Sony BVH-3100PS Tension Problem?

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Sony BVH-3100PS Tension Problem?

Post by oldtvgear » Thu Apr 20, 2017 7:17 am

I've read with interest some of the very informative threads for Sony BVH machines and its prompted me to reach out and pose my current dilemma and see if the knowledgable folks here can shed some light on it.

I have a BVH-3100P machine that has just had a spare head assembly put into it - the machine is working for except for two main faults with the servo or tension.

Fault 1: If you rewind fast, tension is lost and chaos happens (tape spills, snaps etc) - stuff of nightmares!

Fault 2: In Jog mode, when going back and forth (ie slow mo) the tape will randomly slap/bounce about on the last guide before the take up reel as seen in this video here: ... 9.mp4?dl=0

It doesnt quite get bad enough for it to shut down, but you can hear the tape sometimes flailing as it bounces..surely that cant be normal..however...

...I then compared all the other "good" machines, and they seem very similair, but if anything I'd say this one does it worse. The thing is it can be random, at times not doing it, then try again and it does it quite bad.

Playback does not seem to result in tension issues or even shuttling slowly - it only seems to be when it gets up speed in rewind that disaster happens.
(I've not tried FF yet!)

With the BVH3100 its pretty much all internal menus via the keypad and writing things to NVRAM - I've performed the motor torque tests but initially
torque self tests failed for the take up motor, it should read between 63-65, but never gots over 57/58 ( by comparison a "good" machine gives around 63 on the test) also brake torque is not within spec either, but nor does it seem to be on a "good machine". I have been told this is not critical for now.

So, i swapped the entire take up motor and associated assembly, this time the torque test/s ran by the book and passed, and settings were updated. However this did not cure any of the problems

I swapped all boards, such as SV90, SY103, etc and also tried changing the reel motor and other boards inside, but none results in any change to the issue at hand.

All capacitors through the machine (except for the audio board) have been replaced (big job!).

Another suggestion was it could be down to a malfunctioning or out of alignment tension arm (there is only one on a BVH-3100), but to perform the test and alignment it appears i need this test jig below

Which of course cant be obtained anymore!. So again I appeal to any techs out there who may have a Sony service kit, or the tension alignment post & weight, to get in touch!, even if i can just borrow it to rule out if it is the problem or not.

I am confused as to why what i call "the tape slapping problem" on the last guide seems to happen across all the machines to some extent. I questioned if this was normal, but not knowing the long term service history of the other machines its possible they are out of spec as well.

But, if it is a tension arm issue, why does only this machine spill tape on fast shuttle/rewind - is this a separate problem? - or is it related to the tape slapping issue that when it gets enough out of spec, it may progress to the tape spilling issue on the other machines also?

The only way i think to really know what the problem is, is by obtaining that tension arm alignment jig/set and seeing it it cures all !

What are your thoughts? It seems the bulk of techo's out there only have experience with the BVH-2000's, but i am hoping someone out there knows the 3100's inside out and can assist!

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