The V303J English Continental II - Vibrato Circuit




Close-up of the "Block 7200" V303J Preamp Circuit Card

Under the orange lid of the organ, near the power supply, is the vibrato prnted circuit card, called "Block 7100" on the V303J schematic.

The vibrato board has two circuit board mounted controls. The flat mounted potentiometer adjusts vibrato depth. The vertical, conventional control adjusts vibrato speed.

The circuit card has ten pins that plug into a matching ten pin socket in the organ chassis, and is the card is held in place by one screw.


Diagnosis of vibrato problems:

The Vox Showroom and North Coast Music accepts no responsibility for personal injury or damage to property while using this information to attempt an organ repair. Proceed at your own risk.

What malfunctions on the vibrato boards? The first thing I would check is the vibrato speed and depth controls. I would spray some tuner wash or contact cleaner into the contact area of both pots and try readjusting each control. A dirty control could cause the vibrato to malfunction, and this is the easiest and first thing to check.

The next most likely culprits are the four electrolytic capacitors on the vibrato board. One of these is 1000 uf (uf = micro farads), one is 25 (or 30) uf, and two are 10 uf, all rated at 15 volts. Electrolytic capacitors typically have a life expectancy of ten years, so forty plus years after their original installation on these circuit cards, these capacitors are prime candidates for replacement.

The capacitors needed for this repair are commonly available at a Radio Shack or Tandy. The replacement capacitors will probably have a 50 volt rating, but that will not be a problem. Please observe the location of the + end of each capacitor and install the replacements the same way. The cost to replace all four capacitors will be around $4.

If changing these capacitors does not fix the problem, then one would next look at the three germanium transistors as the other part that is likely to fail. Marginal or defective germanium transistors often work momentarily after they are chilled. An easy way to diagnose this issue is to give a shot of "freeze spray" or "component cooler" (again available at Radio Shack for about $10) on each transistor. This should help reveal which of the three transistors is bad.

Perform the transistor freeze test with the vibrato switch "on" and any key on the organ depresssed. Listen for the vibrato to return as you freeze each of the three transistors. If you locate a defective transistor, any of the three on the vibrato board may be replaced with an NTE 102A from www.mouser.com.

You might wish to purchase the Vox V303J schematic to help you repair the vibrato circuit. Parts values for all capacitors, resistors, and diodes are included in this schematic. Click here to purchase this from North Coast Music.


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Photos and editorial content courtesy Gary Hahlbeck, North Coast Music


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