Amp gets a bit hot, can i add a small fan?

rg12 · 19th September 2010, 10:23 PM

I have a Pioneer SA-7300 amp that is powerful enough to drive my
big speakers, but after some time it get very hot and from my experience
i know it won't last after a few weeks playing like that.

If i add a one or two computer fans blowing at the aluminum transistors heatsink, will it help? and if the temprature does drop, will it prevent future damage or it will just help it run a bit more?

wakibaki · 20th September 2010, 12:03 AM

Yes, it'll help, it'll help prevent future damage.

w

rg12 · 20th September 2010, 12:09 AM

Good to know, thanks alot.

My next question is, where can i take the electricity to the fan?
It's a 9v computer fan (maybe i will add two if i will find the place).

This is the scematic: http://www.milkbands.co.il/Pioneer-SA-7300-int-sch.pdf

Any ideas?

nigelwright7557 · 20th September 2010, 12:16 AM

You can use a dropper resistor from B+ and drive the two fans in series.
I have done that a few times.

rg12 · 20th September 2010, 01:10 AM

Quote:

Originally Posted by nigelwright7557

You can use a dropper resistor from B+ and drive the two fans in series.
I have done that a few times.

Im sorry, but my knowledge in electronics is limitted.
Where exactly is the B+? and what value of resistor do i need?

indianajo · 20th September 2010, 05:31 PM

I have the same problem after 12 hours on of my ST120, not designed for that. I'm going to put 2 12VDC computer fans under the floor of the amp (slotted ) powered by wall-transformer with rectifier outside amp chassis, so I don't induce AC noise inside. can be done inside chassis if you're careful, but outside the steel box makes it a lot more stupid proof. Adapting a little junk sub chassis to go under the actual amp chassis.

rg12 · 20th September 2010, 09:32 PM

Oh right, i didn't think about the noise the fan motors can cause.

If i do it with external power adapter, how can i connect it to the
amp that it won't add any noise and still start the fans when i power
the amp on?
I don't want to have a separate switch for the fans.

nigelwright7557 · 20th September 2010, 09:38 PM

Quote:

Originally Posted by rg12

Oh right, i didn't think about the noise the fan motors can cause.

If i do it with external power adapter, how can i connect it to the
amp that it won't add any noise and still start the fans when i power
the amp on?
I don't want to have a separate switch for the fans.

I have built about half a dozen amps with fans running off the B+ and never had a problem with noise. Could be my amps are more resistant to power supply noise tho.

boyofwax · 20th September 2010, 10:08 PM

Rg12 you might be lucky if you locate the POP-ON reduction relais on the PCB. In the diagram it is listed as S8 RELAIS. If the coilvoltage is something like 9v or 12v you could use these coilpins to solder the wire's of the fan. (check polarity!) In the worst case you should lower the resistance of R111. (100 Ohm or something)

rg12 · 21st September 2010, 01:45 AM

Quote:

Originally Posted by boyofwax

Rg12 you might be lucky if you locate the POP-ON reduction relais on the PCB. In the diagram it is listed as S8 RELAIS. If the coilvoltage is something like 9v or 12v you could use these coilpins to solder the wire's of the fan. (check polarity!) In the worst case you should lower the resistance of R111. (100 Ohm or something)

If it is more or less than 9v? what can i do? those fans work on 9v from
what i remember.

What can happen if polarity is reversed? the fan will just spin backwards
right?

What did you mean when you said "In the worst case lower the resistance of R111"? What is the worst case and what does this R111 resistor do
in the schematic?

19th September 2010, 10:23 PM	#1
rg12 diyAudio Member Join Date: Aug 2010	Amp gets a bit hot, can i add a small fan? I have a Pioneer SA-7300 amp that is powerful enough to drive my big speakers, but after some time it get very hot and from my experience i know it won't last after a few weeks playing like that. If i add a one or two computer fans blowing at the aluminum transistors heatsink, will it help? and if the temprature does drop, will it prevent future damage or it will just help it run a bit more?

20th September 2010, 12:16 AM	#4
nigelwright7557 diyAudio Member Join Date: Apr 2008 Location: Carlisle, England	You can use a dropper resistor from B+ and drive the two fans in series. I have done that a few times. __________________ http://www.murtonpikesystems.co.uk PCBCAD40 pcb design software.

20th September 2010, 05:31 PM	#6
indianajo diyAudio Member Join Date: Jan 2010 Location: Jeffersonville, Indiana USA	I have the same problem after 12 hours on of my ST120, not designed for that. I'm going to put 2 12VDC computer fans under the floor of the amp (slotted ) powered by wall-transformer with rectifier outside amp chassis, so I don't induce AC noise inside. can be done inside chassis if you're careful, but outside the steel box makes it a lot more stupid proof. Adapting a little junk sub chassis to go under the actual amp chassis. __________________ Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,SP2-XT's, T-300 HF Projs, Steinway console, Herald RA88a mixer, Wurlitzer 4500

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20th September 2010, 12:03 AM	#2
wakibaki Banned Join Date: Jan 2008 Blog Entries: 2	Yes, it'll help, it'll help prevent future damage. w

20th September 2010, 12:09 AM	#3
rg12 diyAudio Member Join Date: Aug 2010	Good to know, thanks alot. My next question is, where can i take the electricity to the fan? It's a 9v computer fan (maybe i will add two if i will find the place). This is the scematic: http://www.milkbands.co.il/Pioneer-SA-7300-int-sch.pdf Any ideas?

20th September 2010, 09:32 PM	#7
rg12 diyAudio Member Join Date: Aug 2010	Oh right, i didn't think about the noise the fan motors can cause. If i do it with external power adapter, how can i connect it to the amp that it won't add any noise and still start the fans when i power the amp on? I don't want to have a separate switch for the fans.

20th September 2010, 10:08 PM	#9
boyofwax diyAudio Member Join Date: Feb 2004 Location: Arnhem Netherlands	Rg12 you might be lucky if you locate the POP-ON reduction relais on the PCB. In the diagram it is listed as S8 RELAIS. If the coilvoltage is something like 9v or 12v you could use these coilpins to solder the wire's of the fan. (check polarity!) In the worst case you should lower the resistance of R111. (100 Ohm or something)

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