JCM900-4100 OT connundrum
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TimmyP1955
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JCM900-4100 OT connundrum
The Z switch works, and everything seems to be wired correctly. No shorts between the secondaries (different output voltages on all three). Here's the oddity: With either an 8 Ohm or 16 Ohm load, the power output (and of course voltage swing) are highest on the 8 Ohm tap. ??
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martin manning
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Re: JCM900-4100 OT connundrum
Sounds like the secondary leads are not correctly identified. Put an AC voltage on the primary (across the plate leads) and measure the voltage on each secondary tap. Lowest is 4 ohm, next is 8 (and 1.4x the reading on the 4), highest is 16 (and 2x the reading on the 4). It's possible that the lead colors are not per the diagram.
Re: JCM900-4100 OT connundrum
yes, if you apply roughly 10v on the primary, you should be getting something like 500mv, 700mv and 1000mv on the secondary for 4, 8, and 16 ohms respectively
(I'm going by memory here and these are only ballpark figures)
(I'm going by memory here and these are only ballpark figures)
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Stevem
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Re: JCM900-4100 OT connundrum
Use the amps heater voltage to do the test out on the OT as you have that voltage right at hand, and note that the red lead on the primary is not the center tap on a lot of there OTs!
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martin manning
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Re: JCM900-4100 OT connundrum
It's easy enough to identify the plate leads; they are the ones connected to the plates.
If you use the amp's filament voltage to put AC on the primary, leave the standby off, and double check to be sure that there is no high voltage on the primary before you do the test.
If you use the amp's filament voltage to put AC on the primary, leave the standby off, and double check to be sure that there is no high voltage on the primary before you do the test.
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TimmyP1955
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Re: JCM900-4100 OT connundrum
The voltages: 8 is higher than 4, 16 is higher than 8.
Re: JCM900-4100 OT connundrum
sounds right to meTimmyP1955 wrote:The voltages: 8 is higher than 4, 16 is higher than 8.
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Re: JCM900-4100 OT connundrum
What are the voltages, across the primary and at each secondary tap?
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