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 |
GQ-4X Programmer PCB: VPP Boost Circuit Failure
Posted - 05/20/2026 : 22:29:52
