MF A100 fans problem

miligor · 6th June 2011, 11:08 AM

Fans not working. After one hour amplifier is very hot, but fans still not started up... Is it problem with termo-switch or what?

jez · 6th June 2011, 11:37 AM

There is no thermal switch for the fans on an A100. They should be running all the time! If not then the most likely fault is dry soldered joints. The wires to the fans sometimes get broken when people open up the case also...

effebi · 6th June 2011, 11:46 AM

Measure voltage at fan input.
If voltage present replace fan. If you can't find the original, get a good one, like PAPST (sold by major electronics distributors). Avoid cheap chinese computer fans.
effebi

jez · 6th June 2011, 12:02 PM

It's very unlikely that the fans are faulty. They are Papst.... They sometimes become noisy but I can't recall one stopping altogether other than from dry joints/faulty wiring or the other common one is that the aluminium ducts around them can easily become bent and foul the fan blades.

miligor · 6th June 2011, 05:40 PM

Yes, it is Papst TYP 971TR 12V 50/60Hz 68uF ??? What's this? One wire is cut off from pcb, and both of them are connected over one bipolar 20uF elko??? TYP971TR have 3 wires, brown, blue and yellow... What is this 3 wires?

miligor · 8th June 2011, 08:23 AM

Something like this:

jez · 8th June 2011, 10:42 AM

It's certainly something like that yes. There may be a resistor (a Wirewound) in circuit also from memory but can't swear to it..... I have repaired loads of these (used to work for MF) but I don't have one here to check at the moment and the schematic does not show the wiring to the fans.

miligor · 29th August 2011, 07:45 AM

Fans are OK. One brown wire was de-soldered from pcb...

adespade · 31st December 2011, 12:31 AM

Following on from this issue, the (2) my fans in my A100 are noisy (especially when I switch off.
I havent confirmed the exact specification of mine but is there a direct replacement avaialble?

adespade · 24th January 2012, 12:25 AM

I've since confirmed mine are the same type - 2x PAPST TYP971TR 12V AC 50/60HZ 68microF.

I also checked with PAPST UK and they dont have a direct replacement

"........... was made obsolete many years ago. Looking at the specification of the fan unfortunately there isn’t anything we could offer as an alternative from our current range....... airflow of the fan was 6.8 litres/sec (24.5 m3/hr), was rated at 12 volts A.C. and had a maximum ambient temp of 70 degrees C."

Also the mounting bracket is 85mm (between centre of each mounting hole) and fan diameter is 60mm. It obviously need to be quiet as well.

If ayone has an idea where I can get replacement I'd be glad to hear from you

6th June 2011, 11:08 AM	#1
miligor diyAudio Member Join Date: Nov 2004 Location: KI	MF A100 fans problem Fans not working. After one hour amplifier is very hot, but fans still not started up... Is it problem with termo-switch or what?

6th June 2011, 11:37 AM	#2
jez diyAudio Member Join Date: Jan 2004 Location: n.e england	There is no thermal switch for the fans on an A100. They should be running all the time! If not then the most likely fault is dry soldered joints. The wires to the fans sometimes get broken when people open up the case also... __________________ Repairs and mods to Real Hi-Fi, guitar amps and P.A. in North East England. http://www.arklesselectronics.com

6th June 2011, 12:02 PM	#4
jez diyAudio Member Join Date: Jan 2004 Location: n.e england	It's very unlikely that the fans are faulty. They are Papst.... They sometimes become noisy but I can't recall one stopping altogether other than from dry joints/faulty wiring or the other common one is that the aluminium ducts around them can easily become bent and foul the fan blades. __________________ Repairs and mods to Real Hi-Fi, guitar amps and P.A. in North East England. http://www.arklesselectronics.com

8th June 2011, 10:42 AM	#7
jez diyAudio Member Join Date: Jan 2004 Location: n.e england	It's certainly something like that yes. There may be a resistor (a Wirewound) in circuit also from memory but can't swear to it..... I have repaired loads of these (used to work for MF) but I don't have one here to check at the moment and the schematic does not show the wiring to the fans. __________________ Repairs and mods to Real Hi-Fi, guitar amps and P.A. in North East England. http://www.arklesselectronics.com

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6th June 2011, 11:46 AM	#3
effebi diyAudio Member Join Date: Nov 2010 Location: Milan	Measure voltage at fan input. If voltage present replace fan. If you can't find the original, get a good one, like PAPST (sold by major electronics distributors). Avoid cheap chinese computer fans. effebi

6th June 2011, 05:40 PM	#5
miligor diyAudio Member Join Date: Nov 2004 Location: KI	Yes, it is Papst TYP 971TR 12V 50/60Hz 68uF ??? What's this? One wire is cut off from pcb, and both of them are connected over one bipolar 20uF elko??? TYP971TR have 3 wires, brown, blue and yellow... What is this 3 wires?

29th August 2011, 07:45 AM	#8
miligor diyAudio Member Join Date: Nov 2004 Location: KI	Fans are OK. One brown wire was de-soldered from pcb...

31st December 2011, 12:31 AM	#9
adespade diyAudio Member Join Date: May 2009	Following on from this issue, the (2) my fans in my A100 are noisy (especially when I switch off. I havent confirmed the exact specification of mine but is there a direct replacement avaialble?

24th January 2012, 12:25 AM	#10
adespade diyAudio Member Join Date: May 2009	I've since confirmed mine are the same type - 2x PAPST TYP971TR 12V AC 50/60HZ 68microF. I also checked with PAPST UK and they dont have a direct replacement "........... was made obsolete many years ago. Looking at the specification of the fan unfortunately there isn’t anything we could offer as an alternative from our current range....... airflow of the fan was 6.8 litres/sec (24.5 m3/hr), was rated at 12 volts A.C. and had a maximum ambient temp of 70 degrees C." Also the mounting bracket is 85mm (between centre of each mounting hole) and fan diameter is 60mm. It obviously need to be quiet as well. If ayone has an idea where I can get replacement I'd be glad to hear from you

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