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Author Topic: 1970s HH amplifiers brought back to life.  (Read 8787 times)

Ivan Beaver

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Re: 1970s HH amplifiers brought back to life.
« Reply #10 on: May 17, 2015, 01:53:30 pm »

There is nothing on those amplifiers which you could call a heatsink.  Just the metal case.  I wouldn't want to run them at 100 watts for too long!


Steve.
This was real common back then. 
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Ivan Beaver
Danley Sound Labs

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Steve M Smith

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Re: 1970s HH amplifiers brought back to life.
« Reply #11 on: May 17, 2015, 02:20:58 pm »

It was quite a revelation in the 1980s to see the large heatsinks on the Peavey XR series compared with the minimal attempts to get rid of heat employed by HH and Carlsbro.


Steve.
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duane massey

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Re: 1970s HH amplifiers brought back to life.
« Reply #12 on: May 19, 2015, 12:07:07 am »

There was a local company during the early, early 70's that mounted the power transistors on pieces of wood with holes for ventilation. Now THAT was a heatsink.....
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Duane Massey
Technician, musician, stubborn old guy
Houston, Texas

John Roberts {JR}

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Re: 1970s HH amplifiers brought back to life.
« Reply #13 on: May 19, 2015, 10:37:59 am »

There is nothing on those amplifiers which you could call a heatsink.  Just the metal case.  I wouldn't want to run them at 100 watts for too long!


Steve.

For <100W a moderate sized metal chassis/case "could" supply sufficient surface area to dissipate heat from. If the chassis is made from the typical steel, that will provide lower heat transfer so not work as well as a full aluminum chassis (an aluminum heat spreader could help some). The familiar finned aluminum heat sink gets the extra surface area from all the fins, and in top of the fins, if you look closely there are small grooves in the surface of the fins, this grooved surface increases the total surface area even more. 

While large enough chassis could dissipate much of a small amplifier's heat, using a compact "real" heat sink allows you to design a standard power module that could be used in multiple SKUs, instead of every product requiring a different new heat sink design.

JR
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Steve M Smith

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Re: 1970s HH amplifiers brought back to life.
« Reply #14 on: May 19, 2015, 10:49:36 am »

I think the chassis is steel.  The transistors are mounted on the back behind a cover plate.




Steve.
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Mike Diack

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Re: 1970s HH amplifiers brought back to life.
« Reply #15 on: May 22, 2015, 06:05:30 am »


 *** ironically perhaps, the original (slow) 2n3055 have become collectors items for audio-phools trying to replicate the exact sound of old legacy products that used them as line driver buffers and the like. Device manufacturers probably couldn't make one that slow now if they tried, and they aren't trying. The 2n3055 was so ubiquitous in designs that several versions of them came out trying to hold on to all those design-ins.
Does this mean my big box of OC35s (Ft=220kHz) is going to be worth something some day ?.
I live in hope :-)
M
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John Roberts {JR}

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Re: 1970s HH amplifiers brought back to life.
« Reply #16 on: May 22, 2015, 12:06:00 pm »

Does this mean my big box of OC35s (Ft=220kHz) is going to be worth something some day ?.
I live in hope :-)
M
Not to me...  ;D

The driving force for popularity of original 3055 devices is apparently some old Neve recording products that used them back in the day. I don't even recognize OC35s, 3055 were used everywhere, in everything (long time ago).. 

JR
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Steve M Smith

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Re: 1970s HH amplifiers brought back to life.
« Reply #17 on: May 22, 2015, 12:59:01 pm »

OC35 was a germanium power transistor in a TO3 package.


Steve.
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John Roberts {JR}

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Re: 1970s HH amplifiers brought back to life.
« Reply #18 on: May 22, 2015, 01:29:09 pm »

OC35 was a germanium power transistor in a TO3 package.


Steve.

These may have some use in special effects, like fuzz tone guitar pedals.

JR
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Steve M Smith

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Re: 1970s HH amplifiers brought back to life.
« Reply #19 on: May 22, 2015, 02:08:59 pm »

These may have some use in special effects, like fuzz tone guitar pedals.


The OC71 was the low power version.  Scrape off the paint and you turn it into an  OCP71 phototransistor! (I think I remember that correctly).


Steve.
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