All Forums  MCUmall Forums  True USB Willem Programmer (GQ-2X,3X,4X & GQ-4x4)  GQ-4X Programmer PCB: VPP Boost Circuit Failure

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Screensize: 640 x 480 800 x 600 1024 x 768 1280 x 1024 UserName: Password: Format Mode: Basic  Help  Prompt  Format: Font Andale Mono Arial Arial Black Book Antiqua Century Gothic Comic Sans MS Courier New Georgia Impact Lucida Console Script MT Bold Stencil Tahoma Times New Roman Trebuchet MS Verdana   Size 1 2 3 4 5 6   Color Black Red Yellow Pink Green Orange Purple Blue Beige Brown Teal Navy Maroon LimeGreen Message: * HTML is OFF * Forum Code is ON Smilies [quote][i]Originally posted by Dianaya[/i] [br]Troubleshooting a Faulty VPP Boost Circuit on a GQ-4X Programmer PCB — Seeking Repair Advice Hello everyone, my GQ-4X programmer is currently unable to supply the required 12V VPP voltage to EPROM chips. The symptoms are as follows: When attempting to read chips from the 27-series, the software displays the message: "Insufficient VPP voltage; unable to enter programming mode." Using a multimeter to measure the VPP output pin on the programmer, the voltage reads only 3.3V, failing to reach the standard 12V level. Upon inspecting the programmer's PCB, I noticed burn marks (blackening) on #8203;#8203;one of the surface-mount diodes within the VPP boost circuit; however, I am unsure if the component is actually damaged. I have already replaced the power adapter, but the problem persists, effectively ruling out a power supply issue. I am not very familiar with PCB repair, so I would like to ask the community for advice: What are the common failure points within this VPP boost circuit? (e.g., the boost converter IC, diodes, capacitors) Is there a schematic diagram available for the GQ-4X PCB that I could use as a reference? This would greatly assist me in systematically troubleshooting the issue. When replacing damaged components, which specific parameters (specifications) must be carefully matched to ensure compatibility? [url=https://www.pcbwdx.com/]PCB manufacturer[/url]: PCBWDX [/quote]    Insert an Image File Check here to include your profile signature.