Ed in Tx, is you out there?

[Barry777]

Hi Ed,

All my JVC's are working fine now, but I do have one rather silly question. My machines (BR-S822U, 500U and 800U) have very similar mechanisms and appear to be "older" versions according to my service manuals. Thankfully, the alignment procedures weren't much affected. All my machines lack the tension sensor (the one that looks a little like a full erase head), which was my first clue that the machine doesn't exactly match the manual. I was pulling the reel motor assembly to replace the worn brake pads with small pieces of leather, which was a great way to earn some brownie points since I took the wife to the craft store for the leather!

My question is about this weird little sprocket-looking wheel on the underside of the mechanism right by the takeup reel motor. It's part of the chassis-mount stuff and you have to be careful to work the reel motor assembly back under it during reassembly, without disturbing its position. I remember seeing this sprocket somewhere in the manual but can't seem to find it, now that I want to learn about it. I think I remember it having something to do with tension. Would you happen to know what this is? It can be turned from above, but that requires a special tool I don't have - smaller in diameter and with finer "teeth" than the standard one. Of course, I'll have to pull the mechanism if I ever need to adjust it - thankfully I don't seem to have any trouble with it right now.

The sprocket itself is maybe just over 1/2 inch in diamater, with very fine teeth. Looks like stainless steel, very bright and silver. Thanks in advance for your help! As a side note, I got some weird performance when I put it back together; the FF function actually slowed way down when it was supposed to really start cooking. Also, the tension arm would slam violently back and forth when I loaded my JVC torque meter tape. Turns out the back tension was more than 70 grams as opposed to the spec of 54. A quick tension bias adjustment fixed that. I'm learning! These pro machines are a different animal altogether.

It's monsoon season here in Arizona, and the house is at 50 % humidity, even with the A/C running constantly. I thought I'd better pull all my capstans to lubricate the bearings to keep the moisture out and prevent rust forming in them. This is what started this little career underneath the mechanism. I have my Alesis BRC on the way, so it was time to start tip-topping these machines for the long haul. Thanks again Ed ~~~

Barry

[Ed in Tx]

Can you post a picture? It's not coming to me... a picture would help! Been too many years.

Leather? Never tried rebuilding brake pads.

Tension problems.. I generally use a Tentelometer. I have stored away somewhere a couple of torque tapes but those didn't work right in some machines, so I rarely ever used them. I have a little hand held take-up reel torque gauge, but usually I can tell just by feel if the TU reel has too low or too much torque. It doesn't work with all mechanisms either.

Anyway post a picture if you can. Could be a variation I have not seen or never into that far.

[Barry777]

Hi Ed, thanks for replying so quickly. Looks like that little sprocket adjusts the resistance of the takeup tension arm. Funny how several minutes of scrutiny didn't reveal this, but a quick glance later did. I looked on a BR-S500U which simply had a retaining washer instead of the sprocket, and that told me all I needed to find out.

I use the Tentelometer more than the torque tape for the same reasons you mentioned, but when the tape does work, it seems to give me a steadier reading than I can obtain when holding the Tentelometer - and possibly just a touch more accurate. Definitely nice to have both on hand. If I could find the JVC alignment tapes I don't yet have, that would be a glorious day in my life. Thankfully, the electrical alignment seems to be fine on all the JVC's and I haven't found an urgent need for them.

I found out something about lithium grease - it's terrible after a few months. It gets hard, gums up, etc. I'm going to start using Dow Corning High Vacuum grease instead - it has proven itself to stay greasy and safe for plastics. We use it at work where a brass leaf spring snaps against a plastic detent wheel. Anyway, I'm rambling - thanks again Ed!

[Barry777]

That sprocket thing is the takeup guide arm height adjustment.