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PostPosted: Thu Dec 21, 2017 4:30 am 
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Hi all,

I have a PrimaLuna Dialogue 4. I bought it from a dealer about a year ago, but I know this unit is at least a few years old, but have been assured that it has sen little use, and I do trust this dealer. So far it sounds great. But i've been wandering when is the right time to re-cap it?

And in general when does one re-cap a tube amp? Is it a do it when you need to thing, or should it be done periodically?

Also, i'm pretty handy with a soldering iron (but am far from a pro), so, is re-caping something one could do themselves, or are there particular tricks of the trade that make it advisable to have a pro do it?

Lastly, even if not necessary, are there significant benefits to be had from re-caping with say mundorf caps, or any other "high-end" caps?

Cheers,
M,

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PostPosted: Thu Dec 21, 2017 7:09 am 
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Hi,

Recapping can follow a few schools of though.

1) Do it when it's necessary
2) Do it before something goes wrong
3) Do it to improve or modify the circuit

Based on the age of your tube amp, you will not likely need to do it for a while yet. A few things can cause capacitor failure, one of them is age - another environmental (heat, etc.), and another is related to the quality of the cap, or the purpose/ function of the capacitor (i.e. more stress on the cap).

Usually, a well made capacitor in the correct application and without undue stress will last well over a decade. It's not unusual for people to have amps in service where the capacitors are nearly three or four decades old! I'd say though the average capacitor should last 15-20 years minimum, some can fail in less than 10.

Your amp is a quality unit, there is no reason to believe that you'll have to do anything within the next 10 years unless something goes wrong with the amp. Of course, maintenance of the amp and periodic use (at minimum) helps...Some amps requiring Biasing (yours is likely self biasing) as well letting a amp sit without use does not fair capacitors well.

As for upgrading, it's a very debatable topic. Many will say it makes a significant difference, others will say it does not.
I've never owned a amplifier that I A/B'd the capacitors in to tell you if it really will make it sound better. This would require comparing a amplifier that has (presently) new factory capacitors and then swapping them out for a comparison...It would not be fair to swap out old capacitors and claim the higher end ones made all the difference as it may have been simply due to the fact that they were new/ that made the difference, not the type.

I will say however that I believe that a quality capacitor will make a difference. From my experience, they last longer, have tighter tolerances, and the construction of higher end capacitors ought to make a noticeable difference. So, in my case I have always opted for upgrading mine when the time comes to do it. I am a big fan of Solen because of the combination of the practicality of the cost as well as the quality of the product. Any speaker I recap gets Solen. I have also opted for factory upgrades on capacitors when budget allowed - why not I figure.

As for tricks of the trade, really - there is only one. Practice.
Cold solders are your enemy - get a good iron, some good solder, and practice first.

Anyhow, take care - gather some information from others and make your own decision if a upgrade is in order; however, replacing them because of potential failure should not really be a consideration at the age of your amp.

Merry Christmas, Happy Holidays - be well!


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PostPosted: Thu Dec 21, 2017 7:37 am 
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Personally I wouldn't be concerned for a couple decades

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PostPosted: Fri Dec 22, 2017 3:02 am 
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Thank you JGP and Blinky for your replies.

JGP, I do listen to it daily, so its getting quite a bit of exercise.

Can you please tell me what would be considered signs of a cap going bad?

And happy holidays to you as well.
Best,
M,

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PostPosted: Fri Dec 22, 2017 4:03 am 
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The amp may benefit from replacing the four RealCaps which are Chinese copies of RelCaps. Buy what your budget can afford. The real RelCaps available from PCX may be a good start. Russian K40 oil caps are nice.

The e-caps should be good for around 20 years, but check periodically for leakage and/or bulging. If you won't be able to sleep at night until they're changed, then go ahead. Buy good Nichicon, Panasonic, CD, Sprague, etc. caps from Mouser, DigiKey, Allied, etc. Don't change out the big Nichicon NX caps until they start leaking.

Replace caps with the same uF value which was there. Rated voltages can be increased, but don't go lower. IE if the existing cap is rated at 400vdc, don't use a cap with a 250vdc voltage rating, but 630vdc is fine

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PostPosted: Fri Dec 22, 2017 5:27 am 
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It's a dialogue...will have solens.

Coupling caps if you want to play but the ones on the autobias board you can leave be as not in audio circuit.

If you want to "improve" the electrolytics consider also using 105 caps.

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PostPosted: Sat Dec 23, 2017 4:03 am 
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Thanks for these suggestions.

I suppose then, I would have to periodically check the caps for leakages.

Also if I were to go ahead and change some of them, is there any particular solder that would be better to use over another? And my soldering iron can be set to a particular temperature, so is there any temperature, that may be too high and damage the component that i'm soldering?

Cheers,
M,

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PostPosted: Sat Dec 23, 2017 6:35 am 
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martin_manolov wrote:
Thanks for these suggestions.

I suppose then, I would have to periodically check the caps for leakages.

Also if I were to go ahead and change some of them, is there any particular solder that would be better to use over another? And my soldering iron can be set to a particular temperature, so is there any temperature, that may be too high and damage the component that i'm soldering?

Cheers,
M,


I can tell what not to use ... lead free solder!! Lol Unless you're into tin whiskers:

https://nepp.nasa.gov/whisker/background/

Use 60/40 or 63/37 rosin core solder, or quad eutectic solder such as Cardas if you want to spend a few extra $$. The 63/37 is also a eutectic solder but without the silver and copper.

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PostPosted: Sat Dec 23, 2017 9:30 am 
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You be experienced tin disease?

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PostPosted: Sat Dec 23, 2017 9:47 am 
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Cheers,

I already have some Johnson's IA-423. So that should be good then.

Happy holidays :)

Cheers,
M,

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PostPosted: Sat Dec 23, 2017 10:07 am 
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Should be...but then you could possibly be mixing silver solder with lead based solder.

Yet another debate.. ..paranoid?

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PostPosted: Sat Dec 23, 2017 10:11 am 
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I would go with WBT silver solder...fast, easy to work with and best sound.


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PostPosted: Sat Dec 23, 2017 10:11 am 
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They do use premium parts such as the Solen and Nichicon caps just to name a few on the Premium model but the Premium model cost twice as much as the regular one. So the question is which model do you have? If you have the premium one you're good to go, however, if you have the regular one then you may have to make a decision whether it's worth to upgrade the caps or not.

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-- 23 Dec 2017 18:18 --

BinkyTheCat wrote:
Should be...but then you could possibly be mixing silver solder with lead based solder.

Yet another debate.. ..paranoid?


It's possible if the manufacturer of the unit that's being worked on used the old lead-based solder. It's best to test the unit's existing solder first before using either silver and or lead-free solder. I know I'm being anal about this but if you want less degradation in the sound you have to use good quality MATERIALS.


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PostPosted: Sat Dec 23, 2017 11:45 am 
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tube54, op's very first post - he has the dialogue 4.


and is it just the caps that differ in the premium? cause dat don't justify double the price.

think yer looking at 2 different ballparks.

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PostPosted: Sat Dec 23, 2017 12:31 pm 
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BinkyTheCat wrote:
You be experienced tin disease?


Nope, but if NASA thinks it's an issue and can't find a solution and the US Military specs don't allow tin solder ... if it smells like $hit, and if it tastes like $hit, it must be $hit.

I've had conversations with techs who work on newer equipment and it has a higher than average failure rate due to tin whiskers which results in the pc of equipment being scrap. Google the term, there's lots of info out there.

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