Anyone got RGBHV out of this YPbPr to VGA converter

[asprinwizard]

Hi,

I bought this relatively cheap converter to convert a YPbPr component signal to RGBHV (VGA). I got no signal from my LCD monitor, and a rolling image on my CRT. After some investigating it seems I get no output from the VSYNC pin on the DB15 socket. The HSYNC pin is outputting some kind of pulse but the VSYNC is merely a flatline. See images below:



I looked at the PCB looking for some kind of jumper to toggle the RGB mode but there doesn't seem to be anything there. It is advertised as offering RGBHV/VGA so I should be possible, why else is there a DB15 connector? but perhaps this description is erroneous. Can anyone shed any light?

Thanks.

[fidde_se]

Measure pin 13 (V-Sync) and pin 14 (H-Sync) of LMH1251

[asprinwizard]

That's a very good question. I checked this evening and can confirm the same output coming off the chip as in the images I posted, i.e. nothing on vsync.

Any idea what might be going on here?

[fidde_se]

I would actually assume somethings wrong with the chip itself.

As in Component in the Y (green) is sent both to pin 10 and 11, and if sync is present on pin 11 it's divided into pin 13 (V) and 14 (H).

And you got sync on pin 14 (H) meaning you do get sync into pin 11 otherwisw you would get nothing, so something inside the chip must be at fault.

[Guspaz]

What resolution is the signal you're feeding in? Is the LMH1251 set to auto or manual format detection mode (is pin 23 high or low)?

It'd also be worth checking pin 24, which should be high (YPbPr input), but I can't imagine why it wouldn't be unless there was a defect.

[asprinwizard]

Thanks. I will check those pins. The input is 480p@60 but tried different resolutions and the same seems to occur. I had hoped I just had a dodgy unit so I ordered one from Amazon (different seller) but that had exactly the same issue. I think I will need to experiment with different sources. I definitely had it working previously so the source is the only variable I can think of.

The board has no jumpers or settings like the Garo Lite does. I'll also check the scart outout although I assume that needs a 15khz source?

Thanks again.

[kitty666cats]

Pin 13 is Hsync and Pin 14 is Vsync.

Unless you’re saying you’ve used this transcoder before and for some reason it’s got the two syncs going to the incorrect pins…


https://www.js-technology.com/store/ind ... er=product

Or you could spend more and get this, and likely have no problems at all

[Guspaz]

vsync is going to have a sync pulse much less often than hsync. For 480p60 input, you will only have a vsync pulse for every 525 hsync pulse. Is it possible that you're just missing the vsync pulses since they happen so much farther apart?