Heathkit ol-1 oscilloscope help. Can't get solid spot during setup procedure.

[Enzo]

Well, we have some vertical stuff with no input, right? SO pull V1. Now what is on the screen? You have four 12AU7s in this thing, two for each direction. Try swapping them around. ANything changes we kinow the tube is what made it change.

And that couple volts of riple you had on B+ A? Try slapping another 20uf cap from A to ground. See if that smooths anything out.

[jasonguitar]

Well, we have some vertical stuff with no input, right? SO pull V1. Now what is on the screen? You have four 12AU7s in this thing, two for each direction. Try swapping them around. ANything changes we kinow the tube is what made it change.

And that couple volts of riple you had on B+ A? Try slapping another 20uf cap from A to ground. See if that smooths anything out.

Okay, so adding another 22uf cap got rid of the ripple at point A but the display didn't change.

Removing V2(vert ctr) shifts the diagonal line to a straight vertical line(actually a very tight elipse). Swapping different tubes in this position displays the same diagonal line again.

Removing V5(hor ctr) shift the diagonal line to a straight horizontal line(elipse). Swapping different tubes in this position displays the same diagonal line again.

Removing both V2 & V5 gives me a solid dot! But of course I can't do anything with it!

Removing V1(vert gain) with V2 and V5 removed, the dot remains the same.
Removing V4(hor gain) with V2 and V5 removed and V1 in place, the dot remains the same.

Moving tubes around and substituting other 12au7s, 12at7s, 12ax7s, produces the same diagonal line but differing lengths according to the gain of the tube.

[Enzo]

But the point was to remove V1 and see what happens, not to remove the V2 and V5 first and then V1. Clearly with V2 removed, V1 can;t have any effect. What we wanted to find out was if V1 was sending any odd unwanted signal to V2.

Look at the circuit, V2 and V5 directly drive the deflection plates in the CRT (picture tube). When either is removed, then the exact same voltage is sitting on opposing plates, and you lose deflection completely in that direction. The unmoving dot as you found.

Now V1 is the inoput amplifier tube. It takes the input signal and amplifies it for V2. And V4 does the same thing for V5.

If you pull V1, the functions of V2 remain, so the position control should still work. What we want to know is if pulling V1 eliminates the odd vertical deflection signal you have. Just as we might remove V1 from a guitar amp to see if it removed some hum. Just exactly like that. And we are trying to isolate the problem, even if the tube itself is OK, that doesnlt mean the circuit around it is. We need to determine just where this unwanted deflection arises.

Pulling V1 SHOULD kill any vertical movement. Pulling V4 would kill horizontal movement, but that would also include teh sweep. SO lets concentrate on the vertical for now.

[jasonguitar]

But the point was to remove V1 and see what happens, not to remove the V2 and V5 first and then V1.

Sorry, I forgot to mention that pulling V1 gives no display at all. Same with pulling V4.

The diagonal line(or elipse) shortens a bit when I remove V3.

[Enzo]

Well now that is odd. Those stages are capacitance coupled to the V2 and V5 stages, there should be no DC problems there. I would have expected no deflection, not no display.

We never did determine those other caps did we.

Pull V1, set the vertical position control to its mid point, and measure DC voltage at pins 2 and 7 of V2. What do you get?


And let us not forget the high voltage. Note that the voltage coming off pin 9 of V7 is NEGATIVE, as are the voltages derived from that for the CRT. Look at the voltage chart, if your meter is up to it, check them. Mainly I want to know what you get with meter set for AC volts - ripple. If the voltage at V7 is too high, just worry about the voltages going to the CRT. Ripple here can cause beam problems that can affect deflection. There is very little current in that supply, so the filtration is those two little .1uf 1200v caps.


OH, and another check. Put V1 back in. Measur DC voltage at pin 2 of V1 as you turn the vertical gain control up and down. If it goes positive at all, then there is a problem, probably that 20uf/150v cap from pin 8. or done a different way, is there any DC voltage across either horizontal or vertical gain controls themselves?

[jasonguitar]

Pull V1, set the vertical position control to its mid point, and measure DC voltage at pins 2 and 7 of V2. What do you get?

pin2: 33v pin7: 17v

And let us not forget the high voltage. Note that the voltage coming off pin 9 of V7 is NEGATIVE, as are the voltages derived from that for the CRT. Look at the voltage chart, if your meter is up to it, check them. Mainly I want to know what you get with meter set for AC volts - ripple. If the voltage at V7 is too high, just worry about the voltages going to the CRT. Ripple here can cause beam problems that can affect deflection. There is very little current in that supply, so the filtration is those two little .1uf 1200v caps.

Okay, AC ripple probs. Time to order those .1@1200V caps. Shoulda checked em on the Capacitor bridge I just restored.

So V8 pins: 1=6vac, 3=1vac, 4=5vac, 6=4vac 8=3vac, 10=10vac, 11=8vac

V7 has 33vac at pin 9

OH, and another check. Put V1 back in. Measur DC voltage at pin 2 of V1 as you turn the vertical gain control up and down. If it goes positive at all, then there is a problem, probably that 20uf/150v cap from pin 8. or done a different way, is there any DC voltage across either horizontal or vertical gain controls themselves?

Voltage seems to fluctuate between negative and positive milliamps at pin 2 of V1

[Enzo]

Well, keep it in context, on the CRT V8 note what the pins do. Pins 3,6,8,9 are deflection plates, and whatever voltage you find on them is coming from V2 and V5 plates. And pins 1 and 11 are the CRT tube's heater, which runs on 6VAC. However I do expect pins 4,7, and 10 to be smooth DC.

If that final test I suggested just gives a few millivolts, then it is fine.

Look at the schematic for vertical drive tube V2. Note grids pin 2 and 7 have identical resistances betweem grid and ground. Note further the position control is just a 50k pot between the grids with the wiper connected to B+ through the 100k resistor. By turning the control back and forth we change the balance between the voltage at the left and right grids. Centered, I expect the control to put aboput the same voltage on both grids. You got 33v and 17v. You might turn the control back and forth and see if it balances the two out at some setting reasonably close to center on the control.

A leaky 0.1uf cap to pin 2 COULD be upsetting the balance. I hope I am not leading you down the garden path.

And furthermore, the plates of V2, pins 1 and 6, connect to pins 6 and 9 of the CRT. DO you see about the same DC voltage at each?

[jasonguitar]

Look at the schematic for vertical drive tube V2. Note grids pin 2 and 7 have identical resistances betweem grid and ground. Note further the position control is just a 50k pot between the grids with the wiper connected to B+ through the 100k resistor. By turning the control back and forth we change the balance between the voltage at the left and right grids. Centered, I expect the control to put aboput the same voltage on both grids. You got 33v and 17v. You might turn the control back and forth and see if it balances the two out at some setting reasonably close to center on the control.

A leaky 0.1uf cap to pin 2 COULD be upsetting the balance. I hope I am not leading you down the garden path.

And furthermore, the plates of V2, pins 1 and 6, connect to pins 6 and 9 of the CRT. DO you see about the same DC voltage at each?

The vert ctr does balance the voltages near the middle. Guess I was off. No pointer on the knob.

V2 pins 1 and 6 have very close voltages.

These .1@1200 caps are definitely failing. They are starting to ooze out of the seams. Actually they are only 1000v but the schematic calls for 1200v. Just placed an order with Digi-key. Nobody local has these.

[Enzo]

I hope that solves it. When you have unwanted deflection, it is like in an audio circuit where you have unwanted sound - usually it is hum.

[jasonguitar]

I hope that solves it. When you have unwanted deflection, it is like in an audio circuit where you have unwanted sound - usually it is hum.

Great lesson for me. Never tinkered with a scope before. God one to learn on eh? As basic as it gets. I'll have to test the other caps for leakage too to be sure. I'd like to have confidence that this thing is up to snuff, for what its worth.

Spent most of the day restoring a clean Eico 377 signal generator I got from a local Ebay seller for $15 this morning. Every single cap in the thing was VERY leaky. $15 bucks later it works like a gem. My uncle gave me an Eico 950b Capacitance bridge a few days ago which I restored and its really coming in handy. Really looking like a 60's amp repair shop over here!

[Enzo]

Oh that 950b is a great little piece. My first piece of test gear was an EICO VTVM. They had two of them, and I went for the one with the big oversized meter movement.
Photo from Tone Lizard - Tales From The Tone Lounge; The Idiot's Guide To Oscilloscopes!


I still have it and recently got it out to restore to use. Why not? But as I learned, I realized I needed to be able to measure and identify caps and coils, as well as test them. I told my dad I wanted to buy this capacitor bridge, and he told me, "You already have a tester, don;t waste your money." To him a VTVM was a "tester" and how many testers do you need?

Ultimately I prevailed and built the 950b. A lot of molded paper caps in the 1950s had color codes that I couldn;t then read, so this let me measure them, at least approximately. But the beauty of the thing is it included the leakage test that actually put up to 500v on a cap. I haven't fired it up in ages, but it is sitting right behind me on the shelf. it was my second kit, 50 years ago.

Here is a great web site with old stuff resources: Boatanchor Pix
Lotta Heathkit stuff near the bottom.

Also from Tone Lizard, read this: Tales From The Tone Lounge: The Idiot's Guide To (analog) Oscilloscopes!

[jasonguitar]

Very cool. A tech I used to assist gave me an Eico 232 VTVM with the Uni-probe which I restored. I love this good old gear. Must have been so cool to be able to buy and build those kits! If they stll made these things today they would be priced in the boutique range for sure.

Love that 950B. Being able to do leakage tests under real voltage, can't live without that thing now!

Those resources have come in very handy. Its so great that you can pretty much get complete documentation, even construction manuals for these units.

[SpunkyMonkey]

OL-1 Oscilloscope Help

I also have an OL-1. I bought it from my boss in the early 80's. It worked flawlessly until a few months ago. Very bad ripple. I replaced all the caps and re-stuffed the multicaps with modern parts. I have some problems though.

1. The intensity no longer seems to work like it did. It is a 50K pot with a switch that applies power. I did a temporary replacement with another pot but the effect was the same. When the scope worked right the intensity pot was able to dim the trace to nothing. Now it seems to be always full on. There is some play between the focus and the intensity but I can't get it to work like it used to.

2. Focus drifts constantly. I also tried to switch out pots for it but it didn't help.

3. My scope spot on setup looks just like the one from the original poster. Even after replacing the tubes that showed up as weak and redoing all the old caps.

4. When evaluating square waves I have tons of ripple. I've tested voltage levels according to the manual and everything is within a few volts of what is indicated. I am using a 555 IC to generate the square waves and in the past I used to get a perfect readout. Now it looks like crap.

Here are some images:
The initial test has a diagonal but it is hard to get it focused:

On the second test I have a tube shape. Again focus is lame:

The third test is connecting the 60 cycle to the vertical and extending the vertical gain:

This is increasing horizontal gain and it looks right to me. A bit out of focus but acceptable:

This is the square wave. Lots of ripple. I used to see a nearly perfect square:


Should I replace all the resistors too? I've tested volts coming off of the power supply and don't detect ripple on the A, B, C, and D points out of the multi-cap.

Here is a schematic: http://www.qsl.net/wy3a/Heathkit%20OL-1/OL1_sch.pdf:

Any help you could give would be much appreciated! It has served me well over the years and I don't want to junk it.

[SpunkyMonkey]

Jasonguitar....

I don't know if you still have your OL-1 but mine is now working perfect thanks to a user on antiqueradios.com. After replacing all the caps I had a short diagonal like you had. In my case I had bad caps, and a shorted grid in the CRT which didn't allow me to control intensity. After fixing all that I had a very crisp diagonal. The user on antiqueradios.com suggested running twisted pair to the heaters for the tubes on the PCB. I removed the wire from the 6X4 to the heater traces and connected each tube individually with twisted pair. Perfect solid dot and zero detectable ripple. The heater supply was injecting ripple into everything.

[diydidi]

Hi Spunkymonkey
I know this is sn old thread. With regards to the Heatkit scope from a post a couple of years ago. Could you explain in more detail how you routed the twisted heater wires.
Did you cut the pcb heater traces at the tube sockets and run new twisted heater wires from a common point to each tube?
Or did you leave the pcb also cunducting the heater voltages along with the new heater wires?
Also did you stand the twisted wires up in the air or down against the chassis.
A photo or would be real nice.
Thanx man!!