Need some advice on a 122 Mk. II that runs way too fast

[Seankerns]

I have a 122 Mk. II. I inherited it and a 112 from my Dad's voiceover studio. Over the last couple of years, each of them has developed some problem or another that has made it unusable, but we'll start with the 122, because it's by far the fancier machine, and I used a lot of its features.
I used it usually for transfers from cassette to digital media, so I used it usually every few weeks. The last time I fired it up to use it, as soon as I put in a tape and closed the door, this high speed, high pitch whine started from inside the unit. Not just the usual "motor running" noise. Much louder. When I hit play, the tape appeared to be going, like, 4x speed, way too fast. And no output. The heads don't engage. The speed correction doesn't make any difference at all. On/off, full up/full down, no difference. Obviously the whine was just the first sign that something had failed somewhere. I opened the machine up, and this is a video clip of the sound that the unit makes when a tape is inserted (i.e., that little switch at the top of the tape compartment gets pushed:

The noise is coming from that motor at the bottom with the big flywheel.

So, my question is, what is likely to have failed there? I don't see any place that this particular motor would have driven a belt or anything. The reel motor up top has a belt, and it ffwds and rwds just fine. It's the play transport that's busted. Looking for anywhere to start here.

The other option, are the transport units the same on the 122 and 112, or do they use different units? I ask that because I'm pretty sure the 112 has a broken belt, and I can fix that pretty easily, but if I could "fix" the 122 by swapping in the transport from the 112 (after putting a new belt on it), that would be at least a temporary solution.

Thanks in advance!

Sean

 

[Seankerns]

Okay, so to update my own thread:

I have taken the 112 apart, and found where there was a belt which is missing, and I ordered a new one for that. I also could plainly see that the transports are nowhere close in design. It's immediately apparent where the belt goes in the 112, but not the 122 Mk. II.

The belt for the 122 Mk. II got here, but I don't see where it's supposed to go. Nothing. I have the service manual, but it doesn't show it, unhelpfully enough. You'd think that would be basic information.

Can anyone with one of these decks describe where the other end of the belt goes, assuming that one end goes around the capstan flywheel, but please correct me on that too, if not?
Pics would be great, but any idea would be appreciated. I'm assuming I'll have to dissassemble something more in the transport to get the belt in, but I'l like to have some idea of what I'm looking for.

Thanks in advance!

Sean

 

[SkywaveTDR]

The 112 is not a direct drive unit so it has a capstan belt. The 122 Mk II is a direct drive motor unit and so there is no belt at all for the capstan function. The only belt a 122 Mk II will have is a 6.7" square belt that goes on a motor pulley and then to a intermediate pulley that drives the cam system. This is typically called a Cam Belt.

The very common problem with the 112Mk II as is with the Mk III is that the junk SMD caps on the servo control board have leaked and compromised the circuit eating and separating foil patterns so that not only the caps need to be changed but the foil patterns repaired. I have done about 50 of them so far. The whine you have is the capstan servo going full speed because it is not seeing the FG signal.

 

[Jack Saturn]

This is an old thread, but I have a related question that you might be able to answer, SkywaveTDR. I am refurbishing a Tascam 122 mkII which came to me halfway through someone else's attempted repair, so the belts and such had already been removed.

I have had no trouble locating sizing information and replacements for the cam belt (Tascam part number 5800106800), but the service manual also lists another "timing belt" which I haven't been able to find any discussion about anywhere (Tascam part number 5800933600). This belt is also used in the Tascam 122 mkIII, so I'm assuming that perhaps the mkII and mkIII just use the same belts altogether.

In another forum I read that perhaps this "timing belt" doesn't control timing at all (http://www.tapeheads.net/showthread.php?t=28736), but having not seen it firsthand, I can't say. But it would be positioned on the front side of the tape reels, and if I look downward into the tape mechanism I can see the groove in the right-hand reel where it would loop around.

As I've seen no signs of a replacement belt for this part number and no one really discussing it in the forums, am I to assume that this belt is not necessary for the machine's operation? Or further, that its inclusion in the service manual was a typo or a hold-over from some other machine that used the same mechanism? Thanks for any advice you can provide!

 

[SkywaveTDR]

There is NO cam belt in the MK III and I just replaced a Gear C is the pat that moves this cam and it breaks in combination to age and brittle plastic but also due to hardened grease. In the same model the motors need to get through hole caps put on them and well as a good oil like AMS in the capstan bearing. The cam belts are not hard to find and they are not hard to understand where they go- just look at the mechanical parts break down of the deck to see where if any belt goes in the unit. The 122 Mk III does not have any belts in them. I sell the Gear C part in case you need one plus there are two sources on E bay for them as well.

 

[Kirk Anderson]

The very common problem with the 112Mk II as is with the Mk III is that the junk SMD caps on the servo control board have leaked and compromised the circuit eating and separating foil patterns so that not only the caps need to be changed but the foil patterns repaired.

On the off chance that someone might see this ten years later, is this a typo for

"The very common problem with the 122Mk II as is with the Mk III... " ?

I'm not sure that the 112 mkii has a servo control board, but then I've been wrong before.

 

[Jack Saturn]

Yes, that was a typo on Skywave's part. The Tascam 122mkII and 122mkIII both have direct drive motors, but the 112mkII is belt drive.

The Tascam 122mkII does use belts for cam/control and timing, but not for the capstan.

Earlier in the thread the OP referred to a 122mkII that they inherited from their father, but then went on to refer to it by the shorthand of "122," which is technically a different machine. So the mix-up is understandable.

Jack

 

[Kirk Anderson]

Thanks Jack! I'm the owner of a couple of 112 mkii, which I love. Happy to know the notorious failing motor capacitors (I've read about them before) won't be a problem for me.