Long-term storage of tube maps

Vinsanitizer

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I've heard it around the vibrating waves of time since long ago, that tube maps need to be powered up and played periodically to keep the filter caps from "drying out". (I suppose this would also apply to solid state or modeling maps, or any audio circuit that has filter caps, but I'm not asking about those right now.)

Is this true, or is it a conspiracy theory?

If true, then what would be a good periodic interval?
 

PelliX

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I've heard it around the vibrating waves of time since long ago, that tube maps need to be powered up and played periodically to keep the filter caps from "drying out".

Yes, electrolytics like a bit of action from time to time to keep them in good shape. Other things like the pots may appreciate it, too.

(I suppose this would also apply to solid state or modeling maps, or any audio circuit that has filter caps, but I'm not asking about those right now.)

To a lesser degree as they generally have smaller caps - but yes, the same applies.

If true, then what would be a good periodic interval?

3 - 6 months would be a good, safe interval. A year might be stretching it a bit. It also depends slightly on the conditions (temperature, etc). Basically, if you give every a good blast every few months it should help to keep things in good shape.

Adding to that, *ideally* for your valve amps (maps) you could hook them up to a variac and bring up the voltage slowly over the course of a few minutes.
 

Vinsanitizer

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Yes, electrolytics like a bit of action from time to time to keep them in good shape. Other things like the pots may appreciate it, too.

To a lesser degree as they generally have smaller caps - but yes, the same applies.

3 - 6 months would be a good, safe interval. A year might be stretching it a bit. It also depends slightly on the conditions (temperature, etc). Basically, if you give every a good blast every few months it should help to keep things in good shape.

Adding to that, *ideally* for your valve amps (maps) you could hook them up to a variac and bring up the voltage slowly over the course of a few minutes.
Perfect! Thanks, PelliX. :yesway:
 

PelliX

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I wonder how many pacs on average are in a 100w map that could be affected.

Actually, any electrolytic capacitor can/will degrade over time just sitting doing nothing. Even brand new caps that have had a while on the shelf can degrade and need to be 'reformed'. The smaller capacitors *tend* to suffer less as a rule of thumb. So, taking your question literally, you're asking for the average number of e-caps in a 100W amp - to which I'm afraid I don't know the answer, but I'd guesstimate around 40 (some will have a lot more and some considerably less).
 

Dean Swindell

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I've heard it around the vibrating waves of time since long ago, that tube maps need to be powered up and played periodically to keep the filter caps from "drying out". (I suppose this would also apply to solid state or modeling maps, or any audio circuit that has filter caps, but I'm not asking about those right now.)

Is this true, or is it a conspiracy theory?

If true, then what would be a good periodic interval?
Electrolytics will dry out over a couple decades anyway, even if they never get installed. It can't be stopped. They always need to be changes at some point.
 

KB0NES

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Powering up the amp from time to time does nothing to prevent electrolytic capacitors from 'drying out'. But it does help reform the oxide dielectric layer that forms inside an electrolytic cap that degrades over time. An electrolytic capacitor that has sat inactive for years can have the insulating dielectric degrade to the point that when powered on again instantly causes the capacitor to short. This is why people instruct that vintage gear should be brought up slowly on a Variac if it has been inactive for a long time. Powering up unused amps once a year or so for a few minutes would be more than adequate to prevent this.

Proper storage would be in a climate controlled space that isn't too hot or with big swings in humidity or temperature. The capacitors will dry out faster at high temperatures. Of course actually using the amp will increase the capacitor temps and speed their degradation from drying of the electrolyte.
 

PelliX

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Just had a quick count from a photo of the main PCB on my JVM410, and counted 24 electrolytics. I don't think there are any on the front control PCB (all plastic/Polyester).....

Yeah, maybe my guess was a little on the high side, I was thinking of all the DSL's and Mesas out there that are full of them. TSL's are pretty packed, too. I was also factoring in the fact there will be a lot more DSL's and Bugera amps in the wild than, say, handwired Marshalls or vintage Fenders.
 

guitarzan2525

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When I want to play my tube map after long storage time I variac it over several days. Let that tube map see a little voltage for say a long time (hours). Then I will come back the next day and variac it (Tube map) up a little more. And the next day a little more until the tube map knows where to go on it's own...........:)

Ok, kidding aside I do variac my old amps over many days a little at a time until full voltage (a little less than full say 110V - US voltage). That is with standby on at all times & listening to any strange sounds (and speaker load connected). I will then variac to 110 and turn the amp off standby and listen without playing and then play. A little overkill but it has worked for me...
 

jmp45

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Teh, all maps in the bunker get turned on every month or two at the most. I take them out of standby for at least 15 minutes to keep the cappys happy.
 

PelliX

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When I want to play my tube map after long storage time I variac it over several days. Let that tube map see a little voltage for say a long time (hours). Then I will come back the next day and variac it (Tube map) up a little more. And the next day a little more until the tube map knows where to go on it's own...........:)

What time do you consider 'long'? There's really not much benefit to stretching the process out over days, you're effectively just wasting component life, I'd say...

Ok, kidding aside I do variac my old amps over many days a little at a time until full voltage (a little less than full say 110V - US voltage). That is with standby on at all times & listening to any strange sounds (and speaker load connected). I will then variac to 110 and turn the amp off standby and listen without playing and then play. A little overkill but it has worked for me...

If the amp is on standby there's no *need* to have a speaker load connected. I agree on listening for strange sounds (though, generally smoke, smells or fuses will be the telltale signs of something going wrong...), but if you have that little 'faith' in the components - are you sure you want to them running in your house for days while you (presumably) leave it unattended?
 

deee

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I've heard it around the vibrating waves of time since long ago, that tube maps need to be powered up and played periodically to keep the filter caps from "drying out". (I suppose this would also apply to solid state or modeling maps, or any audio circuit that has filter caps, but I'm not asking about those right now.)

Is this true, or is it a conspiracy theory?

If true, then what would be a good periodic interval?
electrolytic filter caps will 'dry out' over time regardless. using them on occasion won't prolong anything. the best way to store an amp or any electronics long term is to have it at a reasonable humidity and temperature, shielded from dust and dirt by a cover. sealing it in plastic can trap humidity, but consider putting silica jell pouches used for packing guitars long term. don't put an amp in a non conditioned garage, basement or hot /cold attic for storage. my experience is that filter caps last far longer than people on the web, tube amp gurus, profess. i have caps in one amp in place for 15 years and there's no sign of any problems. actually filter caps aren't that expensive to replace. a filter recap job which some people seem to dread is actually only $40 dollars in parts and an hour bench time even for a big amp like a marshall 100w plexi. if you're handy you can do it yourself. i've messed with using caps of different values to experiment with tone changes. it's a simple procedure involving soldering 3 wires. there's the lore about using a variac to slowly bring up voltage in the caps...really, the parts are n't that sensitive. there's a horror tale about needing to bring new caps up slowly or else you'll 'blow holes' in the electrolytic...and they will never sound right. fender didn't do any of that stuff, ever. they built the thing and then plugged it for testing at final inspection.
 
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