Thermal chart recorder goes to the scrappie

[SeanB]

Here is an old retired chart recorder, was bought a few years ago on auction as part of a lot, and has been sitting around till now. going to parts and then the leftovers to scrap.


IMG_1348 by SeanB_ZA, on Flickr

Thermal paper and a thermal moving coil print head are what drives this unit.


IMG_1352 by SeanB_ZA, on Flickr

Back panel, yes it is 120VAC 50Hz internally, with a very poor job of placing the step down transformer in it.


IMG_1353 by SeanB_ZA, on Flickr

The step down transformer, just lying in there loose..... Pot luck as well as to what the output voltage will be with respect to ground as well, either close to it or close to the live input.


IMG_1354 by SeanB_ZA, on Flickr

Main capacitors, made in 1976 by Nichicon. After 37 years of use capacitance is 5200uF, close to the marked 5000uF and ESR is pretty much zero, dissipation is pretty close to zero at 0,06. Still, as they are a wound construction I could only test at 120Hz, at 1kHz or higher they appear as a very poor inductor. In fact they are still usable as mains filter capacitors.


IMG_1356 by SeanB_ZA, on Flickr


Back panel with the 2 power transformers and the 2 plug in cards.


IMG_1357 by SeanB_ZA, on Flickr

The 2 cards, one on the left is a power supply giving plus and minus 15V rails, the positive being a regulator chip in a TO3 package and the negative being a zener diode. the other card has a 555 timer with a 15uF wet slug tantalum capacitor as the timing capacitor, 10M and 15uF with some fine cotrol via the control voltage pin. Probably used to generate an adjustable 1-3 minute marker on the paper tape.


IMG_1360 by SeanB_ZA, on Flickr

The moving head assemblies, with the heaters inside them. Heaters are fed with AC from the internal transformers with a simple variable resistor providing heater control.


IMG_1362 by SeanB_ZA, on Flickr

Drive for the head, with adjustable damping and gain and offset.


IMG_1363 by SeanB_ZA, on Flickr

Drive for the paper is done by a synchronous motor with 2 speeds, selected by a switch that adds an extra capacitor in parallel with the 1uf already there on the synchronous motor.

img1351


IMG_1365 by SeanB_ZA, on Flickr


IMG_1367 by SeanB_ZA, on Flickr


IMG_1369 by SeanB_ZA, on Flickr

The drive board, with 2 741 opamps. The Siemens capacitors there providing the power supply decoupling do seem to be well past their best, one has vented and has overheated a little. Each board has it's own discrete power supply to power the opamps.