the CXA1145- need to stock up on resistors though

[RGB32E]

If you connect a 47uF Capacitor between GND and 5V from HU C6260 Pin 41 & 25, take 5V for the Amp directly from the 5-Din Connector-Pin and hold the 5V wires for the Amp as short as possible (maybe you still need a 10uF Capacitor between GND and the 5V Directly on the Amp) the picture is fine. However, it doesn`t work on all DUOs with the same values and/or types from capacitors.

Yeah, I was thinking of trying something like that (adding a 100uf cap between GND and +5VDC on the board I built my amp on... I will be building another amp soon and will give that a try... (plus side of the cap to +5VDC and the negative end to ground).

[acem77]

Crap did not know that.....
i bought another duo just cuz i thought the drive was bad many moons ago... the new one did not work much better. many cd loading problems.
just thought it was age of the hardware...

[RGB32E]

Adding a cap between +5VDC and ground for "decoupling" didn't fix the jail bar interference... so it seems that the capacitor needs to be added to the chip directly.  I've ordered a similar type of capacitor (lower V) than the one perscribed by bakuchikujuu to try and remedy the issue.

As mentioned on another thread in this forum, the NJM2267 video op amp can be ordered in the US easily from Mouser and start at $0.51 each:
http://www.mouser.com/ProductDetail/NJR/NJM2267D/?qs=sGAEpiMZZMutXGli8Ay4kLm6t8Ls16dYBLnNV8%2fCckc%3d

So, I will be building bakuchikujuu's amp soon (once all of the parts arrive)!

Looking at the original site for the amp, I don't understand where user "vkp_ashley" got the idea of using a 1000uF cap BEFORE the op amp (buffer section I reposted before in this thread).