Broken Philips PCS150 dial

Hi,

I recently encountered a problem with my Philips PCS150 enlarger control unit. This device has four dials, one for the timer and three for each colored light (red, green, and blue) in the enlarger's head. Each dial is a solid plastic piece that slips over a small cylindrical piece with a notch cut out of it. The part of the dial that slips over the cylindrical piece has two protrusions that "grip" the notch, enabling the dial to turn the cylinder in a clockwise or counterclockwise direction, controlling the appropriate feature. I've seen similar setups on other electronic devices with knobs (radios, etc.).

My problem is that one of the two small protrusions in the timer dial piece has broken or been eroded away, with the result that I can turn the dial in one direction (clockwise), but if I turn it in the other direction it just slips for a while until it eventually turns, but then the markings are out of alignment. The underlying cylindrical piece in the control unit is fine; I can move a dial from one of the lights to the timer position and it works fine, but then of course the "donor" light's control no longer works properly.

The question is: What can I do about this? The PCS150 has long been out of production, so a spare part will be hard to find and presumably expensive if I can find one. I'm quite willing to use a part for some other device if it would fit, but I have no idea where to begin looking. (I'm in the US, so a North American source would be best.) I'm also open to any repair ideas -- maybe filling in a piece of the broken part with some sort of rubber cement or epoxy, but I'm not sure what procedure would be most likely to work. This is a mechanically trivial problem, but I don't know where to look for a solution. So: Any suggestions? Thanks for any ideas.

I have a PCS150, but I'd prefer not to disassemble it to make any measurements.

These kinds of electronic controls (potentiometers in this case) have standard shaft sizes in either metric or fractional inch measurements. I'd expect metric on the Phillips. You should be able to find a knob of the correct diameter to fit your shaft at an electronics supplier such as Digikey or Mouser. Some are designed for flatted shafts, some for slotted, and some for round shafts. A knob with a set screw (usually an allen socket or flat head set screw) might be the most adaptable for you. You'll need to rig up a way for it to drive a pointer over the scale as the clear plastic knob on the original dial does.

Take a look through the online electronics catalogs and see if you can find something that will work for you. First google hits on Digikey and Mouser are the starting points, and I'm sure there are other suppliers as well. Some places have a minimum $25 order, but it's worth it to keep the PCS150 going, and you might want to order spares or different options.

Lee

For a temporary fix you could fill the groove in the knob with epoxy.
smooth it out & file a notch for the protrusion to fit into. You will need towait until the epxoy is fully cured before you install it or it will become one with the enlarger.

Philips PCS 150 units are dumped in Europe, often e.g. on marktplaats in the Netherlands.
The big problem is how to get the unit in the USA with acceptable costs and if they are willing to ship it to the USA.
Complete enlagers + control units Eur. 50,- to Eur. 100,-. If the seller is willing to ship the control unit and head (with the 3 expensive bulbs) it's maybe a solution.
Shipping to the USA is about Eur. 23,00 for 5 kg.
http://www.marktplaats.nl/ (fotografie--> doka toebehoren) search (= zoeken) on philips PCS.

(Eur. 40,00 is the cheapest price asked for a complete unit + controller at the moment)