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Amplifier Recap

Posted: Sun Nov 02, 2014 4:00 pm
by VA Bigdog
My Rockola 440 is still rocking all of the original 45 year old equipment. Lately I've been noticing some sound quality issues and one side is a bit weak until it's been on for a little while. I'm sure it's past time to do a full recap on it before something blows.

I know I can buy a recap kit from one of the suppliers listed. I also know that I can send a message to said supplier and ask about the contents of the kit. What I'd like to ask here, from people that have recapped amps, is if these kits usually contain every capacitor in the amp, or do they just cover what commonly needs replacing. Should a full recap actually be a replacement of every capacitor?

If I'm going to go through the trouble of doing this job, I want to make sure I do it thoroughly and cover all the bases. I'm more than capable of performing the job, just not familiar with what the entire job actually entails. If the kit will cover it, great. If I should be replacing items in addition to the kit items, then I want to make sure I have everything in hand.

Thanks for any tips/pointers!
Nelson

Re: Amplifier Recap

Posted: Sun Nov 02, 2014 6:17 pm
by Ron Rich
Hi Nelson,
I purchase kits from Tisdale ( see listing above), when I need one--his kits generally contain all of the caps--
However, I usually do not replace the disc type, as they seldom fail ( an exception here is the "Solar" brand, and any with a broken lead, naturally). Ron Rich

Re: Amplifier Recap

Posted: Sun Nov 02, 2014 6:22 pm
by MattTech
While the wildly popular "recap" of various electronics seems to dominate the internet blogs, nevertheless it can only remedy part of the issues with aged electronics.

What people don't seem to realize, or care about, or have the technical training knowledge for, is the fact that other age-related issues need to be addressed as well, for the full effect to be realized.
A.K.A. a solid successful overhaul/restoration.

Various resistors in circuits, particularly biasing and B+ feeds often change value over time, forcing tubes or transistors to run outside their peak operating ranges.
This can even worsen the situation if a mere "cap replacement" is done, causing even more rapid failure of the tubes/transistors.
Out-of-balance phase inverters due to aged balancing resistors can "sour" the sound substantially - making people always think "it's a cap!"
The same goes for critical RF circuits, and the Golden Screwdriver Crowd winds up twiddling the unit into a pile of poop because of their lack of knowledge.

So, the "recap" craze is only doing the job half-way, and sometimes produces dismal results.

Another known issue is oxidation and corrosion, due to age - on metals contained in contacts, switches, controls, and sockets.
Even when kept in spotless conditions, oxidation progresses over time regardless.

Re: Amplifier Recap

Posted: Sun Nov 02, 2014 6:49 pm
by Ron Rich
Hi Matt,
I agree 100 %--I get "re-capped" items in, for repairs, all the time, because they still don't work !
But I do have a question about your post---
Does the golden screwdriver crowd "twist", or, "tweak" those items into a "pile of poop" ????
Ron Rich

Re: Amplifier Recap

Posted: Sun Nov 02, 2014 7:44 pm
by VA Bigdog
Thanks Ron - I had planned on purchasing from Tisdale as most everything I've heard/read has been positive on his kits.

Matt - I totally understand what you're saying and I appreciate the warnings. Fortunately the world of electronics is something I'm fairly comfortable with. I started working on audio equipment in 1981 for JC Penney, then went to RCA (getting my Master Electronics with IBEW) and did everything from tube television to commercial satellite and phone systems. I have no intentions of ordering a cap kit and then simply installing it in paint-by-number fashion. I'll certainly be looking for anything else that appears sketchy and running through all the appropriate test points and settings. That's really why I posed this question, to seek out advice on items outside of the "kit" that others have found to cause issues.

I'll keep the diddle sticks in the toolbox unless absolutely required :wink:

Thanks!!
Nelson

Re: Amplifier Recap

Posted: Mon Nov 03, 2014 1:47 am
by Ron Rich
Hi Nelson
After reading what you have written, I have no concern about you using "diddle sticks" !
I am concerned about the "average Joe" using a metal "diddle stick" where a wooden, or plastic one, is called for !
Ron Rich

Re: Amplifier Recap

Posted: Mon Nov 03, 2014 6:34 am
by MattTech
Ron Rich wrote:Hi Matt,
I agree 100 %--I get "re-capped" items in, for repairs, all the time, because they still don't work !
But I do have a question about your post---
Does the golden screwdriver crowd "twist", or, "tweak" those items into a "pile of poop" ????
Ron Rich


Ronnie, for what it's worth, the usual problem with people "diddling" with critical circuits such as RF tuned coils is that they don't understand electronics at all.
poor operation, even after that wildly famous "re-capping" is usually due to failing resistors, or leached-over padder caps - the goonbag then attempts to "correct" the problem by sticking their uneducated hands into "re-tuning" said coils.

Sorry guys, t'aint the way to go about it.. you'll wind up with a mess anyhow.

Critical lead-dress is another factor to a successful repair, particularly in RF circuits - but, again, the backyard mechanic doesn't know anything about this procedure, them'z just wires, and not the famous "caps" that always need attention.

And lord knows how many times I've dealt with sloppy soldering jobs by putzes - they just don't know anything, and should stay the hell out of things.
But I digress - they've always done and they'll always will "try" to putz with things they don't understand, regardless.

Oh, and if some guy in California reads this by chance - the one who sold a "restored" 1930 Jackson Bell "Swan" radio to someone on Epray...
I had to completely undue and RE-DUE that slopped-up chassis.
It was a fire hazard, improperly worked on, and just plain butchered up.
Whoever put their props in that chassis needs his hands cut off, and given a citation or lawsuit for selling such a mess.

Re: Amplifier Recap

Posted: Mon Nov 03, 2014 6:04 pm
by Ron Rich
Hi Matt,
When I wrote the above, I was thinking of the guy, I saw, who attempted to "adjust" a tuning coil with a metal Allen wrench--Blistered his thumb and index finger, it did !
The same "diddling problems" applies to jukebox "adjustments"--99% of the time, NO "adjustments" are needed, unless (sometimes) a part has been replaced. I find that one must first understand what the machine is supposed to do, when, then figure out what it really IS doing, then plan on taking corrective action--which more often then not, in a jukebox, is just proper oiling ! Ron Rich