Enjoy the benefits of a premium membership!
Upgrade Account
-
TalkBass has been independent since 1998. Add your voice.
Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
Join free Log in
Want zero display ads or expanded classifieds tools? Compare plans.
Mesa Boogie Walkabout Mega-thread Part 10
- Thread starter Chef
- Start date
Yep.
Here are the figures I noted :
Noctua fan working fine : 9.5v and 60mA
Sunon fan spinning very slowly and inefficient: 10v and 30mA
Sunon on independent power supply : 12v and 110mA - spinning fast and efficient
I don’t know what to think
Last edited:
- Feb 12, 2006
- 60,970
- 5
- 220,705
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
I need to look at my documentation. I wonder if your amp was modified when the fan was installed???
Maybe but it seems intact inside.
Thank you for your time, I appreciate.
- Feb 12, 2006
- 60,970
- 5
- 220,705
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
The fan dropping resistor should be 20 ohms and either 1 or 2 watt (doesn't matter). If it's higher than this, it will be a problem. I suspect that your amp was modified. Can you post a picture of the power supply PCB?
There were several versions, but this resistor value didn't change according to my documentation.
- Feb 12, 2006
- 60,970
- 5
- 220,705
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
That's an older revision than my benchmark unit.
The 20 ohm resistor was an approved mod for lower fan noise, production units and my benchmark unit doesn't have it.
If the 20 ohm resistor has drifted upward, or is defective, that will cause this issue for sure. It's possible the the EF series fan that's the direct replacement for the EE series is in fact different at lower voltage because this fan revision is part of IEC 62368 updates to components, as well as some changes to the internal commutating circuitry (that creates the rotating magnetic field so that the fan spins) to newer EMC standards.
Try this with the resistor removed, I think your problem will go away. If I was updating the circuit for the new fan, I would use a 4.7 ohm, 1W resistor in place of the 20 ohm resistor. There should also be a 100 uF/25V cap across the fan, it's on my documentation, but it may not be on the earlier amps.
The 20 ohm resistor was an approved mod for lower fan noise, production units and my benchmark unit doesn't have it.
If the 20 ohm resistor has drifted upward, or is defective, that will cause this issue for sure. It's possible the the EF series fan that's the direct replacement for the EE series is in fact different at lower voltage because this fan revision is part of IEC 62368 updates to components, as well as some changes to the internal commutating circuitry (that creates the rotating magnetic field so that the fan spins) to newer EMC standards.
Try this with the resistor removed, I think your problem will go away. If I was updating the circuit for the new fan, I would use a 4.7 ohm, 1W resistor in place of the 20 ohm resistor. There should also be a 100 uF/25V cap across the fan, it's on my documentation, but it may not be on the earlier amps.
Thank you.
Still not good : I measured 20 ohm for the resisor.
I connected directly the sunon fan to the board and no luck, same slow spinning.
I don’t know if it helps : I measured 11.3 before the 20 ohm resistor when I start the amp. After a few seconds, there’s a tiny click sound and the voltage drops to 10.5 v.
Still not good : I measured 20 ohm for the resisor.
I connected directly the sunon fan to the board and no luck, same slow spinning.
I don’t know if it helps : I measured 11.3 before the 20 ohm resistor when I start the amp. After a few seconds, there’s a tiny click sound and the voltage drops to 10.5 v.
- Feb 12, 2006
- 60,970
- 5
- 220,705
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Is there a 100uF cap present across the fan?
Is the fan spinning any faster without the resistor?
There’s something else going on here, either a defective or modified power supply. You should have ~12V at the fan.
There are a lot off mids out there, many of them end up causing issues.
Is the fan spinning any faster without the resistor?
There’s something else going on here, either a defective or modified power supply. You should have ~12V at the fan.
There are a lot off mids out there, many of them end up causing issues.
there is no cap
The noctua fan spins faster without the resistor. There is now 11.5v.
The sunon fans spins a bit faster but still too slow.
I will bring the amp to a workshop. I have reached my limit of competency. I suspect too that there is sth wrong somewhere else.
Thank you for your help.
The noctua fan spins faster without the resistor. There is now 11.5v.
The sunon fans spins a bit faster but still too slow.
I will bring the amp to a workshop. I have reached my limit of competency. I suspect too that there is sth wrong somewhere else.
Thank you for your help.
Did this get sorted? I’m tempted to order that fan but wanna make sure it works.
Not yet. I still have to find a good tech in my area. There was one but he is retired now.
I’m going to try this fan from Amazon as a cheap solution. The CFM is 39.35 so it should be a good replacement. Not silent but shouldn’t matter.
I will keep you posted
StarTech.com 92x25mm Dual Ball Bearing Computer Case Fan w/ LP4 Connector - 90mm Fan - computer case Fan - pc Fan (FANBOX92) : Amazon.ca: Electronics
this was going to be option 2:
Amazon.ca
Last edited:
- Feb 12, 2006
- 60,970
- 5
- 220,705
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Don’t.
It’s the wrong size, the wrong connector, wrong wiring/control and likely the wrong voltage. Looks like a 5V fan, but even this detail is fully unclear/midsing)!
This is how folks damage otherwise perfectly functional amps.
Ok thanks for advice. I’ll try calling Mesa next week with the proper replacement. Just curious why it’s not working for Chris.
- Feb 12, 2006
- 60,970
- 5
- 220,705
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
I think there are other issues with his amp, possibly related to the modifications previously done or a failure within the power supply.
I have been practicing a lot with my band at rehearsal studios with amps provided. I decided this week to bring the walkabout and bypass the provided amp. Man what a difference. The amp was huge and there was plenty of headroom to spare. I was playing through a mark bass 4x10 on top of a 1x15. I didn’t really touch the dials just gain and master. The tone was phenomenal.
I have a pretty big show coming up I’m tempted to rent an 8x10 Ampeg fridge and plopping the walkabout on top. Anyone ever try that before?
I have a pretty big show coming up I’m tempted to rent an 8x10 Ampeg fridge and plopping the walkabout on top. Anyone ever try that before?
Yep! Walkabout and an 810 is great. Not quite as much headroom as an SVT but a good thick tone was plenty of volume for the stage I was on.
Al Kraft
Supporting Member
- May 2, 2016
- 10,768
- 40,442
- Disclosures
- Mesa Boogie beta product tester and player support
I haven't used that combination but would have thought that headroom would likely be an issue if you needed fairly high volume.
