AKG 451 troubleshooting

[ubxf]

I have a 451E (3 transistors) that passes audio but lacks bass and is noisy. The connector to the capsule is clean and the xlr pins are clean as well. The service manual recommends checking C1 and C11/C12 can this be done in circuit? Any suggestions would be greatly appreciated

 

[radardoug]

Are you sure the capsule is good? The foil on those capsules used to come loose, and then they are unusable, with no bass.

 

[ubxf]

yes i have another 451EB mic with a CK1 capsule that works well and i use that capsule to test it

 

[Rob Flinn]

Noisy & lacking bass can be a symptom of the output being "one legged".  i.e if you lose hot or cold on the connector. 

 

[ubxf]

Thanks Rob, i'll check into that right away. But if that were the case wouldn't that prevent the phantom power from working ? then no sound would pass.

 

[ubxf]

the connector seems ok, no short and good continuity from pcb to pins. The ck1 capsule still works with the other 451. I thought for a second i might have fried it by trying it with a defective mic

 

[ubxf]

It's working but instead of the 33uf capacitor i have now a 22uf because that all i had on hand that would fit in the mic. I will get the proper capacitor ordered and installed but do you think it's ok to use the mic the way it is in the meantime or do i risk to damage something.

 

[RuudNL]

As far as I see that is the transformer coupling capacitor.
No problem! Even if you keep it permanently.

 

[ubxf]

Yes it's the transformer coupling capacitor. I will leave it in then. Thanks Ruud