This is a board for a dual relay time delay with some extra protection feature for use in fixed bias tube amplifiers.
The supply of the boards consists of a 230V transformer, but if there is enough demand i'l make a version with a 115-115 primary transformer.
Included are two 12V coil relays that are driven directly by the 555 outputs. The 555 forms a simple time delay, that activates once the charge across the capacitor reaches 2/3VCC.
There is an on board thyristor that will trigger from a 1.0-1.3V signal from the cathodes of your output tubes, this means that with a 10R sense resistor in the cathode leads the circuit will trigger at 100-130mA. Once it triggers it will pull the input of the 555 low, disabling the output relays until the power is reset.
There is also an optional TL431 based protection circuit, that guards the bias supply, once the bias supply sags in enough, the reference pin of the 431 will be pulled high, and it will in turn discharge the timing capacitor as well. So if there is no bias there is no HV, but if the bias is enabled by means of the relays the module wont start. but like i said this part of the circuit is optional, and perhaps a nice addition if you plan on using a separate transformer for bias.
These would be ideal for example for class A amps with 845/211/GM70 that use a separate transformer for the high voltage and bias.
Aksing €5 each for a black ENIG finish board, with the parts available at a 20% markup.
You can ask for a quote on shipping beforehand and i will look up the price for shipping. However if you are from some far-flung destination you can get the gerbers from me for €5 and order the boards yourself instead.
The supply of the boards consists of a 230V transformer, but if there is enough demand i'l make a version with a 115-115 primary transformer.
Included are two 12V coil relays that are driven directly by the 555 outputs. The 555 forms a simple time delay, that activates once the charge across the capacitor reaches 2/3VCC.
There is an on board thyristor that will trigger from a 1.0-1.3V signal from the cathodes of your output tubes, this means that with a 10R sense resistor in the cathode leads the circuit will trigger at 100-130mA. Once it triggers it will pull the input of the 555 low, disabling the output relays until the power is reset.
There is also an optional TL431 based protection circuit, that guards the bias supply, once the bias supply sags in enough, the reference pin of the 431 will be pulled high, and it will in turn discharge the timing capacitor as well. So if there is no bias there is no HV, but if the bias is enabled by means of the relays the module wont start. but like i said this part of the circuit is optional, and perhaps a nice addition if you plan on using a separate transformer for bias.
These would be ideal for example for class A amps with 845/211/GM70 that use a separate transformer for the high voltage and bias.
Aksing €5 each for a black ENIG finish board, with the parts available at a 20% markup.
You can ask for a quote on shipping beforehand and i will look up the price for shipping. However if you are from some far-flung destination you can get the gerbers from me for €5 and order the boards yourself instead.
