Push pull amplifier – tube troubleshooting
Below are procedures that customer needs to complete to identify faulty tube, before submitting a warranty request:
- For Push Pull tube amps – 2 power tubes (either EL34 or KT88 – these are the most commonly used power tubes in push pull amps are used per channel. You may also see 2*300B or 2*845 type power tubes in recent years’ design) Total 4 tubes are used for two channels together.
- If your amp is making abnormal noise such as loud static noises or obvious humming etc, you need to identify exactly which channel (left or right) have problem, and exactly which tube is causing the problem.
- As amplifiers are of stereo channel – i.e. 2 channels symmetrically, a simple way to identify a faulty tube is ‘divide, swap and confirm’.
- Split 4 tubes to 2 groups first, then only install 2 tubes (Group #1) in left channel and use your two previous known good tubes in the right channel. Turn on the amp and see if problem presents in left channel that you installed the new tubes (Group #1) . If No, go to step 6. If Yes, go to step 5.
- Split the 2 tubes and install one in EACH channel (in two symmetric sockets in left and right channel), and split your two previous known good tubes in the other two symmetric sockets in left and right channel. (Do not worry about ‘blending’ your new tube and previous tube in one channel in this troubleshooting process.) Identify which channel (left or right) presents problem – the tube in the problematic channel is the faulty tube.
- Since you didn’t find problem in step 4 with 2 tubes (Group #1), now use your other 2 tubes (Group #2) and repeat the same process in Step 4. The tube in the problematic channel is the faulty tube.
- If you found more than one tube is of problem in the troubleshooting process, identify EACH tube’s problem and describe THE PROBLEM SEPARATELY on a piece of paper, along with that tube’s serial number (if the tube has a serial number on the base, or on the metal tag inside the tube).
- Now take a CLEAR & HIGH RESOLUTION picture of the tube and the paper (showing the problem message you have written down) together. You need to submit this picture when contacting us to file for factory warranty claim.
- Wrap this piece of paper containing the information to the corresponding tube and attach it with an elastic ribbon and have it ready for shipping. DO NOT USE ANY MARKER TO WRITE ON THE TUBE ITSELF.
- Contact us via email to file factory warranty claim – Please provide ALL information you feel pertinent about the tube problem, including but not limited to: your amp make and model, describe the event of tube problem you have experienced, and if using an entirely different set of tubes resolved ALL problems. If problems still exist when using other tubes – chances are that your amp might need a check-up by amplifier service technician before you use a new set of tubes again in the amp. A problematic amplifier can damage a perfectly fine set of tubes, and this will not be covered by tube factory’s warranty.
- Once your email is received by us, we will reply you within 48 hours about warranty return shipping instruction. There is NO NEED to ship known good tubes back to us – extra shipping and handling can easily damage fragile but perfectly good tubes. Only ship known faulty tube for warranty process, unless we instruct otherwise.
We appreciate you take the time to isolate the problem. Refusing to conduct the troubleshooting process will not move your warranty process forward – not all tube problem can be reproduced in the lab testing equipment, if it is intermittent only. We need customers to work with us to quickly have your tube problem resolved under factory’s tube warranty policy. It is a team work between buyer and seller.
Thank you.
Grant Fidelity