TELEQUIPMENT D53A

NOTES	This 'scope uses the same six 'Y' channel plug-ins as the earlier D43 model. This particular example has the odd combination of a type 'C' very high sensitivity plus the type 'H' wideband amplifiers. The type 'C' amplifier is built up on a chassis and utilises 6 valves (an ECF80, three EC88's plus a couple of EF184's). However, perhaps as a result of the higher bandwidth requirement, the type 'H' amplifier, built up on a PCB, mainly uses transistors (8-off) with just two valves (EF184's again) taking care of the high voltage drive to the tube plates. The timebase is also a plugin module (type TD51) and like the type 'H' amplifier is a hybrid design, with 12 transistors and 6 valves (a 50:50 mix of EF184's and ECC88's). In both modules, all transistors are mounted in sockets. This being a professional piece of equipment the sockets can't be due to expecting trouble. More likely the PCB itself was soldered by machine (flow soldering process) and the heat involved in this process would have risked damage to the transistors. Plug in modules make stripping the scope down a doddle, I timed it at 1 min 15s to get to the state shown opposite.
SERVICE DATA	You can download a copy of the service manual plus most of the plug-ins from the service data page. Thanks to Fernando for sending a copy of the manual.
CURRENT STATE	Dirty on the outside, but internally very clean. However I bet this electrolytic made a big noise when it let go ; theres some nice holes surrounded by gunk and the force broke the wire between two of the terminals. Owch ! This is the sort of damage to expect if you just switch on long dormant equipment.
WHERE FOUND	Rescued from death row ... another week and it'd be in a London skip.

The timebase plug-in unit.

Interior view of the Type 'H' amplifiers. Note the
heatsinks on the four transistors to the left of the module.