Old Ampeg V4B

The amp has several electrolytic capacitors in the power supply. Electrolytics need voltage applied occasionally to keep them in operational condition. If the amp has not been powered on for 20 years, there is a good chance the eletrolytics are degraded or totally ganked. Some people believe you can recondition old electrolytics by bringing them up slowly on a variac over a couple of days. There is no guarantee that this will save all of the electrolytics.

If you power up the amp yourself, the results will be unpredictable. If the amp has or develops a fault, more damage could occur and it could be catastrophic. A full service repair center will most likely have something like a variac or perhaps something better like a variable AC power supply with a current limiter. The idea here is a good tech will know how to power up the amp in a way that is less likely to incur collateral damage.

As a courtesy it would probably be appreciated if you cleaned out the major dust bunnies.

 

Have I turned on an amp that hadn't been used in years just to see what happens? Yes, but I did clean out the inside first. Would I recommend it for everyone? Absolutely not. Capacitors that have sat for years can do bad things if you power up an amp that hasn't been powered up in years. It's best to hook it up to a Variac or similar voltage-control device and slowly bring up the power to normal so the caps can reform themselves, with less chance of blowing any right away. No guarantee they won't, but all the same...

After this long, even I wouldn't turn it on right away, and I'm about as impatient as it gets. I would take it to a tech for a once over just for peace of mind. The old saying...pay me now or pay me later. Just clean it out first unless you want to pay $85 an hour for someone to clean out your amp.

 

@April Hughes take the amp to a tech and let him/her bring it up slowly on a Variac with current limiting in case something catastrophic happens. Shouldn't cost you too much and it's safer for both you and the amplifier.

 

I agree to finding a tech but I would do a ton of research to make sure the Tech is trustworthy and qualified.

 

Take credit for asking what to do April.

After 20 years of storage, as mentioned, the power supply and bias circuit electrolytic capacitors will need attention. So there will be costs. Ask for an estimate, this is usually waved if the work is done.

I would clean the amp. Note what make tubes you have, especially the power tubes. Many of these old amps have, what are today, very expensive tubes in place. Just because they are old doesn’t mean that they have to be changed. If they are worn out, that’s a different story.

If it helps your tech, here is a 1974 schematic and a service manual.

https://www.talkbass.com/attachments/v4b-1974-schematic-pdf.2880196/

https://www.talkbass.com/attachments/v4-v22-service-manual-pdf.2880201/