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-   -   JVC HR-S5990AM gives large number of dropouts? (http://www.digitalfaq.com/forum/vcr-repair/12173-jvc-s5990am-large.html)

servese43 09-13-2021 04:03 AM

JVC HR-S5990AM gives large number of dropouts?
 
1 Attachment(s)
(Hardly surprising because this unit was a $20 ebay gamble)

Hi everyone,
My HR-S5990AM has given me a large number of dropouts (comets) on every tape I've thrown at it. I put the same tape(s) in my old 2-head Panasonic VCR I had lying around in the garage and the Panasonic gives me much fewer dropouts. It's safe to say the JVC is definitely the item at fault here. I've tried cleaning its heads and they're clearly not the issue (barely any dirt came off on the paper) and tried manually adjusting its tracking, which didn't help either. What do you think the issue could be? Do you think it might have gone out of alignment slightly? (a known issue with these particular decks)

I've also attached a sample of the ABC's tasteful mid-80s ident captured using my troublesome VCR. The sample does a pretty good job at showing the large amount of dropouts I get.

latreche34 09-13-2021 09:30 AM

I don't see a lot of drop outs in that sample, and no comets at all. Could you attach a sample from the working VCR to see the difference that you are seeing?

servese43 09-13-2021 07:01 PM

I'm probably using the wrong language to describe it then. There are a lot of "horizontal lines" (dropouts?) towards the end of the sample. Dropouts appear at a similar rate throughout the whole video (and every other video I've put in the VCR) which really isn't ideal. Definitely a lot more than what I get with my Panasonic. I'll do a capture of the same bit using my Panasonic VCR after I get home from work.

latreche34 09-13-2021 07:54 PM

One of the causes of excessive drop outs when the tape works fine on other VCR's is head wear, When the heads wear out they loose firm contact with the tape and the DOC goes nuts trying to make up for the signal loss, One of the remedies is to add more tension to the tape by re-adjusting the tape tensioner to increase head-tape contact (see service manual how to adjust tape tension). This only buys you more time, the head will eventually wears out more and needs to be replaced which means get another VCR.

Again the sample you posted doesn't indicate such scenario, so I don't know exactly what are you referring to.

RobustReviews 09-14-2021 05:08 PM

Agree: it sounds like head wear.

JVC heads are usually 'harder' than Panasonic ones, that's about the only positives I've found with JVC video machines - they were distinctly seen as 'mid-market' here - I've always found them quite inferior machines to Sony or Panasonic for VHS and the transport components are clearly a lot cheaper than Panasonic or Sony machines of similar cachet.

It may need adjustment, you'll find plenty of guides showing how to adjust the transports in these machines but remember to go very carefully with this.

Failing that it could be a DOC that needs adjustment, but I find that's usually more of a Betamax issue - that said we often tweak our standalone deck DOCs with much improved results. Don't do this blindly though, it needs a bit of knowledge and careful adjustment as it's a fine line these things tread.

servese43 09-14-2021 06:00 PM

4 Attachment(s)
Thanks for all the tips. I was quite busy last night but I hopefully should be able to capture a sample tonight.

Apparently these lower-end JVC units are known for going out of alignment, so that's probably the issue. I'd like to narrow down what exactly is the problem before I start messing around with that though.

-- merged --

Here is a sample from my Panasonic. It does have a few dropouts, but still much fewer than what I get with my JVC.

-- merged --

Here are a few side-by-side images (JVC on right) showing how the JVC has dropouts where the Panasonic doesn't:

hodgey 09-15-2021 09:29 AM

I'm not sure if it's the root cause here, would have to look at the clip in detail, but I've noticed that there is some oddness about the dropout-corrected lines on JVCs of these years. They end up not lining up and miss detail which tends to make dropouts much more noticeable, and on the Philips VR1100 we got if it's more than a line or two it throws off the TBC in the deck. Idk if it's some error or a design flaw, I've seen it in a bunch of clips now. Of the decks I've used myself, my 1998 HR-J658 and HR-S8500 do not do this, the newer Philips VR1100 (HR-S7700 ish) and J681 does, while my late model XVS20 combo does not.

timtape 09-15-2021 05:14 PM

In the first comparison image I see what you call comet tails on the white dots or stars but I wouldnt call that dropout. Wouldnt the technical term for the tails be ringing?

servese43 09-15-2021 05:48 PM

So the issue is likely caused by the dropout compensation then? Are there any other tests/samples you'd like me to try/put up that would help with diagnosing the root cause of the higher number of dropouts?

timtape 09-15-2021 06:04 PM

No, I suggested it is not dropouts. Comet tails are not dropouts. They are a continuation or smearing of the signal, a bit like reverberation or echo.

hodgey 09-15-2021 07:10 PM

1 Attachment(s)
Comparing the videos it looks like it's mostly just the panasonic masking the dropouts a bit better, e.g if you look closely on this image, the dropout is present in both, it's a bit hard to spot when it on a single line:
Attachment 14155

There are some spots where the pana lets out some noise on a line but the JVC looks cleaner.
Not seeing any "comet tails" other than at the head switch point.

servese43 09-15-2021 07:34 PM

Just to clarify, I don't think there are any comets in the capture. I just mis-used that term in my first post, thinking it was just a synonym for dropout, but now that I've looked up what comets are specifically, I don't think that they're any in my captures.

Is there anything I can do to improve the effectiveness of my VCR's DOC (maybe adjusting it like RobustReviews briefly mentioned) or remove the dropouts in software?

RobustReviews 09-16-2021 04:05 AM

Quote:

Originally Posted by servese43 (Post 79897)
Is there anything I can do to improve the effectiveness of my VCR's DOC (maybe adjusting it like RobustReviews briefly mentioned) or remove the dropouts in software?

You'll need the service manual for your machine - I personally avoid JVC at all costs (their cachet seems, in my opinion, somewhat overinflated on here) so I'm not familiar with their procedure.

Most machines have a way of doing it (unless it's fully digitally processed, then you're SOL) but if it's an amplifier stage system there's usually a pot' to adjust it. Like all video machine adjustments, you need to be very, very careful as small adjustments can have massive (and often detrimental) impacts.

Alternatively, there's plenty of software options to try and recover it. We've dialled in some settings in the new Topaz 'engine' which is very good at seamlessly removing dropout lines, but AviSynth I'm sure has a range of options.

Unless you understand how a Dropout Compensator works, I'd go with software options.

hodgey 09-16-2021 04:17 AM

On late-model VRCs like this the DOC is not really adjustable even though it is analog. Older ones often had trimpots for adjusting the level of the delayed signal, and even older ones may have more adjustments but these modern ones were designed to be mostly adjustment free (newer VCR video ICs seem to have some sort of automatic gain control for the delayed signal used for dropout compensation and noise reduction).

servese43 09-16-2021 04:41 AM

So there's not much I can do then. That's a shame. Do higher-end digipure JVC models have better dropout compensation than the lower-end models?

Edit: Would a median of multiple captures do the trick?

-- merged --

Never mind, the dropouts are baked into the tape so a median of multiple captures obviously won't do anything.

lordsmurf 09-18-2021 04:14 AM

I don't think this is DOC related, perhaps variable in-frame timing errors. This is common with nth gen.


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