So, where's the problem? No doubt, there were a real problem if the opposite would have occured - the caps growing in size. It appears to be easily fitting a smaller componentn into ample space, doesn't it?
Is keeping the look of these amps as original as possible your problem? Well, in this case I'd consider opening the old caps' cans, pulling out the innards, fitting new, better, and smaller ones into the cans and closing them again.
OTOH, I don't see any practical (and economical) value in gear that is not functional due to worn out components. So, why bother?
Best regards!
For new-old-stock big electrolytic capacitors take a look at this:
https://www.surplussales.com/Capacitors/Electrolytics/10000uF-300000uF.html
Crown DC-300A is a good amplifier for 1960s, 1970s and 1980s standards. 30 years is an outstanding time period for a product to become outdated. The output stage design is about as good as it can be done with vintage NPN power transistors. The full bandwidth is extracted from old components. If a tech marketing text had to be written:
- Class AB all-NPN output stage (by that time NPN were more rugged and faster than PNP).
- Extensive output stage switching glitch compensation. Extra networks are used to improve lag of output transistors at zero-current crossing events: the VAS (current limited) with an extra PNP for high-side output stage base discharge, LRC networks in series with driver bases, and a "miller" capacitor connected directly to amplifier output.
- DC coupling. This is made safe for the amplifier by the next feature.
- Pseudo safe-operating-area protection of output transistors. This is an interesting circuit, involving two 22uF bipolar electrolytic capacitors and two pairs of series diodes. Peak dissipation per output transistor appears to be limited to 250W short term, transitioning to 150W with 5ms time constant (mismatching not counted). It becomes just 150W when the 22uF capacitors dry.
https://cdn-ak.f.st-hatena.com/images/fotolife/p/platycerus/20080927/20080927235303.jpg
https://www.surplussales.com/Capacitors/Electrolytics/10000uF-300000uF.html
Crown DC-300A is a good amplifier for 1960s, 1970s and 1980s standards. 30 years is an outstanding time period for a product to become outdated. The output stage design is about as good as it can be done with vintage NPN power transistors. The full bandwidth is extracted from old components. If a tech marketing text had to be written:
- Class AB all-NPN output stage (by that time NPN were more rugged and faster than PNP).
- Extensive output stage switching glitch compensation. Extra networks are used to improve lag of output transistors at zero-current crossing events: the VAS (current limited) with an extra PNP for high-side output stage base discharge, LRC networks in series with driver bases, and a "miller" capacitor connected directly to amplifier output.
- DC coupling. This is made safe for the amplifier by the next feature.
- Pseudo safe-operating-area protection of output transistors. This is an interesting circuit, involving two 22uF bipolar electrolytic capacitors and two pairs of series diodes. Peak dissipation per output transistor appears to be limited to 250W short term, transitioning to 150W with 5ms time constant (mismatching not counted). It becomes just 150W when the 22uF capacitors dry.
https://cdn-ak.f.st-hatena.com/images/fotolife/p/platycerus/20080927/20080927235303.jpg
The closing of Crown Elkhart factory is another interesting subject. The old designs clearly explain that there was people in the company knowing how to design things to last, while getting the best out of the parts. Since "the physics of the world" are the same as "the physics observed in the lab", it was just a matter of following the math derived in the lab for management, to ensure company stability.
What happened to that company and many others? I only got the reply recently, when I ran into the same situation. In the US there are two moral codes. One is scientific. The other isn't. Human specie is the most serious predator for human specie.
First the non-scientific moral code helps companies to grow, the representatives of this code buy from the company more product than would be needed to ensure an economically stable society, creating a false expectation of infinite growth, infinite chances for profit, infinite power of money.
Then, the representatives of non-scientific moral code anticipate economic difficulties (the ones they have created), but they try to pass the problem to the companies, by starting to impose conditions and blaming scientific moral code for the inability to match surreal goals.
Effectively, the representatives of non-scientific moral code manage to exclude the representatives of scientific moral code from management decisions of the company, by feeding the company in excess, then starting to impose non-scientific conditions for feeding the company.
Of course, the solution is: make less product ranges, dedicate more time to suit each product to more applications, do not dream with selling so much, reject customers pretending to feed the company disproportionately, keep an exhaustive equivalence between the logic used in the circuits and the logic used in management.
Then again, they would not be in the need to shrink if they hadn't failed badly in the calculations for expansion.
EDIT: Incidentally, there seems to be a problem in the US (and other countries) with correct transmission to next generation of leadership in technological companies, which end up controlled by monetary speculators, and from that moment, the careers and creativities of the engineer "workers" freeze. The creativity of an engineer only works at full performance when the company is led by engineers. For some reason, the scheme employed differs from the one that works: older engineers/managers training other successful younger engineers to replace them as managers.
What happened to that company and many others? I only got the reply recently, when I ran into the same situation. In the US there are two moral codes. One is scientific. The other isn't. Human specie is the most serious predator for human specie.
First the non-scientific moral code helps companies to grow, the representatives of this code buy from the company more product than would be needed to ensure an economically stable society, creating a false expectation of infinite growth, infinite chances for profit, infinite power of money.
Then, the representatives of non-scientific moral code anticipate economic difficulties (the ones they have created), but they try to pass the problem to the companies, by starting to impose conditions and blaming scientific moral code for the inability to match surreal goals.
Effectively, the representatives of non-scientific moral code manage to exclude the representatives of scientific moral code from management decisions of the company, by feeding the company in excess, then starting to impose non-scientific conditions for feeding the company.
Of course, the solution is: make less product ranges, dedicate more time to suit each product to more applications, do not dream with selling so much, reject customers pretending to feed the company disproportionately, keep an exhaustive equivalence between the logic used in the circuits and the logic used in management.
Then again, they would not be in the need to shrink if they hadn't failed badly in the calculations for expansion.
EDIT: Incidentally, there seems to be a problem in the US (and other countries) with correct transmission to next generation of leadership in technological companies, which end up controlled by monetary speculators, and from that moment, the careers and creativities of the engineer "workers" freeze. The creativity of an engineer only works at full performance when the company is led by engineers. For some reason, the scheme employed differs from the one that works: older engineers/managers training other successful younger engineers to replace them as managers.
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