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Peavey CS800  Doorstop to Decent
Peavey CS800  Doorstop to Decent
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Old 12th December 2018, 11:34 PM   #51
Peter S is offline Peter S  Canada
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Join Date: Dec 2014
Location: Hillsdale, Ontario, Canada
Hi Folks;
Moving on, sort of! I see that leakage current at 24 V, after 2 days is less than one half micro amp. (.004 V across 10,000 ohm), so something is happening---probably good?
I am going to power up (reform) the caps using the CS800 transformer and the 10k resistor. This requires straightening out the AC wiring mess in this amp. I found a set of schematics with version A, B, and C. This amp has a (Triac) on a steel plate, but not connected in the amp. Only version C has this, and yet this amp does not have the version C pull-out volume controls to engage the clip reduction.
The power switch contacts are rated at 16 Amps. It is a double ganged switch, is there any point to paralleling the contacts? The triac (pictured) had no connections, I thought of re-installing the steel plate, for any shielding benefit for the input board. I don't know how to test the triac, and being disconnected, wouldn't the odds be that it has failed?
Any thoughts on the Triac start circuit? I have had the power switch fail on two Phase Linears, but one of those switches was only rated at 4 Amps.
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Old 13th December 2018, 01:28 PM   #52
indianajo is offline indianajo  United States
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Location: Jeffersonville, Indiana USA
Peavey used the triac as a power switch to eliminate stress on the real power switch. Also probably allowed them to use a cheaper power switch.
They used the triac between transformer AC bottom and neutral. Turn on surge stresses the contacts on the power switch without the triac. They rectified Ac to DC and fed it through a small resistor to get the 50 ma necessary to turn on a typical triac. The power switch turned on the DC feed to the triac instead of the AC to the transformer.
I've put a CL-150 NTCR between the fuse and the transformer AC hot on my PV-1.3k to cut the turn on surge. It was dimming the lights in the room. Time marches on, components get invented or get cheaper.
Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,1.3K, SP2-XT's, T-300 HF Proj's, Steinway console, Herald RA88a mixer, Wurlitzer 4500, 4300

Last edited by indianajo; 13th December 2018 at 01:30 PM.
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Old 13th December 2018, 01:41 PM   #53
wg_ski is offline wg_ski  United States
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The triac doesn’t eliminate the turn on surge - only keeps it from frying switch contacts. If the triac has died then the solution is a bigger triac. One that can handle 600 amps surge current (same as the bridge rectifier). You could design a soft start circuit using a 10 ohm 50 watt resistor, which gets bypassed by the triac after a few seconds. Then you wouldn’t need a bigger triac.
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