Yet more VCR help needed....

[fmctm1sw]

I picked up a Japanese version of this today: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=15074&item=3865747779&rd=1&ssPageName=WDVW

The audio makes a helicoptor type noise and the picture looks as though the heads need cleaned. I cleaned the heads but still have unviewable picture and this audio noise. Sorry, this is a shorter version of a post I typed up before my computer crashed. Any ideas?

*edit* Hmmm, not good. I did a comparison with my 8mm camcorder and it looks as though the tape is moving faster in my camcorder. This leads me to believe the capstan isn't turning fast enough.

[samijubal]

Clean the audio/control head with alcohol and a q-tip, that's what controls tape speed. How did you clean it? You need to use a chamois that's made for head cleaning on the video heads. The only good ones I've ever seen are Chemtronics.

[fmctm1sw]

I cleaned the pinch roller with alcohol and Q-tip because I figured it was slipping. No change. The head with a 8mm cassette type cleaner.

[fmctm1sw]

At risk of sounding like an idiot... Aw, why bother now... I don't see any eads other than the video frum...

[Capmaster]

[fmctm1sw]

Upon closer review of that part, it appears to be a motor of some sort. The tape never makes contact with it. I actually dug up something that says 8mm VCRs use the video head to record the audio also.

Although the 8mm format calls for a linear audio track, it
is not used in today's VCRs. Instead another technique called
PCM (Pulse Code Modulation) is used to record audio with the
video head but separate from the video. How do they do this?
The video head takes a swipe across the tape. When it reaches
near the bottom, it stops recording video and starts recording
digital audio using the same head. Thus, one swipe of the head
does two jobs.

Oh well, back to the drawing board...

[samijubal]

HiFi is done with the video heads. I don't know much about 8mm, but if they record in different speeds, there should be a control head by the capstan somewhere that controls tape speed.

[Capmaster]

I actually dug up something that says 8mm VCRs use the video head to record the audio also.

Huh ...I learn something new here every day. I never owned one and assumed they used a scaled-down version of a VCR, with separate video and audio/control heads.

Well good luck

[samijubal]

If they are like the Beta, they use the video heads for HiFi too. The Beta had some extra useable space for HiFi, so they didn't need seperate heads, they just squeezed it into the extra space. The VHS uses the entire tape space, so they had to use seperate heads and put the audio on the same part of the tape but underneath the video.

[fmctm1sw]

I actually dug up something that says 8mm VCRs use the video head to record the audio also.

Huh ...I learn something new here every day. I never owned one and assumed they used a scaled-down version of a VCR, with separate video and audio/control heads.

Me too. I figured after I fixed that Sony VHS VCR I have (twice), this would be a snap as well. Guess not...

[Roundabout]

The capstan motor is servo locked, so if it's running at a different speed, it most likely is running at LP (half) speed. Makes sense, if it can't detect the signal from the tape.

Tell you the truth, I don't have as much experience repairing the 8mm format vs. VHS. Another guy in the shop used to fix these, I tried to stay away from them as much as possible.

I have a similar unit to this one packed away, I haven't looked at it in so long that I've already forgotten the model #. I also have an EV-S1, semi-portable 8mm deck that still works OK.

Most of the problems I've had with these units over the years is related to the heads getting clogged. IIRC the head gap is smaller than VHS and they get clogged with junk easily, esp if someone FF/RW the tape while it's playing.

I have a "Lapping Tape" that I use to really clean the heads, because we found out in the shop that a normal cleaning often just wouldn't do it for these units. The lapping tape is much coarser than a normal cleaning tape, and you can't run it for more than a few seconds because it causes a great amount of wear on the heads in a short time. I have needed to use it many times on these decks, they seem to clog at the drop of a hat. When the heads would clog, I'd just pop in my lapping tape for a couple of seconds and I was back in business.

I suspect that your heads may be badly clogged too, and it may be all that's necessary to restore it to normal working order. Of course, it's also possible that the deck is out of alignment instead

Have you tried recording something and see how it plays back?

Here's some basic info about lapping the heads:

Why can't I use Sony ME tapes with DVCPRO equipment?

This is a continuing problem that is being addressed by both manufactures, but at the present time no suitable compromise has been reached. The problem is complicated and is due to a combination of video head construction materials and tape composition. Metal Particle (MP) tape is used on DVCPRO and Metal Evaporated (ME) tape is used on DV and DVCAM. Both these tape formats have very different tape compositions and characteristics.

In an effort to optimize the tape/head combination for minimum wear with maximum stability and signal recording, both manufacturers have developed different combinations. There is a problem concerning tape lubricant incompatibility between Sony tapes and DVCPRO transports. The Sony tape has been found to have increased levels of phosphorus, which is typically used as a lubricant. This is used to counteract the inherently greater stiction that ME tape has due to the lack of binder material and the increase in metal content of the tape composition in comparison to MP tape. It is this phosphorus when mixed with the cobalt from the metallic layer of the ME tape that can cause head clogging and staining. This staining appears like a brown oxide smear and is not confined to the video heads but will build up on any transport components that the tape has contact with.

If this clogging and staining is left to build up, the effects can be a permanent glaze that is formed on the video heads that is very difficult to remove. In most cases if detected early enough, a special lapping tape can be used to remove the head clog but with a penalty of reduced head life as a result of the process. This headwear of course is dependent on how long and how often you have to use the lapping tape. If you must use Sony ME tapes, then make sure that the tape path and all its components are thoroughly cleaned using a wet cleaning method with isopropyl alcohol. This must be done before you start using the Sony ME tapes in the DVCPRO, then when you are ready to start working with MP tapes again, clean the transport tape path again, using the same technique. It is important that the tape path is thoroughly cleaned of any trace of tape lubricant before inserting a different tape type, otherwise you will run the risk of permanent clogging.