Re: Quick question 564B

Cliff Carrie

I own a 561A and two 564Bs. They were mainstream in the mid 1960s. 10MHz bandwidth and a far sharper trace than you will ever see on a DSO. They all take the same series of two plugins, Vertical and Horizontal; (interchangeable if you like vertical traces or you could use two Vertical units for Lissajous figures and LF phase comparisons). The A version in both cases had a vacuum tube-based LV power supply, the B was all solid-state. Not such a big differentiation since the plug-ins were all hybrid tube/transistor units. There were lots of plug-ins, including sampling to about 500 MHz IIRC, SAs, single and dual differential amps, a wireable dual op amp unit, and up to 4 input channels. I have around 20 different plug-in types. The biggest deal about this family was the 564. It's a split-screen STORAGE scope storing waveforms electrostatically on the phosphor screen using secondary emission, with the upper and lower halves of the screen separately eraseable and settable to storage or non-storage mode. I believe this was the first widely adopted storage scope from any manufacturer. More than any other Tek units, this was the family that popularized plug-in scopes, so much so that HP started by disparaging them and ended by imitating them. One of my 564Bs is a Mod 121, which adds variable time delay auto-erase. The remark that the storage function is "finicky" is mostly only true if you try to calibrate it without following the manual. Once properly adjusted, mine have remained stable. Storage display contrast is a bit low, but very useable within the 10MHz bandwidth. They are also cheap to buy today. They're mostly reliable, with two well known problems: the CRT filament is supplied by a dedicated winding on the main power transformer but is elevated to -3300V by the HVPS. This has led to failures of the paper insulation on that winding. I fixed my 561A by adding a separate transformer with the secondary rewound (on a side-by-side nylon bobbin) with suitable insulation and leads long enough to reach directly into the HVPS box without splices or terminals. The leads were individually insulated with small tubing (there's only 6.3VAC between them, and double insulated with shrink tubing over that to withstand the 3300V. The other problem is the potting failure on the HVPS transformer. I think it may only affect the B series, but I have never had the problem. The 561/564 family could be thought of as the precursor to the 7000 series, and my main scope today is a 7854.


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