Our technicians decontaminate and clean all equipment upon arrival and upon purchase to create a neutral environment for lab use. Once we finish our rigorous testing and decontamination procedures, your order will be packaged to best protect it during shipment and will include delivery insurance. Any electronic deficiencies detected are immediately repaired.įinal testing cycles ensure your equipment performs fully at manufacturer specifications, guaranteeing you receive a properly working product ready for use. Upon completion, we replace all faulty and/or under-performing parts with original manufacturer parts that perform up to specification.Īny parts known to fail or malfunction on the piece of equipment are removed and replaced to insure the extended lifetime of your equipment.Īny necessary preventative maintenance is performed alongside repairs, so your purchase will be ready to go as soon as it arrives.Īll of the electronics and boards are tested for proper function and response by our industry trained technicians. Preliminary testing is then conducted on our equipment to identify potential defects. Our technicians decontaminate and clean equipment upon arrival at our facility and upon your purchase to create a neutral environment for your labs use. Pretty simple.Marshall Scientific's Refurbishment Protocol Either there is an open somewhere, possible a loose wire, or one of the FETS is blown. Thats all the circuitry that was on the PCB. At the operating frequency the transducers look like a large lossy capacitor. The 250 W unit used two transducers connected in parallel. After the transformer was a large choke coil to resonate the transducers. My units used feedback from a small series transformer on the output to drive the FETS into oscillation. If you have B++ and no output then the FETS are the likely suspect. The unit first rectifies the AC so check the ouput of the diodes for about 250 VAC. My units had a fuse soldered onto the circuit board so check this. Added capacitance on the output can cause spurious oscillations and damage the output transistors so don't probe there with anything but a high impeadance probe. The output forms a resonant circuit with the transducers. These units generate high voltages when on so be carefull. Mine were smaller 250 watt units but there could be similarities so I'll post what I know and see if it helps. I worked harder than I needed to figureing out the feed back paths in the oscilator as the it wasn't related to the problem but I finally figured it out. I just opened them up and traced out the circuits in my notebook. I fixed a couple of cleaners for my wifes work and they weren't hard.
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