I've stumbled across a "grail" tube preamp for me for a decent price. However, it is about 20 years old. Should I re-cap it or, assuming everything functions properly, assume it's fine? I'm torn on this one ...
The power supply caps mighty be dried out by now. Use the same value and either the same or higher voltage. Film caps are most likely ok. If it has carbon comp resistors measure them as they absorb moisture and drift value. Don’t spray the pots unless a whole bunch of turns doesn’t clean them. Spray can destroy the element inside some pots and lots of older tube stuff had custom values no longer available. Look for burnt parts too. Good luck!
If it has been in regular use, the capacitors should be fine.
Check them for swelling or leakage first. They dry out when left for years unused.
Check them for swelling or leakage first. They dry out when left for years unused.
For the power rail caps, I would just make sure the value is not way off. I tend to keep them original.
For the dc blocking caps connected to tube grid. I would just replace all of them. I don't want to take the risk.
I would leave the rest of caps untouched, such as bypass caps of cathode bias resistor, and the cap on the negative feedback loop.
For the dc blocking caps connected to tube grid. I would just replace all of them. I don't want to take the risk.
I would leave the rest of caps untouched, such as bypass caps of cathode bias resistor, and the cap on the negative feedback loop.
