Ok i have this JVC combo XV3EF that can't play the tape properly as if there is lack of back tension. (tried messing with the A/C head and guides heights a little, no luck).
Thing is on the supply side the band/pad that provides tension is already tight (almost too tight) thus the only possibility is on the take up side , i can see there is room (see picture) but i don't find the procedure to increase it on the service manual (and no extra holes on the band). For the supply side yes ( page 14) but i'd need the special gauge tape ( i read somewhere here one can bypass the gauge tape using weights, can't recall the details)
If someone here knows his back tension stuff, please guide me
Edit: take up side i believe that's for the brake only actually, so i guess it's only about the spring for that guide
I get a picture but never stays stable too long and also almost forced to have the tape at the limit of the tape path on the drum (exit side) or lower(!) to get something watchable, that's not normal i know that much.
To me that's back tension issue, i see and feel by hand some tension is missing somewhere
If you move the tension arm manually to increase the tension and you get a stable picture then it's a tension problem, otherwise look somewhere else. Also never re-align a VCR to repair it, VCRs don't go out of alignement on their own, It's either someone messed it up before, or something happened by accident that broke off the factory alinement.
If you move the tension arm manually to increase the tension and you get a stable picture then it's a tension problem, otherwise look somewhere else. Also never re-align a VCR to repair it, VCRs don't go out of alignement on their own, It's either someone messed it up before, or something happened by accident that broke off the factory alinement.
Yes!
For example understand what each of the normally 3 A/C head screws are there for. Never just twiddle the A/C head's screws randomly. If you must adjust them, first mark their original positions with a suitable fine tipped marker pen.
The A/C head's face must be 90 degrees to the deck plate. If this angle is wrong it can be difficult to correct it. If it's well out, temporarily changing the back tension can cause the tape to ride up or down the head face, losing or finding the control track signal, which may make it seem like a back tension problem when it's actually a tape height problem, caused by a head tilt error.
The only screw which can be safely adjusted a little without affecting head height or head tilt is the Azimuth screw, usually to one side of the head, not the screw in front of the head or the screw behind.
Ok so i'm following the procedure Page 14 of the service manual (4.2.1 Tension pole position), first thing i spot is i can't align the "P" triangular stamping with the stamping mark on the plate, that's the maximum i can reach on the picture.
Last edited by themaster1; 02-09-2025 at 05:08 AM.
I did fiddle with it some more, found a way to get them aligned. I have increased the tension by 1 good turn (clockwise) as preconised (tip of the T.guide on the mark) , don't see much improvement, everything is aligned as far as tape/guides/drum/A/C (not too high, not too low).
If only back tension was weak we'd normally see a noisy picture all over. Here most of the picture is good, just poor in those three narrow bands in top half.
Maybe unrelated but linear audio here is terrible.
Usually if linear audio isn't good, then there's an alignment problem as that is purely a result of how the tape falls onto the audio head. I suppose if there wasn't enough tension that could also cause it, but my guess is it's an alignment problem for P2 and P3 as well as possibly some alignment issues with the AC head if they've been messed with. It's pretty tough to tell if slight adjustments are helping or harming without an oscilloscope though when things are that far off.
