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 Post subject: Akai VT-100 Restoration
PostPosted: Mar Tue 29, 2011 5:54 pm 
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Location: Planet Claire
(I hope I'm in the right forum. If not, perhaps a moderator could move the thread. Thanks.)

Well, it's time to begin my latest project - an Akai VT-100 1/4" open reel video tape recorder from 1974. Here's what we're dealing with:
Image

I am fortunate to have the complete set-up: deck, camera, "side car" video monitor, external power supply, RF modulator, and a custom A/V out cable.

The Akai VT-100 was an astonishing piece of electronics back in 1974. At that point, video was pretty much only a commercial entertainment medium you got fed over the air. Video tape was largely limited to big networks that could afford the monstrous Ampex quad machines, or schools that had smaller but still bulky Sony 1/2" gear.

Then along came Akai with a machine that could record and play video on 1/4" tape (although it was special video tape, not standard audio tape), ran on batteries, and could be easily carried by one person.

Of course, the video it produced wasn't very good. It was pretty awful in fact. It was half-resolution (220 lines) black and white. And the VT-100 was notorious for poor tracking. Exchanging tapes between machines rarely worked. Even playing back a tape on the same machine it was recorded on would fail after a while.

This, along with its steep price (something around $1400 in 1973 back when that was a lot of money) may explain why this beast never really gained much popularity. And today it has pretty much vanished. There is next to no information about it on the web. A few photos, some ads, the service manual (if you want to pay $15 for it) but that's about it. Fortunately, I already had the service manual.

But despite the negatives, what was amazing about this machine wasn't how well it did it as much as that it did it at all. And over the years I accumulated a little collection of home movie type video that I'd now like to watch again. But the machine needs some work before that will happen.

I'm actually fairly optimistic on this one. I opened the covers and found that the two drive belts were all brittle and that the playback idler tire and rewind idler had turned to mush. Fortunately, I was able to find generic replacements for these items that fit. In the photo above, you can see the new playback belt about to be installed (below the take-up reel). The critical capstan pinch roller was in perfect shape. thankfully.

I powered up the deck and was pleased to see that all the motors started right up and sound normal. I tried the play, FF, and rewind functions and all of the appropriate levers move and the turntables move, so that's another big plus.

Next step is to load up a tape and see if it will run through the transport. Then we can get down to the business of actually getting images off the thing. Stay tuned!


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 Post subject:
PostPosted: Mar Tue 29, 2011 6:12 pm 
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Location: Omak,wa,usa
Hello Michele
that is the second one of those machines that I have ever seen .

The first one was back in the late 80s my college electronics teacher had a collection of old video equipment and among his stuff was a working one of those :D .

Rich


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 Post subject:
PostPosted: Mar Tue 29, 2011 6:29 pm 
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Location: Planet Claire
Thanks for the comment, Rich. I'm just glad to know I'm not alone here :)

I'd be curious as to how many of these they actually made. I'll bet it couldn't have been more than a few thousand. I've never seen one on Ebay. However, oddly enough there is a VT-110 up for sale on Ebay.de (search for the string "VT110") right now. It has 5 days to run, two bidders (up to a whopping 1.5 euros now). Unfortunately, the seller will only ship within Germany. I'll be curious to see what it goes for. Rare rare rare.

The VT-110 was basically just a VT-100 with a few tweaks, like an external tracking control (I guess they finally figured out they really needed that :) ) and the ability to record video in from an external source (the VT-100 can only record from its camera).


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 Post subject:
PostPosted: Mar Tue 29, 2011 6:35 pm 
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I hate to burst your bubble, but the 1967 Sony "Video Rover" DV-2400 Portapack was the 1st ever portable reel to reel video recorder, not the VT-100. For home video recording (not-portable) the first was made by Telcan in 1963, and Sony's CV-2000 in 1965 was the first one could call 'practicable.' That said, the VT-100 is an amazing machine and well worth restoring. I have a Sony AV-3400 (or at least I think that is the model number - it is still back in Seattle) which I plan to restore someday. It uses these oddball round belts that I had a very hard time finding last time I tried. If I remember correctly, that was the second portable video recorder model made by Sony.

-Matthew D'Asaro

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 Post subject:
PostPosted: Mar Tue 29, 2011 7:17 pm 
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Location: Planet Claire
I don't think I said the Akai was the first portable open-reel video recorder. I'm aware of the Sony Porta Pack, and even used one in the early 70's. In fact I still have one reel of 1/2" tape I'd like to watch too - but 1/2" machines seem to be even harder to find than VT-100's these days.

Anyway, I do believe though that the Akai was the first (and only, AFAIK) quarter-inch open reel video recorder. And although this is just my opinion, despite its name the "Porta Pak" wasn't all that portable, unless you were on the Bulgarian national Olympic weight lifting team. I could lift one (barely) but carrying it around while taping was out of the question.

Anyway, if anyone has a lead on a Sony 1/2" machine (portable or not), I'd be interested in that too.


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 Post subject:
PostPosted: Mar Tue 29, 2011 7:26 pm 
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My apologies. :oops: I misread your post.

-Matthew

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 Post subject:
PostPosted: Mar Tue 29, 2011 7:31 pm 
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No problem! I'm just happy anyone's reading my ramblings :)


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 Post subject:
PostPosted: Mar Wed 30, 2011 12:41 am 
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Joined: Nov Thu 11, 2010 6:03 pm
Posts: 404
Location: Pewaukee, WI
I have two working(last time I used them) EAIJ units a Sony AV-5000A (standard monochrome nonstandard color) and a concord monochrome unit. If you live nearby I could lend you one or you could send me the tape and have me copy it to VHS, S-VHS or DVD (I hesitate to mention DVD because my A to D converter tends to Introduce some noise to the signal, though it might not be noticable on a low low def video tape signal). I collect audio and audio-video recording formats in adition to tube radios and TVs so I'm too attached to sell. I found my decks at the extravaganza radio meet in Mi back in 08' the sony cost me 50$ if I recall, and the concord was 2$ in the donation auction! I did not even know of reel to reel video formats before that meet (which is just my luck find some thing I did not know I wanted one day go on a multi year search the next! :shock: :roll: :lol: ).

check out this link.
http://labguysworld.com/VTR-Museum_001.htm

Tom C.


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 Post subject:
PostPosted: Mar Wed 30, 2011 6:37 am 
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Very cool. I appreciate the offer. I'm not local to you but if I can't turn up anything closer, I may just send you my tape. It was recorded on a Sony Porta-Pak in 1974. I just took a look at it and physically at least the tape looks fine.

I did see the lab guy's web site. He's got a complete user's guide for the VT-110 on there (along with a ton of other way cool stuff). That was the one piece of documentation I was missing, so it was nice to find. I thanked him for it and he wrote right back.

I should mention at this point my other antique VTR - a 1970 Norelco LDL-1000. B/W, half inch tape running at an odd 7.9 ips., totally non-standard. That one was unfortunately submerged in a basement flood and is going to take a lot more work to restore than the Akai.


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 Post subject:
PostPosted: Mar Wed 30, 2011 6:49 am 
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Well we're making some progress. I loaded up a tape today and hit play. The transport started up smoothly and packed nicely on the takeup reel. The good news is that the audio is coming through clear and steady. The bad news is that the picture looks like this:
Image

The vertical and horizontal hold controls do affect the image but can't stabilize it. So does this sort of thing ring a bell with anyone? I honestly have no clue where to begin. It looks like a sync problem of some sort, but I don't know if I should start by twiddling one of the 2,000 different adjusting screws on the transport or checking waveforms with the scope. Any advice would be most appreciated.


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 Post subject:
PostPosted: Mar Wed 30, 2011 7:01 am 
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That streak through the picture is either dirty or damaged heads, or a misalignment of the rollers. You need to make sure the tape loads properly and the rollers are moving freely.
The rest of the picture looks like poor video, which can be anything from a lousy recording to a defect in a video amp (bad caps?). Can you check tape tension? This is critical in VCRs.


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 Post subject:
PostPosted: Mar Wed 30, 2011 7:28 am 
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Which streak? The horizontal one? I sure as heck hope the video heads are OK, because if they're not, it's game over. There's no way I'll ever find another head drum for this thing. It's certainly possible they need cleaning though. I'll give them a look with my pocket microscope tomorrow.

I know the tape is loaded correctly. However, I can check the rollers that control the wrap around the head drum, and also try a different tape.

I also have a spring balance and there's a whole detailed procedure in the service manual for testing the tape tension. I can go through that too.

A video amp problem isn't out of the question either for that matter. I've had repeated problems in that section in the past. Thanks for the suggestions.


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 Post subject:
PostPosted: Mar Wed 30, 2011 1:21 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: MI
Hi Michele,
Nice to see someone else with an interest in these Akai VTRs. I've got 4 of them (100/110) but none of them work. The tape back then was fairly abrasive (when people used the correct tape and worse when they didn't), and these heads were not known for durability, so all mine are shot. I've looked at some of them under a microscope and it's unbelievable how worn they are, and how big the gap is now. Why someone would continue to use the machine after one of the heads wore is a mystery.

Good luck on your restoration.

Darryl


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 Post subject:
PostPosted: Mar Wed 30, 2011 5:23 pm 
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Hi Darryl - I'm just so happy that there are other people who have not only heard of this museum piece but actually have one.

I hear ya about the video heads. Akai claimed a 1,000 hour life for them but my machine actually already had its heads replaced once before (by Akai) after less than 200 hours of use :( . And I was always extremely careful with it and never ran audio tape through it.

I'm hoping the current problem is either tracking error, tape tension, or maybe the tape I chose for the test was itself bad. I know my machine was always screwing up one way or another. I'll be very happy if I can just run a dozen more reels through it to recover the video on them.

How did you end up with four of these??


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 Post subject:
PostPosted: Mar Wed 30, 2011 5:39 pm 
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Location: MI
I worked at a repair shop in the late 70's and 80's and started collecting them. The belts and idler wheels are always like you described and need to be replaced. I had one that sort of worked years ago (the heads were just about gone) but haven't tried it in years.
I met "The Lab Guy" a couple of years ago and he mentioned he might try to make replacement heads available, but I don't know how this effort is going.

Darryl


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 Post subject:
PostPosted: Mar Thu 31, 2011 1:52 am 
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Well I didn't have much time to work on it today but I did get a look at the video heads. It's pretty difficult to get decent photos through the magnifier. This is the best I could do. They basically look OK to me. I don't really see any crud on them and they don't look worn out. What do you think?Image


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 Post subject:
PostPosted: Mar Thu 31, 2011 2:09 am 
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I generally use a 40 power microscope to view the heads. I can't tell from your photos. Have you put an oscilloscope on the RF from the head amp to look at the envelope?


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 Post subject:
PostPosted: Mar Thu 31, 2011 6:01 am 
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Location: Planet Claire
I know. I did those photos with a 5x loupe and a 20x loupe. If that's not enough I also have an 80x pocket microscope I can try.

"Have you put an oscilloscope on the RF from the head amp to look at the envelope?"

Not yet. I want to run through the various tape tension and roller tension adjustments first. There's about a half dozen things to measure, according to the service manual.


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 Post subject:
PostPosted: Apr Fri 01, 2011 6:59 am 
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Location: Planet Claire
Well I made a little progress today. I decided to start by checking the takeup torque and drive idler pressure. The takeup torque is supposed to be between 100 and 120 grams. I pulled 80. The drive idler pressure measured 150 grams. It's supposed to be 200 to 500. Here's the parts in question:

Image

I set the drive idler screw to move the takeup idler closer to the takeup reel drum but this had no effect on the takeup torque. It did however increase the idler pressure to 205 grams, just inside the lower limit. I then tried fiddling with the torque adjustment screws A and B, which oddly enough are listed in the procedure for idler pressure, not torque adjustment.

The manual says to "make adjustment" but not which direction to turn them. So I tried both ways. Neither one did anything. The takeup torque was still low.

I then tried playing a different tape from the one I used yesterday. I'm still not getting a picture, only now the sound is all warbly :( . The only difference is that this was an 1800' reel while yesterday I used a 1200' tape. When I relieved the holdback tension on the tape by helping it along with my finger, the audio smoothed out. So I'm thinking that the tape holdback tension may be set too high. There's a procedure for that too but this is as far as I got today.

I also still need to figure out why the takeup torque is low. I did replace the drive idler and takeup idler belt. Possibly the new idler tire is too small or the belt is too weak. All of these adjustments seem to interact with each other so it's very frustrating.

I still have yet to get around to making any electronic checks. However, I'm starting to think I have a video problem. Even if the sync is all screwed up from mechanical tracking problems, I should still see some sort of brightness variations in the image, and all I'm getting is dark.


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 Post subject:
PostPosted: Apr Fri 01, 2011 2:58 pm 
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How is the takeup reel coupled to the rest of the mechanism? Through a friction clutch of some kind? Have you cleaned the rollers?

Should you need to get one rebuilt, I highly recommend Terry's Rubber Rollers. He's rebuilt some tough ones for me.

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