B+ value

[kambo]

when a schematic states for x,y,z values for  B+ voltages,
is that mean, i should read those values under load, (all tubes attached, all circuit in working condition)
or,  ?

thanks
kambo


edit : 
i have always been going with date sheets, and keeps things close to max values...

 

[saxmonster]

Should be under load with everything in the circuit on.

 

[kambo]

ie: slow blow mic pre : 5687 max plate voltage is 300 volt...
how do i feed 370 volt to it?

i am not using regulated B+, so i should feed like 500VDC do read 370VDC

currently i am running at 294VDC ( 5687 plate voltage)

thanks
kambo

 

[rock soderstrom]

The two systems of the triode and the two cathode resistors are working in a series  circuit.

http://en.m.wikipedia.org/wiki/Series_and_parallel_circuits

 

[kambo]

The two systems of the triode and the two cathode resistors are working in a series  circuit.

http://en.m.wikipedia.org/wiki/Series_and_parallel_circuits

this doesnt help much... what DCV should i be reading at plate of 5687 ?

 

[PRR]

294V is fine. Tubes are NOT fussy.

> what DCV should i be reading at plate of 5687 ?

Obviously the top one better read 294V (direct connection).

The plate of the bottom section should be very close to half of that, almost 150V.

 

[kambo]

thank you PRR,
my confusion is, schematic says 370 V...  and its directly connected to the 5687's plate
and from data sheet: max plate voltage for 5687 is 300 V !

 

[rock soderstrom]

Series Circuit 

The maximum plate voltage of a triode is relatve to its  cathode, so a B+ of 370V is ok.
Please watch the Ufk ( maximum heater to cathode voltage), probably its a good idea to elevate  the heater of your SRPP output circuit.

Have fun!

 

[PRR]

> schematic says 370 V...  and its directly connected to the 5687's plate
and from data sheet: max plate voltage for 5687 is 300 V !

Tube ratings are measured from cathode.

So *plate-cathode* voltage can be 300V max.

Please re-review Rock's comment. SERIES CIRCUIT.

If you put 370V at the top, and the two parts of the 5687 split it equally, there is 185V across *each* part. (Maybe 180V, because the resistors take some.) 185V is safely less than 300V.

 

[kambo]

> schematic says 370 V...  and its directly connected to the 5687's plate
and from data sheet: max plate voltage for 5687 is 300 V !

Tube ratings are measured from cathode.

So *plate-cathode* voltage can be 300V max.

Please re-review Rock's comment. SERIES CIRCUIT.

If you put 370V at the top, and the two parts of the 5687 split it equally, there is 185V across *each* part. (Maybe 180V, because the resistors take some.) 185V is safely less than 300V.

i get that serial thingy... what i dont get is
should i  be reading 185V at pin 9 of 5687?
i am reading 70something V...
or how do i measure that 185 V?

 

[CJ]

go from 0 Volts to plate of tube B,

then go from plate of tube B to plate of tube A and report the  results here immediately.

 

[kambo]

go from 0 Volts to plate of tube B,

then go from plate of tube B to plate of tube A and report the  results here immediately.

sorry been working, long night...
( edit : measurements of 5687 (a) and (b))

0 Volt to Tube (b) plate :  74 Volt
plate  tube (b) to tube (a) : 186 Volt
0 Volt to plate of tube (a) : 260 Volt


edit :

thanks CJ, all making sense know