ESAB Plasmarc EPP-450 - Power Rectifiers and Blocking Diodes; Troubleshooting Negative Plate Components

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SECTION 6 TROUBLESHOOTING
6.4.1 Power Rectiers and Blocking Diodes
1. Removetopcoverandsidepanels
2. Locateanddisconnectpluginrearofammeter(attached
toneredandoneblackwire)
3. Removepilotarcswitch
4. Disconnectvoltmeter
5. DisconnectorangeandyellowwiresfromrelayK4.
6. Removetwoboltsholdingtheleftsideofthefrontpanel
tothebase.
7. Removethreeboltsholdingacrossthecenterbaseofthe
frontpanel.Theseareaccessedfromunderneath.
8. Removeoneoftheboltsholdingtherightsideofthe
front panel to the base.  Loosen the second bolt.  Of
thesetwobolts,removetheboltontheleftandloosen
theboldontheright.
9. Swingthefrontpanelouttogainaccesstopowerrecti-
ercomponents.
Troubleshooting Procedures –Negative Plate
1. VisuallyinspectfusesF8andF9.Replaceiftheyshowsigns
ofbeingblownormelted.Inspectdiodes.Ifruptured
orburned,replacealldiodesontheNEGPlate.Ifdiodes
appeartobeOK,proceedtonextstep.
LocationofNeg.Plate
LocationoffusesF8andF9
PowerRectiers
Proceduretoaccessbehindthefrontpanel
BlockingDiodes
PowerRectiers