What is wrong with my VCR?

[TinCanAlley]

I am trying to revive a Mitsubishi HS-U50 VCR and after changing a belt that turned to goo, cleaning all the normal areas of the transport assembly, I am left with this (see attached). The image is "rolling" but it's not on the TV end. If I fast reverse or forward, the image sometimes stabilizes for a moment, then goes back. Pause will sometimes provide a decent, stable image. It's hard to capture it with a single image, but what I see is the image as rolling so fast it displays 4 time, each being a 1/4 of the screen. Since I can't uploat video, this is the best I can do.

The only thing I haven't been able to replace yet is the idler tire, but I don't think what I'm seeing is a result of a bad idler tire.

Any assistance will be greatly appreciated.

Also, does anyone know where to find the small incandescent bulbs used for end of tape detection? I have a Fisher FVH-730 that is having loading issues, but I found that the dew sensor light is on and the motor runs while off and I was pointed to the bulb. Upon inspection I found it to be burned out, so I want to replace that and see if all other electrical issues go away before I tackle the tape transport.

Thanks!

[redk9258]

I'm not an experienced technician, but one thing I am learning is the power supply must be right! Do you have a scope? Make sure all voltages are correct and have no ripple. These units are 30-40+ years old now and it's not uncommon for there to be a bad cap or 2 in the power supply!

Is this VCR new to you? Are all of the guides, etc. tight?

For the bulb, can you post a picture, dimensions, voltage, etc? You may have to improvise and substitute something. AK member dgwojo sells bulbs and may have what you need.

[ARC Tech-109]

Doesn't the Mits HS-U series have some sort of timebase correction in them? I had a U-52 before global warming and seem to remember it having some sort of smarts behind the scenes.

[damen]

The small electrolytics Mitsubishi used were prone to leakage. Look for corrosion on the circuit traces where they are soldered and electrolyte leaking down the legs.

[TinCanAlley]

I just put the unit back on the bench for more diags and this time connected it to a small LCD monitor via the composite output. Upon playing a tape, the image was as perfect as an old VHS can look. No rolling, tearing, etc. I am attaching a pic.

So, is it the unit's RF output or my TV? I currently have a laserdisc, DVD and Atari 2600 on the TV's RF and none of them have any image issues.

One thing I did notice, and it might be normal, but I figured I'd ask. When doing FF, the tape is tight from cassette all the way around the transport to the other end. If I FR, the tape gets loose on the right side from the guide arm to the cassette body. I've attached 2 pics of both FF and FR.

Lastly, when I stop the tape, it doesn't fully retract as there is an arm that pulls it out of the cassette when loading, but doesn't put it back until you eject the tape. In this position I can't see to get it to RW or FF. It seems to be doing something, but gives up shortly after pressing either of those controls. Could it be the idler tire I haven't replaced?

Thanks again!

[TinCanAlley]

New update. Upon connecting the VCR to composite to RF unit, it seems to work fine. Directly connected to the TV and it rolls. Figured it wasn't the H-Hold as all other images are fine, but nope, with this one I have to adjust the H-Hold to fix it and then adjust it back for the others. Don't know enough to figure out why, just know now what to do.

Now with a number of tapes, the top of the image is pulled to the left and wiggles back and forth. I seem to remember talk about this issue, but can't remember if it's the limitation of my TV or something else. I think it is unavoidable on at '74 TV, but if not, is there a fix. I've already tried the two video boards from Zenith in my TV. I thought someone noted a certain board revision that fixed, or greatly reduced this image distortion.

Now I'm off to AudioKarma to get help fixing a Sansui QRX 6001 with protection issues. Then power supply fixes for IBM 5150 and TRS-80 model 4. I'm sure my fixit list isn't as long as some here.

[redk9258]

Originally Posted by TinCanAlley

Now with a number of tapes, the top of the image is pulled to the left and wiggles back and forth.

An image stabilizer or TBC would probably fix that.

[TinCanAlley]

Originally Posted by redk9258

An image stabilizer or TBC would probably fix that.

Any inexpensive recommendations?

[TinCanAlley]

Originally Posted by ARC Tech-109

Doesn't the Mits HS-U series have some sort of timebase correction in them? I had a U-52 before global warming and seem to remember it having some sort of smarts behind the scenes.

Nothing that I can tell. It's from '86 I believe and not sure if something like that was common then.

[TinCanAlley]

Originally Posted by redk9258

For the bulb, can you post a picture, dimensions, voltage, etc? You may have to improvise and substitute something. AK member dgwojo sells bulbs and may have what you need.

I'll have to pull it, but it is small, judging by the plastic housing it is in. From the service manual I'm assuming it's 9.5V. I'm uploading the section of the schematic where it shows the end lamp. The SM also gives a part number, but all attempts on searching that number were useless (PN: 4-6124-00020).

[jhalphen]

Hi to all,
Hi TinCanAlley,

About "top of the picture flagging when playing VHS/Betamax tapes":
Before VCRs became common, TVs horizontal AFC had a long time constant to ensure good sync when receiving a TV RF signal from a transmitter, especially with a noisy signal.

Consumer VCRs have jitter and cannot ensure the precise timing of a Broadcast TV station, hence the flagging when replaying a consumer tape.

As VCRs became popular, TVs began to have a channel preset with a shorter time constant to accomodate VCR signals and of course on the SCART/EuroConnector on Euro TVs (i live in the Eu).

Older TVs usually had a maintenance bulletin issued by the manufacturer instructing how to modify the H AFC circuit to solve the VCR flagging issue. It's usually a simple modification involving the change of a few R/C values in the H AFC circuit.

In your position, i would look for the service bulletins from the manufacturer of your exact TV model and find their recommended modification.

VCRs with TBCs are a luxury item which came very late in consumer VCR technology when reasonably priced A to D, D to A and Field/Frame digital storage memory could be offered at consumer prices.
95% of consumer VCRs don't have TBCs and millions of consumers have enjoyed flagless TV playback of VHS/Beta cassettes.

I used to sell TBCs as companions to 1" type C Broadcast VTRs (Ampex Corp).
a TBC was 35k$ to 70k$ in the 80s/90s.

Best Regards
jhalphen
Paris/France
PS: on this topic in VK archives, dated 2013:

http://www.videokarma.org/archive/in.../t-258501.html

Video Monitor modifications; Dropbox file by Cliff Benham (RIP):

https://www.dropbox.com/s/1fw8311noq...ing%20Modifica tions%20-%20HI%20Speed%20Hor.%20Timing%20for%20VCRs.PDF

or here, same file:

https://www.dropbox.com/scl/fi/qm4xa...31c2w7ninl&e=1

General knowledge about TBCs, if anyone is interested:
https://www.digitalfaq.com/forum/vid...time-base.html

[ARC Tech-109]

End bulb looks more to be 12.6v similar to the early Panasonic models. I've used model railroad bulbs for these in the past. Current draw was around 60ma to satisfy the lamp fail detection circuit and the 9v on a 12v bulb ensured long life without becoming a spotlight.

[DVtyro]

Some (most?) DVD recorders have built-in TBC. Some TBCs are better that other.

I made a video about the Panasonic DMR-ES35V - a VHS+DVD recorder with built-in time base corrector (TBC). You can see some samples in the video.

[Dude111]

Hi TinCanAlley

I assume pressing TRACKING CONTROL doesnt stop the rolling??

On my older tapes (WCI HOME VIDEO,etc) it has 'STOP COPY' ON IT and I guess the hold is barely enough to keep it stable on a direct connection but trying to copy it will result in rolling galore I believe......

Those tapes say to adjust TRACKING CONTROL if the picture rolls....

It would be nice if it helped you


Good luck!!

[TinCanAlley]

Originally Posted by Dude111

Hi TinCanAlley

I assume pressing TRACKING CONTROL doesnt stop the rolling??

On my older tapes (WCI HOME VIDEO,etc) it has 'STOP COPY' ON IT and I guess the hold is barely enough to keep it stable on a direct connection but trying to copy it will result in rolling galore I believe......

Those tapes say to adjust TRACKING CONTROL if the picture rolls....

It would be nice if it helped you


Good luck!!

I tried with auto tracking and manual. I can live with adjusting the vertical on the TV.