• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Strange request for a valve for a special job :-)

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi,

Here is one for you. I need a B9A base valve that has the heater on 4 & 5 which draws 300mA or less, that also has one or more pins that are NC.

Here is why: I have a Yaqin MC-5881A amplifier, the two indicator valves look ugly and are next to useless unless you have the volume high enough to rattle the windows.

I want to replace them with something else just for aesthetics, the heater and any NC pins will be kept, while the others will be snipped off. Three pins should keep the valve stable and it will still appear to be functional.

I have looked on the net but can't find anything that has all three requirements, hence this post to pick the brains of the experts. :)
 
Last edited:
I need a B9A base valve that has the heater on 4 & 5 which draws 300mA or less
I see your problem. The non-working substitute for the 6E2 magic eye must not overload the amplifier's heater supply. The likes of an EL84 draws 760mA.

The E180F satisfies your pin 4 &5 and 300mA requirements, but has no n/c pins.

E180F @ The Valve Museum

E180F/CV3998-MULLARD

Why not simply isolate the other valve pins from the circuit? As far as I know, this can be done without impeding the normal operation of the amplifier.
 
I intended to attach the circuit diagram showing the magic eye connections.
 

Attachments

  • MC-5881A.jpg
    MC-5881A.jpg
    79.2 KB · Views: 408
You can take most sockets and remove as many connections as you want, but have to leave enough to get the tube to remain stable.
You may have to wiggle the tabs and work them off, then drill out that hole.

I have easily done it for octal, 7 pin, and 9 pin.

I'd rather not do that, as if I decide to sell the amp in the future, I would like it to be easily returned to its original configuration.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.