Hello all,

I have been fooling (emphasis on fool) with an old Heathkit 10 MHz two 
channel oscilloscope, which I believe was built in 1976 (it was given to me 
several years ago).  I have been able to calibrate the voltage on one 
channel, but not the other.  Sometimes, after I have spent some time probing 
old pinball machine circuit boards using the one good channel, the voltage 
flakes out such that there is minimal amplitude in the waveform, and I can 
no longer observe good signals from the board in test.

Does anyone here have experience with such a dinosaur?  When the device 
works it has helped me diagnose these old boards; I am just wondering if 
there are any tips from the wisemen here in order for me to set this thing 
up better, recalibrate, etc.

Thank you in advance for reading.

Regards,
Dan

Dan Beck wrote:
> 
> Hello all,
> 
> I have been fooling (emphasis on fool) with an old Heathkit 10 MHz two
> channel oscilloscope, which I believe was built in 1976 (it was given to me
> several years ago).  I have been able to calibrate the voltage on one
> channel, but not the other.  Sometimes, after I have spent some time probing
> old pinball machine circuit boards using the one good channel, the voltage
> flakes out such that there is minimal amplitude in the waveform, and I can
> no longer observe good signals from the board in test.
> 
> Does anyone here have experience with such a dinosaur?  When the device
> works it has helped me diagnose these old boards; I am just wondering if
> there are any tips from the wisemen here in order for me to set this thing
> up better, recalibrate, etc.


   Does this scope have a model number?


-- 
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

"Michael A. Terrell" <m...@earthlink.net> wrote in message
news:4...@earthlink.net...
> Dan Beck wrote:
> >
> > Hello all,
> >
> > I have been fooling (emphasis on fool) with an old Heathkit 10 MHz two
> > channel oscilloscope, which I believe was built in 1976 (it was given to me
> > several years ago).  I have been able to calibrate the voltage on one
> > channel, but not the other.  Sometimes, after I have spent some time probing
> > old pinball machine circuit boards using the one good channel, the voltage
> > flakes out such that there is minimal amplitude in the waveform, and I can
> > no longer observe good signals from the board in test.
> >
> > Does anyone here have experience with such a dinosaur?  When the device
> > works it has helped me diagnose these old boards; I am just wondering if
> > there are any tips from the wisemen here in order for me to set this thing
> > up better, recalibrate, etc.
>
>
>    Does this scope have a model number?
>
>
> --
> Service to my country? Been there, Done that, and I've got my DD214 to
> prove it.
> Member of DAV #85.
>
> Michael A. Terrell
> Central Florida

I'm thinking the IO-4510 or 20..

"Dan Beck" <biscuitbecks@*nospam*cableone.net> wrote in message
news:1...@corp.supernews.com...
> Hello all,
>
> I have been fooling (emphasis on fool) with an old Heathkit 10
MHz two
> channel oscilloscope, which I believe was built in 1976 (it was
given to me
> several years ago).  I have been able to calibrate the voltage
on one
> channel, but not the other.  Sometimes, after I have spent some
time probing
> old pinball machine circuit boards using the one good channel,
the voltage
> flakes out such that there is minimal amplitude in the
waveform, and I can
> no longer observe good signals from the board in test.
>
> Does anyone here have experience with such a dinosaur?  When
the device
> works it has helped me diagnose these old boards; I am just
wondering if
> there are any tips from the wisemen here in order for me to set
this thing
> up better, recalibrate, etc.
>
> Thank you in advance for reading.
>

I  assembled one of those in college as part of a physics
project. 10 years later i purchased at an alumni day /reunion lab
clearout sale. It came with the original assembly instructions
manual, schematics and user manual.  I also see these on  THe-bay
occasionally.

if you have trouble solving problem, can not find info already
posted somewhere , and i have the same model them let me what you
need  i can try to  post something somewhere.

robb

Thank you all for the responses!

I apologize for omitting the model number.  It is a Heathkit IO-4550 two 
channel oscilloscope.  The individual who gave it to me also built it, so I 
have all the assembly and operation manuals.

Another flaky behavior is when I connect to the 1 V peak-to-peak calibrator 
on the front, I do get the square wave, but sometimes it only lasts for a 
few seconds, and then the voltage craps out and I lose the waveform 
amplitude, as I discussed previously.

Could any of these symptoms be explained by dried out electrolytic 
capacitors?  I also noticed when I was attempting to calibrate the second 
channel's voltage (the one that doesn't work at all) the potentiometer I was 
supposed to turn was sticky, and rough feeling.

Again, thank you in advance for any and all responses!

Regards,
Dan

"Dan Beck" <biscuitbecks@*nospam*cableone.net> wrote in message 
news:1...@corp.supernews.com...
> Hello all,
>
> I have been fooling (emphasis on fool) with an old Heathkit 10 MHz two 
> channel oscilloscope, which I believe was built in 1976 (it was given to 
> me several years ago).  I have been able to calibrate the voltage on one 
> channel, but not the other.  Sometimes, after I have spent some time 
> probing old pinball machine circuit boards using the one good channel, the 
> voltage flakes out such that there is minimal amplitude in the waveform, 
> and I can no longer observe good signals from the board in test.
>
> Does anyone here have experience with such a dinosaur?  When the device 
> works it has helped me diagnose these old boards; I am just wondering if 
> there are any tips from the wisemen here in order for me to set this thing 
> up better, recalibrate, etc.
>
> Thank you in advance for reading.
>
> Regards,
> Dan
>
> 

"Dan Beck" (biscuitbecks@*nospam*cableone.net) writes:
> Thank you all for the responses!
> 
> I apologize for omitting the model number.  It is a Heathkit IO-4550 two 
> channel oscilloscope.  The individual who gave it to me also built it, so I 
> have all the assembly and operation manuals.
> 
> Another flaky behavior is when I connect to the 1 V peak-to-peak calibrator 
> on the front, I do get the square wave, but sometimes it only lasts for a 
> few seconds, and then the voltage craps out and I lose the waveform 
> amplitude, as I discussed previously.
> 
Have you made sure the probe (including the cable and connector) are
actually good?  If any of that was flakey, the amplitude would suddenly
go away.  And sometimes it's worth looking at the simplest solutions.

Just use a piece of wire to connect the input to the calibrator output,
and see what happens.

  Michael

Hi Michael,

thank you for your comments.  Yes, indeed it is profitable to keep things 
simple...Here are some observations:

Y1 (Good channel)  Using a plain wire per your suggestion reveals a stable 
square wave of appropriate amplitude, with the following exception.  If I 
gently tap the AC-GND-DC switch for that channel, without even changing the 
position of the switch, the waveform decays to a trace with noise.  This new 
trace looks like it's "trying" to return to a square wave, but doesn't.  If 
I rapidly move the switch up and down it usually corrects; otherwise I have 
to power down the 'scope and return to it minutes later.

Y2 (Bad channel)  Using the plain wire test again all I get is a trace with 
noise on it, very similar to what I described above.  Messing with the 
corresponding AC-GND-DC switch does nothing.Sometimes I am able to use this 
channel to read signals from one of my circuit boards, but the amplitudes 
are much lower than they should be, given the voltages I expect them to be 
at.

I was able to perform the compensation procedure for the probe on its 10X 
setting, using the supplied calibrator square wave on the 'scope, so I think 
it is safe to conclude the probe is ok.

Both AC-GND-DC switches feel sloppy in their respective actions; I wonder if 
they need attention...

I do appreciate your efforts with this.

Regards,
Dan


"Michael Black" <e...@FreeNet.Carleton.CA> wrote in message 
news:fke7b5$qgd$1...@theodyn.ncf.ca...
> "Dan Beck" (biscuitbecks@*nospam*cableone.net) writes:
>> Thank you all for the responses!
>>
>> I apologize for omitting the model number.  It is a Heathkit IO-4550 two
>> channel oscilloscope.  The individual who gave it to me also built it, so 
>> I
>> have all the assembly and operation manuals.
>>
>> Another flaky behavior is when I connect to the 1 V peak-to-peak 
>> calibrator
>> on the front, I do get the square wave, but sometimes it only lasts for a
>> few seconds, and then the voltage craps out and I lose the waveform
>> amplitude, as I discussed previously.
>>
> Have you made sure the probe (including the cable and connector) are
> actually good?  If any of that was flakey, the amplitude would suddenly
> go away.  And sometimes it's worth looking at the simplest solutions.
>
> Just use a piece of wire to connect the input to the calibrator output,
> and see what happens.
>
>  Michael 

On Thu, 20 Dec 2007 11:57:31 -0700, "Dan Beck"
<biscuitbecks@*nospam*cableone.net> wrote:

>Hi Michael,
>
>thank you for your comments.  Yes, indeed it is profitable to keep things 
>simple...Here are some observations:
>
>Y1 (Good channel)  Using a plain wire per your suggestion reveals a stable 
>square wave of appropriate amplitude, with the following exception.  If I 
>gently tap the AC-GND-DC switch for that channel, without even changing the 
>position of the switch, the waveform decays to a trace with noise.  This new 
>trace looks like it's "trying" to return to a square wave, but doesn't.  If 
>I rapidly move the switch up and down it usually corrects; otherwise I have 
>to power down the 'scope and return to it minutes later.

My first thought would be dirty switch contacts, but the power off/on
remedy confuses things.  Could also be a cold solder joint on the
switch connections.

>
>Y2 (Bad channel)  Using the plain wire test again all I get is a trace with 
>noise on it, very similar to what I described above.  Messing with the 
>corresponding AC-GND-DC switch does nothing.Sometimes I am able to use this 
>channel to read signals from one of my circuit boards, but the amplitudes 
>are much lower than they should be, given the voltages I expect them to be 
>at.

Possibly poor connections to/around the gain switch/pot.

You could try connecting corresponding points in the two channels
while feeding one channel - that may help to locate the fault in the
bad channel.

Of course, once you have one channel working fairly well, you can use
it to trace the signal through the bad channel.

If the original builder wasn't too experienced soldering, you should
check carefully for cold solder joints.


>
>I was able to perform the compensation procedure for the probe on its 10X 
>setting, using the supplied calibrator square wave on the 'scope, so I think 
>it is safe to conclude the probe is ok.
>
>Both AC-GND-DC switches feel sloppy in their respective actions; I wonder if 
>they need attention...
>
>I do appreciate your efforts with this.
>
>Regards,
>Dan
>
>
>"Michael Black" <e...@FreeNet.Carleton.CA> wrote in message 
>news:fke7b5$qgd$1...@theodyn.ncf.ca...
>> "Dan Beck" (biscuitbecks@*nospam*cableone.net) writes:
>>> Thank you all for the responses!
>>>
>>> I apologize for omitting the model number.  It is a Heathkit IO-4550 two
>>> channel oscilloscope.  The individual who gave it to me also built it, so 
>>> I
>>> have all the assembly and operation manuals.
>>>
>>> Another flaky behavior is when I connect to the 1 V peak-to-peak 
>>> calibrator
>>> on the front, I do get the square wave, but sometimes it only lasts for a
>>> few seconds, and then the voltage craps out and I lose the waveform
>>> amplitude, as I discussed previously.
>>>
>> Have you made sure the probe (including the cable and connector) are
>> actually good?  If any of that was flakey, the amplitude would suddenly
>> go away.  And sometimes it's worth looking at the simplest solutions.
>>
>> Just use a piece of wire to connect the input to the calibrator output,
>> and see what happens.
>>
>>  Michael 
>

-- 
Peter Bennett, VE7CEI  
peterbb4 (at) interchange.ubc.ca  
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

On Thu, 20 Dec 2007 08:50:31 -0700, Dan Beck wrote:

On Thu, 20 Dec 2007 08:50:31 -0700, Dan Beck top-posted:

> I apologize for omitting the model number.  It is a Heathkit IO-4550 two
> channel oscilloscope.  The individual who gave it to me also built it,
> so I have all the assembly and operation manuals.
> 
> Another flaky behavior is when I connect to the 1 V peak-to-peak
> calibrator on the front, I do get the square wave, but sometimes it only
> lasts for a few seconds, and then the voltage craps out and I lose the
> waveform amplitude, as I discussed previously.

When you say, "the voltage craps out", which voltage do you mean? Knowing
that will go a very long way toward helping us help you troubleshoot 
this thing.

Good Luck!
Rich

"Dan Beck" <biscuitbecks@*nospam*cableone.net> wrote in message
news:1...@corp.supernews.com...
> Thank you all for the responses!
>
> I apologize for omitting the model number.  It is a Heathkit
IO-4550 two
> channel oscilloscope.  The individual who gave it to me also
built it, so I
> have all the assembly and operation manuals.
>
you are quite fortuneate to have those...

have you already run the  initial diagnostic setup tests ? how
accurate were the voltages  and resistances at the test points ?
were any out of the specified range ?

I have a note in the margin of ny manual that says "No trace"
even though only a few of the values were slightly out of
specified range

>
> Another flaky behavior is when I connect to the 1 V
peak-to-peak calibrator
> on the front, I do get the square wave, but sometimes it only
lasts for a
> few seconds, and then the voltage craps out and I lose the
waveform
> amplitude, as I discussed previously.
>
I am no expert buy any stretch  but the little i have leaned,
flaky electronic behavior  seems accompanied by some physical
connection problem (i like the  poor solder joint idea from one
of te experts) or possibly a close but not exact component
substitution

since it was a kit i would worry about incorrect connections,
swapped or in correct components placement. Looking inside, i
remember how easy it was to  make incorrect  connections on the
switches, using the wrong valued parts (resistors / transistors )
and  putting the parts in the wrong place etc...

 i am sure i overheated several parts soldering / de-soldering /
re-soldering.

>
> Could any of these symptoms be explained by dried out
electrolytic
> capacitors?  I also noticed when I was attempting to calibrate
the second
> channel's voltage (the one that doesn't work at all) the
potentiometer I was
> supposed to turn was sticky, and rough feeling.
>
 scope seems like a restoration project in-itself.
sounds like fun
robb