What to check before buying a used amp: a quick, real counter guide

You hand over $240 cash for a vintage combo at a parking-lot meet. the person selling says it sounds great, but the tremolo is noisy. You plug in later at home and hear a hum under every note. That $240 deal just turned into a $120 fix and a $40 resale loss. Use this printed checklist at the counter: look, listen, and test before you pay.

What to look at first

**Check the speaker**. Look for rips or soft spots in the cone. Press the cone gently. If it caves, plan for a $60–$180 speaker replacement. Open the back panel if possible. A loose cone or frame bushing is an easy repair to spot.

What to listen for when you plug in

**Listen for hum, crackle, and rattles**. Play clean and dirty. If a single knob makes crackle, the pot likely needs cleaning or replacing ($15–$45). If the amp hums even with no instrument, note if the hum drops when you touch the chassis. That hints at a grounding issue.

How to test electronics in 90 seconds

**Test basic functions quickly**. Turn off effects. Set EQ flat. Play a steady note at low volume, then at performance volume. Watch for these failures:

• No sound from one speaker

• Volume jumps when you move the amp

• Weird noises only on certain channels

• Footswitch jack that wobbles or doesn't change channels

• Missing power cord or wrong voltage label

• Lessee repairs obvious like taped jacks or multiple loose knobs

• Signs of water damage (rust, salt lines, dark stains)

A quick price reality check

**Know typical used prices**. Expect a small practice amp to be $60–$120. Expect a mid-range tube combo to be $420–$900. Expect tube replacement cost of $60–$180 and tube calibration or tech time of $50–$120. If the asking price leaves you less than a $100 margin after repairs, pass. Micro-moment: You meet a seller in a cafe lot. The amp powers on and a cheap clip plays. the person selling leaves before testing. You plug in and hear intermittent dropout after five minutes. The amp has a loose internal jack that only shows after heat builds. If you can't test for five minutes, walk away.

How to know it's safe to buy

**Check for proof and condition**. Ask about service history and original power rating. Look for a clean chassis and solid handles. Confirm the amp's voltage matches your outlet. Ask if tubes are original or new. If the amp was recently listed at $780 and now $420, ask why.

Final quick checklist to bring

**Bring cash, a cable, and a loud friend.** Bring a small screwdriver to open panels legally. Bring $25 spare for a quick pot cleaner if you plan to buy. A-1 Trade & Loan on Commercial Drive tests and prices everything on the spot. What this means for you: If the expected repair costs more than 25 percent of the sale price, walk.