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Peavey CS 800 heating
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Old 13th April 2016, 01:07 AM   #11
Michael Chua is offline Michael Chua  United States
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Hi Duke

I didn't know it was a copy of the BGW. No wonder the layout looks the same. Two heatsinks on top with fins facing up.

I had a BGW 750G in my humble recording studio during the 80s. Beautiful piece of engineering. And I love those LEDs in the display panel.
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Old 13th April 2016, 03:21 AM   #12
Michael F is offline Michael F  Canada
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Quote:
Originally Posted by Audio1Man View Post
Hi Michael

I have not seen the inside of the CS800 in 30+ years. It was a copy of the BGW750 family. The top cover must stay on. It is part of the thermal management and HUMAN SAFETY. The 80 volts and the AC LINE are open to touch when the cover is OFF. Many of our 750 were modified with small low speed fans (Special service amplifiers). The thermal switch on top of the TO3 has one side of the AC line that feeds the fan. The fan runs very slow as we had a series power resistor that was bypassed when the amp was hot.
Duke
I wouldn't dream of running the amp "topless", it was removed strictly for testing purposes. While not quite as deadly as the BGW with its exposed rail voltages, fan switch and output switch, the Peavey will provide a nasty zap if you're not careful.

I used to run a PA rig that consisted of 16x 750 B and C series amplifiers that had the fans reversed. They were configured to draw cool air from the sides and exhaust through the rear. There was no perceivable increase in heat production and reliability wasn't affected either but it made cleaning the amplifiers so much easier. All that was needed was an occasional brushing of the top side heat sinks. The chassis, power supply, protection circuit, potentiometers and mother boards remained so much cleaner, and for longer periods.
I`m sure BGW and subsequently Peavey had valid reasons for configuring the amps the other way around though.
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Old 15th April 2016, 05:10 AM   #13
Michael F is offline Michael F  Canada
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Default UPDATE

After some experimentation, an additional 500R/20W in series with the 250 ohm resistor already in there turned out to be just what was needed.
It dropped the RPMs and subsequently the noise level to barely a whisper and still managed to dissipate the heat while idling quite nicely.
I relocated both resistors to the metal plate behind the Channel A DDT circuit board. Not only are they mounted more securely but the plate serves a heat sink too.

I performed some final power tests into various loads (1khz into 6 ohms mono yielded 1003.62 watts ) and the amp barely broke a sweat.
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Old 15th April 2016, 12:39 PM   #14
indianajo is offline indianajo  United States
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Congratulations. May the amp live long in its second life as a home audio unit.
I put sticky fiber batting from mcmaster.com over my fans, tied on to the grill. Not roady proof, but I'm still my own roady.
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Dynakit ST70, ST120 (modified), PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800s, M-2600, MMA-875T, SP2 (2004) speaker, PV8 mixer, Herald RA88a mixer (modified), Steinway console, Wurlitzer 4500, 4300
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Old 14th September 2021, 03:43 PM   #15
sherwin rambally is offline sherwin rambally
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Default peavey cs800

can somone tell me the purpose of the pull switch on the right side on this peavey cs-800
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Old 14th September 2021, 11:13 PM   #16
Enzo is online now Enzo  United States
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Um, which version CS800? And do you mean on a volume control? If so does not the other volume control also have a pull switch?

The two volume controls - left side and right side of the panel - should have a little printed message below them: "Pull to defeat compression"

And that is what it does.
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Old 15th September 2021, 11:57 AM   #17
sherwin rambally is offline sherwin rambally
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defeat compression ?, meaning ??.........
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Old 15th September 2021, 01:02 PM   #18
wg_ski is offline wg_ski  United States
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PV calls it the “DDT circuit”. It just detects when the amp clips, and feeds back a proportional DC signal to a gain reduction circuit at the input of the amp. Over a useful range, it will keep the amp out of gross clipping when over driven. Most modern PA amps have this feature, and you can turn it on or off.
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