Fisher VCR model FVH919 snowy pix.

snipped-for-privacy@yahoo.com ha escrito:

this reminds me of a common fault with early 90s JVCs. a cap on the drum motor pcb of about 3.3 uF used to go leaky and cause this problem, i expect you've got similar.

-B

I got a question of my own. WHY THE FUCK ARE YOU STILL USING VHS, RETARD?

More useful input, I see. A pattern is emerging...

The video head's drum motor assembly has a magnetic cover that is secured on with 2 or 3 screws (usualy non magnetic metal). On its rim you'll see 1 or 2 black dots which are tiny magnets glued on to generate a "pg" pulse. This pulse reports phase of drum rotation and tells the head preamp when to read the video heads and when to switch off in one rotation. A pg sensor is situated close to the lower drum assembly to pick up these pulses.

1) Have you removed this part while cleaning and reinstalled it incorrectly?. 2) I've had a case or 2 where the magnets were worn down and they wouldn't generate enough of a pulse. 3) I've had cases where the allignment of lower drum with respect to upper drum was out. An allen key locks the drum position to the shaft. Has this loosened? Can the upper drum be shifted (with a bit of force) while holding the lower drum tight?. 4) Bad pg sensor or a fault somewhere down the pg processing line. 5) Bad rotary transformer. The upper drum assy has a rotary transformer primary winding housed in a ferrite base. This couples the video signal to a similar secondary winding which is stationary. I've seen breaks in these windings, and have rewound them to some degree of usability. Jango

I've seen a shorted cap on the main board take out the PB 9v line...

Mark Z.

I put the other set of heads back on but that made no

Hate to piss on your bonfire, but it might be time to call it a day. After all we're dealing with a 20 year old unit here, you've already done what you can. With very good Hifi stereo VHS decks around cheap second hand, it seems silly to waste more time on this one. Sometimes it's best to know when to stop and spend time more productively. Good luck.

-B.

No, don't give up. I just made a killing fixing 2 Leak valve amplifiers which were more than 55 years old. . Have you checked out all the other leads we've been giving you?. We're here to help u crack this case. Jango.

jango2 ha escrito:

Jango, Just so there's no misunderstanding here - and I am often one who keeps going on a device way beyond what others would call reasonable - I'd never tell anyone to just give up. But in this case, we're dealing with an awkward fault in a critical and expensive part of the machine, with a user who admitted himself he does not usually work on vcrs. Prognosis isn't good.

Not only that, there is a huge difference between investing time and money in rare 55 year old amplifiers which are collectable and fully usable today, and an old video machine from a standard on its way to obsolescence, the like of which can be had for peanuts in any number of second hand places - usually in better shape and for less cost and time than repairing this one or finding the necessary parts. Sometimes it pays more to be reasonable and know when to stop.

-B.

Been ages since i repaired any VCR. The head preamp pack outputs an RF envelope waveform. Do you have any kind of oscilloscope? We need to observe a clean output here.Set your time base to 1msec/div and sensitivity to 0.1 volts/div. A typical waveforms looks like this:

We need to find out if the fault lies in the drum assembly + preamp or later on in signal processing circuits. Tape path alignment is critical here. A head switching pule is applied to the preamp, this signal is derived from pg.

To Rev : Sometimes the feeling of accomplishment out weighs any amount of money received as repair fees. As long as Captainvideo has the time and inclination to proceed i don't see any reason not to encourage him.