Spent $80 on a variac for tube amp testing and it paid for itself in one weekend

I was too cheap to buy a proper variac for years, thinking I could just use a light bulb limiter for everything. Finally dropped $80 on a used 3A variac off Craigslist last month. First weekend I had it, I was recapping an old Fender Bassman and found a shorted filter cap that would have blown my meter or worse. The variac let me bring it up slow and catch the problem at 30V instead of full wall voltage. A shop would have charged me at least $150 to diagnose that same issue. Now I can't believe I went so long without one. Any of you guys run a variac on every unknown amp or just the old ones?

2 comments

2 Comments

claire_ramirez221mo ago

$80 for a variac or $150 for a shop diagnosis sounds like the math checks out to me. I just tell myself it's cheaper than a funeral for a good transformer.

alexlewis1mo ago

Yeah I used to be in the same boat, thinking a dim bulb was good enough for everything. But after I fried a power transformer on an old Silvertone by not catching a short soon enough, I kinda changed my tune. Grabbed a variac off eBay for about $70 and it's paid for itself twice over. Now I bring up every unknown amp slow, even the solid state ones. That Bassman story hits close to home, I had a similar scare with a dead short in a can cap. It's just not worth the risk to skip it.