>
>
>>I removed the chassis from the case to first find the ALC
>>electrolytic capacitor strewn about the bottom in confetti and
>>foil.
>
>:There is no such capacitor in the ALC circuitry -- in the 110VDC
>supply,
>:yes.
>
>Correct, wrong label and most of the 110 volt supplies measure close to
>120 vdc resting.
>
>>Parasitics and or a tube problem might be the next thing to
>>investigate.
>
>: Parasitics that are intermittent are not easy to investigate.
>
True enough, however, there are clues.
>It's interesting that the excessive voltage happens after both tubes have
>been sitting on for a few minutes. As soon as I get more time to set
>things up, I'll have the spectrum analyzer log what it sees.
>
>>The unit fired up without tubes showed no problems at the
>>alc point, then each tube was tried in individually at both
>>locations. Again, no abnormalities observed.
>
>:Be sure to remove the wire between the bias contacts on the relay and
>the
>:110VDC power supply. If you don't do this, a shorted tube can easily
>:destroy the filament transformer.
>
>In your opinion, would a series glitch resistor in the bias supply
>prevent xmfr damage?
yes. 10k ohm, 2w to the bias contacts ought to limit the short circuit
current to a safe value.
>Since the meters are near hens teeth to replace,
Harbach has them.
>I'd like to protect the movements if possible.
A meter/shunt protection circuit is at Figure 2 on my Web site.
>I hope to work up a
>circuit to do that properly. Notes in the original owners manual about
>the meter movement values to follow once I confirm them.
>
The movements are 200uA and approx 1k ohms.
- Rich..., 805.386.3734, www.vcnet.com/measures.
--
FAQ on WWW: http://www.contesting.com/ampsfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|