DX-100 audio problem

[joe]

Hi Dale:

Sorry but dont hv schematic, but looking over my maintenance record on
a dx100b tt i had back april 10/1960 a 860 ohm cathode bias resistor
burned up burning out the 12by7.  a good place to staart. hi

73 de Joe w0tut

----- Original Message -----
From: "Dale KG4KZG" <Accrider3 at AOL.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Wednesday, October 30, 2002 2:14 PM
Subject: DX-100 audio problem


> Hi fellow greenies, Have no audio on my DX-100 I pulled the mod. trans. to
> check potting and it seemed ok. No shorts to ground and the resistances
> seemed with in limits. Also, checked the driver trans, found no shorts.
Last
> night  plugged it back in and the 12BY7 driver and it got very blue and
plate
> started glowing a dull red then got brighter red to where  turned it off
and
> subbed it with a ok but marginal  tube and it did the same thing. Removing
> the 5V4 LV rect. of course kept it from turning red again. The audio
failed
> during a 20m am qso about 6 months ago, no crispy critters no blown fuses.
> I presume something in the screen circuit or cathode bias is the problem.
> There are no voltages listed in the manual for the tube pin out.
> Voltage on the plate is 375-380V and on pin 2, one of the screens its
175V.
> Any ideas?
> Can reply off list if you wish 73 and TIA
> Dale
> kg4kzg
>
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