Pages: [1] 2 3   Go Down

Author Topic: Turning off tube amp after going QRT  (Read 1237 times)

K1KIM

  • Member
  • Posts: 1556
    • HomeURL
Turning off tube amp after going QRT
« on: March 11, 2023, 09:35:42 AM »

How long does anyone wait, if at all, to turn off their tube amp after a long last transmission?

My though is that when the tube is hot and fan is running shouldn't their be a certain amount of time to let the amp sit idle with the cooling fan before shutting it off.

As a precaution I have always been putting it into standby for 5 minutes before shutting down, in lieu of "riding it hard and putting it away wet"

I'd like to hear other's opinions.

Logged
So Many Toys.......So Little Time!

K6AER

  • Member
  • Posts: 7159
Re: Turning off tube amp after going QRT
« Reply #1 on: March 11, 2023, 10:26:43 AM »

You will not hurt the amplifier by letting it idle to reduce the internal cabinet temperatures but the main internal heat source is no longer operational. Glass tube amps have a small heat source and they will not have much temperature mass. The do relay on the fans to route the heat out of the chassis.

Metal tetrodes run at a much lower temperature, typically below 50 degrees C, and generally have the vent holes right above the tube. Natural heat convection will vent the anode with out the fan running.
« Last Edit: March 11, 2023, 10:30:14 AM by K6AER »
Logged

W7CXC

  • Member
  • Posts: 335
Re: Turning off tube amp after going QRT
« Reply #2 on: March 11, 2023, 10:29:16 AM »

I follow your procedure. Sometimes a bit less if not being pushed to hard. Just to cool off the seals.
73's
Logged

K1KIM

  • Member
  • Posts: 1556
    • HomeURL
Re: Turning off tube amp after going QRT
« Reply #3 on: March 11, 2023, 11:59:56 AM »

You will not hurt the amplifier by letting it idle to reduce the internal cabinet temperatures but the main internal heat source is no longer operational. Glass tube amps have a small heat source and they will not have much temperature mass. The do relay on the fans to route the heat out of the chassis.

Metal tetrodes run at a much lower temperature, typically below 50 degrees C, and generally have the vent holes right above the tube. Natural heat convection will vent the anode with out the fan running.

My ACOM has a single Svetlana ceramic metal tetrode with the vent holes above it in addition to a built in fan.
It appears to be hotter than 50C when I am long winded even at a modest 400W.

I'll have to check with the temp gun next time.

I'll continue to let it idle a while before shut down since it doesn't hurt anything other than a penny in electric.
Logged
So Many Toys.......So Little Time!

ZL1BBW

  • Member
  • Posts: 1912
Re: Turning off tube amp after going QRT
« Reply #4 on: March 11, 2023, 12:06:39 PM »

The OM2000+ on my desk, takes the temp down to under 40, then it will begin shutdown, think its another 1 min of fan running.

I try to never get it above about 50 -55max, gives me all the power I need at that level.

Runs noticeably cooler in the spring,autumn, winter  February is the worst time.

Hopefully IF an aircon company ever rings us back we get the house a bit cooler.

Logged
ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.

KB2FCV

  • Member
  • Posts: 3285
    • homeURL
Re: Turning off tube amp after going QRT
« Reply #5 on: March 11, 2023, 12:09:01 PM »

I never really thought of it... but my SB-200 will usually run 5-10 mins before I shut it down. That isn't intentional.. usually if I made a QSO I'm putting it in the logbook, maybe look at something related online.. then I get distracted... then "oh, I'm done with the amp.. I guess I'll shut it off". With that amp, I don't think it matters a whole lot.. unless maybe you were on long rag chews or were driving it hard (which I don't). Most of the time I'm using it in CW when chasing DX in a pileup or rarely SSB.

I do plan on upgrading perhaps next year to a newer amp that covers 160-6 and I will certainly follow whatever the manufacturer says to do.
Logged

K4WH

  • Member
  • Posts: 108
Re: Turning off tube amp after going QRT
« Reply #6 on: March 11, 2023, 04:17:59 PM »

What you are doing is just fine.  I normally just put my had over the air outlet and see if the air feels "cool".  By that I mean does the air feel close to the temp of the air at start up.  To be honest I probably wait about 10 min if the amp has been used for several contacts.  I never have just turned off an amp that has just been used. Better safe than sorry.
Logged

VE7RF

  • Member
  • Posts: 1608
Re: Turning off tube amp after going QRT
« Reply #7 on: March 12, 2023, 10:33:44 AM »

Let it run for a few minutes before shutting down.

On my HB amps, I  switch amp to standby, then shut off the B+.    Then shut OFF the filament.  Then run the blower for several minutes.  Those fil terminals are stupid hot.
Logged

WB8PFZ

  • Member
  • Posts: 624
Re: Turning off tube amp after going QRT
« Reply #8 on: March 12, 2023, 02:01:14 PM »

I am surprised with all the neat add ons for Heath and other amps (soft start, soft key too name a few) that there is not a time delay circuit to run the blower after power down?
Logged

VE7RF

  • Member
  • Posts: 1608
Re: Turning off tube amp after going QRT
« Reply #9 on: March 12, 2023, 08:25:25 PM »

I am surprised with all the neat add ons for Heath and other amps (soft start, soft key too name a few) that there is not a time delay circuit to run the blower after power down?

The Kenwood TL-922 does just that, called...'fan over run'.  We put it in my buddy's hb amp. He used a delay timer module, adjustable from 0-15 mins.  It activated after the fil was shut OFF.   Ok, everything off...except the blower.   Somebody on here posted a SS   adjustable timer months ago...tiny thing   They were dirt cheap, and  would run on either 120 / 240 vac.
Logged

KM4AH

  • Member
  • Posts: 1614
Re: Turning off tube amp after going QRT
« Reply #10 on: March 13, 2023, 04:43:38 AM »

My Collins 3-1000 amp has a plug in relay with a dial on the top. Different time ranges available. You can make the delay anything you want.
Logged

K1KIM

  • Member
  • Posts: 1556
    • HomeURL
Re: Turning off tube amp after going QRT
« Reply #11 on: March 14, 2023, 06:21:31 PM »

You will not hurt the amplifier by letting it idle to reduce the internal cabinet temperatures but the main internal heat source is no longer operational. Glass tube amps have a small heat source and they will not have much temperature mass. The do relay on the fans to route the heat out of the chassis.

Metal tetrodes run at a much lower temperature, typically below 50 degrees C, and generally have the vent holes right above the tube. Natural heat convection will vent the anode with out the fan running.

My ACOM has a single Svetlana ceramic metal tetrode with the vent holes above it in addition to a built in fan.
It appears to be hotter than 50C when I am long winded even at a modest 400W.

I'll have to check with the temp gun next time.

I'll continue to let it idle a while before shut down since it doesn't hurt anything other than a penny in electric.

My temp runs 60 degrees C after a long QSO via temp gun reading at the chassis vent.
Logged
So Many Toys.......So Little Time!

VE7RF

  • Member
  • Posts: 1608
Re: Turning off tube amp after going QRT
« Reply #12 on: March 15, 2023, 02:37:05 PM »

You will not hurt the amplifier by letting it idle to reduce the internal cabinet temperatures but the main internal heat source is no longer operational. Glass tube amps have a small heat source and they will not have much temperature mass. The do relay on the fans to route the heat out of the chassis.

Metal tetrodes run at a much lower temperature, typically below 50 degrees C, and generally have the vent holes right above the tube. Natural heat convection will vent the anode with out the fan running.

My ACOM has a single Svetlana ceramic metal tetrode with the vent holes above it in addition to a built in fan.
It appears to be hotter than 50C when I am long winded even at a modest 400W.

I'll have to check with the temp gun next time.

I'll continue to let it idle a while before shut down since it doesn't hurt anything other than a penny in electric.

My temp runs 60 degrees C after a long QSO via temp gun reading at the chassis vent.

Buddy's  4x10 grid driven amp runs at 150 F  (65 C)  exhaust air temp, while blathering away on ssb, using ptt / footswitch. Once released, it takes a full minute to get back down to 90 F  (32 C) ...where it remains.  The 90 F is coming from the cathode sucking a lot of fil power.  I just found it easier on the hb amps, to switch to standby, then kill the B+, then the  fil xfmr, then everything is off.   Then let blower run for a few minutes, before shutting off the blower.

On  RTTY/  FM / DATA modes / AM, average plate current is a lot higher..and so is exhaust temps.  Tank coils / band switches will also dissipate more heat, since  quadruple the watts is being dumped into them.  It's just I squared X R..or in this case,  RF current squared X the ESR (rf resistance) of the tank coils.   RF current in the tank coil is aprx plate current  X input loaded Q of the PI net..+ 10%.   I was surprised at just how hot tubing coils got on 15m, with a brief cxr applied, then removed, then touched the 15m tank coil, yikes, fn hot.   I would have thought the heat would have migrated into the 20m portion of the same 20-10m tubing coil, but it doesn't.   20m end of same coil runs at ambient room temp.  It's all localized heat.   Then toss in still more heat from the plate xfmr etc.
« Last Edit: March 15, 2023, 02:40:10 PM by VE7RF »
Logged

W4JFA

  • Posts: 133
    • HomeURL
Re: Turning off tube amp after going QRT
« Reply #13 on: March 21, 2023, 06:51:44 AM »

How long does anyone wait, if at all, to turn off their tube amp after a long last transmission?

My though is that when the tube is hot and fan is running shouldn't their be a certain amount of time to let the amp sit idle with the cooling fan before shutting it off.

As a precaution I have always been putting it into standby for 5 minutes before shutting down, in lieu of "riding it hard and putting it away wet"

I'd like to hear other's opinions.


I always let em run a few minutes afterwards.
Logged

KM3F

  • Member
  • Posts: 1103
Re: Turning off tube amp after going QRT
« Reply #14 on: March 21, 2023, 03:12:29 PM »

I fail to see a provable benefit in forced fan cooling after on air use over letting it cool slower by convection.
Same thing happens, just at a slower rate.
Logged
Pages: [1] 2 3   Go Up