How to measure High tension of a FBT. . .

Hello!
If you read the post below (sorry for two post....), I have a E500 Sony
monitor.
I have replaced the varistor that regulate hte high tension of the
FBT...because the previous is quite "cooked"....
So, now I must regulate the high tension to the valour of 27 kV.
I don't have the high tension probe for my meter (they are quite expensive,
and I don' t want purchase their....).
There is any safe method (for example, using a voltage partitor, or
something other!) to measure this voltage with a standard meter?
Thank you!

 

You could build a voltage divider, but to do it safely it would require more
effort and cost than the probe.

Used units are out there ... ebay?

 

I think...
27KV requires a good isolation...

Uhmm...only the high voltage probe...very difficult to find for my Protek
608...
I can search, probably, a full meter ...but I use it only this time..
probably, the cheapest solution is to ask help to an alectric laboratory.. I
think that probably is the better solution, finally....

 

Starflex:
Gosh.... I would forget about a dedicated, add on, HV probe for your
Protek.... instead, get a stand alone high voltage probe with meter and
ground clip... brand new around $60 - $70 from MCM and used ones are VERY
very much cheaper on Ebay.... it appears that you have not tried an Ebay
search yet??? .... or a google search yet???? .... Lots of stuff to
look at regarding HV probes.
And, as a very FIRST resort since you are on the SCI.ELECTRONICS.REPAIR
newsgroup you should have FIRST gone to the REPAIRFAQS that discuss HV
probes... safety, design and so on.... there is even a sample circuit there.
I found this article in just a minute or two. Go to this link:
http://www.repairfaq.org/REPAIR/F_hvprobe.html

and the following two Ebay items in less than a minute:
(I searched for "high voltage probe" ..... obviously)
http://cgi.ebay.com/Leader-high-voltage-meter-probe-LHM-80B-n-r_W0QQitemZ270
104401076QQcategoryZ25411QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

http://cgi.ebay.com/40-KV-HIGH-VOLTAGE-PROBE-400-MA-DC-NO-RESERVE_W0QQitemZ2
50098396960QQcategoryZ50971QQrdZ1QQcmdZViewItem

If you can pick up a used Ebay HV Probe for just a few bucks it would most
likely be much cheaper and much safer that building your own.

Best Regards,

Daniel Sofie
Electronics Supply & Repair
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snipped:

 

Go to the website for this newsgroup at
http://www.repairfaq.org/
there, with a little search time you will find what you are looking
for.

Also there are alot of cheap used high voltage probes on ebay all the
time, many of them do not require a meter or scope to hook up to, they
have their own meter built in, much handier and safer?

electricitym

 

Let's see... a piece of plastic pipe about two feet long... a hundred 1
meg resistors soldered in series... 100 megohms... one end connected to
ground, the other to 27 kV... that's a current draw of only 270
microamps... and the voltage across the resistor connected to ground
will be only 270 volts.

 

I found a probe on ebay, but in a pinch you can build one out of a bunch
of 10 meg resistors in a piece of 1/2" PVC pipe filled with mineral oil.
Shouldn't cost you more than 10 bucks to make.

Another option is to measure one of the other voltages produced by the
flyback, usually there's several and they follow the HV pretty closely.

 

You need an HV probe or a stand alone HV meter for testing CRT high tension.
You will not easily or feasibly be able to build your own. There are some
very serious safety issues involved if you were to try to build your own. If
you are going to be in the business of servicing TV sets and monitors, then
you will have to buy the necessary tools to do the job.

--

JANA
_____


Hello!
If you read the post below (sorry for two post....), I have a E500 Sony
monitor.
I have replaced the varistor that regulate hte high tension of the
FBT...because the previous is quite "cooked"....
So, now I must regulate the high tension to the valour of 27 kV.
I don't have the high tension probe for my meter (they are quite expensive,
and I don' t want purchase their....).
There is any safe method (for example, using a voltage partitor, or
something other!) to measure this voltage with a standard meter?
Thank you!

 

I would be very leery about the accuracy of a probe bought on Ebay. The
voltage divider resistors in these probes are very fragile, sort of a
glasslike construction.
If the probe gets dropped, or banged the resistors can get hairline cracks,
and the readings will be way off.

 

Too much load. The Fluke HV probe is 1000 Megohms,rated to 50KV,IIRC.

 

Sofie wrote:
[snip]

Hi Sofie, and many thanks for your reply.
Before searching in Google, I prefer to ask to a "real man" if it is safety
or not: this is "my first monitor" and I'm not very sure of what I can do or
not.
I have already search on Ebay about High Voltage meter, about two weeks
ago...
Yes, the price that I can find -especially for used item- is very low...but
I live in Italy..and there is the shipping cost!!
Consider that, if i choose an economical shipping, it cost about 20
dollars..and it requires VERY OFTEN three months (!!). In the better chance,
it arrive in "only" 8 weeks.
If I choose, instead, a faster shipping, the cost is higher...40 dollars.
So, the total cost is quite high, for a item that probably I'll use once in
my life..!
I'm not a "repair man", I don't work in a laburatory: I'm only a student, of
course, with the passion for those things..but only a passion...and the
CRT's monitor are almost dead...
Thank you for the link about the FAQ's: I don't know that this newsgroup had
the faq's...!
So, finally...thank you for your reply, and sorry for the "stupid" question!

 

....some sellers don't sent to Italy, or the shipping cost is too high, if I
want to receive it in a resonable time.... :-(

 

I had seen many items, but I have a doubt..and I've found a seller that can
ship it to Italy for only 25 $, S&H included.
I had seen that all the items included the meter (probably, a galvanometer),
but it is quite little.
I think that is very difficult to read a valour of 27kV, +- 0,1 kv.
Is only my imprerssion, or it is really correct..?

 

It is no harder to read 27 kv on a meter than to read any voltage on any
other meter. Usualy around 27 kv would be in the most accurate area of the
meter.
But, it would be good to test the meter against a known voltage.
We used to have 4 or 5 of these, but kept one locked up as a standard to
check against.