These flash guns have been around for ages and are built like tanks so there's loads of used flash guns available for purchase online.
Many new strobists buy a used 283 to start experimenting and are usually tempted with customising this flash gun to their needs, but struggle to take it apart.
I recently bought a used 283 for a few quid to use a slave unit but the PC sync socket was not working properly with my Wein optical trigger, so decided to take the apart flash gun to see if I could fix this.
After digging around online for recommendations, and using tips and partial instructions from various different forums, I managed to safely disassemble my 283, fix the PC sync socket and put it back together with no problems.
This instructable combines in one place the tips, instructions and recommendations I found online, in an attempt to save new strobists the hassle I went through.
DISCLAIMER: if you disassemble your Vivitar 283, you do this at your own risk!
Step 1: SAFETY FIRST! Read before you open the unit
These instructions assume that you power your 283 with regular AA batteries. If you use an A/C adaptor or other external power supply, find out how you can discharge the capacitor before following any of the instructions on this instructable
Although they use regular AA batteries as main power source, flash guns work with high voltage.
Discharging capacitors with your bare fingers will be very painful and can produce significant harm so be very careful!
With a fully charged capacitor, the voltages inside the 283 can be around 200-300V DC.
The main capacitor inside a 283 (see picture on the last step of the instructable) holds a substantial charge for a long time after the unit was switched off and the batteries have been removed, so you must discharge it before you open the unit.
To do this, turn the flash on, set it to the highest power and wait for the "ready" light (test button) on the back of the unit to start flashing.
Once the light/button is flashing, switch off the unit, very quickly remove the batteries and fire the flash by pressing the test button (the one that was flashing).
This should eliminate most of the charge in the capacitor but be aware that there could be some residual charge left on it.
If you want to be 100% sure, check the voltage in the capacitor with a multimeter before you touch anything inside the flash gun.
If the capacitor still holds a charge, you can discharge it by shorting the terminals with a 100-Ohm resistor (re-check the voltage after doing this). DON'T hold the bare wires of the resistor. Solder some short leads to it first and insulate with heat shrink or insulated tape. Alternatively, use insulated pliers to hold it.
RECOMMENDATION: When you open the flash, do it on a soft surface to protect it and to keep little things like screws from rolling away. A mouse pad works nicely.