how to replace a JVC SVHS video head? lordsmurf?

[Blackout]

hi all,

i am going to replace the upper video head on my HR-S9500 JVC vcr. Ive replaced video heads before on VCRs before (panasonic etc) , usually involving some screws and soldering. For the JVCs tho, it doesnt even require soldering as it uses floating coil motors and floating circular connectors underneath the head which pick up the signals. Great.

however for my "test run" before the new head arrives in the mail i have simply removed the head and placed it back down, and re-assembled the PCB coil motor on the top with the screws etc. It seems though with the simple lifting and placing back down of the video head it has caused the picture to permanently be "snow". (The head spins freely and fine when in Play with a tape loaded.)

What has happened here...anyone with experience doing this? surely the heads have some kind of timing sensor system, as the head is not soldered in, so it must know what position the head is in at the time. Its possible i lowered the head back down on a different angle but with it all free-spinning and working on floating coils i woulda thought this would not make a difference and the jvc timing senses the head position. i mean, what if you turn off the vcr at the power plug and give the head a spin, surely upon powering up again it would just re-sense the head position...

any help from a JVC vcr expert would be appreciated. lordsmurf you are an expert on JVC VCRs any knowledge from you would be great

Many Thanks,
Blackout

[Blackout]

ok it seems i have fallen victim one of the oldest traps in the book when it comes to replacing video heads, installing the head 180 deg out of phase.

for a JVC its harder to figure out as theres no soldering. it was the circular magnetic plate that i screwed in spun around. it looks the same either way but obviously its a magnet so it would have a north and south end that you cant see visually but the head sure can. so problem part 1 solved. i have a picture back.

but...in the process of trying to fix it i have fallen victim to trap #2 and twiddled the adjustable tape guides either side of the head, thinking previously it was a tape alignment problem. now i regret it, believe me. but the picture has bands thru it.

I twisted both guides 4 or 5 turns either way. So for all i know between the two guides there is 10 twists difference. The question is...which one to twist back.

Is there some rule of thumb on how to adjust the wheel tape guides ? where is the tape meant to sit on the head...on the low side of the head, how far from the top of the side of the head should the tape go up to?

many thanks,
Blackout

[SLK001]

Maybe you should have been taking copious notes on exactly what you were doing - especially without a service manual. Also, take many in-process pictures, so you won't be blindsided trying to remember where "something goes".

Since service manuals are almost impossible to find for consumer electronic products, this is the way that I tear into electronics when they have to be repaired. Consumer electronics aren't made to be repaired anymore - once they break, you have to buy a new one (at least that is what the manufacturers want you to do). Don't get me wrong... I vehemently disagree with that mindset. I always try (at least try) to obtain a service manual when I buy my electronics, but usually this it a futile effort.

Anyway, good luck on your repairs.

[lordsmurf]

Several of us have been archiving manuals for that very reason.
Admin has organized them here: Free User Manuals and Service Manuals for VCRs.

Anyway, what I do is take photos before I start, and then every step of the way I take detailed notes. I mess around with JVC tape guides all the time, to restore misaligned-recorded tapes. Watch the video on TV as you twist the guides. Obviously use an unimportant tape, because you WILL screw it up in that process, unless you're very experienced with it. You can use special tools, or even jimmy-rig your own for the JVC models.

I avoid head replacements, choosing to send it in for servicing.

You could always send it to Jots Electronics in Arlington, Texas. They do good work.

[robjv1]

I mess around with JVC tape guides all the time, to restore misaligned-recorded tapes. Watch the video on TV as you twist the guides. Obviously use an unimportant tape, because you WILL screw it up in that process, unless you're very experienced with it. You can use special tools, or even jimmy-rig your own for the JVC models.

Do you have or know of any good guides for this? I've been interested in messing with it on a secondary VCR I have, but I've had some trouble understanding the process.