akg c28c broken. help!

Archived from groups: rec.audio.pro (More info?)

Kurt Ballou <godcity@aol.com> wrote:
>hi. i just bought a c28c (nuvistor) and it's messed up. the guy i
>bought it from offered to fix it, but he's in germany so i don't want
>to send it back if i don't have to.
>here's what it's doing:
>it's quiet and midrangey with the ck28 capsule in.
>it's horribly tinny with ck1, ck2, ck3, and blue lollipop caps.
>ck28 capsule sounds fine on a 451 body, as do all the other caps.
>the n28 power supply says it accepts 110 and 220v at 50 or 60 hz. i
>tried 110 and 220 at 60 hz without much diffence.
>all the solder joints seem ok. any other ideas what it could be?

Check the power supply voltages before doing anything. If the supply
voltages are okay, check the cathode and plate voltages on the nuvistor
and make sure it's in the right operating region. Check coupling caps.
Check transformer.

Injecting a 1 KHz square wave through a 1G resistor into the input and
tracing it down through the circuit can tell you an awful lot too.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:
> Kurt Ballou <godcity@aol.com> wrote:
>
>>hi. i just bought a c28c (nuvistor) and it's messed up. the guy i
>>bought it from offered to fix it, but he's in germany so i don't want
>>to send it back if i don't have to.
>>here's what it's doing:
>>it's quiet and midrangey with the ck28 capsule in.
>>it's horribly tinny with ck1, ck2, ck3, and blue lollipop caps.
>>ck28 capsule sounds fine on a 451 body, as do all the other caps.
>>the n28 power supply says it accepts 110 and 220v at 50 or 60 hz. i
>>tried 110 and 220 at 60 hz without much diffence.
>>all the solder joints seem ok. any other ideas what it could be?
>
>
> Check the power supply voltages before doing anything. If the supply
> voltages are okay, check the cathode and plate voltages on the nuvistor
> and make sure it's in the right operating region. Check coupling caps.
> Check transformer.
>
> Injecting a 1 KHz square wave through a 1G resistor into the input and
> tracing it down through the circuit can tell you an awful lot too.
> --scott


get your money back. buy another.