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 .
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 .
