Heathkit oscilloscope?

Does this scope have a model number?

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

MHz two

given to me

on one

time probing

the voltage

waveform, and I can

the device

wondering if

this thing

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

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

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.

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.

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

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

IO-4550 two

built it, so I

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

peak-to-peak calibrator

lasts for a

waveform

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.

electrolytic

the second

potentiometer I was

scope seems like a restoration project in-itself. sounds like fun robb

Hello all,

many thanks for all the responses to my questions. They are very much appreciated, and more importantly, learned, where I had to learn!

An update: I reflowed the solders on the BNC connectors for both probes, and the solders on the AC-GND-DC switches. I also tried to clean out these switches using solvent on a cotton swap. Both switches are improved, but one still exhibits flakiness. I have new switches on order. As for the BNC connectors, the connector for the dead trace I had turned out to be the problem. Both traces work properly now, with appropriate amplitudes.

Regards, Dan

On Sat, 22 Dec 2007 08:22:51 -0700, Dan Beck top-posted:

Cool!

But bottom-posting is the convention.

Cheers! Rich