|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
1.124.48.19
In Reply to: RE: Installing a current meter.. posted by DAK on June 18, 2017 at 13:24:13
As already mentioned a good ole fashioned Simpson ie not china made meter should be fine. I still reckon any form of fusing is ideally suited in the HT side.
The alternative which is more expensive but bullet proof is to use a Volt meter across the kathode resistor. Jacmusic has some good info at there website under panel meters ie Yamamoto Panel meters
Verbatim below from above website
Yamamoto Shunt designed current meter, for tube autobias only
Please take a moment time, to understand those intelligent meters, because these are not like any other. When measuring the plate current of a tube, it is generally not desired that the signal path will go through the ampere meter. Reason is, that Ampere meter has a coil inside, and any Audio signals would be disturbed by this coil. The intention of these meters is to prevent frequency dependent effects, and other kind of interference. Besides not all low cost meters will indicate precise.
Yamamoto has found a nice solution for this. The meter is connected in parallel to the cathode resistor, and the meter is high impedance. This method is really genius. The meters gets a series resistor, which you can conveniently calculate.
What is also good to know, is by this method the meter has excellent short circuit protection. If by any mistake you make a short circuit, the cathode resistor will absorb the short circuit energy, not the meter"
Johno
Follow Ups:
G'day as per attached link the reason why fusing the Kathode is not such a great idea.
Verbatim from link
It took me quite a while before I could reconstruct the chain of events which led to this result. Mr. Jadis decided to protect the power valves with a fuse in series with the combined cathodes of each output channel. This seems sensible but it now appears it is not. Think of what happens if a valve looses its vacuum. The valve will develop full conductivity. Now the fuse blows. The cathode will be lifted to a voltage near the +500 Volt of the HV supply present at the anode.
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: