Old Tek Scopes, was Oscilloscope question

A few words about the older (500 series) scopes, which have had a few mentions in the main thread: they do suffer from switch failure, usually due to poor maintenance, and the switches are specials, the only source is another scope, and it usually has to be one of teh same model. The Paxolin wafers are also susceptable to insulation breakdown ( the insulation has to be good, some of the trigger switches have 500V potential difference between adjacent contacts), though this is often caused by the use of inapropiate switch cleaner, or excessive lubricant - NEVER spoary WD40, Duck Oil or the like on a switch! Use the proper cleaner, and contact lubricant, sparingly. Clock oil is useful for lubricating the bush part of the switch (where the spindle goes through the frame), and a light grease for the detent mechanism. I have had some luck at recovering these switches when contaminated, but it involves removing them, properly - not for the faint hearted. The all valve (tube) scopes are usually fairly easy to get parts for (545, 545A, 535, 535A etc), and fairly easy to maintain and repair (I know 100 valves looks daunting, but they can be broken down into small sections for fault finding. The hybrid scopes like the 545B can have some strange transistors in them, which are very difficult to source, and expensive to buy. Some of the later models (including the 545B and 547) have an EHT transformer that is prone to failure - it can be re-wound, but it will cost you $50 (more if your outside the USA). A lot of the later, high speed units (547, 585, 453, 454 etc), as well as some of the faster plugins (1S1, 1S2, and some of the 3 series timebases) have tunnel diode trigger circuits. These are excellent, fast, stable trigger circuits, but the tunnel diodes are now very rare and expensive. Having said that, I have several of these beasts (535A, 545A & B, 547, 585, 561, 564 and 564A), in various states of repair. The 535A gets used regularly, and is currently at work, as I needed a scope with a stable low frequency trigger, and a differential input - our modern Philips scopes don't like triggering at 25Hz! The 564 is a useful analogue storage unit, though it only has a 10MHz bandwidth. The 547 is a good 50MHz scope (with the right plug-in), and the 585 should go to 100MHz (but only for the first 5 minutes after calibration, 85MHz is more like it - still not bad for an all valve scope!). They are all good scopes to use, but you do need to understand them and play with them before you try to do serious work, the have lots interesting little idiosynchrasies. Jim. Please see our website the " Vintage Communication Pages" at WWW.G1JBG.CO.UK