Lexicon 224xl - Fan replacement /12v

[jackson5]

Hi guys,

bought an 224xl some time ago and was able to fix some of the problems it had thanks to the input of fellow members here on the board. Thanks to all of you who helped me out back then.

Today I am asking again for support as I would like to silence the Lex a bit. Initially the built in fan at the time of my purchase was pretty much done. As an easy fix I decided for a drop in replacement Papst fan with same voltage but better spec..The issue though is while the fan cools down my Lex pretty close to 0° Kelvin , the downside is - as you can guess - that it is way too loud. First it did not bother me as the unit wasn‘t in the control room with me. Anyway, I currently have no possibility to put it in another room so I would need to find a way to silence the unit.

As cooling technology is far advanced today thx to the PC industry, there should be a smart way to mod the Lex to make use of all the 12v based stuff. On top, I feel that dust is an issue, too and there are so many good solutions for PCs that it would be stupid not to consider a conversion.

I recall the Lex has a 12v rail in there but would it be a good idea to make use of it for the fans? I fear that the fans motors could create interactions and will affect the cards  thatmthe 12v was initially designed to supply. Just guessing, I am no expert.

On the other hand, one could think of buying some  extra12v power supply (i.e. a wall wart with some mods) to run the fans indepedent from the mains. These are just some ideas. I would appreciate if someone who is experienced or who did something similar to his own unit could chime in.

Thx
Tom

 

[analogguru]

You could install one (or more) of these instead and have the loud cooling fan seperated in another room:

https://www.ekwb.com/shop/kits

 

[pvision]

What does the 12V rail on the Lexicon feed? If it's a utility rail (relays, lamps, etc) you may be able to run the fan off it if there is sufficient capacity

One problem with DC fans is a high-startup current. You might be able to get round that problem, and reduce noise, by using a temperature sensor and a fan speed controller. There are quite a few pre-built FSC boards on eBay

Maybe you could stick with the PAPST fan and fit a speed controller? You don't say what voltage the PAPST is

A speed controller might create new problems by creating noise in the audio circuitry: something to consider

Nick Froome

 

[PRR]

Resistor usually works great.

 

[Gene Pink]

Resistor usually works great.

I believe it is a 120VAC fan, so a capacitor works even greater, no extra heat.  Start with 5uF / 250VAC rating, and go up or down from there. The sweet range will be between 2 and 7uF.

Gene

 

[jackson5]

@analogguru
As I understand the kits you are proposing are liquid based. That might work when you have a single part like a CPU that the cooling is build around. The problem with the fan on the Lex is that it is not for cooling a specific part but whole unit by creating an airflow which cools the psu and the cards alike.

@Nick
This is exactly my problem: The 12v rail is supporting the audio cards so putting the fans in there will surely introduce  noise.
The fan btw is a 115v Papst..

@Gene
Thanks for the idea with the capacitor. The  only problem I see is that I would need to find a suitable value first that has the best ratio between noise and cooling. Anyway, as it is a fixed value I will be missing the ability to change the speed on the fly if necessary. Anyway , if I stick to the Papst fan and modifiying the speed I might not get below its min. noise level.

My idea would be to use  2 or 3 fans 120mm PC fans instead of the big one with speed control, ideally fed by the existing non-audio 120v rail.

Thx for all your input so far!

 

[PRR]

> a 120VAC fan, so a capacitor works even greater

One would think.

I had a 47VA duct-fan, basic induction motor. I put a few-uFd cap in series. It ran *faster*. Even though the cheap motor's L is low-Q, R is small enough to get a resonance going.

Anyway doesn't the thread title say "12V"?

 

[radardoug]

Fan noise varies as the fourth order of the rotational speed, so reducing speed a little bit makes a big difference to the noise. Just choose one of the quiet Papst models with a bit less airflow. Then check temperature in the Lexicon frame.

 

[Gene Pink]

I had a 47VA duct-fan, basic induction motor. I put a few-uFd cap in series. It ran *faster*. Even though the cheap motor's L is low-Q, R is small enough to get a resonance going.

Yeah, that one once got me too. Had an old '40's style oscillating 10" desk fan, that beige baked enamel, something you would see on Sam Spade's desk in an old movie. Retro-cool. It had a bad switch. So I figure replace it with a center-off toggle and add a low-speed option with a cap. But what value? Time to play.

Well looky there, a 22uF cap just laying on the bench unspoken for, let's start with that. Power on, and the thing dang near flipped over backwards from the air thrust. Measured something like170V at the motor. 

Having done this many times to quiet up various boxer fans venting ampracks, loud is fine for outdoor festivals, but hotel ballrooms need quiet, the sweet range always seems to fall in that 2-7uF area, regardless of fan.

Too bad they don't make variable caps that big. 

Gene

 

[jackson5]

Hi all,

while you guys were indulging yourselves in happy memories  of nearly breaking stuff I made up my mind and I decided for a dual strategy. I ordered a Papst 4840N fan, which is pushing less air than the current one but given the specs in the data sheet it has only 26db. After some research that looks like the most silent one in their whole product line. That should make a difference but not sure if it is enough cooling. BTW whats an acceptable temperature level for such a box?

Apart from,the new fan I ordered a small power transformer in parallel as I would like to try to stepdown those 110v AC  on the fan rail to 12v DC. Not sure if I can make it fit into the box but at least that would give me the option of using the 12V PC stuff in case the new fan is still too loud. As I bought both units online I can return them , given I don‘t blast them in the process of trying out  ;D  I’ll keep you posted...


Tom

 

[Pip]

Dane Beamish Cleveland Ohio

Has all the parts and can restore and cal to beyond factory spec

 

[jackson5]

Thanks for the hint. Anyway I will not ship the unit. As you know it is a bit delicate due to all the cards, it’s way to easy to break something. Aside from that I have been able to calibrate the Lex myself, same with all the repairs that had to be done. I don‘t know what I would gain from shipping it hundreds of miles other than risking to get back a non-functional piece of junk. At least not because of a fan replacement. Thx anyway...

 

[Pip]

You could ask if he would sell you a fan?