Fixing Heathkit Oscilloscope

[Ivan Vegvary]

Picked up the above for $ 10. Fuse was blown. Don't have a 125V 1A fuse but used 125V 1/2 amp fuse instead. Front indicator light went on and 30 seconds later the 1/2 amp fuse blew. Will pic up a 1 amp fuse. If it keeps blowing, where would be a good place - method - to start diagnosis? I did get a manual and schematic with the scope.

I realize that I could probably buy an equivalent "working" scope for about $ 50, but I would like to get this one going. Tools available are VOM, VTVM and one hand safely in the pocket.

Thanks, Ivan Vegvary

 

[Phil Allison]

"Ivan Vegvary"

Picked up the above for $ 10. Fuse was blown. Don't have a 125V 1A fuse
but used 125V 1/2 amp fuse instead. Front indicator light went on and 30
seconds later the 1/2 amp fuse blew. Will pic up a 1 amp fuse. If it keeps
blowing, where would be a good place - method - to start diagnosis? I did
get a manual and schematic with the scope.


** But we did not.

What model number is it ??


I realize that I could probably buy an equivalent "working" scope for about
$ 50, but I would like to get this one going. Tools available are VOM, VTVM
and one hand safely in the pocket.

** You need a scope to fix a scope.



..... Phil

 

[ehsjr]

On 11/19/2012 11:05 PM, Ivan Vegvary wrote:

Picked up the above for $ 10. Fuse was blown. Don't have a 125V 1A fuse but used 125V 1/2 amp fuse instead. Front indicator light went on and 30 seconds later the 1/2 amp fuse blew. Will pic up a 1 amp fuse. If it keeps blowing, where would be a good place - method - to start diagnosis? I did get a manual and schematic with the scope.

I realize that I could probably buy an equivalent "working" scope for about $ 50, but I would like to get this one going. Tools available are VOM, VTVM and one hand safely in the pocket.

Thanks, Ivan Vegvary

Well, based on the available information, it's guesswork.
That said, check the electrolytic capacitor(s) in the DC supply
with your VOM set to measure resistance. If you don't know what
you should see on the meter, get a new 'lytic of the same
value and measure it to get an idea. You want to leave the
meter connected for a while to watch the measurement climb
up toward infinity. 'Lytics often fail with age and can
show leakage on that test.

Ed

 

[Michael Black]

On Mon, 19 Nov 2012, Ivan Vegvary wrote:

Picked up the above for $ 10. Fuse was blown. Don't have a 125V 1A
fuse but used 125V 1/2 amp fuse instead. Front indicator light went on
and 30 seconds later the 1/2 amp fuse blew. Will pic up a 1 amp fuse.
If it keeps blowing, where would be a good place - method - to start
diagnosis? I did get a manual and schematic with the scope.

I realize that I could probably buy an equivalent "working" scope for
about $ 50, but I would like to get this one going. Tools available are
VOM, VTVM and one hand safely in the pocket.

Thanks, Ivan Vegvary

People have said in the past that the transformers on the Heathkits were

pretty cheap, and did often burn out in the long run. I have no
experience, but I can imagine that. The problem being of getting a
replacement that not only has the needed windings, but fits the sapce.

SO that's something to look into.

Michael

 

[Michael A. Terrell]

Phil Allison wrote:

"Ivan Vegvary"

Picked up the above for $ 10. Fuse was blown. Don't have a 125V 1A fuse
but used 125V 1/2 amp fuse instead. Front indicator light went on and 30
seconds later the 1/2 amp fuse blew. Will pic up a 1 amp fuse. If it keeps
blowing, where would be a good place - method - to start diagnosis? I did
get a manual and schematic with the scope.

** But we did not.

What model number is it ??

I realize that I could probably buy an equivalent "working" scope for about
$ 50, but I would like to get this one going. Tools available are VOM, VTVM
and one hand safely in the pocket.

** You need a scope to fix a scope.

Not always. I've fixed several with just a VTVM and a calibrated
eyeball.

 

[Michael Black]

On Tue, 20 Nov 2012, Michael A. Terrell wrote:

Phil Allison wrote:

"Ivan Vegvary"

Picked up the above for $ 10. Fuse was blown. Don't have a 125V 1A fuse
but used 125V 1/2 amp fuse instead. Front indicator light went on and 30
seconds later the 1/2 amp fuse blew. Will pic up a 1 amp fuse. If it keeps
blowing, where would be a good place - method - to start diagnosis? I did
get a manual and schematic with the scope.

** But we did not.

What model number is it ??

I realize that I could probably buy an equivalent "working" scope for about
$ 50, but I would like to get this one going. Tools available are VOM, VTVM
and one hand safely in the pocket.

** You need a scope to fix a scope.


Not always. I've fixed several with just a VTVM and a calibrated
eyeball.

My Tektronix from 1959 (the model came out that year, don't know the date

mine was manufactured) developed ripple in the trace. So I opened up the
case, and put the probe on each of the filter capacitors in the power
supply. At one point, the ripple is worse, so that's the bad capacitor.
I was surprised (this was about 20 years ago) that the local "surplus"
place had a capacitor of the right value, since it was higher capacitance
than the average tube-era power supply filter capacitor. I put in the new
capacitor and the trace was nice and flat like it had been before.

Michael

 

[Tim Wescott]

On Mon, 19 Nov 2012 20:05:37 -0800, Ivan Vegvary wrote:

Picked up the above for $ 10. Fuse was blown. Don't have a 125V 1A
fuse but used 125V 1/2 amp fuse instead. Front indicator light went on
and 30 seconds later the 1/2 amp fuse blew. Will pic up a 1 amp fuse.
If it keeps blowing, where would be a good place - method - to start
diagnosis? I did get a manual and schematic with the scope.

I realize that I could probably buy an equivalent "working" scope for
about $ 50, but I would like to get this one going. Tools available are
VOM, VTVM and one hand safely in the pocket.

Thanks, Ivan Vegvary

30 seconds sounds about right for a tube to heat up and go over current.

1/2A may not be enough fuse, so blowing the fuse may just be a diagnostic
that the fuse is doing its job -- get the right fuse to start with.

With Heathkits, you always need to ask the question "did it ever work?".
Then you need to ask "did it ever work _right_?". Then "was it
modified?". Then, finally, open it up and visually inspect everything
not just for the obvious like burnt components or wires, but for the less-
obvious assembly errors like cold solder joints, wires broken because of
improper assembly, wires put in the wrong places*, etc.

Inspect with your eyes _and_ your nose -- if you get a whiff of "that
expensive smell" then track down what's burnt. When you turn it on (out
of the case, of course), go over it with your nose again -- your nose not
only smells, but it's a pretty good heat sensor, sometimes you can
"smell" warm air coming from a too-hot component before it actually
starts smelling burnt.

If it still blows the same way with a 1A fuse then start checking tubes
for proper bias and shorts and stuff. Then check all of the power supply
voltages to make sure they're correct.

If it's solid state other than the CRT this'll be easy. I would think
that if the CRT is pulling too much current that you'd have seen a honkin'
bright spot, but I suppose that if the biases were really all shot to
hell then you may have just lit up the whole screen and not noticed it --
power it up in a dark room the next time and see.

And tell us what model it is, and other essential things like how many
tubes!

* I'm partially color blind in green and red, so my Heathkit oscilloscope
got assembled with a green wire swapped for a gray wire. One was a 160V
bias, the other was a 5V signal. I made expensive smells with that one.
But then, I fixed it, too.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

 

[Fred Abse]

On Mon, 19 Nov 2012 20:05:37 -0800, Ivan Vegvary wrote:

Picked up the above for $ 10. Fuse was blown. Don't have a 125V 1A fuse
but used 125V 1/2 amp fuse instead. Front indicator light went on and 30
seconds later the 1/2 amp fuse blew. Will pic up a 1 amp fuse. If it
keeps blowing, where would be a good place - method - to start diagnosis?
I did get a manual and schematic with the scope.

I realize that I could probably buy an equivalent "working" scope for
about $ 50, but I would like to get this one going. Tools available are
VOM, VTVM and one hand safely in the pocket.

Thanks, Ivan Vegvary

A perennial problem with tube 'scopes is the CRT heater winding on the
supply transformer going leaky or short to frame, or to another winding.
The heater is connected to the cathode, to take the stress off the
heater-cathode insulation, and is floated at negative HV, hence the
transformer insulation must stand several thousand volts DC.

The only cure for that is to fit a separate heater transformer with
sufficiently good insulation, such as one of those that used to be sold to
fix mono TV heater-cathode shorts. They used a split bobbin.

BTDT many times ;-(

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[Phil Allison]

"Michael A. Troll"

Phil Allison wrote:

"Ivan Vegvary"

Picked up the above for $ 10. Fuse was blown. Don't have a 125V 1A fuse
but used 125V 1/2 amp fuse instead. Front indicator light went on and 30
seconds later the 1/2 amp fuse blew. Will pic up a 1 amp fuse. If it
keeps
blowing, where would be a good place - method - to start diagnosis? I
did
get a manual and schematic with the scope.

** But we did not.

What model number is it ??

I realize that I could probably buy an equivalent "working" scope for
about
$ 50, but I would like to get this one going. Tools available are VOM,
VTVM
and one hand safely in the pocket.

** You need a scope to fix a scope.


Not always.

** There is no "always" in my comment.

You illiterate moron.

 

[Michael A. Terrell]

Fred Abse wrote:

On Mon, 19 Nov 2012 20:05:37 -0800, Ivan Vegvary wrote:

? Picked up the above for $ 10. Fuse was blown. Don't have a 125V 1A fuse
? but used 125V 1/2 amp fuse instead. Front indicator light went on and 30
? seconds later the 1/2 amp fuse blew. Will pic up a 1 amp fuse. If it
? keeps blowing, where would be a good place - method - to start diagnosis?
? I did get a manual and schematic with the scope.
?
? I realize that I could probably buy an equivalent "working" scope for
? about $ 50, but I would like to get this one going. Tools available are
? VOM, VTVM and one hand safely in the pocket.
?
? Thanks, Ivan Vegvary

A perennial problem with tube 'scopes is the CRT heater winding on the
supply transformer going leaky or short to frame, or to another winding.
The heater is connected to the cathode, to take the stress off the
heater-cathode insulation, and is floated at negative HV, hence the
transformer insulation must stand several thousand volts DC.

The only cure for that is to fit a separate heater transformer with
sufficiently good insulation, such as one of those that used to be sold to
fix mono TV heater-cathode shorts. They used a split bobbin.

BTDT many times ;-(

Prior to split bobbin types, Triad & Stancor both used to sell scope
filament transformers rated for 2500 volts between windings. I would
guess that Merit and a couple dozen other transformer companies had them
in their 'Universal Replacement' lines. I used some in the '60s on old
Eico & Heath scopes.

 

[Michael A. Terrell]

Phil Allison wrote:

"Michael A. Troll"
? Phil Allison wrote:
??
?? "Ivan Vegvary"
??
?? Picked up the above for $ 10. Fuse was blown. Don't have a 125V 1A fuse
?? but used 125V 1/2 amp fuse instead. Front indicator light went on and 30
?? seconds later the 1/2 amp fuse blew. Will pic up a 1 amp fuse. If it
?? keeps
?? blowing, where would be a good place - method - to start diagnosis? I
?? did
?? get a manual and schematic with the scope.
??
?? ** But we did not.
??
?? What model number is it ??
??
?? I realize that I could probably buy an equivalent "working" scope for
?? about
?? $ 50, but I would like to get this one going. Tools available are VOM,
?? VTVM
?? and one hand safely in the pocket.
??
?? ** You need a scope to fix a scope.
?
?
? Not always.

** There is no "always" in my comment.

You illiterate moron.

You always pull this stupid shit. You make a wrong statment, then
showing your infected ass when someone shows that you're wrong. You
didn't say 'You sometimes need another scope to fix a scope', you
declared that: "** You need a scope to fix a scope." which leaves you no
wiggle room. Suck it up and go away. Iv'e fixed more scopes without a
scope that required one. If you did morte than fix toasters & old
vibrators you pick up from the dumpsters behind porn shops you mihght
have a clue. I'll bet you still claim that there are no 'CHEMICAL
FUSES', even though I posted links to them.

 

[Phil Allison]

"Michael A. Trolling CUNT "

?? I realize that I could probably buy an equivalent "working" scope for
?? about $ 50, but I would like to get this one going. Tools available
are VOM,
?? VTVM and one hand safely in the pocket.
??
?? ** You need a scope to fix a scope.
?
?
? Not always.

** There is no "always" in my comment.

You illiterate moron.


You always pull this stupid shit. You make a wrong statment, then
showing your infected ass when someone shows that you're wrong. You
didn't say 'You sometimes need another scope to fix a scope', you
declared that: "** You need a scope to fix a scope." which leaves you no
wiggle room.

** You are TOTALLY and UTTERLY wrong - as fucking usual.

Comes with being a congenital, autistic mental RETARD.

The sooner fucking nut case TROLLS like YOU drop dead, the better.


..... Phil

 

[Michael A. Terrell]

Phil Allison wrote:

"Phil Allison Trolling CUNT "

Tell us something we haven't known for over a decade, idiot. You
always turn into a real asshole when anyone points out any if your
faults.

As far as dropping dead, show everyone the Phyllis way to do it.
Make sure that you teach the other idiot trolls how, before you stumble
out in front of a garbage truck that's backing down the alley. It'll
save the city the cost of a plot in 'Potter's Field'.

 

[Phil Allison]

Michael A. Trolling CUNT "


** You are TOTALLY and UTTERLY wrong - as fucking usual.

Comes with being a congenital, autistic mental RETARD.

The sooner fucking nut case TROLLS like YOU drop dead, the better.



..... Phil

 

[Michael A. Terrell]

Phil Allison wrote:

Phil Allison CUNT "

 

[David Eather]

On Wed, 21 Nov 2012 23:21:10 +1000, David Eather <eather@tpg.com.au> wrote:

On Wed, 21 Nov 2012 09:16:36 +1000, Phil Allison <phil_a@tpg.com.au
wrote:


"Michael A. Trolling CUNT "



?? I realize that I could probably buy an equivalent "working" scope
for
?? about $ 50, but I would like to get this one going. Tools
available
are VOM,
?? VTVM and one hand safely in the pocket.
??
?? ** You need a scope to fix a scope.
?
?
? Not always.

** There is no "always" in my comment.

You illiterate moron.


You always pull this stupid shit. You make a wrong statment, then
showing your infected ass when someone shows that you're wrong. You
didn't say 'You sometimes need another scope to fix a scope', you
declared that: "** You need a scope to fix a scope." which leaves you
no
wiggle room.


** You are TOTALLY and UTTERLY wrong - as fucking usual.

Comes with being a congenital, autistic mental RETARD.

The sooner fucking nut case TROLLS like YOU drop dead, the better.


.... Phil





Phil,

If you keep calling people names, i will tell them WHY you think
'autistic' is the worst possible insult.

Also would you mind having the courage to use a real email address
rather than spit venom from a pathetic alias?

 

[George Herold]

On Nov 21, 8:22 am, "David Eather" <eat...@tpg.com.au> wrote:

On Wed, 21 Nov 2012 23:21:10 +1000, David Eather <eat...@tpg.com.au> wrote:
On Wed, 21 Nov 2012 09:16:36 +1000, Phil Allison <phi...@tpg.com.au
wrote:

"Michael A. Trolling CUNT "

?? I realize that I could probably buy an equivalent "working" scope
for
?? about $ 50, but I would like to get this one going.  Tools
available
are VOM,
?? VTVM and one hand safely in the pocket.
??
?? ** You need a scope to fix a scope.
?
?
?   Not always.

**  There is no "always" in my comment.

      You illiterate moron.

 You always pull this stupid shit.  You make a wrong statment, then
showing your infected ass when someone shows that you're wrong.  You
didn't say 'You sometimes need another scope to fix a scope', you
declared that: "** You need a scope to fix a scope." which leaves you
no
wiggle room.

** You are TOTALLY and UTTERLY wrong  -  as fucking usual.

Comes with being a congenital, autistic mental RETARD.

The sooner fucking nut case TROLLS  like YOU drop dead,  the better.

....   Phil

Phil,

If you keep calling people names, i will tell them WHY you think
'autistic' is the worst possible insult.

Geesh, nothing wrong with being a bit 'autistic',
I heard Temple Brandon (sp) on npr the other night saying she thought
of it as an advantage!

George H.

Also would you mind having the courage to use a real email address
rather than spit venom from a pathetic alias?- Hide quoted text -

- Show quoted text -

 

[Phil Allison]

"David Eather"

If you keep calling people names, i will tell them WHY you think
'autistic' is the worst possible insult.

** For the umpteenth time, fuckhead - is not being used as an insult !!!!

The REASON Terrell continually makes ridiculous reading errors like this
one IS because he IS autistic !!!!

It is one of the classic symptoms of autism to interpret other people's
words absurdly LITERALLY.

It relates to an absence of having a working " theory of thought " when
reading or listening to people's words.

FFS pal - YOU have the SAME problem.

And it is genetic.

Get over it.


..... Phil

 

[Michael A. Terrell]

Phil Allison wrote:

"David Eather"


If you keep calling people names, i will tell them WHY you think
'autistic' is the worst possible insult.

** For the umpteenth time, fuckhead - is not being used as an insult !!!!

The REASON Terrell continually makes ridiculous reading errors like this
one IS because he IS autistic !!!!

Put up or shut up, Phylllis. Show the medical records that state I
am like you.

 

[David Eather]

On Thu, 22 Nov 2012 10:31:40 +1000, Phil Allison <phil_a@tpg.com.au> wrote:

"David Eather"


If you keep calling people names, i will tell them WHY you think
'autistic' is the worst possible insult.


** For the umpteenth time, fuckhead - is not being used as an insult
!!!!

The REASON Terrell continually makes ridiculous reading errors like
this
one IS because he IS autistic !!!!

It is one of the classic symptoms of autism to interpret other people's
words absurdly LITERALLY.

It relates to an absence of having a working " theory of thought " when
reading or listening to people's words.

FFS pal - YOU have the SAME problem.

And it is genetic.

Get over it.


.... Phil

" ** For the umpteenth time..is not being used as an insult "

Show me ONE other time! You have NEVER said that it is not an insult. In
fact your favorite variation is to use it as "you vile autistic pig". Are
you trying to say you are so out of it that you really think a four legged
pig with trotters can type on a keyboard and you are just providing an
anthropologically accurate description? And the "vile"?

You are rather badly caught out in a story of your own making. Do you
really think anyone will believe your fantasy edit of your *years* of bad
behavior?

And in this thread you did say "you need a scope to fix a scope" which
does because of the absoluteness of the statement also means you can't
fix a scope without one - and that is incorrect.

Someone corrected you - which is not a big deal, just a nit-pick as
everyone knew your statement was 90%+ correct - most of the time you do
need a scope to fix a scope - but you went, typically for you,
over-the-top-life-or-death-rant-rave-insult-and-spit-venom.

It's not even a big deal except you made it so.

Read that bit again. YOU made it a big deal. No one else would have cared
at all, they would have seen the comment correcting you as a nit-pick, a
very small thing, and your comment as 90%+


You called me autistic so ...

(I sniped what I was going to say and put in what follows instead. Let me
know if you want me to put the original back and explain what is going on
to anyone who has not managed to connect the dots)

If I had autism I could do this: (I am not making any sort of
recommendation - there are easier ways to achieve the same thing)

I could announce the fact plain and simple, and the response would be
exactly this:

From one or maybe two posters who already have rather severe personality
disorders a post or two of ridicule until they got board. Who in the
entire news group gives a shit about what they think anyway?

And...

and nothing.

Despite what you might think, in a technical newsgroup with the level of
interpersonal relationship that requires, autism makes no difference. All
I have to do to be perfectly productive is remember not to rail when
people don't use or read with the same precision I normally do and on the
rare occasion that I am not 100% correct and someone might nit-pick me, NO
ONE EVEN *BOTHERS* to judge me unless I make an issue of it.