Date
21 - 25 of 25
New Member intro and needing help
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The method suggested by John Kolb is somewhat similar to a method
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described at https://www.londonsound.org/Vintage%20valve%20hi-fi.htm And although the "London Sound" method was apparently intended to apply to vacuum tube audio equipment, I suspect it's equally applicable to older vacuum tube Tek scopes. I tried the London Sound method only once; it was successful in the sense that an old vacuum tube radio transmitter powered up without any component failure. But as they say- "caveat emptor." Mike Dinolfo On 7/2/22 13:01, John Kolb wrote:
In my younger days, I've turned on a long unused scope, and after a |
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druid_noibn
Hi Jim,
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Thanks for the comments. Kind regards,DBN, aka John On Saturday, July 2, 2022 at 07:48:22 AM EDT, Jim Adney <jadney@...> wrote:
On Fri, Jul 1, 2022 at 09:50 AM, druid_noibn wrote: What would be a good or appropriate power-up procedure for for older 'scopes that sat on the shelf for a few years?There are two good approaches: Bring it up slowly on a Variac. This has the advantage of giving alum electrolytic capacitors time to reform before they get full voltage or Build a fixture that puts an incandescent bulb in series with the old device. I built mine using a 2x4 box and a cover that had an outlet and a socket for a screw-in (Edison base) lamp. Choose a bulb that will almost, but not quite, blow the fuse. As long as the lamp doesn't glow brightly, you're okay. If the lamp suddenly goes bright, you know that something in your old device has shorted. You could also do both, using the Variac to bring the voltage up slowly, while watching the lamp to monitor the current. |
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druid_noibn
Hi David,
Indeed, there are a few circuits that don't do well with ramping currents - thanks for the comments. Kind regards,John aka DBN On Saturday, July 2, 2022 at 11:17:21 AM EDT, David C. Partridge <david.partridge@...> wrote: > Bring it up slowly on a Variac. This has the advantage of giving alum electrolytic capacitors time to reform before they get full voltage Just don't do this if the 'scope has a switching Power Supply (like most 7000 series and later 'scopes). Just plug in an turn on (after checking the voltage selector is set correctly). Dim bulb approach is fine. D. -----Original Message----- From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Jim Adney Sent: 02 July 2022 12:48 To: TekScopes@groups.io Subject: Re: [TekScopes] New Member intro and needing help On Fri, Jul 1, 2022 at 09:50 AM, druid_noibn wrote: What would be a good or appropriate power-up procedure for for older 'scopes that sat on the shelf for a few years?There are two good approaches: Bring it up slowly on a Variac. This has the advantage of giving alum electrolytic capacitors time to reform before they get full voltage or Build a fixture that puts an incandescent bulb in series with the old device. I built mine using a 2x4 box and a cover that had an outlet and a socket for a screw-in (Edison base) lamp. Choose a bulb that will almost, but not quite, blow the fuse. As long as the lamp doesn't glow brightly, you're okay. If the lamp suddenly goes bright, you know that something in your old device has shorted. You could also do both, using the Variac to bring the voltage up slowly, while watching the lamp to monitor the current. |
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druid_noibn
Hi John,
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Ah...theory vs. practice - sometimes it works well.... Thanks! Kind regards,DBN aka John On Saturday, July 2, 2022 at 01:01:41 PM EDT, John Kolb <jlkolb@...> wrote:
In my younger days, I've turned on a long unused scope, and after a couple of minutes, heard a loud bang as a cap exploded. The electrolytic cap anode is a metal with a thin insulating oxide layer. After long idle periods, the oxide layer disappears. When voltage is applied without the insulating oxide layer, large current flows, causing heat, pressure, and eventually BANG. I power up unknown equipment by turning power on for 10 sconds, then off again, Wait awhile so that if heating occurred, the cap can cool off again. Another power on, 15 seconds, this time; another cooldown. The process continues with increasing on time periods until I run out of patience. The applied voltage causes the oxide layer to form again I don't know if this theory is correct or not, but I haven had any explosions while using it. John On 7/2/2022 8:17 AM, David C. Partridge wrote: Bring it up slowly on a Variac. This has the advantage of giving alum electrolytic capacitors time to reform before they get full voltageJust don't do this if the 'scope has a switching Power Supply (like most 7000 series and later 'scopes). |
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druid_noibn
Hi Mike,
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I likely have a VTVM in my collection that needs a little TLC as well...now, getting those mercury batteries.... Thanks! Kind regards,DBN aka John On Saturday, July 2, 2022 at 04:12:32 PM EDT, Mike Dinolfo <mdinolfo@...> wrote:
The method suggested by John Kolb is somewhat similar to a method described at https://www.londonsound.org/Vintage%20valve%20hi-fi.htm And although the "London Sound" method was apparently intended to apply to vacuum tube audio equipment, I suspect it's equally applicable to older vacuum tube Tek scopes. I tried the London Sound method only once; it was successful in the sense that an old vacuum tube radio transmitter powered up without any component failure. But as they say- "caveat emptor." Mike Dinolfo On 7/2/22 13:01, John Kolb wrote: In my younger days, I've turned on a long unused scope, and after a |
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