Ampeg SVT-3 Pro fan?

[soundguruman]

The fan will not run at all times, because of huge variations in LM 35...
And the LM35 goes bad with age.
Recommend replacing it when the amp is serviced, every time.

It's not that the 35 is defect if the fan does not run cold...but...

There "should" be a calibration pot, to adjust for variations of LM 35...and, according to your ambient room temperature.

Manufacturer of LM 35 recommends calibration of device. This is being ignored by manufacturers.

but since there is not, bypassing from input to output, with a resistor, to set the "cold" speed, is a good method.
I use 1 meg approximately, but 930 K is not unusual. It helps to have some 1% resistors handy...

Then the fan starts when the unit is cold, and speeds up as it gets hotter, slows down as the amp idles and cools off. Works every time...till the 35 goes sour.

You should buy the correct 35 from the amp manufacturer, since there is more than 1 version then calibrate it w/ a resistor, I recommend.
There are plenty calibration methods, but bypass resistor is super easy, and reliable.

The Chinese convention which I hate:
1. The amp turns on cold, you start playing...
2. The output transistors start to heat up, then get plenty hot...
3. The heat sink then becomes pretty hot...
4. Then the heat is transferred to the LM 35, and it starts warming up...
5. Then last and least, the LM 35 starts to get warm, and turns the fan ON at a slow speed....

It's all too little, too late.
That's why the bypass resistor is a better method, to calibrate the device.

I would rather have the fan run at all times.

We have seen so many people fed up with this...
That they just install a 120 volt cooling fan, and let it rip. I can't blame them at all.

Cooler temperature = extended amplifier service life, less service downtime, and less cost. I do not agree with Chinese designer.

I think the whole idea is pretty silly to start with. Just turn on the fan, and cool the amp, big deal.

OR just start with an adequate heat sink...not included in Chinese amp.

It's pretty obvious that the manufacturer is not terribly concerned with long term reliability, anyhow. They want you to keep buying more amplifiers.

[R.G.]

There are several versions of LM 35, with different temperature ratings.
They turn on / off at different points, with different performance curves.

SGM, you might want to go read this:LM35 datasheet
There are several different *packages*, different *operating temperature ranges* and *accuracies*, but they're all out of the same vat, just selected and packaged differently. As the maker, TI says about the whole LM35 series:
Linear +10mV/°C Scale Factor
Low Cost Due to Wafer-level Trimming

That means (1) they're all the same scale factor, just different selected accuracies and (2) they're calibrated on the silicon wafer before there is any cutting into dies and putting in packages. There are no different temperature ratings, and no different turn on/off points, as they do not *have* turn on/off points. They are completely linear, not on/off devices.

In fact, the whole point of the LM35 is that, as National Semi said before TI swallowed them, "The LM35 does not require any external calibration or trimming to provide typical accuracies of ..." - that is, no trimming, no selection, no special cases.

Are you somehow confused about the LM35 being different from the LM34, which reads in F?

Chinese thermal management, in general, I do not agree with.

Did you simply not read my reply to you? There is, in general, no "Chinese thermal management". Can you not get over xenophobia long enough to think?

I think the thermal management in most of these amps sucks.

That's as may be, and I might even agree with you, but it is not a Chinese characteristic.

I would go for a much bigger heat sink, and a much cooler amplifier, overall.
The Chinese concept is too minimal for me.

So would I (on the heat sink and cooler), but once again, do you simply refuse to read or consider anything other than your preconceived notions? It's not a *Chinese* concept.

And, I really don't give a crap if you agree or not. I don't care, at all.

Here's another thing I picked up at Atomic Rockets that is really pertinent:

Science
If you don't make mistakes, you're doing it wrong.
If you don't correct those mistakes, you're doing it really wrong.
If you can't accept that you're mistaken, you're not doing it at all

.

Let me ask a pertinent question that I asked Gary Moore a ways back. If you are so opposed to what you find here why do you bother posting here at all? It seems like it only gets you grief.

[R.G.]

The fan will not run at all times, because of huge variations in LM 35...

I suggest you read the LM35 datasheet I posted in my last reply. It is very likely that what goes bad is the calibration of the comparators and other stuff, not the LM35. Or, entirely possibly, the physical mounting of the LM35 to the sink. Get that wrong and the LM35, no matter how good/accuate/immortal, is not sensing sink temps.

The phrase "The fan will not run at times" is probably true. Assigning that all to the LM35 is very, very shortsighted. I suspect you've pushed yourself into defending why you're painted into a corner.

And the LM35 goes bad with age.

So does everything. But it's very much more likely to be other things about the thermal sense than just the LM35. I would welcome a rational discussion of the thermal management design with you, in detail.

Recommend replacing it when the amp is serviced, every time.

... thereby correcting any possible mounting issues and tossing away a good LM35?

It's not that the 35 is defect if the fan does not run cold...but...

Excellent!! You're starting to make sense! Keep it up!

There "should" be a calibration pot, to adjust for variations of LM 35...and, according to your ambient room temperature.

Do you know the failure rate and drift rate for cheap pots? Do you know what the consequence is to the thermal management system if that pot goes open with age? There is a reason that pots are actively designed out where possible.

Manufacturer of LM 35 recommends calibration of device. This is being ignored by manufacturers.

No. See the datasheet I posted in my last reply. The point of the LM35 is to make calibration NOT needed in most cases. Can you point to the manufacturer's recommendation for calibrating the LM35? I picked up the following from the first text paragraph of the TI datasheet:

The LM35 does not require any external calibration or trimming to provide typical accuracies of +/-1/4C at room temperature and +/- 3/4C over a full -55C to +150C temperature range.

The Chinese convention which I hate... I do not agree with Chinese designer.

Can you explain why you think this is a Chinese convention?

It's pretty obvious that the manufacturer is not terribly concerned with long term reliability, anyhow. They want you to keep buying more amplifiers.

And finally, something that is not way out in the tall grass. It's the manufacturer that you disagree with. The manufacturer is:
Ampeg
LOUD Technologies, Inc.
16220 Wood-Red Road NE
Woodinville, WA 98072 USA
Whichever factory Loud Technologies picks will make it the way that Loud Technologies says to make it, and if they don't make it exactly that way, they don't get paid. Ultimately, the responsibility for the design rests on the guy who pays for it to be made and sells it, not the guy who has to run the soldering machine. Is that too complicated for you to understand?

[soundguruman]

The fan:

You can consider that the fan goes bad with age also.
Failure to start with a lower voltage may be a sign that the lubrication is drying out or partially seizing the shaft.
But if it's stuck, noisy, there is a temporary fix, until you buy a new fan.

There is probably nothing better than a new fan when all else fails.
The bearings and lubrication do not last forever.
One sign that the fan is dying is the noise it makes.

If the fan sounds like a wounded screech owl, dying in the forest, it's time to lube the fan, or replace the fan.

The paper label is removed from the fan hub.
A small shot of motor lube like LPS1, between the shaft and the bearing.
rotate the fan by hand several times and allow the lube to sink down into the bearing.

Turn the fan upside down and allow the excess lube to drain out, into a rag, etc...

Use a non-shorting cleaner recommended for electric motors, such as: LPS1

Replace the paper label after cleaning all excess lube off the fan housing, with something like isopropyl alcohol...
excess lube attracts dirt so keep it clean, gene.

[g1]

Wow! A coherent post that actually is in context .
Is that your way of conceding that all your other posts in this thread were wrong as JM and RG have shown?
Man up for once.

[R.G.]

I believe he is simply pretending not to see posts he does not like.

[Jazz P Bass]

Wow!
Selective sight.



I have been aware of selective hearing, though.(ask my better half)

[R.G.]

We have Golden Retrievers. They are masters of what I call "situational deafness", as are many children.

The training the Goldens have given me has been a great aid in my previous career, and sometimes comes in handy in this career.

[gui_tarzan]

I know I have tried to assist you a few times over the years, and I am sure you have some notion of how reliable my help is or is not.

A friend of mine knows of Enzo and his reputation and when I asked him about him he said - and I quote - "he's probably THE best amp tech in this part of the country" so I take what he (and a handful of others here) say very seriously.

It's not hard to figure out when someone is a BS artiste' and I just ignore them. Although sometimes they're good for a laugh or two. I've been around the 'net almost twenty years and BBSs before that. You can get a good idea of someone's "worth" just by reading their posts.

[J M Fahey]

There are several versions of LM 35, with different temperature ratings.
They turn on / off at different points, with different performance curves.

Absolute bullshit.

The datasheet specs 10mV/deg C PERIOD
No different versions mentioned by the makers, who should know.

They do not turn on or off.

You think they are thermal switches, they are not.

They are temperature controlled voltage references, which not only don't turn on/off but are LINEAR all over the working range.

So linear that they are used to *measure* temperature, go figure.

Chinese thermal management, in general, I do not agree with.

Bullshit, no such thing as "Chinese Thermal management" exists.

[Enzo]

This is what is so dangerous about SGM, he doesn;t understand data sheets.

As Juan points out, the thing puts out a voltage that changes with temperature. Now they do make different versions. Some are commercial level and work from 0 to +100 degrees C. But there are also versions that work from -40 to +110- degrees C. They work the same and make the same output, just the one version will work over a wider range of conditions.

But either one of those will work the same in this amplifier, although if you chill the amp down to -30C the commercial grade one won't work reliably. But then I am not too worried about the fan at -30C.


They make them in several shapes, but again, all those shapes work exactly the same.


And you can chose some with a higher degree of precision, but the difference is that the worst precision one is within 2 degrees while the best one nails it within half a degree. That difference is irrelevant to a guitar amp.

[catstrat]

Chinese design/build quality. I work on all kinds of stuff and some of the Peaveys, Ampegs, and lord knows what else is being made overseas. So i would assume the designs and final QA procedures are still American no matter where it's made at. I've found that most all of the Chinese built stuff to be reliable from my experiance, except Bugera. Now those i wonder about. All in all, i think the chinese stuff is quality on a budget. Cheap does not always mean junk.

[J M Fahey]

True.
Even more if cheap means cheap salaries (think U$ 65 to 240 a Month) but not cheap parts, machinery or test procedures.
And of course they must meet or exceed UL, IEC, TÜV, CSA, SEMKO, etc tests to be sold in different parts of the World.

[catstrat]

Hi J m. That's the one thing i do have problems with is the cheap labor issue.

[J M Fahey]

Me too, that´s also my big problem.

I find it fair that some Tech gets a job instead of me because he´s better, and that will make me try to improve, but that somebody steals my customer because he repairs amps for $3 an hour makes me REAL pissed off.