CRO Powerup Puzzle

[John Smyth]

Bought a Hitachi V550B oscilloscope via this NG a few months ago.

What puzzles me is that the power on led doesn't come on immediately.
It takes between say 2 - 60 seconds for the LED to come on and then the
trace appears almost immediately.

Anyone know if that's a fault or normal operation?

Also anyone have a manual for sale / copying?
I Can get one from Telford in the UK for about $100 AU, but thats a bit too
much methinks.

Thanks
John

 

[Bill Bailley]

"John Smyth" <smyth@tpg.com.au> wrote in message
news:418f44d9@dnews.tpgi.com.au...

Bought a Hitachi V550B oscilloscope via this NG a few months ago.

What puzzles me is that the power on led doesn't come on immediately.
It takes between say 2 - 60 seconds for the LED to come on and then the
trace appears almost immediately.

Anyone know if that's a fault or normal operation?

Also anyone have a manual for sale / copying?
I Can get one from Telford in the UK for about $100 AU, but thats a bit
too
much methinks.

Thanks
John

In general, especially with older equipment, you will find that a number of
electrolytic capacitors will test poorly. Power supply capacitors are
particularly prone to partial failure and this can give intermittent
results.

I know nothing about the oscilloscope you mention, but I do know that a good
purge of those older electrolytics can bring many an old piece back to life.

As always, your mileage may vary.

An ESR meter designed by Bob Parker here in Aus is highly recommended for in
circuit capacitor testing. http://bob.parker.web1000.com/ I would guess
that the tester is likely to bring you better results than having a
schematic to hand. I am not spruiking for Bob, just passing the good word. I
am almost sure he pops up on this group from time to time.

Bill.

 

[Bob Parker]

"Bill Bailley" <JustMe@Home> wrote in message news:<41900e94$0$3841$afc38c87@news.optusnet.com.au>...

An ESR meter designed by Bob Parker here in Aus is highly recommended for in
circuit capacitor testing. http://bob.parker.web1000.com/ I would guess
that the tester is likely to bring you better results than having a
schematic to hand. I am not spruiking for Bob, just passing the good word. I
am almost sure he pops up on this group from time to time.

Bill.

Thanks Bill!
I do sometimes have a look around this newsgroup. Now that I'm
gainfully employed by someone else, I don't get as much time for this
kind of thing as I used to when I was working for myself.
I appreciate your nice comments about the ESR meter.

Regards,
Bob Parker

 

[Retired Telco]

John,
Did you find a schematic/manual yet?

The power led (D1401) works directly off the -12v lead which is
regulated by a 7912 (IC 1121). No delays are built into the PS. The
led may be faulty & requires "warming up".

Warren