Norlin Lab Series L4 - Info on fan

[5595bassman]

I just bought this bass amp head for a very good price but without having the possibility of testing it.
In fact I took it mainly with the intention of using the cabinet for a project.

Since the condition is quite nice and everything work fine I might reconsider.
I cleaned all the pots and jacks then I played bass (USA Fender Jazz Bass) with it and I really liked what I could get out of this not well known (at least to me) amp.

My problem is the fan mounted on the left side runs very fast and is quite noisy ( wind noise ), as much as my kitchen hood fan is, and I suspect the actual fan not being the original. The actual fan has a CSA certification while the amp wears no such logo, probably because produced before CSA implementation. But it has an Ontario Hydro approval sticker.
It does not make sense to me that they would have produce an amp with such a loud fan.

Searches in the Web were not helpfull to see pics of a the original fan.

A ) Can somebody owning such amp provide info on the original fan please?

Or

B ) Is there a way of lowering the speed by adding some resistor?

That heavy duty cast metal fan is connected via a lamp cord with a standard molded plug in a regular chassis mounted 2 prungs AC outlet provided in the bottom of the chassis near the big transformer.

Thanks!

 

[muchxs]

Just remove the fan. It's probably something someone added to play loud during a long gig.

 

[Rich_S]

Does it look to be original to the amp? You can usually tell an after-the-fact hack job.

If it's original, then the design probably relies on the fan to provide sufficient cooling at full power. Fans wear out, and getting noisy is the first symptom. There are dozens of different models that will bolt in there. You need to get the voltage right first, then you get to choose lots of trade-offs among air flow, RPM, and noise level (dB).

Look at Mouser Electronics; they'll have a huge array of options.

 

[5595bassman]

The opening on the side and the grill ( not shown on my pics ) do not look like a DIY job.
Same for the AC outlet on the bottom of the chassis the fan is plugged in, but the fan itself is probably a replacement not well adapted to the original.

The noise is not from a mechanical source, only too much air flow at very high speed type of noise.

I do not even know if this head was produce with a fan to begin with since I'm not able to find a pic taken from a proper angle to show it.

I'm still very impressed with this amp. It sound as good as my Traynor YBA-1A Mark II ( tube amp ) or my Acoustic 370 ( SS amp ). All three feeding each an identical single 15" 8 ohms cab. I'm not a loud player but I like to use powerful amps in order to get headroom for clean sound. I play Blues and instrumental Rock ( The Ventures type of music ).

The project I referred to on OP was to transplant a SF Fender Bassman 10 ( 4 x 10" combo ) chassis in the L4 head cab.
This combo, while being very good for guitar use, does not deliver enough low ends to my taste. But when I use this Bassman hooked on the same single 15" cab without the 4 x 10" I like it.

Thanks for your comments!

 

[Rich_S]

I kinda remember Lab heads having fans, but it's been a long time since I've seen one. I would just search Mouser for a similar fan with a lower noise rating.

 

[rrroo]

I've got a L4 too. Great amp. I was also having problems with the fan noise. There is also some litle electronic noise caused by the fan.

Then I realised that the amp gets hot only when you're playing very loud. And when you play loud, you won't hear the fan anyway. So I added a little component called "thermal switch", screwed it to the heat sink and connected power to the fan through it. This way the fan turns on only when the amp heats up. And this happens only during long, intensive and loud (also drunken) jam sessions.

There are switches with different switching temperatures. Not sure what it should be but I chose one which turns on at 60 degrees celcius and the amp has been working fine.

 

[5595bassman]

I've got a L4 too. Great amp. I was also having problems with the fan noise. There is also some litle electronic noise caused by the fan.

Then I realised that the amp gets hot only when you're playing very loud. And when you play loud, you won't hear the fan anyway. So I added a little component called "thermal switch", screwed it to the heat sink and connected power to the fan through it. This way the fan turns on only when the amp heats up. And this happens only during long, intensive and loud (also drunken) jam sessions.

There are switches with different switching temperatures. Not sure what it should be but I chose one which turns on at 60 degrees celcius and the amp has been working fine.

Thanks for the tip!

I corrected the problem by getting a fan that is supposed to work on 240V. When fed by the actual/original 120V source, speed drops enough to not being a concern anymore and still have a noticeable flow providing what seems proper evacuation.

 

[rrroo]

Yeah. Thats A good idea too. I guess the original fan is more than enough and most of the time it is not needed.

The thermal switch looks something like this

https://www.radio741.com/87769-large_default/70c-thermal-switch-thermostat-l70c-elmwood.jpg

costs just few dollars and is an easy mod.