Am chasing a combined switch/tone control and seem to be having some trouble finding same.

Need a 5k linear pot with just a simple 2 terminal on/off switch at the rear.

Can someone give some direction?

5K sounds awfully low for a tone control. Linear also sounds dodgy

How, What, Where, is it in the circuit of what?

Double check value and feedbak what it is in.

Marc

Marc..

Have checked. The pot itself is branded "Aerostat" and clearly stamped on the back "5000 Lin" so that would appear to be correct.

It's from my problem child, the Rolltop Breville Precedent radiogram for which we don't seem to have a schematic - at least not one that matches the valve components on this chassis which include a 6AC7 that everyone tells me should not exist in this set!!!???? (Go figure)

Leaving aside the 6AC7 question, essentially it sounds like you have a model 534A, which shows a 1 meg volume pot and a 5K tone pot with power switch.

If you unhide your address in your member profile I'll email you that schematic.

Futurelec has half watt ones but these have short spline shafts. You might contact them.

The pain with those is that you may have to get / make an extension shaft?

6CA7/ 1852 is a metal RF valve designed for TV. The socket may have been rewired for it to replace 6J7, which is also a sharp cut of pentode (RF)

Marc

GTC...

unhidden as requested.. have located some long shaft 5k linears but using one of them means adding a power switch somewhere else on the set.

Maybe Evatco could help?

Schematic would be a huge help!

Okay, schematic sent.

Here's a guy selling short shaft ones:

http://www.circuitspecialists.com/31vm305.html

RS componenents 4.7K 20mm shaft 387-830 with switch

www.rsaustralia.com

Marc

Depending on what is broke about the old pot, you might be able to transplant the power switch from the new ubit onto the old one. Usually, the shells of pots have tabs you can pry so the shell gets loose. Pot wiper mechanisms usually have a small pin that engages the power switch, and if the new unit is similar enough to the old unit, it might mechaically work.

Or have a shaft coupler machinened, and use the long shaft you'd cut off the old pot to extend the new shaft (it would also accept the radio knob as before as well).

I wouldn't try to solder, weld or braze the old shaft to the new shaft, pots have plastic parts that would't survive the heat.

Unfortunately "Aerostat" tends to be a larger pot & of "vintage" procuring a switch may not be easy, as the majority of duds would have been tossed and the only source now would be salvage.

A new switch pot is available and that presents less of a hassle in this instance. I have actually used a short shafted, splined type pot in a radio recently as it required an extension, to the shaft, in the order of 40mm.

No matter what, there was likeley to have to be a mod to an existing pot. shaft. I avioded touching this pot, as I merely "turned" an adaptor that fited the spline and was made the desired length.

Nucky's issue is easily solved.

Marc

I merely "turned" an adaptor that fited the spline and was made the desired length

I can picture turning a suitable shaft but what did you use to mate with the pot's spline?

It would be a matter of including a socket end at one end of thee extension with a hole large enough for a tight interference fit. You could go one better and knurle the socket to match the pot shaft but this is very delicate work.

One other way is to make the hole in the extension shaft easily fit the pot shaft and fit a grub screw to the extension that will hold it to the pot shaft.

This particular pot has a shaft similar to Jaycar RP-8610.

An interference fit hole in the adaptor socket, that covers the entire length of the shaft, will see it not wobble.

Putting "knead it", or similar strong filler, in the slot, If it has one, is wise. You then drill and tap the lock screw hole in such a position that it drives into the gap behind the spline.

Use the proper High tensile "lock" (has teeth) / grub screw /s (one for Alen Key). I normally chop the adaptor out of the ordinary Aluminium rod that you can get at Hardware places (light).

Depending on the situation the adaptor is made in one piece. You can often just use / buy, a socket and salvage some shaft off a dud pot.

In my case, running the "Toolpost" (die) grinder along the shaft with the lathe stopped, allows the flat to be cut to make it a "D" shaft.

The lock screw is sourced from an Industrial Bearing supplier. Metric & Imperial available, 3mm is adequate.

All easy if one has the machines & wants to try it.

Addendum: Soon in Silicon Chip " Vintage Radio" There is a photo of the Breville 730 with the new pot & Aluminium extension shaft I made for it..

Marc

Hi,
RadioDaze in the US sell a range of pots. and they sell a switch which can be fitted to the single gang pots.

http://www.radiodaze.com/.

Cheers.