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Old 18th Oct 2020, 8:22 pm   #1
Nickthedentist
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Default Philicorda GM751 organ

Hello,

A friend has bought a late-1960s Philicorda organ, like this one here: http://www.peel.dk/Philips/Philicorda_GM-751.html

All solid-state (look at all those Lockfits!), with two speakers but driven by a single push-pull amp as far as I can work out. (There are similar-looking models with stereo amps and/or full of valves).

Full model number is 13GM751/15T.

He's done a great job of getting it working, though switching on the "Reverbeo" feature has no effect; the sound comes through normally with no added reverb. Tapping the reverb unit inside causes its resonance to be heard from the speakers though.

There's a service manual for the 22GM751 here: http://www.peel.dk/Philips/Philicord...ice_manual.pdf but this appears to have a stereo amp, I think, which makes fault finding in this area problematic.

Is the 13- vs. 22- prefix significant?

Anyone got a manual for the 13- version?

All pointers welcome.

Thanks,

Nick.
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Old 18th Oct 2020, 10:56 pm   #2
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Default Re: Philicorda GM751 organ

The circuit diagram you have linked to shows a unit with a stereo amplifier and the spring line getting an output from one channel and feeding it into the other channel.
The notes are generated by neon oscillators.
There are no lock fits in it.

The photos show a mono amplifier with some lock fits in it and the notes being generated by oscillators with lock fits in them.
The output from the spring line is there as you have tested by tapping on the casing.
The input must be missing.
A common fault is an open circuit driver coil.
In the old days spring line drivers were made by stripping a cheap battery radio for the audio transformers and using them.
If you do find that the driver coil is open circuit and open the spring line up up you will be able to see what I mean about stripping cheap radios for there transformer parts.
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Old 19th Oct 2020, 7:00 am   #3
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Default Re: Philicorda GM751 organ

Thanks for your input, Refugee.

Yes, that's what I concluded, i.e. although the photographs on the Danish site match my friend's instrument exactly, the circuit diagrams don't.

I did have a cursory resistance check of the driver transformer with my meter, and it seemed to be OK as far as I could tell without service data.

Time to fire up the scope, perhaps.

Nick.
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Old 19th Oct 2020, 9:00 am   #4
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Default Re: Philicorda GM751 organ

This was an unloved beast that's come back into fashion thanks to the band Metronomy. It was something I always fancied when a teenager, though lack of pocket money was a slight obstacle...
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Old 19th Oct 2020, 9:03 am   #5
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Default Re: Philicorda GM751 organ

There was one in the music "hut" at my primary school in the 1970s/1980s, presumably bought as a cheap alternative to a piano.
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Old 19th Oct 2020, 9:41 am   #6
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Default Re: Philicorda GM751 organ

Here's the performance that put the Philicorda on the map:

(Mark Ratcliffe wrongly introduces it as an omnichord).

PS, I agree the usual problem with a non functioning spring line reverb is the driver transformer, very fine windings and go open alot. (No idea if this is a specific fault on the philicorda)

https://www.youtube.com/watch?v=0NDoKK-5zYw
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Old 19th Oct 2020, 10:11 am   #7
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Default Re: Philicorda GM751 organ

Hi, there are different version of the Philichorda organs, they look similar from the outside !
the early ones have valves, neon dividers and a separate valve amplifier underneath with stereo reverb !
the later ones are transistorised.. and may have a mono amp..
I seem to remember that the later ones ( GM754 ? ) have lockfit transistors.
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Old 19th Oct 2020, 11:00 am   #8
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Default Re: Philicorda GM751 organ

This generation of cheapo electronic organs at the time were seen as lousy attempts to get the Hammond sound, and even further from a real pipe organ. But they're what a lot of people and beginning band could afford.

Seen from the 21st century, they have the charm of remembering a golden era. There's nothing wrong with it and it's very powerful.

Have fun, Nick. You have a lot of the spirit of the 1960s fitted into a small box.

David

The Farfisa sound on early Pink Floyd was there because the Compact Duo packed a lot of function into a very low weight. It wasn't chosen for its sound, it was chosen for being lightly built, then it created their sound.
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Old 24th Oct 2020, 12:50 am   #9
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Default Re: Philicorda GM751 organ

Strange there would be a separate UK commercially specified version (13... instead of 22...) instead of just a different execution (/15 instead of /00). If I may ask, what are the letters in front of your serial number?
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Old 24th Oct 2020, 8:57 am   #10
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Default Re: Philicorda GM751 organ

Here’s the label:
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Old 25th Oct 2020, 9:05 am   #11
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Default Re: Philicorda GM751 organ

Hi Nick,

That's really interesting, with the rating of 50w consumption it got me thinking that this cannot be a 100% solid state device so I had a little look around on the net and according to Wikipedia the GM751 series of organs were indeed hybrid and manufactured in 1967, the GM752 was launched sometime later and was fully transistorised.

Cheers
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Old 26th Oct 2020, 11:46 pm   #12
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Default Re: Philicorda GM751 organ

I had one of the early valve ones with the neon dividers. I really wanted a Vox Continental but the Philicorda was all I could find at the time. I'm fairly sure I worked out a way to use the reverb in the effects loop of an MM mixer.

Unfortunately I gave up on it and it ended up as a stand for other things thanks to its flat top. I got rid of it in the end - a year or two before Blur decided they were cool and featured it in one of their videos. There are a few shots in this one

https://youtu.be/6oqXVx3sBOk

but I'm fairly sure I saw some better shots in another video (or possibly TV appearance).
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Old 27th Oct 2020, 9:21 am   #13
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Default Re: Philicorda GM751 organ

That organ has a very pure sound - without sounding shrill or harsh. Rather pleasant. A perfect accompaniment to the jagged guitar of Mr Coxon on that track!

My father used a Farfisa organ for decades in his dance band. It was an unusual looking thing with many toggle switches that (to my ear) made very little difference!

How many basic tones/waveforms does the Philicorda have?

SEAN
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