What makes Wurlitzers unique in the electric piano world is that they have a built in amplifier that generates the sound. This means that the electronics are a major part of servicing these instruments. Because of the power this draws Wurlitzers are connected to mains electricity and have live voltage running through it. This means we have to be much more careful than working with other electronic instruments.
First the basic things: wear electrical safety gloves and goggles when doing invasive amp work. Take frequent breaks. If you’re stressed out, you’ll make mistakes. Mistakes here can lead to getting shocked. Be safe.
This is a guide for 200 and 200A pianos. For 140 models and earlier an extra level of skill required due to the tube amplifier circuits, which can be very dangerous if you are inexperienced with them. We don’t recommend working on these unless you have considerable experience with electronics or amplifiers. For 200 models however, there are challenges but with patience and caution, problems can be solved by yourself.
Note: We don’t say this to discourage or scare, just to inform and caution. These are difficult instruments to work on, with potential dangers. Understand the risks, be safe, and enjoy the process. Also, you can always let us service it for you too.
Electrical safety tips when working on your Wurlitzer:
- Always disconnect the power cable. Even with the power off, mains voltage (240V or 120V AC) is live in the cable going to the volume potentiometer. Whether that’s amp repair, tuning, switching components; always turn the power off disconnect the IEC cable. Again, live current flows to the volume switch with the power off.
- The terminal strip after the volume switch where the fuse and transformer wires are located carries mains voltage (either 240V or 120V depending on where you are). Because Wurlitzers are a vintage instrument these strips aren’t shielded like modern ones so the solder joints here are love when the power is on. so obviously DON’T touch anything here without the power off. Disconnect the power cable to the wall too, it’s just too close for comfort.
- The transformer takes mains voltage and steps it up or down depending on your location. Mains voltage goes into the transformer, and out comes mixed voltages depending on the cable the red cables carry a low voltage but higher current, and the blue cable contains a high voltage and low current. It goes without saying, but don’t touch them with the power off.
- The reed bar comb is a high voltage low current system designed to pick up the vibrations of the struck reeds. The live portion of this is 150DC. If a reed is shorted to the reed bar then this voltage can run through the ground too. Use a multimeter to check voltages before touching. When tuning always turn the power off before adjusting reeds, and remove the power cable from the back to remove any live current before the volume switch.
- The capacitors on the near right hand side (as you would play the keyboard) are part of the high voltage circuit. This is over 150V DC. Once again, power off before working on this area. And discharge the capacitors if you need to remove them.
- The large capacitors on the right side of the amp are part of the power amplifier circuit. They have a low voltage (up to 35V) but draw a high current. These must be discharged before replaced. If they are not properly discharged they can spark and cause other electronic problems.
- Make sure all metal areas of the Wurlitzer are grounded. This includes the reed bar, the pedal mechanism, the left and right brackets on the far side, and in some cases, the pedal. Grounding is the most important thing for safety in any circuit system so check for those green wires.
- Check the whole piano is clean. Often these instruments haven’t been opened up in decades, meaning all sorts of dirt debris and other more serious things can get in there. Just recently we found two pennies that caused a short circuit at the mains power supply that took out power to the whole workshop! It’s been said many York’s, but check every thing. And clean everything. Debris can short the reed bars causing pops, crackles and in the worst case causing it to not sound.
- On that note check the amps. These aren’t clean modern circuit boards made by machines, they were hand soldered in the factory in the 1960s and 70s. Human error will occur like cold soldered joints and components too close together so they short. There’s also a lot of repair work done on these in that time that can be messy, haphazard, or occasionally dangerous. So check everything before you work on your Wurlitzer.
