Solid state relais in stean of standby swtich - diyAudio
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Old 26th August 2011, 09:18 AM   #1
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Default Solid state relais in stean of standby swtich

I understand that it is a good practice to use a standby switch in the high voltage line in a tube-amp.
Most mechanical switches are allowed for max. 250 V. Is is safe to use a mechanical switch as standby switch ? Using a solid state relais seems beter to me ?

Dirk
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Old 26th August 2011, 11:59 AM   #2
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quote:
Is is safe to use a mechanical switch as standby switch


The answer in my opinion would be no.

There are people divided on both sides of the stand by switch. I have amplifiers that I own that use a 5U4 rectifier tube so the B+ is really quick. Some claim cathode stripping but I have never seen it. I have been told to turn the input of the amp down if it has one or turn the preamp down so that no signal passes until the tubes are warmed up. Musicians claim the stand by switch is needed on their guitar amplifiers. Can't answer that.
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Old 27th August 2011, 02:34 PM   #3
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Quote:
Originally Posted by dirklammers View Post
I Using a solid state relay seems better to me ?

Dirk
I have a few 600VDC rated SS relays, and I'm also curious if it's a good or bad idea to use these as a start delay/standby device.......

Is there any downside to using SS relays on the secondary side of the power transformer?
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Old 27th August 2011, 02:48 PM   #4
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Hi!

Actually it is not a good practice to put high voltage in standby and leave heaters on. Many indirectly heated tubes can suffer cathode poisoning when heated without high voltage

best regards

Thomas
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Old 27th August 2011, 02:58 PM   #5
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by boywonder View Post
I have a few 600VDC rated SS relays, and I'm also curious if it's a good or bad idea to use these as a start delay/standby device.......

Is there any downside to using SS relays on the secondary side of the power transformer?
Hi,

From a function point of view:
You can switch with SS relays, however I would prefer a "contact" reasons are that a SS relay is not a voltage free contact IE some leakage occurs so the output is not "dead". Also whenever you use a triac or thyristor on AC to switch you get RFI and this can cause problems on the output plus circuits around the SS relay. I have used SS on DC because the latch current takes over and the device is "locked on". (without GTO operation you will find it hard to turn off).

Regards
M. Gregg
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Last edited by M Gregg; 27th August 2011 at 03:02 PM.
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Old 27th August 2011, 04:36 PM   #6
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Quote:
Originally Posted by Vinylsavor View Post
Hi!

Actually it is not a good practice to put high voltage in standby and leave heaters on. Many indirectly heated tubes can suffer cathode poisoning when heated without high voltage

best regards

Thomas
Nah--Not 'Cathode Poisoning'

You're thinking of Cathode Interface something entirely different and only occurs when there's zero cathode-current for many hundreds of hours....

Cathode Poisoning occurs when there's Ion bombardement of the cathode caused by gas in the tube, Or a VERY high plate-voltage transmitting type is used before the cathode is up to temp....

cathode poisoning doesnt normally occur with audio-tubes....
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Old 27th August 2011, 04:59 PM   #7
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Hi!

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Originally Posted by Alastair E View Post
Nah--Not 'Cathode Poisoning'
Yes you are right, I mixed those up, cathode interface is the one...

Thomas
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Old 28th August 2011, 05:19 AM   #8
TheGimp is offline TheGimp  United States
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Some SS relays are not triacs. They are opto-coupled MOS-FET output devices. Biggest issue after voltage rating is surge current. Most devices I've seenare 2A or less and have a pretty low surge rating.
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Old 28th August 2011, 09:57 AM   #9
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I have some SSR's here....

They are rated at 25A, 360V are switched by a 3-30V control voltage and are 'opto-coupled'
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Old 28th August 2011, 12:51 PM   #10
oshifis is offline oshifis  Hungary
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I used solid state relays for B+ (actually AC on the secondary before the HV rectifier) switching, the heating being permanently turned on. The SSR was controlled by a separate preamplifier. It worked well, but I changed to mechanical relays. No special reason, just wanted to get rid off any silicon
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