Sony TC-K71 Debauchery

[George S.]

I see the brass drive stub contacting the tire.
Is there not a felt disc clutch with a spring somewhere in the mechanism that would permit proper tension and slippage?
The Phase Linear deck I'm working on has two felt clutches.
One clutch for fast F+R, and another clutch for play.
I can already see that I'll have potential issues with tape tension if the felt or springs are out of spec.

 

[ButchJames]

I see the brass drive stub contacting the tire.
Is there not a felt disc clutch with a spring somewhere in the mechanism that would permit proper tension and slippage?

No, not that I can see, and it's the same (from memory) on the TC-K61. The slippage between brass driver pulley and idler tyre determines how much torque. If anyone knows otherwise for definite, then please chip in.

(a) Take Up Reel Table
(b) Idler gear and slippage rubber (to driver contact)

(a) and (b) are geared together as can be seen in above (earlier) photo.

 

[ButchJames]

The Phase Linear deck I'm working on has two felt clutches.
One clutch for fast F+R, and another clutch for play.
I can already see that I'll have potential issues with tape tension if the felt or springs are out of spec.

I've been working on an AKAI GXC-710D, which works off a pressured felt clutch system (PLAY/RW/FF), and indeed I've had to make some changes there too.

 

[George S.]

James, page 10 in the manual I posted, there is a spring loaded adjustable back tension lever.
Don't know, but perhaps this needs adjusted for less tape tension.
Gotta love these electro-mechanical devices!

 

[ButchJames]

Previously, I've been through all the back tension settings to combat the original tape creasing problem. I even added some extra back tension above the max setting - that did the trick, but it is not the answer. The problem is very probably that either one or both pinch rollers are not exerting enough traction; the problem is only with thin tapes. Concurrently, the rightmost reel tension ('take up') was also too high IMO, and this afternoon I reduced take up tension with the silicon grease on the rubber idler. It works great, but I do sense that this isn't going to last for more than a day or two as the silicon grease will begin to dry out under the continual pressure between brass drive and that rubber idler. The friction creates heat of course, accelerating the decline in the effectiveness of the grease.

I need a new idler and new rollers. ITMT, this 'fix' works for now.

 

[ButchJames]

Of interest to mr_rye89, the pinch roller sizes if you need new ones:

Supply = 11mm x 8mm x 2mm,
Take-up = 13mm x 8mm x 2mm.

I went looking for any pinch rollers I had in stock and found that I have two that would fit the Take-up side; a 13x8x2, and a 'chancy' 13.5x8x2. So the little devil in me has put in the 13.5x8x2, with about 0.5mm clearance with the roller frame. Fingers crossed it'll be okay, I don't see why not? if it does create problems, I have a 13mm roller.

I chanced the 13.5mm diameter roller as it should exert slightly higher pressure between capstan and roller.

Naturally the motor loading affect has changed slightly and I get 3155Hhz for a 3150Hz tape, and wow/flutter is as above in an earlier post, no change there; average of around 0.04x% wrms.

I took a photo of the new roller, note the hair on the roller! ... ha ha, sods law or what???

All working well, no tape creasing.

Also, observe the supply side, all nice and calm there now.

PS: I hope I haven't hogged this thread too much, but I just thought points here are relevant also to any TC-K71/75.

Apologies, having trouble uploading images!? ....

 

[ButchJames]

Images .... hopefully.

 

[laatsch55]

Ohh...we hog threads all the time...it's an art held In high regard here...