[HAM] Relay problem?

[Brad Baker]

On 9/16/06, Brad Baker <b3jazz at gmail.com> wrote:
> On 9/16/06, Luther Nallie <lnallie at yahoo.com> wrote:
>
> > Thanks for the tip.  I tried switching the 12AU7's and not any difference.  It
> > seems to switch for a minute or so when it first comes on but then it takes a
> > couple of bumps of the switch to slow down (as it did before).  There is no
> > problem going from slow to fast, just one flip every time.
>
> Measure the DC voltage to ground across R12,  That's the large
> sand-filled 150 ohm power resistor that sticks up through the hole in
> the chassis.  It should read around 25V.  In old amps, leaky coupling
> and other capacitors can cause this voltage to rise (also output tubes
> start glowing).  I've seen this cause intermittent relay switching.
>
> --
> ---  b r a d  b a k e r  ---\\
>

One more thing, this voltage can be measured with the amp in place by
pulling the 12AU7 relay tube and measuring the voltage in pin 3 of the
now empty tube socket (careful, pin 1 has 300V on it).

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---  b r a d  b a k e r  ---\\