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Discussion Starter #1
A friend would like me to bring his 63 Bassman up to snuff. Was thinking it would need all electrolytic caps replaced as the current ones are the originals. A few years ago I would have used Sprague Atoms , but wondered if these are the best choice these days.
Not a gigging amp , it gets a bit of home use now and then. The amp is in excellent condition , and resale down the line is to be considered when I do the work.
Thanks for any suggestions...Jerry
 

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Replace nothing unless you need to (is there anything even wrong with the amp?). I mean the main large power filter caps are probably due on paper, but I have tonnes of gear from the 60s/70s with originals that are fine. Definitely stop there unless there's an actual issue (e.g. leave the cathode bypass caps alone). Atoms are overpriced (but nice and thin; longer than others though - just about anything modern will be smaller than the originals so not a big selling point). Remember these are just power supply caps not tone caps; any brand name you recognize is fine (Nichicon, Kemet, TDK and Panasonic are safe bets and much cheaper... though I don't think Panasonic does axial format anymore). The problem is, depending on where you buy, the only option in the exact same values at the required voltage rating in stock will be Atom (e.g. Mouser), but they might have values that are close enough (considering the originals are like what, 20% tollerence?).

If resale value is a consideration; replace nothing unless causing an identified problem. Full stop.
 

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Sprague atoms are available at Amplified parts dot com. They have decent shipping rates.
 

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If the electrolytic aren't leaking, buzzing or bulging, I'd leave them, esp. if it's not a gigging amp. F&T's would be your best choice if needing replacements.
Yes, F&T are like half the price of Atoms .... unless you get them from TheTubeStore, for some reason (last I checked). Tend only to be stocked by guitar-specific sites/stores (sometimes tube hifi places too) tho.
 

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Replace nothing unless you need to (is there anything even wrong with the amp?). I mean the main large power filter caps are probably due on paper, but I have tonnes of gear from the 60s/70s with originals that are fine. Definitely stop there unless there's an actual issue (e.g. leave the cathode bypass caps alone). Atoms are overpriced (but nice and thin; longer than others though - just about anything modern will be smaller than the originals so not a big selling point). Remember these are just power supply caps not tone caps; any brand name you recognize is fine (Nichicon, Kemet, TDK and Panasonic are safe bets and much cheaper... though I don't think Panasonic does axial format anymore). The problem is, depending on where you buy, the only option in the exact same values at the required voltage rating in stock will be Atom (e.g. Mouser), but they might have values that are close enough (considering the originals are like what, 20% tollerence?).

If resale value is a consideration; replace nothing unless causing an identified problem. Full stop.

I respectfully disagree with this last statement in particular. IME, resale is generally higher on an amp that's been fully serviced and properly maintained. Filter cap replacement is an inevitability on a 55 yr old amp so it's either you, or a future owner, who ends up paying for it and "peace of mind" has value to many buyers. Just save all the original parts and resale shouldn't be negatively affected in the least.

I used to think it was fine to just leave filter caps that had no obvious issues, until one in my brown Pro went "POOF!", sending up a cloud of smoke when the oil hit my hot tubes. It does happen...and it's easily avoided. I now consider filter & bias cap replacement preventative maintenance and so far it's worked out as expected. Last time I ordered, a full set of F&T electrolytic caps for a similar amp was ~$50. It'a a no-brainer for me but YMMV...
 

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If any of the B+ filter caps are bulging or breached, change them all regardless. As a rule, I usually replace all the filter caps in old Fenders now. They're waaayy past their useful life. There's no point doing half the job. Also check the bias filter cap.
 

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Discussion Starter #8
Thanks for the advice everyone . The amp is in fact an early 64 , first filter is two 70uf 350 v electrolytics in series , with 1 watt 100k resistors strapped across them. in case anyone is interested in small changes in the production of these amps. Schematic shows two 40uf in parallel.
 

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New filter caps are never a bad idea. I have yet to see a classic car sold with the original oil in it. As a courtesy, I always package up the original caps and parts I remove and give them to the owner just in case they will need them as a selling point for a future sale.
 

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Thanks for the advice everyone . The amp is in fact an early 64 , first filter is two 70uf 350 v electrolytics in series , with 1 watt 100k resistors strapped across them. in case anyone is interested in small changes in the production of these amps. Schematic shows two 40uf in parallel.
2 70 in series gives 35 uF at 700V. This better than stock schematic. Which is 40 uF at probably 500V.

The higher voltage rating is a good thing. With higher ac wall voltages today, amp in standby mode, the caps are most likely seeing over 500V on them.

I am in the "replace all e-caps" camp. Cathode and bias caps too. B+ resistors too.

For tone, safety and reliability. If you want re-sale. Seal it up as is and put it away in a dry place.
 
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