Thunderbolt 305 Fan Replacement ?

[V8Vega]

I want to replace the LOUD fan in my amp. What would be the best type and size/spec to go with? I'm assuming it's 12volt...correct?
Schematic: http://cbtricks.com/Amp/thunderbolt/305/graphics/thunderbolt_305_sch.pdf

 

[ElectronTubesRule]

Get your Multi-Meter out and set it up on the input to the fan. Select the peak hold function. Turn the amp on then turn it off. Before reaching in discharge any caps in the area pull the VOM leads out and read the peak hold votlage. It will be close to some standard voltage lile 12,24,48,110 etc....It might be a tad higher due to surge but it should be close to one of those 4 voltages above. It might even say on the fan motor itself many of then have a data plate on the back side that tells the voltage and current it is designed for.

What type of fan is it? Is it a squirrel cage like what car's and furnaces use or is it more like a box fan minus the box? I am guessing they where not using brushless muffin fans back when it was built???

Her is the thing you can not eat you cake and have it too. You can have you cake and eat it too but you cannot eat your cake and have it too...People mix that up all the time! LOL Seriously though if you slow it down you get less air and will not properly cool the tubes. So if you put a resistor inline to lower the voltage to slow it down you will have less air flowing to cool the tubes. If it is axial flow type fan like a house hold box fan you would need to either change the pitch of the blades or double the number of blades or increase the size of the blades to make up for slowing it down!

Here goes an idea. When I was a kid in middle school printer where either dot matrix or daisy wheels. When you printed it sounded like a Dillion Mini Gun firing or a pair of two cycle motocross bikes at redline.....So they made these insulated box's that the printer went in to cut the noise. The other idea would be to put the unit as far away from you and your mic as you can get it. No unit with in 2-3 feet of the mic will ever be quite enough unless it does not use any fan at all.

In order to move the air slower you have to move a much larger volume of air. So I doubt you will find a plug and play easy solution. If you slow the fan down with a resistor you really need to make sure you do not drive that unit that hard and that you do not key down for long rag chewing sessions on AM.

 

[Captain Kilowatt]

From looking at the schematic it is obvious that the fan requires 120 volts AC. It is most likely a muffin style fan. Is the noise from airflow or is it from rough/dry bearings? A drop or two of good light oil may help tremendously. If not then finding a simple replacement should not be too hard. there are dozens of types of 120 Volt6 AC fans out there. Look for a CFM (cubic feet per minute) rating on the fan.

 

[V8Vega]

It's not a muffin. It's a round motor with an airplane propeller style fan on it.

 

[rumrunner]

I've rebuilt three of the T-bolt 305's. Fan is 120 volts. Same fan as used in a common refrigerator to move the air from the freezer to the refrigerator section! About $30 bucks new or do like I do and find a junker refrig.

 

[wavrider]

I've rebuilt three of the T-bolt 305's. Fan is 120 volts. Same fan as used in a common refrigerator to move the air from the freezer to the refrigerator section! About $30 bucks new or do like I do and find a junker refrig.

Great advice. Pull from junker frig and I use PB Blaster for lubrication, have not found to much on the market better for freeing up old refrigerator type motors and lubing them.

 

[rumrunner]

Great advice. Pull from junker frig and I use PB Blaster for lubrication, have not found to much on the market better for freeing up old refrigerator type motors and lubing them.

Yep. If that little fan is loud - "Houston, we have a problem" . Mine ain't. (Hint: we call PB blaster "Monkey Piss"). In the nicest way, btw. Good stuff. You can also drill the sealed bearings with a 1/16" drill bit and lube them with something like 3-in-1 oil. Works more better gooder.

 

[V8Vega]

Yep. If that little fan is loud - "Houston, we have a problem" . Mine ain't. (Hint: we call PB blaster "Monkey Piss"). In the nicest way, btw. Good stuff. You can also drill the sealed bearings with a 1/16" drill bit and lube them with something like 3-in-1 oil. Works more better gooder.

I will try it.
Mine is really loud, but it sounds more like air instead of friction noise.

 

[ElectronTubesRule]

I have found on refrigerator motor's for the fan a few drops of plain Jane ATF works like a charm. I use synthetic ATF in all my vehicles with automatics. That might make a difference. I had one stop on me once at 3 in the morning so no place was open and all I had was ATF on hand. 5 years latter that motor is still going strong. I would imagine 3in1 would work even better since it has anti-corrosive package as well. ATF has very anemic additive package just slightly better then most bulk hydraulic fluid. The thing is the more additives in a lubricant the less oil is in the lubricant. So if you do not need a complicated additive package then a oil with out much in it will have better lubricating properties normally.

PB Blaster is the best over the counter penetrating fluid I have ever used. Their are specialty products that are better but they are expensive, you have to order them in bulk etc....... When I was in Flight School the A&P mechanics used some stuff in a small white bottle called Monkey Milk that was also very good!

I have often used a Kroil Penetrating Oil mixed with ATF and Strong Oliec Acid or Crysilic Acid for bore cleaning weapons!