Where is my RF envelope?

[Alex Bird]

Hi there,
I'm having a fiddly time lining up the tape path in a Sony
SLV-ER7UY(uk pal), it's good but I've just put new heads in and I want
it to be perfect ;o)

Where can I find the RF envelope test point?
And what bandwidth is this signal? I have only a 50kHz pc based scope
here.
Do you need a test tape to make use of this?
Is there an envelope for the hi-fi heads too?
Thanks in advance,
Alex

 

[Sofie]

snipped:
"Alex Bird" <alex@redbeastie.fsnet.co.uk> wrote in message

I'm having a fiddly time lining up the tape path in a Sony
SLV-ER7UY(uk pal), it's good but I've just put new heads in and I want
it to be perfect ;o)
Where can I find the RF envelope test point?
And what bandwidth is this signal? I have only a 50kHz pc based scope
here.
Do you need a test tape to make use of this?
Is there an envelope for the hi-fi heads too?
Alex
---------------------------------------------

Alex Bird:
The RF envelope "test point" (it may not even be a identifiable test point
but just a place on board) will usually be on or near the head preamp
board..... and yes, since the HiFi audio heads also operate as a modulated
RF signal you will also be able to visualize the RF envelope of those heads.
There are other adjustments and checks that must be done to properly install
new heads. In order to produce a proper alignment and interchange, a
factory test and alignment tape is required and as far as you scope goes
..... it's low bandwidth and sensitivity is completely and utterly USELESS
for this kind of measurement.
You would be best advised to take your fine VCR to a service shop for proper
head alignment and interchange adjustment..... the money you spend at the
shop will be much less than purchasing an expensive alignment tape, special
head adjustment tools, head penetration gauges,tension gauges, a new
oscilloscope, technical training and procedure manuals, etc. This is a
fairly routine job for an experienced tech with the proper tools and test
equipment, electronics knowledge and repair experience...... for the
novice, you risk misalignment of the heads, poor interchange with other
VCRs, and possible damage to the expensive heads, the vcr, and your tapes.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
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[Alex Bird]

"Sofie" <sofie@olypen.com> wrote in message news:<vqdsmemucov49f@corp.supernews.com>...

You would be best advised to take your fine VCR to a service shop for proper
head alignment and interchange adjustment..... the money you spend at the
shop will be much less than purchasing an expensive alignment tape, special
snip

Oh dear, I wrote that in a rather flippant way. Thanks for your
concern but I'm not a completely ignorant novice, I've just never had
need of especially precise alignment. Now I do, I'm a student with
very little money, enough time, patience and fairly delicate touch to
want to learn to do this, not just pay a one off fee each time it
needs touching up...
Anyway, it turns out it won't be needed. The tapes I was using to
check interchangability turned out to have a rippled bottom edge (well
used by someone else), this was causing random and almost periodic
tracking problems - a lot like misadjusted roller guides.
I'm sure it's all adjusted to within some fraction of what it would be
in a shop, and very clean and well lubricated (with the right
lubricants). Certainly more than an hours work, plus parts; that
would make it similar in price to a new machine, maybe one not so good
though.

Alex

 

[Franc Zabkar]

On 3 Nov 2003 13:15:37 -0800, alex@redbeastie.fsnet.co.uk (Alex Bird)
put finger to keyboard and composed:

I'm having a fiddly time lining up the tape path in a Sony
SLV-ER7UY(uk pal), it's good but I've just put new heads in and I want
it to be perfect ;o)

The only time I use the RF envelope to adjust the tape path is when
the guide posts have been disturbed. Otherwise I leave the adjustment
at its factory setting.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Sofie]

snipped:

"Franc Zabkar" <fzabkar@optussnet.com.au
The only time I use the RF envelope to adjust the tape path is when
the guide posts have been disturbed. Otherwise I leave the adjustment
at its factory setting.
Franc Zabkar
-----------------------------

Franc Zabkar;
I agree with you that unless the roller guide height has been disburbed or
monkeyed with that many times there is no adjustment needed, but don't you
think that head output should at least be checked for symetry upon replacing
the head drum? ?
I replace lots and lots of head drums and there are differences that should
be checked and adjusted if neccessary.... otherwise tape interchange with
other VCRs (especially at the 6 hour speed) can suffer significantly......
resulting in mis-tracking lines either at the bottom or top of the
picture..... non-symetrical head output due to roller guide mis-alignment is
usually the cause and can easily be determined by at least looking at the RF
envelope.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
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