marshall 18 watt tremolo psu question

[intensate]

Hello all,


I am building this circuit .would I have a problem or need to change anything when using a transformer with a 301v 0 301secondary ?


Thanks

 

[OrbitalLex]

You can put a 1N5357B 20V 5W zener diode between your 0 tap and ground on the pt to get you there on the money. The tubes can handle the extra plate voltage, though. Maybe try both and see which you like better.

 

[Printer2]

Or put a resistor between A and B which would drop enough voltage and give you a little better supply filtering.

 

[OrbitalLex]

Or even a 100 ohm 5 watt wirewound resistor at each leg of the HT transformer secondary .One in series with each leg before the rectifier. There are a few ways to skin a cat. Just be sure any resistors used in this area are 5 watt or better.

 

[intensate]

Thanks all will try these out


thanks all

 

[OrbitalLex]

Indeed, sir. Post pics when you are done!

 

[intensate]

finding switch for stanby ht valve guitar

Hi I am having difficulty finding a toggle switch for the standby of the Ht for my Marshall guitar amp project,


It needs to switch 350v dc at about 100ma


can anyone help


thanks

 

[JonSnell Electronic]

If you wire it correctly, before the rectifier, centre tap of transformer to ground through switch or if a single winding, in series with one of the AC feeds to the bridge, that will avoid the need for a DC type switch. A standard 250v AC switch will then be fine.
Some Marshall amps are wired BEFORE the main smoothing capacitor, that reduces the DC across the contacts.

 

[intensate]

hi this is the marshall circuit I am using


thanks

 

[intensate]

ez81 can it be used without load

Hi all


I am building a Marshall clone using 300 0 300v


Can I test it without a load and what sort of voltages dc should I expect to see


I am using a unknown valve and want to protect the transformer


thanks

 

[316a]

Unloaded you will see approx. 1.4 times the input voltage , around 420V

316a

 

[Kay Pirinha]

Yes, if he connects a capacitor between the tube's cathode and ground. I wasn't sure if his »with no load« excluded capacitive loading also .
Best regards1

 

[intensate]

thats with no capacitance



thanks

 

[intensate]

this is the circuit I am making .


It would be handy to know what voltage to expect with capacitance



thanks

 

[Osvaldo de Banfield]

Diodes in the anode of EZ81 have no sense. You would remove them.
Rectifiers vacuum tube/valves has been working pretty fine much time ago than ss diodes was born.

 

[JonSnell Electronic]

Your transformer has 290 - 0 - 290. The 0 on that winding at present goes to the chassis ground. Cut that wire and place your switch between the 0 and ground. There is no point in adding the cap and resistor on the switch, it will do nothing except be prone to failing.

 

[intensate]

this is the circuit I am making .


It would be handy to know what voltage to expect with capacitance



thanks

 

[intensate]

thanks for that

 

[Osvaldo de Banfield]

With capacitance and without load, 290V * √2 = 410VDC.

Again, diodes are useless.

 

[intensate]

thanks all