Tektronix 434 s/n below 500000 faulty ps.

[Craig]

That is looking really good now!

[johnmcgivern]

Trigger not as stable as it should be took a lot of tweaking to get to this will check out later.
Many thanks gents.

[Craig]

Looking at the front panel settings in your post #110 you should have rock solid triggering (the scope should trigger on a signal only 0.3 division high at 1kHz). So the trig generator needs to be carefully checked. Careful because it uses a tunnel diode, which have been out of production for decades. Now TD's can drift with age and get a bit balky in operation. Problem is that you cannot check a TD using a DVM - don't even try. You really need a curve tracer to confirm operation of a TD.

A bit of background on TD's. They were invented by Leo Esaki, and were originally called Esaki diodes. They use quantum electron tunneling to work, and looked so much like the maiden's prayer for high speed computing, efficient power rectifiers, high frequency oscillators and trigger generators that Esaki was awarded the 1973 Nobel prize for electron tunneling along with Ivar Giaever and Brian Josephson. Incidentally Josephson did the theory of the superconducting tunnel junction while he was an undergraduate!

However, tunnel diodes had a short product life, from the early 1960's to late 1970's, because more conventional semiconductors caught up in most of the areas the TD's were used. The only rather specialised TD still available is called a Back Diode, and is used as a microwave rectifier.

Luckily for you in the 434 it (and another in the sweep generator) are vanilla grade 4.7mA 50pF 1N3716, which you can still get on eBay for about a tenner http://www.ebay.co.uk/itm/1N3716-/262085...Swo0JWF94n .

[johnmcgivern]

Would you believe it Timebase cal has no effect when turning to set frequency is the pot on the end serviceable how difficult frequency seems way out triggering ok.
Part number 108 on page 183.

[Craig]

Sorry John - I cannot interpret your sentence. Can you re-word it?

Craig

[johnmcgivern]

Sorry Craig, I am trying to check the frequency. I set 2 scopes tek434 and advance scope both with exact settings advance is bang on but the Tek seems to be more than twice the frequency shown on the advance with as I said the same settings.
Hope this makes sense using a HP 3325B set at 1000hz.

[johnmcgivern]

If I turn the Timebase cal knob fully clockwise or anti clockwise nothing happens to the waveform. The pot does nothing.

[Craig]

Check that your 434 timebase knob is not screwed on to the shaft one step out. Rotate left and right to the end stop to check

[Craig]

If I turn the Timebase cal knob fully clockwise or anti clockwise nothing happens to the waveform. The pot does nothing.

Which Timebase cal knob is this?

[johnmcgivern]

If I turn the Timebase cal knob fully clockwise or anti clockwise nothing happens to the waveform. The pot does nothing.

Which Timebase cal knob is this?

Craig I am really sorry for asking all these questions I have watched many oscilloscope videos and tutorials but its like learning to drive you can read and listen but nothing beats practicle experience and making mistakes which I am trying my best to avoid with this scope due to rarity of parts.
See photo's when timebase set to 0.1m/S should each gradient have a signal?