Waveform monitor in place of an oscilloscope to align a VCR?

[Brad]

Bought a waveform monitor/vectorscope for $50 off Craigslist. PDF attached for specs.

Noob question. I want to attempt to align an old JVC S-VHS, following this video. Can I use the waveform monitor to do this, or is a general-purpose oscilloscope required to display the RF Envelope signal?

[locoeskimo]

i've never used it for that. but i think its possible... you have to interpret it different. waveform analyzer is for checking cameras and other video equipment if they passing video of proper singal and color timing and phase. he's checking the video signal out of the video head amp. wave form analyzer checking video at output connector. Different signals

[premiumcapture]

Did this end up working out for you? If not, what did you end up doing?

[pandy]

Oscilloscope will be necessary as large part of circuitry in VCR is not TV like signal...

[JVRaines]

A waveform monitor is restricted to the voltages and frequencies of a video signal. You may have to measure signals outside this range in other parts of the VCR circuitry and for this will need a general-purpose oscilloscope.

[Brad]

I didn't get very far, because I discovered this isn't a normal alignment error. Here is my comment and the reply.

I've got a symptom that looks the same as your example here before alignment, but the degree of error changes every time that I Eject and then re-insert a tape. While checking this, it randomly played a tape perfectly, then was back to a partially-garbled image when I ejected and re-inserted the same tape. Any ideas what's going on? The VCR is a JVC HR-S5500U that I picked up.

It is probably one of the things I showed on the and other VJC videos I have done. The loose guide is a cause of intermittant alignment issues, and the capacitor in the PG pickup can cause the switching point to randomly appear in the picture and resembles an alignment error.

I was shooting video of the VCR internals when I noticed this. I'd say these photos indicate that the guides didn't move at all between inserting the tape and then ejecting it. So it seems to be an electronic issue rather than mechanical; probably the capacitor failure he mentioned.



In the one 37-minute capture I made while playback was working, I didn't like the picture quality anyway. It has the same "dark trailing" to the right of brights as my JVC HM-DH5U, visible on the "N" in the screenshot. So I may just end up dropping this off to 12voltvids and he can make a video repairing it, if he chooses.

A waveform monitor is restricted to the voltages and frequencies of a video signal.

I have no idea what the electrical properties of the RF signal from the test point are. I haven't seen a service manual that describes that. I did get a display on the WFM that looked similar to the oscilloscope view. But since there is no capability for adding a trigger (in this case the head switch / HSW test point) it is constantly rolling horizontally. The WFM sweep has to be set to 2-field mode, so the 30Hz flickering, rolling display isn't very nice to look at.

[davexnet]

I saw a video by 12voltvids where he had a similar problem on a JVC HR-s3910 .
He solved it by removing the flat ribbon cable from the control head from both ends and reseated it.

His theory was there was one or more poor contacts and the sync pulses were sporadic

If I remember correctly, he also put a small drop of DeoxiT on the ends of the ribbon cable.
Be careful if you try that, it may undermine the cable and the metal figers may part company
with the backing plastic (I've seen this happen)

[Brad]

The recent one? I don't think the symptom is the same. He was getting intermittent picture. Mine was 100% stable during the 37-minute capture where it happened to play nicely. When it appears misaligned, it also seems to be stable in terms of where the garbage on-screen, with the exception of when it jumps around or flips from top to bottom due to failure of the video decoder to lock VSYNC (display side, not playback side).

[davexnet]

The recent one? I don't think the symptom is the same. He was getting intermittent picture. Mine was 100% stable during the 37-minute capture where it happened to play nicely. When it appears misaligned, it also seems to be stable in terms of where the garbage on-screen, with the exception of when it jumps around or flips from top to bottom due to failure of the video decoder to lock VSYNC (display side, not playback side).

Yes that's the one, sorry to hear it may no be relevant. I've seen similar problems helped either by the cable issue
or by careful cleaning of the control head. But I'm not a professional repair guy so my understanding is limited.

Doesn't the automatic tracking try to kick in when the noise bars appear on the picture? Seems your theory
is correct, a mechanical issue.

[pandy]

I haven't seen a service manual that describes that. I did get a display on the WFM that looked similar to the oscilloscope view.

In true SM waveforms and ways how to verify correctness are clearly described, also proper stimulus (signal source) is required (and described).

[Brad]

I said my theory is electronic issue.

There is an indicator on the front panel when the "DIGITAL AV TRACKING" is engaged, but I haven't seen it visibly searching, so I think it finds a lock immediately. Messing with the manual tracking just screws up the part of the image that isn't already grey.

I haven't seen a service manual that describes that. I did get a display on the WFM that looked similar to the oscilloscope view.

In true SM waveforms and ways how to verify correctness are clearly described, also proper stimulus (signal source) is required (and described).

Here is the page from the JVC HR-S5500E service manual that I found online, since I couldn't find a free source for the US version and I'm not interested enough to buy it. The only numbers provided are ratios.

[premiumcapture]

Thanks for the feedback, I was actually just looking to buy a scope for aligning VCRs myself rather than ship them out to have someone do it for $100 a pop.

Any recommendations on scopes?

[pandy]

Datasheet for IC's are your friend - voltages are usually provided there - i can assume that same IC will share large part of SM between different models...

[premiumcapture]

Don't know what any of that means to be honest. Planning to use it on AG1980s that show a 35mhz minimum for measurement according to the service manual.

[JVRaines]

I'd say these photos indicate that the guides didn't move at all between inserting the tape and then ejecting it.

What counts is the position when the tape is loaded. It takes only a minute change to screw up the picture. Make sure those guides with the slant poles have no up-and-down play and that they travel all the way to the stops when the tape is loaded.

[Brad]

What counts is the position when the tape is loaded. It takes only a minute change to screw up the picture. Make sure those guides with the slant poles have no up-and-down play and that they travel all the way to the stops when the tape is loaded.

Hmm, fair point. Unfortunately the mainboard covers the loaded position of the guides. I'm not sure I'll ever get the thing back together if I disassemble that from the body.

[JVRaines]

Now, where is the fun in that? Chapter 1 of the service manual tells you how to pull it apart. Looks like just one screw to remove and then you can flip the video board out of the way.

[Brad]

Oh, I completely missed the fact that the black terminal board with the RCA/S-Video jacks is all one piece with the mainboard that pulls upward completely. I thought I would have to separate them and pull towards the front of the unit. That was simple indeed. Thanks.

EDIT: Eww.

[JVRaines]

Don't eat jelly doughnuts when you work on the VCR.

Seriously, where'd that gunk come from?

[raffriff42]

>where'd that gunk come from?
It's a for mechanical strain relief and stabilization, aka staking.

http://www.directindustry.com/prod/master-bond/product-17407-400723.html
https://www.linkedin.com/pulse/staking-potting-electronics-high-shock-vibration-sean-thomas

[Brad]

Oh. I assumed it was leaked electrolyte. I see now that the first Google result for "leaked electrolyte" quotes Wikipedia's capacitor plague article:

The leaked electrolyte can be confused with thick elastic glue sometimes used to secure the capacitors against shock. A dark brown or black crust up the side of a capacitor is invariably glue, not electrolyte. The glue itself is harmless.

I was actually just looking to buy a scope for aligning VCRs myself rather than ship them out to have someone do it for $100 a pop.

Any recommendations on scopes?

Guess no one here has a suggestion. Did you see this DFAQ thread?

[JVRaines]

You can get a decent digital scope for $300-400 at Amazon. I wouldn't spend the big bucks on a Tektronix unless you're planning to make money with it.

[davexnet]

I said my theory is electronic issue.

Yes sorry, that's what comes from having only one eye on what you're doing, as I was surely guilty of.

Wish you luck on your project

[pandy]

Probably something like Rigol DS1054Z will be more than enough... of course you can buy some used decent HP/Agilent on ebay - if you live in US i would contact with this guy http://stores.ebay.com/watronics92/