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Old 7th Mar 2021, 5:23 pm   #1
wd40addict
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Join Date: May 2009
Location: Stevenage, Herts. UK.
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Default Philips' Rocking Crystal Cartridges

In the early days of LPs Philips produced their own record decks and fitted them with what has come to be known as the rocking cartridge. Its unique feature was that the appropriate stylus was selected by rocking the cartridge either one way or the other:

Green = N = normal = 78, Red = M = Microgoove = 33/45.

The problems started in later years when the crystals dissolved to goo and a replacement was required. Eventually Philips produced the GP235 which used a conventional flipover stylus, but still plugged onto the original arm.

I have two decks of this type: one is fitted to a table top radiogram and the other is a standalone deck badged as a Stella. The radiogram came without a cartridge fitted, the Stella had one, but it had turned to goo.

The photo shows the general form of the Philips / Stella deck.

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The observant among you will notice the washers hanging off the back of the arm to give a counterweight. This is to correct the other issue with this deck: there is no counterbalance - the record / stylus bear the full weight of the arm and cartridge! This might have been fine in 1953, but by the time stereo arrived something better was required. Philips must've realised this and made an accessory counterweight, though they are very rare.

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Some years ago I purchased a copy GP235 to get the radiogram going, but was never happy with it due to the stylus pressure which was almost compressing the suspension. For some reason it was also fitted with a lead weight which made things even worse! I eventually managed to remove this by heating the weight with a soldering iron until the glue gave way...

The next photo shows the copy GP235 together with the modified rocking head to be described later. the arrow shows where the weight was removed.

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Seeing a Philips being 'fixed' on TV I wanted to see if I could improve things further, so the counterweight was constructed by bending a PC bracket so it could hook under the arm and then using a bolt to hold an appropriate number of washers. Stylus pressure could thus be reduced to a sensible 4 grams.

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To be continued
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