wrote:
Hi, I have an IO-4555 Heathkit O-Scope that started spewing out smoke
15 seconds after turning it on.

One of two things happened. Either an electrolytic cap failed, or the
power transformer failed. The power transformers on these were very
cheaply made, and the high voltage winding had a bad tendency to short
to the case. If it made a loud snapping sound, it was probably the
transformer. If it made a smell that was more sharp and chemical than
ordinary burning, it was probably a cap.

Would like to find someone that can shoot me a PDF of the assembly
manual with schematics. The operations manual would be nice also.

I've checked Google and Dogpile for variations and can only find a
schematic for the dual trace version. (IO-4550)

That'll probably be sufficient since the supply is more or less the same
and it's a power supply problem you've encountered. You may also look on
BAMA.

You should not need the manual. Find the high voltage winding that
generates the anode voltage for the CRT.... measure resistance to ground
and you should see at least hundreds of ohms across the winding. Then
look at the supply caps.

You can also try powering it up with the case off and seeing what smokes.

If the transformer is good, it's worth it to replace the caps. If the
transformer has failed, scrap it for parts and get another scope.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 25 Apr 2009 08:37:36 -0400, (Scott Dorsey) wrote:

wrote:
Hi, I have an IO-4555 Heathkit O-Scope that started spewing out smoke
15 seconds after turning it on.

One of two things happened. Either an electrolytic cap failed, or the
power transformer failed. The power transformers on these were very
cheaply made, and the high voltage winding had a bad tendency to short
to the case. If it made a loud snapping sound, it was probably the
transformer. If it made a smell that was more sharp and chemical than
ordinary burning, it was probably a cap.

Would like to find someone that can shoot me a PDF of the assembly
manual with schematics. The operations manual would be nice also.

I've checked Google and Dogpile for variations and can only find a
schematic for the dual trace version. (IO-4550)

That'll probably be sufficient since the supply is more or less the same
and it's a power supply problem you've encountered. You may also look on
BAMA.

You should not need the manual. Find the high voltage winding that
generates the anode voltage for the CRT.... measure resistance to ground
and you should see at least hundreds of ohms across the winding. Then
look at the supply caps.

You can also try powering it up with the case off and seeing what smokes.

If the transformer is good, it's worth it to replace the caps. If the
transformer has failed, scrap it for parts and get another scope.
--scott


Thanks for the trouble shooting tips. The smell and color reminded me
more of frying resistors :-) I haven't opened her up yet to peek at
the damage.

Tim...

wrote:
Thanks for the trouble shooting tips. The smell and color reminded me
more of frying resistors :-) I haven't opened her up yet to peek at
the damage.

Pull the case open and look inside! If you see some big resistors in
the power supply gone open, check the capacitors downstream of them for
a dead short. You'll never know until you open it! They are fun and
easy to work on... everything is laid out very openly and the basic
design you can figure out by looking for the most part.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Apr 25, 7:37 am, (Scott Dorsey) wrote:
wrote:
Hi, I have an IO-4555 Heathkit O-Scope that started spewing out smoke
15 seconds after turning it on.

One of two things happened. Either an electrolytic cap failed, or the
power transformer failed. The power transformers on these were very
cheaply made, and the high voltage winding had a bad tendency to short
to the case. If it made a loud snapping sound, it was probably the
transformer. If it made a smell that was more sharp and chemical than
ordinary burning, it was probably a cap.

Would like to find someone that can shoot me a PDF of the assembly
manual with schematics. The operations manual would be nice also.

I've checked Google and Dogpile for variations and can only find a
schematic for the dual trace version. (IO-4550)

That'll probably be sufficient since the supply is more or less the same
and it's a power supply problem you've encountered. You may also look on
BAMA.

You should not need the manual. Find the high voltage winding that
generates the anode voltage for the CRT.... measure resistance to ground
and you should see at least hundreds of ohms across the winding. Then
look at the supply caps.

You can also try powering it up with the case off and seeing what smokes.

If the transformer is good, it's worth it to replace the caps. If the
transformer has failed, scrap it for parts and get another scope.

If you want a vintage scope get a Tek, since the toob models have
excellent parts availability since no revenue users want them. The
Heathkit trafo could be rewound if you really want an educational
project, but most were not very good scopes except for X-Y use. In the
SSTV days they were ham-popular since they used a commodity jug that
could be had with a P7 phosphor. that also makes a great audio level
indicator if you're too cheap to buy a Dorrough.

On Apr 25, 7:37 am, (Scott Dorsey) wrote:
wrote:
Hi, I have an IO-4555 Heathkit O-Scope that started spewing out smoke
15 seconds after turning it on.

One of two things happened. Either an electrolytic cap failed, or the
power transformer failed. The power transformers on these were very
cheaply made, and the high voltage winding had a bad tendency to short
to the case. If it made a loud snapping sound, it was probably the
transformer. If it made a smell that was more sharp and chemical than
ordinary burning, it was probably a cap.

Would like to find someone that can shoot me a PDF of the assembly
manual with schematics. The operations manual would be nice also.

I've checked Google and Dogpile for variations and can only find a
schematic for the dual trace version. (IO-4550)

That'll probably be sufficient since the supply is more or less the same
and it's a power supply problem you've encountered. You may also look on
BAMA.

You should not need the manual. Find the high voltage winding that
generates the anode voltage for the CRT.... measure resistance to ground
and you should see at least hundreds of ohms across the winding. Then
look at the supply caps.

You can also try powering it up with the case off and seeing what smokes.

If the transformer is good, it's worth it to replace the caps. If the
transformer has failed, scrap it for parts and get another scope.

If you want a vintage scope get a Tek, since the toob models have
excellent parts availability since no revenue users want them. The
Heathkit trafo could be rewound if you really want an educational
project, but most were not very good scopes except for X-Y use. In the
SSTV days they were ham-popular since they used a commodity jug that
could be had with a P7 phosphor. that also makes a great audio level
indicator if you're too cheap to buy a Dorrough.

This is mainly for my son to learn to work on audio amplifiers. He's a
budding rock star that loves the sound of a tube amp. So I'm picking
up some simple test equipment for him to work with. VOM, scope, freq
counter, function generator (computer based), etc.

I also have an old electronics course for him to learn. I hope that
he's going to turn into a good repair tech for his equipment of
choice.

I do have another scope but I would rather he use the Heathkit. When I
get the time I'll tear apart the heathkit and check out that power
supply or make him do it.