G'day Roy,



11 Oct 96 22:43, Roy McNeill wrote to Rod Gasson:



 RG>> If you have a clear/watchable picture your heads aren't dirty.

 RG>> If you do ever get dirty heads (snowy playback picture), they

 RG>> will often clear themselves simply by leaving a tape playing in

 RG>> the machine.



 RM> When that happens, I worry that the grot on the heads is damaging

 RM> the tape that is playing.



A single/solitary SPECK of dust is enough to wipe out the entire

picture.  It is unlikely to cause any damage though.



 RM> We have suspicions about a couple of

 RM> damaged tapes, but it's impossible to prove whether the tape

 RM> stuffed the heads or the heads stuffed the tape.



Heads don't damage tapes..   This is left for things like the pinch

roller or back tension band.

Tapes can damage heads though  (usually only when spliced)



 RM> Would a head cleaning tape do a quicker job than just playing a

 RM> (sacrificial?) normal tape?



Hard to say...  sometimes yes, but at other times, a h/c tape will

actually 'wedge' the speck of dust causing the problem into the

headgap itself, meaning it'll never dislodge of its own accord anyway.



 RM> Btw, did I mention that I've finally retired the NV777? I think



I think you did.



 RM> it's probably a just a power supply problem, but without a diagram

 RM> I'm not touching it. Symptom 1: we often have to hold the Play

 RM> button in for a long time to start a tape - it will load, then

 RM> immediately unload. After a few cycles of this (with the button

 RM> held in) it sometimes relents and starts playing, sometimes it

 RM> refuses.



Can be caused by many things...  load belt slipping, heads not

spinning, reel sensors not working, etc.  (very rarely would a power

supply problem cause this though)



 RM> Sometimes it works on first press. Symptom 2: the lcd tape

 RM> counter locks up, no count, no response to reset button, sometimes

 RM> fixes itself if mains is cycled, sometimes not. This misbehaviour



This is a weird/unusual one....  if it was simply not working I'd say

that your entire problem is a faulty/dirty reel sensor, but the fact

it won't reset indicates something a little/lot more serious.



 RM> Interestingly, it plays one of our old ratty tapes much better than

 RM> the NV777 did - a noise bar near the top of the screen has

 RM> disappeared.



"Noise bars at the top of the screen" is generally what we call 'Flag

waving'  -   it is a result of the TV being tuned to the wrong

channel.  Chances are that you 'cured' this simply by retuning the TV

for the new VCR.



Cheers,

Rod



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