Help with My 67 solarus (possible recap)

[solarus b]

 My 67 solarus has a problem. The volume jumps around quite a bit when turned up past 5. It has a new bias and tube job. I think it may need to be recaped. If anyone has had an issue like this or knows of this symptom could you please let me know. I would really like to start using this amp more.
Best wishes,
BB

[basiklybass]

Old caps may cause the problem you describe...I would strongly suggest new caps on any amp over 20 years old in almost every case. If the power caps go too far out, you end up burning up the power transformer and other components. For the cost....replace them all.

[Ryanx]

see now how would you know that it's time to replace the caps, etc.  i'm weary to get my model t serviced and run through because of the price.  how worth it would it truly be?

[Soundmasterg]

Well the elecrolytic caps often will function for years and years, but they will be working below their specs and tolerences and are at risk of failure which can cause other parts to fail. If it is a vintage amp with original caps, it is really not very smart to use it often with old electrolytics in it, especially if you're gigging with it. If it is a newer amp, then generally 10-15 years is the expected lifespan of electrolytic caps depending on operating conditions and use. Some amps when not used for long periods of time will have the E-caps go bad in them because the electrolyte dries up inside the cap. Moreover with many of these old Sunn amps, and today's wall voltages, the stock caps are over-voltage and series connected discrete caps are a better and usually cheaper idea than sourcing a replacement can cap. Its certainly worth the peace of mind you have when you know your amp is and will be working properly for the foreseeable future.

Greg

[basiklybass]

As I stated, if the amp is over 20 years old, new caps are cheap compared to what happens when they go completely bad. SMG hit it right on the nail. I have seen many electrolytic caps rated for 2000 hours of operation.

A general rule might be; if the sound changes after playing through it for a bit (1/2 hour)...suspect caps. Distortion, hum, tone changes can all point to caps that are weak and as the signal goes through them and the electrolytes weaken furrther...they get worse and worse...and so does the sound. If you turn the amp on and it is distorted at low levels, suspect caps.  While these are not  hard and fast rules...old amp = old caps = problems. Replace them.

[EdBass]

I have a ritual that I do to keep my amps running strong. When I get up in the morning, I turn on the radio to get the news, let the cat out, make coffee, and change out the electrolytics on all of my amps.
On Mon., Wed. and Fri. I put in new output tubes, every third Tue. I change out the pre amp tubes. Yeah, maybe a bit obsessive, but my amps sound good...

Seriously, I agree with Soundmasterg and basiklybass. Fresh caps are cheap insurance compared to the potential catastrophy of filter cap failure.

[basiklybass]

You get and then change your caps? Gee....I sleep with my amps and change them BEFORE I get up!