VCR signal noise during capture

[ghiga_andrei]

Hello all again,

I have an LG VF28 VCR which I want to use to capture some old VHS tapes. Believe me or not, I have bought a Philips VR1100 which is JVC SVHS clone with TBC/DNR but this LG outputs more real detail than the Philips on the sharpest setting. A LOT more detail (on request I can supply proof). The Philips output is more clean though.
For TBC I have a Panasonic ES15 which does a very good job.

My problem is that there is a lot of noise in the output of this VCR. I tried other VCRs with the same tape and that noise is not there.
I tried different cables, composite and SCART and I noticed when using a SCART-SCART connection between the LG and the ES15 there is slightly more noise than when using a composite cable, I am guessing ground loops ? Connecting the LG directly to a TV or capture card looks the same, so it's not the ES15.

I opened the VCR and found the 12V power supply which I think is the AV power and added an additional 1000uF capacitor on that power line but no change.
Maybe some shielding is missing ? I didn't own the VCR when it was new, I don't know if the problem is new or been there since forever, but I guess not.

Turning on the digital NR in the ES15 removes part of this noise but creates other problems which I don't like, mainly on the chroma.

Do you have any more ideas, what could cause this noise ?

I have attached 2 samples (Lagarith). One is with menu screen to see interference noise and one is with diagonal lines during capture, very nasty noise. Ignore the brightness changes, that's from the tape.

[ghiga_andrei]

Strike that regarding Scart vs composite. It's actually that the noise is stronger when cold, just plugged in, and is reduced after half an hour of playing a tape.

Maybe bad caps that have increased Esr when cold?
Power supply caps or AV circuit caps?

[jagabo]

Get a can of freeze spray. Once the deck has warmed up, start playback and spray components one by one until you see the problem worsen. A diagonal line like that represents something close to the horizontal sync frequency. ~15.6 KHz. My guess is it's something in the flying head motor control.

[ghiga_andrei]

I guess i can do that on the power supply components as they are on the side of the mainboard. Kind of difficult with the av circuits as they are placed under the tape mechanism.
Thanks for the idea.

[JVRaines]

May be a faulty shield ground that makes better contact after the parts warm up and expand.

[LMotlow]

I've seen transmission noise that was much worse. Had to give the avi sample a close look, even on the menu sample I've seen a lot more noise. The attached code seems to have got rid of the floating noise. What's worse is the annoying line flutter, which just won't quit, and the rough gradients in large solid-color areas.

Script: (the FixRips2.avs filter was attached earlier as attachment https://forum.videohelp.com/attachment.php?attachmentid=45745&stc=1&d=1527397208). An explanation is in the post at https://forum.videohelp.com/threads/388978-Help-with-very-old-VHS-tapecapture-differen...Rs#post2520814.

AviSource("Drive\path\to\lg_2.avi")
ConvertToYV12(interlaced=true)
SeparateFields()
ChromaShift(c=4, L=-2)
HQdering()
EdgeCleaner()
FixRipsP2()
RemoveDirtMC(30,false)
ReplaceFramesMC2(332,4)    ### <- this is a progressed frame number in SeparateFields version
MergeChroma(awarpsharp2(depth=30).aWarpSharp2(depth=16))
DeHalo_Alpha(rx=2.5)
AutoLevels(FilterRadius=20)

Dither_convert_8_to_16 ()
GradFun3(thr=0.8,mask=0,lsb_in=true,smode=1)
LimitedSharpenFaster
AddGrainC(1.5, 1.5)
Weave()
Crop(16,28,-16,-40).AddBorders(16,32,16,36)
return last

The attached sample output is encoded for PAL DVD spec.

[ghiga_andrei]

I've removed the mechanical drive, got out the PCB and replaced all the electrolytic capacitors on the power supply secondary and some large electrolytics near the SCART connectors and now the picture is clean, no more noise.

Thanks for the effort anyway, especially LMotlow, i'm sure I'll use some of that script anyway.

[jagabo]

Nice to hear a success story!

[amaipaipai]

Did you replace it with the correct types?
Since this switched-mode power supply works with high switching clocks, is mandatory to use a low ESR type 105 ºC capacitors, otherwise this components will heat up with time because of the internal resistance, making matters worse, they can leak, pop, explode, etc. There is a second option if you want to keep this for life, use a polymer electrolytic capacitors, they use a dry polymer instead of a wet one, it has the exact same look as an standard electrolytic type.

You can use a standard electrolytic capacitor on the signal path for video and audio, but never on the power path.

[jagabo]

Just curios... Did any of the replaced caps show obvious signs of problems? Bulging tops, for example.

[amaipaipai]

If the capacitors just dried out, there will be no external signs to be seen.

[wim72]

Were any of the capacitors out of spec, e.g. low capacitance or high ESR?

[ghiga_andrei]

No external signs of bad caps. I don't really care which of them were bad or why, I just replaced all of them (10 caps) and it cost me 1$. I don't have an ESR meter so I don't know.

I was careful to replace them with 105ºC types and I put a little extra voltage ones, like 35V instead of 25V and 16V instead of 10V.
I don't know about their ESR, the store only had 1 type of electrolytics of this temperature.

I'll just use this VCR for a little time to convert a few tapes and then nobody will ever use it again, so I don't really care about long term. But for now, the picture looks noise free and is fine for me.