RED-25 Troubleshooting

Last modified: 2026-08-25

Table of Contents
  1. General resources
  2. 1. No output, distortion, or excess noise
  3. 2. Intermittent, weak, or muted output
  4. 3. A transistor or resistor looks damaged, or a 68 ohm resistor is smoking
  5. 4. DOA daughterboard doesn't seat, or the RED-25 acts like there's a loose connection
  6. 5. Substituted a third-party transistor and now the RED-25 behaves like Section 1
  7. Request Troubleshooting Support

General resources

No output, distortion, or excess noise

Check the positions of Q7 and Q8 against the assembly guide. Having these two transistors swapped is the single most common cause of problems with the RED-25.

Intermittent, weak, or muted output

Check for cold or blobby solder joints, especially at V+/V- and the transistor leads. See Cleaning Up Solder Joints for how to reflow these properly.

A transistor or resistor looks damaged, or a 68 ohm resistor is smoking

This is often not the RED-25 itself failing, but a fault elsewhere in the host circuit feeding it too much current, most commonly a reversed RGB LED, a short from messy soldering nearby, or a bad socket. Check the surrounding host circuit for one of these before assuming the RED-25 needs replacing outright. If a transistor or resistor on the RED-25 is genuinely damaged, it needs replacing, and in more severe cases the whole module does.

DOA daughterboard doesn't seat, or the RED-25 acts like there's a loose connection

The pin header on the DOA daughterboard needs more force to seat fully than you might expect. If you've assembled everything correctly but you're getting a loose connection or no signal, press it in firmly rather than assuming a fault.

Substituted a third-party transistor and now the RED-25 behaves like Section 1

If you swapped in a third-party BD139/BD140 equivalent, double check its pinout against the datasheet before installing. Third-party parts don't always share the same pin layout as the stock transistors, so a part that looks correct on the outside can still be wired in reversed.

Request Troubleshooting Support

If you weren't able to solve your issue from this guide, you can request email support from one of our troubleshooting experts here: Request Troubleshooting Support.