Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: luthierwnc on March 30, 2024, 09:15:06 am
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Hi All and hope you're well. I'm building an Ampeg/Sano based reverb tank -- one I did before. On this one I'm trying to use a 6 vdc supply to run an engage/bypass switch. It's got a panel switch and led and a footswitch with LED. You can see in the schematic it's an either/or proposition. On both the juice through the LED activates the relay. I've done this before too.
The issue is that the supply doesn't drain enough to kick the relay. It comes in around 7 vdc but with either switch engaged the voltage at the source only drops to about 3.4 vdc. I tested the relay with a 6v lantern battery and it clicked fine. I've tried grounding the FWBR to the chassis and isolating it at the footswitch jack. All components are new. I've also stripped the switches and LEDs just grounding the relay switch directly and it still holds above 3 volts -- not enough to collapse the field. The reverb works great if I short the relay socket.
This has got me scratching my head. I do wonder if somehow the 6v supply is too stiff with those big capacitors (I had them in the bin). If that or anything seems out of whack, please post. Thanks, Skip
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Put a jumper wire across the 470Ω. Will the relay energize now?
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I took both the resistor and LED out. sh
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No LEDs, no footswitch. Coil positive is at 6.5-ish. Coil negative is the same when not engaged. When I ground the negative, the positive falls to about 3.5v and does not recover from the voltage regulator. The negative hovers around zero. However, when I open the circuit, it takes the negative side fully 15 seconds to recover. If memory serves in other variations I've done that was nearly instant.
For kicks I put a 5v relay in the socket and the relay coil doesn't function in either case. I'm using an Antek toroidal power transformer. The heaters are on a separate winding. These two leads only supply the relay circuit. Stumped. Thanks, sh
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Maybe you installed the 7806 backwards or it is faulty. Measure the voltage at the input and out of the 7806 while you do these test. What are the results?
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Which relay ?
What is the specs of the relay, how much current for the coil ? it is a must
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This video actually appeared in my feed today... May explain what's going on?
eature=shared
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I'll have a look at the vid tomorrow.
Regulator seems fine; 7.5 volts on the input, 6.56 volts on the output. The relays are Omron G6A low-signal units -- same as I've used for a long time. What I don't get is why it takes so long to recover. And this is with no load and nothing else connected. I'll try replacing the regulator with a 1 ohm resistor between the caps if nothing else seems likely. Thanks for the ideas, sh
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I think, the 7806 regulator needs more than 0,94 V voltage drop to work fine. Try a voltage doubler or a 7805 or a special regulator with 1V voltage drop or a zener diode 5V instead of the regulator.
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I made it simpler. I'm replacing the relay with a 3P2T mini toggle to control both sides of the bypass and the led. Then I'm just opening the circuit off the .47 cap like the original for the footswitch. I might use the LED on that too if the juice doesn't interfere with the signal. Cheers and thanks, sh