Telefunken ELA M 251 Clone Tube Microphone Build Thread (D-Ela M 251E)

[Delta Sigma]

Continuity, as in a beep from a continuity tester? One side of your heater is tied to the 6.3V supply, the other to ground. The heater is probably 10 or 20 ohms. Likely enough to make a beep.

 

[Homestudio]

Thanks Delta, okay tested R3, R5 both 58.5. R2 is 53.1. My thinking now is the trany’s the culprit since I’m getting no signal out of the mic. Is there a way to test this? Again much thanks.

 

[mihi_fuchs]

Thanks Delta, okay tested R3, R5 both 58.5. R2 is 53.1. My thinking now is the trany’s the culprit since I’m getting no signal out of the mic. Is there a way to test this? Again much thanks.

You can measure the resistance/conductivity of each coil and that they are non-conductive to each other. Other than that you can feed it a sine wave and see what’s coming out on the other end.

BR
Michael

 

[Homestudio]

You can measure the resistance/conductivity of each coil and that they are non-conductive to each other. Other than that you can feed it a sine wave and see what’s coming out on the other end.

BR
Michael

Thanks Michael, I’ll try your suggestions. I’m assuming the trany needs to be removed from the circuit to do the tests.

Much appreciated

 

[mihi_fuchs]

Thanks Michael, I’ll try your suggestions. I’m assuming the trany needs to be removed from the circuit to do the tests.

Much appreciated

for measuring the resistance/conductivity not necessarily. also if you feed the sine wave right into the coil, i do not see a point why it should be removed. just do not power up the mic, as it‘s not nessecary and complicates handling (safety regards).

good luck - hope you find the fix fast.

BR
Michael

 

[Homestudio]

Checked the capsule and the backplates are shorted. Would this be a cause for no signal output?

 

[mihi_fuchs]

Checked the capsule and the backplates are shorted. Would this be a cause for no signal output?

Depends on pattern selection - but at least in cardioid there should be no influence on that (the second Half of the capsule is "offline" in that polar pattern). At least according to the original schematic. Which schematic did you use again?

BR

 

[Tim Campbell]

What capsule did you use?

 

[Homestudio]

This is Danny’s D-Ela M 251E pcb.
Capsule is a JLI-86U. After sorting things out I’ll be installing the Beesneez CK12.
Also using a EH 6072 for testing.

 

[mihi_fuchs]

This is Danny’s D-Ela M 251E pcb.
Capsule is a JLI-86U. After sorting things out I’ll be installing the Beesneez CK12.
Also using a EH 6072 for testing.

Maybe post a pic of back and front of your pcb. In cardioid it should work with conn backplates. Make sure you connected to the right backplate connection. Other than that you can check if you have the right relays (normally closed/open is an option; i don‘t know if the polarization of the coil matters - i‘d need to recheck with the schematics).
Hope you get it running soon - it is a really nice mic …