How do you know when it is time to recap?

[sweetbeats]

Why would one recap a piece of gear? How do you know it is time? I've seen pics of what bad caps look like, and I don't think I've seen any in my gear that I've had open, but I saw a post by an M320 owner who had recapped their mixer, and I'm thinking about my M520 which is of similar vintage and I'm wondering if it is something Ì will need to do eventually, or if it is something that it needs now and I haven't identified that yet...

 

[david winter]

If your mixer works well, don't bother recaping right now if you don't have test equipment.
To see if a capacitor needs to be changed, you have two tests to do:
1) Capacitance
2) ESR (Equivalent Series Resistor)

The first one is trivial to test with multitesters. The latter needs a special tester like the Capacitor Wizard (search Google). While the Capacitance requires removing the cap (at least one leg), the ESR can always be tested without disconnecting anything.

Any capacitor with a weak ESR needs to be replaced. Those with drifted capacitance require attention: if the capacitance is still in the original tolerance and that the ESR is ok, then the capacitor is good. Else, you need to chance it.

There is also a quite large tolerance of capacitance drift. Electrolytics which reduce by 10% and even 20% will generally work well.
The two common troubles with them are either when they are dry (no sound or a lot of distorsion) or get shorted (same with possible damage in specific sections).
Personally I consider recaping a reel recorder when it's 25+ years old. I also got familiar with sertain types of capacitors which are always bad or weak, and which I always change.
With a power amplifier, any noticeable "hiss" ("souffle" as we say in french) in the speakers means that at least the electrolytics in the rectifier section, and/or those before the speakers, need to be replaced.
With reel recorders, it depends whay section is affected by bad capacitors.
In a mixer, I have no knowledge, but would consider recaping only one section and compare the sound with an untouched one by sending the same mono signal to both inputs.
In any case, electrolytics can produce real troubles, especially those from the late 1980s or 1990s which are even worse than the good old ones. I've seen so many VCRs from that era which had leaky caps, whereas my old JVCs HR-3300 from 1978 and HR-7600 from 1983 still work great with their old caps.


David.

 

[Dr ZEE]

ESR-meter diy project here: http://www.ludens.cl/Electron/esr/esr.html, it's a relatively easy to build one. I have a short eMail chat with the man behind it - a nice guy, dedicated to the 'big "hobby" '
I've built one, following Manfred's design (details here: http://www.mzentertainment.com/studio_workshop_test_equipment_esr_meter.html ). It works great from my experience. A nice tool to have around.
**************
"How do you know when it is time to recap?"
I would say - when it's bad - replace it.
*********
Preventive recaping may make perfect sense for some, I guess. I would not argue with that, as long as it makes a "doctor" happy and keeps him busy
If you do a lot of repair work, you get better "sense" about what and when and what is more likely to go bad from experience, just as David said: "I also got familiar with certain types of capacitors which are always bad or weak, and which I always change."

 

[dementedchord]

mid -low end gear use mid-low end parts... duh??? so if we're talking bout this kinda gear then any electrolytic that's in the 15 yr range is suspect... especialy if it has gone sometime without being used... yes lack of use can be VERY bad for electrolytics... do you find that adjacent channels dont sound reasonably alike???? that's a cap problem... have you cleaned the controlls but still find it's scratchy sounding??? often that's coupling caps...

 

[Dr ZEE]

... if we're talking bout this kinda gear then any electrolytic that's in the 15 yr range is suspect...

from wikibicyclopedia :
"The presumption of innocence — being innocent until proven guilty — is a legal right that the accused in criminal trials has in many modern nations. The burden of proof is thus on the prosecution, which has to collect and present enough compelling evidence to convince the judge and jury, who are restrained and ordered by law to consider only actual evidence and testimony that is legally admissible, and in most cases lawfully obtained, that the accused is guilty beyond a reasonable doubt."

 

[dementedchord]

from wikibicyclopedia :

ok... so you're saying that the caps have the right to interfere with the accurate transmission of audio up until the point that any plebe would deem them bad??? no points given for a knowledgeable and/or experienced prosecutor/tech?? or can they only be prosecuted by one having benefit of oscilloscope and knowledge there of???

 

[Dr ZEE]

heh heh, that's a good one I'll do my best trying to follow

... you're saying that the caps have the right to interfere with the accurate transmission of audio...???

Wikibicyclopedically speaking, - Yes.

no points given for a knowledgeable and/or experienced prosecutor/tech??

When the points are due - they shall be given.
Justice!

or can they only be prosecuted by one having benefit of oscilloscope and knowledge there of???

I don't know. Never tried using oscilloscope nor knowledge thereof to specifically determine the guilt of a cap. But then again, there are many things I've never done. So, I don't know.

One thing I know for sure, however, that recaping does not really require any knowledge. It only requires an ability to take a cap out and place a cap in. It's a popular thing to do, and fun too

/respects

 

[sweetbeats]

Hey Mike, I get your point...I think my concern is of the cap with the willful intent to inflict harm, or rather I guess incapacity (no pun intended) to refrain from inflicting harm.

If a cap going bad can take out other components, I want to avoid that. I'm not into "guilty before being proven innocent", or doing needless work, but if the cap has the built in inability to not inflict harm on others as it dies, then it needs to be taken out...like one of these...

 

[Dr ZEE]

the cap has the built in inability to not inflict harm on others as it dies...

I dig that line ,
Would not it be great if there was such thing as a free of 'inability to not inflict harm' cap? .
Have you Ever wondered about the reasons behind the fact that insurance businesses eat us all alive and do so with a wide smile ?

In all seriousness, - recap away! It will not hurt.

 

[fisheric]

if you can do general soldering than you should be able take care of the project in a couple hours, depending on the number of caps.

Also you ONLY have to change electrolytic caps, dont replace all the small ceramic disc and others. unless you dig that sorta thing.

 

[sweetbeats]

Thanks all for everything so far...

dementedchord:

mid -low end gear use mid-low end parts... duh??? so if we're talking bout this kinda gear then any electrolytic that's in the 15 yr range is suspect... especialy if it has gone sometime without being used... yes lack of use can be VERY bad for electrolytics... do you find that adjacent channels dont sound reasonably alike???? that's a cap problem... have you cleaned the controlls but still find it's scratchy sounding??? often that's coupling caps...

I'm asking this question in regard to any of my older Tascam gear: 58-OB (RC-50 and 51 remotes too), 48-OB, M520, PE-40, MX-80, RS-20B. Some of it...most of it, is surely about 25 years old at this point. Hmm....

Dr ZEE:

Would not it be great if there was such thing as a free of 'inability to not inflict harm' cap?

fisheric:

if you can do general soldering than you should be able take care of the project in a couple hours, depending on the number of caps.

Also you ONLY have to change electrolytic caps, dont replace all the small ceramic disc and others. unless you dig that sorta thing.

I'm pretty comfortable with a soldering iron, but there's a lot of 25 year old gear in my studio... Can't really afford the time to go through it all, so I guess I'm just really wanting to know the best route to take that can hone me in on the problem gear and prevent damage.

Everybody, maybe this would be a better thread for the DIY forum...

I think it is time for a new soldering iron. The one I use is a simple 15/30W iron, but I often feel like I wish it had a setting in between. The 30W setting tends to be a bit much...have to be quick to keep stuff from scorching, but the 15W often doesn't have enough heat to get the solder liquefied enough to wick into the joint. Suggestions?

Just so you all know, my experience soldering components on a PCB is pretty limited. Done quite a bit of cabling, but just minor repairs to my 58 and my MX-80, and some mods to an A & H GL3300.

 

[dementedchord]

dementedchord:


I'm asking this question in regard to any of my older Tascam gear: 58-OB (RC-50 and 51 remotes too), 48-OB, M520, PE-40, MX-80, RS-20B. Some of it...most of it, is surely about 25 years old at this point. Hmm....

.

understood... we've all seen your exploits of late... that's quite a collection of stuff ya got there bro... my personal experiences have been more with the console and synth type stuff... so frankly i'm not sure what kind of repercussions exhibit with the recorders and remotes etc... though anything in the audio path is fair game... personally i would do a complete rebuild on that 520 ... op-amps and all... and for the rest i'ld be checking out all the powersupplies... just a bit of noise and/or drift in one of the supply rails can reek havoc... and yes i think you should move this to the DIY forum... someones been concerned with the lack of activity there and you might get some ideas from guys that dont monitor the analog only forum...

 

[sweetbeats]

Thanks again...

Thanks again for the advisement thus far. I am indeed closing this thread and moving it over to the DIY forum.