Amazing looking electron tube 6 channel microphone adder (mixer).
Licensed by Western Electric.
It arrived to Pleiades lab a few days ago.
Customs cost about 300 euros. It came from US but it was found on the www.ebay.de site.
Basic and very careful dusting off was immediatly done. Very gentle movement of knobs, potentiometers etc as a soft welcome to the Pleiades laboratories.
Nothing was known about rack mounted Grommes. But then reading on forums it was realized that it is possibly the best on the planet. It was found by curiosity hitting the see other items button of the seller who provided the Shure SM63 microphones. All this equipment belonged to a church so the quality is like new. After a lot of discussion with the seller very long sheets of bubble wrap and styroflex white foam was used to protect it in transit. It arrived intact.
While waiting for its arrival the downloaded schematics were printed on very large A2 paper. A pretty girl was in the queue at the printing office. Having said hello she was often smiling.
The schematic show simplicity and elegance. There must be a cascade stage as well. Most electron tubes are 12AX7 and a 12AU7. A brilliant output transformer too.
The octal base microphone TL 1A transformers measure 1.7H : 440H.
No mains supply has been connected yet. The fuse was checked in case someone had put a thicker wire one. The wire looked thin enough but it has to be rechecked as there is no printed information on the small fuse or information is erased.
Today the Aperex EZ80 electron tube was removed and the pins were found bent. They were immediately straitened on the military tube tester straitening electron tube noval base.
The minus black lead of the YFE YF-3200 digital multimeter is connected to chassis. The red lead to pin 3 on the removed rectifier tube socket. -400mV was measured meaning the electrolytic capacitors were at a reversed polarity state.
Immediatly +6V were applied though a 1.6MΩ resistor in order to gently and gradually start reforming the capacitors. After about 1 hour the voltage across them is about 2.4V. Good news. While writting this it increased to 2.6 volt. It will be left at least overnight to charge reform mode.
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