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Carver PM 1.5 amp Fan

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ej92126

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Joined: Mon Jan 31, 2005 2:40 am

Location: So. Cali

Post Sun May 28, 2006 4:19 pm

Carver PM 1.5 amp Fan

I'm using a Carver PM 1.5 amp (home system) and was wondering if the fan should always be running? When I push the hi fan button, the fan kicks in and can be heard. However, on low, the fan doesn't seem to do much.

I don't drive it too hard (small room level sound) and the amp pretty much stays cool to the touch.

I had this amp serviced by carver back in '97 to replace the fan. After verfiying it was fixed, it's been boxed up for MANY years and recently have been using it in my system. Hate to think the fan has crapped out again.

Any feedback /thoughts are appreciated.
Thanks.
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MrShow4u

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Location: West Coast

Post Tue May 30, 2006 6:05 pm

The PM 1.5's "Quiet" fan position should still make the fan turn, albiet more slowly. If you can remove the fan filter, check to see that the fan is turning in "Quiet" mode. The fan speed is proportional to chassis temperature. If the fan is turning quietly, that's awesome and you can run the amp near your listening postion. If you run the fan at high speed and it's not making a lot of mechanical noise, the fan is probably in good shape.
....spend money on good speakers!!
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ej92126

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Joined: Mon Jan 31, 2005 2:40 am

Location: So. Cali

Post Wed May 31, 2006 5:47 am

In lowspeed, the fan makes a few feeble attempts to spin but stalls out,
in hispeed mode, the fan spins but, too loud to use in the home. A few months ago when I unboxed this stored unit, I recall the fan working at low speed and maybe a bit faster at hispeed. I'm guessing it's either a fan problem or voltage to fan problem(?).

Other than that, amp functions great. However, I've removed it from my system to risk any heat damage.

Any idea what the correct voltages should be applied to the fan in lo-hi mode? I guess I could use a voltmeter to measure the voltages.

Thanks.
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MrShow4u

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Location: West Coast

Post Wed May 31, 2006 7:52 am

Unfortunately, I don't have the amp or schematic for that one. I did have a Crown SA-2 which has the exact same fan. Once upon a time, I wanted to modify my SA-2 with a die cast boxer type fan. ....you know, to "make it quieter". The stock, strut type fan was already quiet. Low and behold, the boxer, more expensive, better looking fan was noisier. Talk about fixing a non problem. Anyway, I remember the strut type fan needed between 70 and 80 VAC to get started from a dead stop and about 50 to 60 volts to keep turning after it started. It was a long time ago, so my memory may not be the most accurate. Many 117 VAC will operate when a pair are series wired, leaving 117/2 VAC across each fan. In an electromechanical system when you've got to make a guess, go with mechanical faults. I believe that fan uses sintered bronze bearings. If you can get to the bearings, a good light bearing oil might free the bearings enough to let the low speed mode voltage turn the fan. If you can manually turn the fan, when on in quiet mode, with your finger (or pencil!!) and it continues to run, it might be worth investigating if there is a turn on "kick start" voltage that might be missing. As I say, I don't have the schematic, but the kick start approach might be used by Carver to get over the initial current hunger the fan requires to get rolling. Sorry this isn't much direct help, but more a collection of ideas. If worse comes to worse, the fan shouldn't be too expensive to replace, ......or the temperature monitoring circuit shouldn't be too hard to fix. Good luck
....spend money on good speakers!!
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ej92126

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Location: So. Cali

Post Sun Jun 04, 2006 8:09 am

Delayed thanks for the info.( was out of town for funeral). I'll try the kick start. Also, maybe I'll look into adding on a seperate cooling mechanism (for computer gear perhaps) that's lower noise. Guess I'm fortunate the amplification part still works/sounds great.
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Chuck_K

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Location: Vestal, NY

Post Sun Jun 04, 2006 9:49 am

i'd also suggest perhaps a spritz of very light lubricant (silicone) into the bearing. since it's attempting to turn in 'low', maybe it's not an electrical problem at all, but simply old lubricant that has gotten stickier over time, and needs revitalization. i see this alot in old clocks...
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fstik

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Post Sun Jun 04, 2006 10:04 am

Obtain a schematic and check all of your voltages. I had a friend with a PM-1.5 with the exact same problem. Not having a schematic, he called Carver and one of the techs was able to walk him through the test points and make the adjustments to fix the problem. Not sure if you could go the same route, so a schematic/service manual may be necessary. Good Luck!

fstik
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bob p

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Post Tue Oct 02, 2007 3:40 pm

ej92126 wrote:I'm using a Carver PM 1.5 amp (home system) and was wondering if the fan should always be running? When I push the hi fan button, the fan kicks in and can be heard. However, on low, the fan doesn't seem to do much.
...
I had this amp serviced by carver back in '97 to replace the fan. After verfiying it was fixed, it's been boxed up for MANY years and recently have been using it in my system. Hate to think the fan has crapped out again.

i've resurrected this thread because i just did some PM-1.5 fan replacements today.

yes, the fan is always supposed to be running. at cool idle, the fan spins at a low speed. the fan speeds up as the power transformer draws more current. it is NOT regulated by chassis temperature as someone mentioned previously.

if you fan is noisy, or if its sluggish at low speed, then its probably got bad bearings and is worn out and needs to be replaced. as normal PM, the fan is supposed to be removed and cleaned periodically, and the front and rear bearings are supposed to be lubricated. but nobody ever does that.

IME the easiest fix is to replace the fan with a new one. the problem, though, is that Carver parts are hard to find now that Carver Service is gone. OEM sourcing is a problem too, because the OEM will not sell them in single unit quantities. I had to buy a case of them. the good news is that they're the exact fan that was used in the originals, so they're a proper drop-in replacement and no modifications are required.
Carver Preamps: C-1, C-2, BillD's JVD-modded C-4000, C-9
Carver Amplifiers: BillD's C-500, M-1.5t (4) PM-1.5 (4) M-500t (2)
Repair/Restoration/Upgrade expert for all of these components.
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bikerdude523

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Location: Oklahoma

Post Tue Oct 02, 2007 4:44 pm

Bob, would you be interested in selling one of those fans? I've been looking for one for some time now to fix a noisy fan in my Buddy's PM-1.5.
I tried to contact Phoenix Gold, who is the factory repair people now for the PM series amp. But they won't answer e-mails.
2 channel rig
Sunfire Classic vacuum tube Preamp: (3) M-4.0t's: SD/A-490t: Polk Audio SDA SRS: Velodyne SMS-1: (2) Velodyne DLS5000R's
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bob p

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Post Tue Oct 02, 2007 11:15 pm

no problem. send me a PM.
Carver Preamps: C-1, C-2, BillD's JVD-modded C-4000, C-9
Carver Amplifiers: BillD's C-500, M-1.5t (4) PM-1.5 (4) M-500t (2)
Repair/Restoration/Upgrade expert for all of these components.
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bob p

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Post Wed Oct 03, 2007 1:27 pm

BD, if you can send me your email address, then i can send you the before/after photos from the fan replacement.
Carver Preamps: C-1, C-2, BillD's JVD-modded C-4000, C-9
Carver Amplifiers: BillD's C-500, M-1.5t (4) PM-1.5 (4) M-500t (2)
Repair/Restoration/Upgrade expert for all of these components.
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tfm75

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Post Thu Oct 04, 2007 10:49 am

bob p wrote:BD, if you can send me your email address, then i can send you the before/after photos from the fan replacement.


Bob P would you be able to post the pictures on the forum, it would be cool to see a before and after repair project.
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bob p

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Post Thu Oct 04, 2007 5:22 pm

tfm75 wrote:
bob p wrote:BD, if you can send me your email address, then i can send you the before/after photos from the fan replacement.


Bob P would you be able to post the pictures on the forum, it would be cool to see a before and after repair project.

Great minds think alike!

I thought about making a visual documentation of the repair process ;) but I didn't think about taking the photos until after I had already fixed the amps. :(

I have a "before" photo (taken from one of the amps that still has its original fan) and an "after" photo from after the fan replacement. Unfortunately, I don't have any photos of the actual intermediate steps involved in performing the repair.

I'll post what I have later today.
Carver Preamps: C-1, C-2, BillD's JVD-modded C-4000, C-9
Carver Amplifiers: BillD's C-500, M-1.5t (4) PM-1.5 (4) M-500t (2)
Repair/Restoration/Upgrade expert for all of these components.
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bob p

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Post Thu Oct 04, 2007 5:58 pm

OK, here are the photos. I think that actually seeing them is going to be kind of anti-climactic, as the before and after photos essentially look the same.

The replacement fan is the same model, manufactured by the same OEM. It is an exact size replacement for the original fan. Its external dimensions are identical to the original. Its threaded mounting holes are in exactly the same place, and its oval ventilation holes in the case are in exactly the same place. This is important because the vent holes need to line up with the holes in the mounting pedestal that Carver designed for the fan. The mounting pedestal acts as a heatsink for the fan, and its got oval ventilation holes on the left and right sides that are the same size as the oval ventilation holes in the original fan. Those holes need to be lined up so that the fan motor cools itself during operation. They're hard to see in this top view, but they're toward the back of the fan, on the sides.

Here is the "before" photo of one of my PM-1.5 amps. Notice that the PC board for the fan assembly is located to the left.

BEFORE:

Image
Carver Preamps: C-1, C-2, BillD's JVD-modded C-4000, C-9
Carver Amplifiers: BillD's C-500, M-1.5t (4) PM-1.5 (4) M-500t (2)
Repair/Restoration/Upgrade expert for all of these components.
<<

bob p

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Location: Chicago

Post Thu Oct 04, 2007 5:59 pm

Here's the "after" photo, from my PM-1.5 amp that got the new fan.

AFTER:

Image

In the new fan I mounted the ceramic motor start capacitor beneath the fan shaft, instead of above the fan shaft as on the original motor. Why fight gravity? This allowed me to avoid the use of hotmelt glue. IF you look closely, you can see the motor start cap.

Best of all, because the motor is an exact fit, it allows you to retain the original wiring harness that comes off of the fan PCB. Just disconnect the two wires on the back of the old motor, replace the motor, and reconnect the wires and you're done!
Carver Preamps: C-1, C-2, BillD's JVD-modded C-4000, C-9
Carver Amplifiers: BillD's C-500, M-1.5t (4) PM-1.5 (4) M-500t (2)
Repair/Restoration/Upgrade expert for all of these components.
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