Tek 2445A - graticule illumination not working; modify it?

JimB said:

Ha! That is nothing.
Have a look at this schematic, the cooling fan controller for an HP8640B signal generator.

JimB

View attachment 83981

Click to expand...

At least they do things properly

I've just been playing with the delayed sweep features - WOW - what a lovely machine:

Been trying to tell you that!!
My TEK 564 has a simple lamp brightness control but this thing dates from 1960.
It has a big 3W wire wound pot and a 3W wirewound resistor to make it work. Actually, the 564 gets hot enough to cook toast. All those series regulator valves and ballast resistors. As bits and pieces fall over, the thing gets redesigned. The series regulators are now replaced by FET's. The original 6080 had a 15 Watts of heater power.
By contrast, the 'over-engineered' design has low cost potentiometer and a ULN 2003 IC.
Cost wise, and based on RS prices, a 3W wirewound pot is say $15 and a small half watt pot is $7. Add a 3W resistor at say $1.50, and the 'simple' design costs about $16.50 and the 'OTT' costs about $8 for the cheap pot and a ULN2003($0.75). Of course, factory purchasing would give different costs, but the comparison is probably valid.
So the design choice is based on cost, and the extra complexity in manufacture disappears with the way the parts are assembled with flow soldering etc.
Sometimes too, the apparent 'OTT', is actually a part of long term design/development gaining exercise, to assess various design topologies. In the example given for the HP fan control, this looks like a variable speed stepper motor type of arrangement, and again, it is almost certainly cheaper than a commutator type fan motor set-up. So what seems costly and 'OTT' can actually be the reverse.

Actually I just found the video.
I also heard you're accent, and it seems to be an OZ accent.
At about the 1.12 point you seem to have a bit of jitter and this is normal for such a measurement. One manifestation of this is where you have a waveform which repeats at say 1 second intervals and you are looking for a short pulse. For example an electric fence energiser.
These kinds of measurements can have huge amounts of jitter, and on my 564, there is a 'delay' but there is also a 'trigger delay'. This feature is a means of reducing the jitter where there are long time delays between the start of the first sweep and the start of the fast sweep. As you start measure more difficult waveforms, you will find yet another feature to help you. Reducing jitter is a big, need to have, feature.
The video was terrific. Looks like your having fun.

rumpfy said:

Actually I just found the video.
I also heard you're accent, and it seems to be an OZ accent.
At about the 1.12 point you seem to have a bit of jitter and this is normal for such a measurement. One manifestation of this is where you have a waveform which repeats at say 1 second intervals and you are looking for a short pulse. For example an electric fence energiser.
These kinds of measurements can have huge amounts of jitter, and on my 564, there is a 'delay' but there is also a 'trigger delay'. This feature is a means of reducing the jitter where there are long time delays between the start of the first sweep and the start of the fast sweep. As you start measure more difficult waveforms, you will find yet another feature to help you. Reducing jitter is a big, need to have, feature.
The video was terrific. Looks like your having fun.

Click to expand...

Nope, I am English 100%, hehe. Thank you for the compliment; I am trying to find a better way to shoot the 'scope without needing total darkness. I am glad you enjoyed it

I have some great news; a company in Norfolk have new stock of the original Tektronix part for these bulbs, at around £1.X each - if anyone wants to contact them:

https://www.surplus-electronics.co.uk

The brightness is usually quite low in comparison with available film speeds. I think the graticule illumination automatically goes off when 'single sweep' is selected. Photos of cro screen traces is a bit iffy if you try repetitive sweeps and there is jitter. The cro you have has a PDA (post deflection acceleration) crt. With older cro tubes, the beam accelerating voltage is applied between the gun and the cathode and this reduces the deflection sensitivity(and consequently, bandwidth). The PDA crt's have much better deflection sensitivity and the accelerating voltage is much higher (4 to 10 kV) and this gives a really good brightness.
I use a digital SLR (Nikon D80) for taking photos and the highest film speed is 1600 ASA.
Older cro's used to be supplied with a viewing hood; a bit like in the X-ray machines of old where you see people peering into face mask arrangement. Tek probably didnt supply one with your cro, because the available brightness from the crt was good enough. My TEK 564 has a viewing hood, and it is necessary for some waveforms, to cut out all the extraneous light.
The other feature in my TEK 564 is that it has a storage tube. So I can do a single sweep and photograph the still image. The storage feature was a Hughes (as in Howard Hughes) invention I believe, and it uses flood guns to energise the screen phosphor, but not enough to cause it to glow. The electron beam then excites the phosphor and the flood guns keep the image alive.

Hello everyone

Okay, so the company I wanted to buy the bulbs from, now tells me they cannot accept PayPal any more, so I am stumped. Does anyone in the UK have some of these bulbs they could sell me via PayPal?

Many thanks

get on to RS.
I have the RS number and can get it for you. The lamps I have are 6 volt 60 mAmp.
try element 14 too.

rumpfy said:

get on to RS.
I have the RS number and can get it for you. The lamps I have are 6 volt 60 mAmp.
try element 14 too.

Click to expand...

Sorry, you've lost me . Are you saying that if I pay you by PayPal, you can order the lamps to my address? I am in England - I'd be ordering 10x these lamps:

https://uk.rs-online.com/web/p/filament-indicator-lamps/0106458/

Thanks

I have 3 types of wire ended lamp; all from RS. They supply in packs of 10 units.
rs stock no 587670 is 12 V 60 mA made in Taiwan
587068 is 6 V 55 mA made in UK
587074 is 14V 50 mA made in UK
Previously I couldnt find them in the catalog and now I looked up the stock no to find they are discontinued in Australia.
I was suggesting to get you the rs stock number of my samples
I looked up the RS reference you gave, and it is what you want anyway. So go with that.

rumpfy said:

I have 3 types of wire ended lamp; all from RS. They supply in packs of 10 units.
rs stock no 587670 is 12 V 60 mA made in Taiwan
587068 is 6 V 55 mA made in UK
587074 is 14V 50 mA made in UK
Previously I couldnt find them in the catalog and now I looked up the stock no to find they are discontinued in Australia.
I was suggesting to get you the rs stock number of my samples
I looked up the RS reference you gave, and it is what you want anyway. So go with that.

Click to expand...

Ah! Okay, thanks

I bought these in the end; I've spent way too much time and energy on this whole lamp issue:

**broken link removed**

Hello

Today I installed the new lamps, and it's now working 100%; suffice it to say, I am very pleased:


Here's some photos:



https://www.flickr.com/photos/22008695@N03/sets/72157640897509603/


... and a video

Good job, glossywhite!

cowboybob said:

Good job, glossywhite!

Click to expand...

Thank you

Tektronix always had an attention to detail that bordered on the psychotic...

Wouldn't surprise me that the ON/OFF switch detail was a MIL spec.

Just noticed this thread...
Happy to say , recently i got a 2465A and two 2465's for 'spares' and they are all working...one 2465 could use cal though.
Like the 2445 the U800 horiz amplifier (weak point) needs to be cooled. I did some tests and a heatsink drops the op. temp by 30C or so!.

The yahoo group:
https://groups.yahoo.com/neo/groups/TekScopes/info
carries a lot of info and pics of these scopes being repaired etc, plus you can get walkthroughs on common probs. I have uploaded pics of my work on the scopes, esp. the replacement of the LT 'keeper' battery, the heatsink upgrade and the leaking' electolytic caps on the LVPS.

I recently had to diagnose why a PIC ADC was reading unexpected voltages and my Rigol 1102D couldn't clearly reveal the 20 uSec pulse of the Digital output switching to an analog input. False triggering due to embedded waveforms.
The Tek2465a had no probs and even resolved the exact peak value of the adc sample voltage. The prob was the adc spike was embedded in an LCD display pulse train as the pin did double duty.

Similarly I just had to debug an RS232 connection prob and the Rigol one shot storage allowed me to trace every bit pulse over a 1/4 sec sample to resolve the prob. The TEK couldn't help there.


regards Ancel

On my new 2465 oscilloscope, those sub miniature lamps is 5v / 115 mA. The exact dimensions is 2,2 x 4,5 mm. A good replacement will be the above.

**broken link removed**