View attachment 160836 Help required for suggested value of resistor, thankyou in advance Colin

 

hi Colin,
Welcome to AAC.
Do you have a voltage for the rail at the top of the 47K Anode resistor.?
If so you have a 200V on the anode, so you know the current thru the 47K.
The Cathode voltage is marked as 1.46V, so knowing the valve current you be able to work out the Cathode reistance.
E

 

You can try 1.8kΩ ½W for starters.

 

You can try 1.8kΩ ½W for starters.

Thankyou, I would like to find out more about the capacitors, what type and voltage ratings, I’m very new to all this , regards colin

 

hi Colin,
Welcome to AAC.
Do you have a voltage for the rail at the top of the 47K Anode resistor.?
If so you have a 200V on the anode, so you know the current the 47K.
The Cathode voltage is marked as 1.46V, so knowing the valve current you be able to work out the Cathode reistance.
E

Thankyou, I will post the whole schematic, I’m new to all this, I’m a guitarist and a fan of hank Marvin and the shadows, this schematic is of an echo machine I’m trying to restore to get that “sound” they are very rare so learning this is not only very interesting it’s a quest, regards Colin

 

Welcome to the club. I am a big fan of The Shadows myself and do play a number of their songs.

As for capacitors, make sure that the voltage ratings of the capacitor exceed the operating voltage by 50% to 100%.
For example, if the circuit voltage is 200V, it wouldn't hurt to use a capacitor rated at 300V or 400V.

Capacitors over 10μF will most likely be aluminium electrolytics.
Capacitors under 10μF will be non-polar. Choose poly or mica capacitors for reliability. Old paper capacitors should be replaced.

 

View attachment 160852

Welcome to the club. I am a big fan of The Shadows myself and do play a number of their songs.

As for capacitors, make sure that the voltage ratings of the capacitor exceed the operating voltage by 50% to 100%.
For example, if the circuit voltage is 200V, it wouldn't hurt to use a capacitor rated at 300V or 400V.

Capacitors over 10μF will most likely be aluminium electrolytics.
Capacitors under 10μF will be non-polar. Choose poly or mica capacitors for reliability. Old paper capacitors should be replaced.

Thankyou

 

Are all these capacitor values in uf? Some are written as 220 or 200 is that pf of uf?
Thanks

 

hi Colin,
Welcome to AAC.
Do you have a voltage for the rail at the top of the 47K Anode resistor.?
If so you have a 200V on the anode, so you know the current thru the 47K.
The Cathode voltage is marked as 1.46V, so knowing the valve current you be able to work out the Cathode reistance.
E

Yes found it,132v

 

No it's not, it's 247v sorry

 

hi Colin,
If it is 247V at the top of that 47K and the Anode voltage is marked as 200V, thats a 47V drop, 47V/47K = 1mA.

The Cathode is marked as 1.46V, so thats R= 1.46/0.001A = 1.46K,,, nearest preferred value is 1.5K, 0.25Watt resistor.

E

@MrChips educated guess of 1.8K was close enough.

 

I have not looked over the entire schematic carefully, but yes, most of the capacitances are in μF except for two occasions.

There is 200pF on the plate of V2.
Also 200pF on the filter circuit after the output at the plate of V3a.

Note that a lot of the circuit is drawn right to left, which is contrary to accepted convention of having signal flow from left to right.

 

I have not looked over the entire schematic carefully, but yes, most of the capacitances are in μF except for two occasions.

There is 200pF on the plate of V2.
Also 200pF on the filter circuit after the output at the plate of V3a.

Note that a lot of the circuit is drawn right to left, which is contrary to accepted convention of having signal flow from left to right.

Thankyou

hi Colin,
If it is 247V at the top of that 47K and the Anode voltage is marked as 200V, thats a 47V drop, 47V/47K = 1mA.

The Cathode is marked as 1.46V, so thats R= 1.46/0.001A = 1.46K,,, nearest preferred value is 1.5K, 0.25Watt resistor.

E

@MrChips educated guess of 1.8K was close enough.

t

hi Colin,
If it is 247V at the top of that 47K and the Anode voltage is marked as 200V, thats a 47V drop, 47V/47K = 1mA.

The Cathode is marked as 1.46V, so thats R= 1.46/0.001A = 1.46K,,, nearest preferred value is 1.5K, 0.25Watt resistor.

E

@MrChips educated guess of 1.8K was close enough.

thankyou for your help, very much appreciated

 

I have not looked over the entire schematic carefully, but yes, most of the capacitances are in μF except for two occasions.

There is 200pF on the plate of V2.
Also 200pF on the filter circuit after the output at the plate of V3a.

Note that a lot of the circuit is drawn right to left, which is contrary to accepted convention of having signal flow from left to right.

Thankyou for your help

 

Does anyone know what sort of voltage the 470uf caps should be? I'm not familiar with these, thanks Colin

 

View attachment 161228 Can anyone help with the voltage for the 470 uf caps please? Here's a picture of the project so far, I've put the meazzi chassis in a project box and got some heads from Italy mounted with spacing for shadows echos , can't wait to get it going regards Colin

Moderators note : removed double picture

 

Does anyone know what sort of voltage the 470uf caps should be? I'm not familiar with these, thanks Colin

hi Colin,
Looking at the above circuit diagram I cannot locate any 470uF caps.?
Can you mark them out.?
E

 

View attachment 161294 I desperately need help with all these caps, if you could post a number and suggestions on value and voltage that would really help me, I was told just 2 of the caps were Pf and everything else was Uf , I'm confused

 

Capacitors #4 and #10 are shunting across the signal.
I doubt very much that these are 470μF, more likely 470pF.

#4 is on a low voltage signal path. 100V should do.
#10 is on the plate of V3a. You will need 300V or higher.

 

hi Colin,
I have photo shopped your circuit diagram.
I am not convinced that they are 470uF.?
That resistor is 6Watt.
Could you post a photo of the board that holds those cap 4 and 10.?
E

EDIT:
I would agree with MrChips ref those caps, I would expect lowish values on those signal lines.