Tektronics 2213A deflection problem...?

[ljcox]

Ray,
I don't know if the figures you quoted are too high or not. 60 mV in 100 V does not seem excessive, but it would be useful to know what the cro spec says.

I assume where you wrote "maybe I should just swap them out" you mean "replace them with new ones".
If one or more of the electros were faulty, I would have expected higher ripple figures.

However, it is worth a try given that the symptoms (ie. buzz in PS, reduced sweep width, etc.) seem to point to the PS.

Good luck, let us know how you go.

 

[rayyolanda]

Hi,
OK......replaced the caps in all low voltage supplies except for 100V...could not get a high volt cap. This has made the supply less noisey but the fault still remains.
I think the problem may be in the sweep generation circuit which is a bit of a loop but I think the problem is the Dual Retriggerable Resettable Monostable 96ls02. Is there an equivalent for this part? Will a 74hc4538 do?
Thanks....Ray

 

[ljcox]

Ray,
Both JayCar & Altronics sell HV caps.

JayCar have 450 V in the range 1 uF ~ 100 uF.

Altronics stock 400 V in the range 68 uF ~ 470 uF.

Farnel may have a greater range (& possibly greater price) They are in Sydney.

As for the monostable, do you have a data sheet for the 96LS02?

It looks like a high speed TTL, so the 74HC series will not be compatible.

The High level of TTL is, from memory, about 2.4 Volt.
The 74HC would not work with this as an input.
There is also the question of the trigger slope, the speed and pin connections.

However, the 74HCT series is designed to work with TTL.

Alternatively, you can still buy the 74LS series.

Both JayCar & Altronics sell the 74LS123 and JayCar also sell the 74LS221.

I buy most of my parts from Semtronics in Mitcham (Melbourne).

They are a small company so their web site is only basic as they don't have the manpower to keep it up to date. However, their prices are generally much lower than the others.

 

[rayyolanda]

H Len,
I don't think the 100V is bad the ripple was only 60mV and it always looks stable. But I would look the fool if it turns out to be the problem....!
I will replace it when I get the chance.

It was late when I was looking at the ICs so I did not think too hard about speed and voltage. The 74hc4538 is pin compatable, I will have to check the other specs. If I need to I can fashion up an adapter for whatever chip works.

Are you familiar with Tek manuals? I see a timing problem..maybe...I am not sure. The manual shows 15 waveforms on one page the first is the input 1-KHz signal. Then the others are for various signals such as; HOLDOFF GATE, SWEEP, END OF SWEEP etc. The thing is that if these waveforms are relative to each other then all the signals are about twice as fast as they should be relative to the 1-KHz input. I am not sure if the input is related to the others however it does seem that all the other signals are relative in time to each other.

I am using a PC scope program to look at signals...it is ok but no DC of course. That is why I am looking at sweep and holdoff generation as these signals look bad compared to the manual. This is a LOOP......it is hard to know where the problem starts. That is why the 96ls02 is a possible, I check the caps around it..ok..but the waveform is not as it should be...but it does get triggered by a filp flop which also has bad waveform....which is driven by the 96ls02....as I said...a loop.

I need to think about this more....or maybe less..!

Thanks.....Ray

 

[ljcox]

H Len,
I don't think the 100V is bad the ripple was only 60mV and it always looks stable. But I would look the fool if it turns out to be the problem....! Yes, 60 mV in 100 V seems small but it would be good to eliminate it.
I will replace it when I get the chance.

It was late when I was looking at the ICs so I did not think too hard about speed and voltage. The 74hc4538 is pin compatable, I will have to check the other specs. If I need to I can fashion up an adapter for whatever chip works.

Are you familiar with Tek manuals? No. I see a timing problem..maybe...I am not sure. The manual shows 15 waveforms on one page the first is the input 1-KHz signal. Then the others are for various signals such as; HOLDOFF GATE, SWEEP, END OF SWEEP etc. The thing is that if these waveforms are relative to each other then all the signals are about twice as fast as they should be relative to the 1-KHz input. I am not sure if the input is related to the others however it does seem that all the other signals are relative in time to each other. I would need to see the circuit and the waveforms to be able to offer an opinion.

I am using a PC scope program to look at signals...it is ok but no DC of course. That is why I am looking at sweep and holdoff generation as these signals look bad compared to the manual. This is a LOOP......it is hard to know where the problem starts. That is why the 96ls02 is a possible, I check the caps around it..ok..but the waveform is not as it should be...but it does get triggered by a filp flop which also has bad waveform....which is driven by the 96ls02....as I said...a loop.
The PC scope would be very limited in bandwidth, ie. the sample rate may be too slow.
I need to think about this more....or maybe less..!

Thanks.....Ray

Do you have a data sheet for the 96LS02?

Have you considered using a PIC? It would be fairly simple to programme it as a monostable and the 16F series is compatible with TTL.

 

[ljcox]

I have a Tek 2213A scope. i turned it on the other day for thefirst time in a while and all was ok. Then I heard a buz and higher pitch from the power supply. After this the scope only seems to display the trace in about 80% of the screen in both X and Y scales....so the trace is shrunk by about 20%, but it does seem to be correct otherwise, trigger etc all ok.
Ray

Ray, I just re-read your original post as above and notice that the statement in red seems to me to indicate that it is not the timebase, but rather a PS problem.

I don't know what the effect of a reduction in the High Voltage supply to the CRT would be, but I suspect it would be as you described.

Certainly, a reduction of the supply voltage to the X & Y amps would reduce the deflection in both directions.

So I'm wondering if you're on the wrong tram with the Timebase line of investigation.

 

[rayyolanda]

Hi Len,
My original thought was that is was a drop in high voltage but a couple of people suggested no. I did measure the high voltage 2KV supply with my home made 10:1 probe and it was 1850V but when I add in the error I think I have it was close to 2000V. I have not measured the other high voltage so I guess the trippler (? x6 ?) could be bad.
All low voltages 100V and below measure fine.
The PIC sounds fine, I did give that a little thought.
I have a datasheet for the 96ls02.
Thanks
Ray