Not relevant here since it's confirmed that it's a 2 wire fan, but 3 wire is conventionally DC voltage for speed control (red and black wires) and speed sense (yellow wire). This is why the PWM signal is always the fourth wire on the fan connector.
Hi Radni,
I'm glad that you gave the list of tubes, because Bill is right. Do not power it up without the tubes installed. You didn't list a rectifier tube, so that means you have solid state rectifiers. Nothing wrong with that, and that is how I design tube gear.
So again, do not power your amplifier up without all the tubes being installed. In addition to that, you must also have a load connected (speakers).
-Chris
I'm glad that you gave the list of tubes, because Bill is right. Do not power it up without the tubes installed. You didn't list a rectifier tube, so that means you have solid state rectifiers. Nothing wrong with that, and that is how I design tube gear.
So again, do not power your amplifier up without all the tubes being installed. In addition to that, you must also have a load connected (speakers).
-Chris
Hi Radni,
Yes, you can use the standby mode. You'll have to be extremely careful that you don't hit that switch by mistake when handling the product as you test. If you do take it out of standby accidentally, you have a very short time to switch back to standby before severe damage to your filter capacitors occurs. They can usually take a short surge without damage.
If the standby switch is easy to come into contact with, consider removing one wire (and tape it up well!) so that it is impossible to activate the high voltage section.
-Chris
Yes, you can use the standby mode. You'll have to be extremely careful that you don't hit that switch by mistake when handling the product as you test. If you do take it out of standby accidentally, you have a very short time to switch back to standby before severe damage to your filter capacitors occurs. They can usually take a short surge without damage.
If the standby switch is easy to come into contact with, consider removing one wire (and tape it up well!) so that it is impossible to activate the high voltage section.
-Chris
The bleed resistors can also provide a source of heater bias of around 50VDC (as a voltage divider). Tubes have less hum from the heater leaking into the cathode circuits with this voltage bias. I'm assuming that the tubes are indirectly heated, and the heater supply is easily isolated from chassis ground.
Hi Chris,
Thanks for your reply , it now gives me confidence to put the amp in stand bye mode ( with tubes taken off) and take measurement, see if fan is getting 12 Vdc . The switch on my amp is a Mini Rocker type, rather hard to operate, but I am going to tape it to make it a bit fixed in position. Will mostly do the job over weekend before leaving on a trip of about 9 days .
I am glad I asked for help here and I thank you all FMs here for guiding me to do the job safely. This is one great place to be even for new bee like me. Thank you all FMs and contributors.
Thanks for your reply , it now gives me confidence to put the amp in stand bye mode ( with tubes taken off) and take measurement, see if fan is getting 12 Vdc . The switch on my amp is a Mini Rocker type, rather hard to operate, but I am going to tape it to make it a bit fixed in position. Will mostly do the job over weekend before leaving on a trip of about 9 days .
I am glad I asked for help here and I thank you all FMs here for guiding me to do the job safely. This is one great place to be even for new bee like me. Thank you all FMs and contributors.
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You can get a fan controller on ebay.
This one runs one or two fans and is powered off 12 volts.
It drives PWM fans.
It will be off when amp is cold but turn on as it warms up.
Dual amplifier fan temperature controller | eBay
This one runs one or two fans and is powered off 12 volts.
It drives PWM fans.
It will be off when amp is cold but turn on as it warms up.
Dual amplifier fan temperature controller | eBay
Hi Everyone !
I am back from a trip to China.
I did the small repair job after tubes removed , mini rocker switch taped on "stand bye" position and found the wiring connection was not proper with a loose solder. Now the new cooling fan runs nicely , very quietly. The problem is resolved. Thanks to you all here.
I will also consider the fan controller as suggested by nigelwright7557. Would it introduce any noise ( RF) in the amplification? I was wondering.
Do all these 12 VDC cooling fans ( size 50 x 50 x 10 mm : L x W x thick ) run at half the speed or RPM when 6 VDC is supplied ( thereby quieter! ) ? I believe my amp has a relay or something which makes fan run at normal speed when in stand bye mode but runs at about half the speed when in "operate" mode.
I am back from a trip to China.
I did the small repair job after tubes removed , mini rocker switch taped on "stand bye" position and found the wiring connection was not proper with a loose solder. Now the new cooling fan runs nicely , very quietly. The problem is resolved. Thanks to you all here.
I will also consider the fan controller as suggested by nigelwright7557. Would it introduce any noise ( RF) in the amplification? I was wondering.
Do all these 12 VDC cooling fans ( size 50 x 50 x 10 mm : L x W x thick ) run at half the speed or RPM when 6 VDC is supplied ( thereby quieter! ) ? I believe my amp has a relay or something which makes fan run at normal speed when in stand bye mode but runs at about half the speed when in "operate" mode.
I understand now that I cannot power up my amp ( due to solid state rectification ) with tubes removed. But if I wish to measure voltage coming to my cooling fan in "operate" mode , can I do power it up only for a short time , (say for 15 seconds max) , just to quickly take a reading of the voltage to the fan ? Or can that be also be hazardous or likely to damage caps ?
Failure to connect speakers to an Amp output is like:
Removing the maximum rpm limiter of a car engine, disconnecting the drive line, and then fully* pressing on the accelerator. How long will it last? depends on the engine.
(What is the first thing you do when you can not hear the music because the loudspeaker is not connected . . . you turn the volume control up fully*). How long will the amp last? depends on the amp.
Before you test any amplifier with the tubes removed, check that the electrolytic caps have a voltage rating that is more than 1.414 x the transformer secondary Vrms rating.
If the the tube rectifier is left in the amp (or if the rectifiers are solid state diodes), check that the peak reverse rating of the rectifiers is more than 2 x 1.414 x the transformer secondary Vrms rating (2.828 x the secondary rms).
By the way, the secondary will have more rms voltage than its Vrms rating when it is unloaded (like with no tubes).
Removing the maximum rpm limiter of a car engine, disconnecting the drive line, and then fully* pressing on the accelerator. How long will it last? depends on the engine.
(What is the first thing you do when you can not hear the music because the loudspeaker is not connected . . . you turn the volume control up fully*). How long will the amp last? depends on the amp.
Before you test any amplifier with the tubes removed, check that the electrolytic caps have a voltage rating that is more than 1.414 x the transformer secondary Vrms rating.
If the the tube rectifier is left in the amp (or if the rectifiers are solid state diodes), check that the peak reverse rating of the rectifiers is more than 2 x 1.414 x the transformer secondary Vrms rating (2.828 x the secondary rms).
By the way, the secondary will have more rms voltage than its Vrms rating when it is unloaded (like with no tubes).
Do all these 12 VDC cooling fans ( size 50 x 50 x 10 mm : L x W x thick ) run at half the speed or RPM when 6 VDC is supplied ( thereby quieter! ) ? I believe my amp has a relay or something which makes fan run at normal speed when in stand bye mode but runs at about half the speed when in "operate" mode.[/QUOTE]
There is minimum turn on voltage to get it up and running. 6 volts is usually not enough for it to start turning.
Regards
David
There is minimum turn on voltage to get it up and running. 6 volts is usually not enough for it to start turning.
Regards
David
Hi David,
Many DC fans have control circuits built in. Those won't work properly at low voltage. If you get a DC fan without a speed regulator built in, 1/2 speed might be some value of voltage between 1/2 and full. Easy enough to figure out what voltage you need by varying the voltage with an adjustable power supply.
-Chris
Many DC fans have control circuits built in. Those won't work properly at low voltage. If you get a DC fan without a speed regulator built in, 1/2 speed might be some value of voltage between 1/2 and full. Easy enough to figure out what voltage you need by varying the voltage with an adjustable power supply.
-Chris
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