Philips Philicorda repair advice

[Carpae]

Hi all,

Please be gentle as I've just joined the forum and I'm a very new organ user, so I'm sure I'll have to ask for lots of explanations to abbreviations etc!!

I've recently started using a Philips Philicorda organ that I really like, but all of a sudden, during use, all of the A keys stopped working. They produce a very low tone if you listen closely but it's hardly there at all. I have no idea if this is a common fault or something that could be easily talked through, but I've looked everywhere local to me for an organ repair service but can't find any!

Hopefully someone will be able to help; many, many thanks in advance!

[Carpae]

If no-one has any suggestions for technicals fixes, if there are any members who're UK based and recommend someone who could look at it for me, preferably in/around the midlands, that would also be very much appreciated!

[JQA]

Hello, and welcome to the forum!

The most likely cause of the problem you describe is that the master oscillator responsible for the A pitch has stopped running. Since all other octaves of A are derived from its signal, all A keys will be dead on all registers if the master oscillator is faulty.

I am not very familiar with Philicordas, but from your picture and some brief searching, yours appears to be model 22GM751. This model uses vacuum-tube-based master oscillators, and so it is quite possible that the relevant oscillator tube has failed, which is very easy to diagnose and fix. If you open the top (with power off, unplugged), the six master oscillator tubes should be visible in a row towards the back. All you need to do is identify which one is responsible for the A, and swap it with an adjacent tube. Let me know if you have trouble identifying which one generates which pitch. If the problem moves to another pitch, the tube is at fault. These tubes are type ECC83, also known as 12AX7, which is among the most common and inexpensive tubes of all time, being produced by many factories to this day.

If the problem does not move with a tube swap (and you are sure you've swapped the right tubes), then it is possible that some component has failed, or that the fault is actually in the first frequency divider stage (since the master oscillator signal is not used directly). But first things first - check the master oscillator tube!

Jesse

[Carpae]

That's amazing, thank you! That's my evening tomorrow planned!

Will let you know how I get on!!

[Carpae]

I'm looking around at places to order those valves just in case, and one more question occurred to me: Is it worth replacing all 6 of the valves while I'm in there? I'm just wondering whether having one brand new one and 5 older ones might lead to issues with the sound?

[JQA]

Great, I look forward to hearing how it goes.

As for replacing all six tubes, I don't recommend it. Even if the others are somewhat weaker, it will make no difference in the sound, not least because the master oscillator signals are not used directly. As long as the oscillators are running, everything should be fine. The remaining tubes may operate for many years still, perhaps decades, even if one has failed (which is still yet to be determined).

Tubes are almost never replaced preventatively, since they do not age just by sitting the way some other parts do - after all, they are completely sealed off from the atmosphere, and with nothing inside to react. I have some tubes from the 1920s and 30s that still test new, and work fine in my old radios. I also have vacuum-tube organs that still work perfectly on almost all original tubes - for example, my Conn "Caprice" 430 which uses 37 tubes, only 3 of which have been replaced since it was built in 1960, and it has been quite well-used!

Jesse