Rerurn to Romy the Cat's Site


In the Forum: Melquiades Amplifier
In the Thread: Planning my DSET
Post Subject: Shot too early...Posted by anthony on: 1/3/2019
 anthony wrote:
Hi Romy,

So, six channels are now operational in the first DSET.  By up I mean the anode voltages on all tubes is about right and the currents are in the ballpark of where they need to be.  I am yet to check the DC Offset so hopefully that goes ok.



Looks like I spoke too early.  When I made that statement I'd only tested the voltages in the DHT Channel and they were pretty close to correct...but when I put a tube in there it glowed a little too hot so I quickly shut it down.   Bugger!  

Romy, without any DHT tube in place, I have 403V coming out of the big filter cap for the DHT Channel (separate power supply) and 147V/8.3mA at the anode of the 6e5p which is a little higher/lower than the 140V/10mA on your schematic.  I am wondering if this lower current could be the problem?  I added some more resistance to drop the anode voltage and although I thought it was going to drop it 9V it only dropped it 3V, and the anode current remained at 8.3mA.  Tomorrow I will drop the anode voltage further so see if that raises the current.

On the schematic at the DHT tubes you have annotated a couple of red voltages and I am unable to measure the 184V at the cathode and the grid is measuring very low (without a DHT tube in the socket) at 148V where 224V is required.  

It would be great if you could remember some of your time with the DHT Channel.  I've only just got my head partially around your IDHT Channels and this circuit is almost entirely different again. 

Rerurn to Romy the Cat's Site