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TFM-24 problem

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engtaz

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"TAZ"

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Post Thu Aug 14, 2008 8:08 pm

Re: TFM-24 problem

Nice and very nice optical display.
engtaz


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otis30223

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Joined: Sat Aug 02, 2008 11:22 am

Post Thu Aug 21, 2008 11:35 am

Re: TFM-24 problem

Hey, I having a harder time tracking down the .25 watt resistors for the service upgrade than I though I would. I tried ordering through Ken's Electronics but there appears to be some problem. I can find .5 watt resistors through parts express-other than they are slightly larger-will this adversely affect the circuit. My basic feeling is that they should not since the only difference is the power handling capacity. Any thoughts or do you know a alternate supplier that ships in small quanities that I could get them from. I've recieved the transistors and am ready to proceed, but on close examination the resistors show signs of overheating and really need to be replaced as well.
Carver C-11, TFM-24, Polk SDA Compacts
"You don't know until you ask"
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OBI56

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SILVER-7 TUBE AMP

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Post Thu Aug 21, 2008 12:45 pm

Re: TFM-24 problem

Substituting a higher wattage resistor should not affect performance but substituting a smaller one will probably blow. Resistors are usually chosen based on the smallest size that will do the job. The only other consideration is that it has enough air space around it to properly dissipate the heat it will generate, so if the original was tightly packed in there between other components, mounting it a little higher than the others should be adequate.
Why let facts or common sense get in the way of your opinions.
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otis30223

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Post Thu Aug 28, 2008 4:19 pm

Re: TFM-24 problem

Okay, I have all the parts and have begun the service modification. When I perform the rebias of the circuits I assume I will follow the instructions in the service manual, but I have one question. It states no input, but should I connect speakers or place some type of load across the output terminals? The manual doesn't make mention of wether a load should be placed on the circuits.
Carver C-11, TFM-24, Polk SDA Compacts
"You don't know until you ask"
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BillD

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(pair of) SILVER-7 TUBE AMPs

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Post Thu Aug 28, 2008 4:41 pm

Re: TFM-24 problem

No, you don't need a load. You're setting the idle bias. Also note — no input either.
It should sound like it isn't there!
There is a difference between hearing and listening...
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otis30223

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Posts: 13

Joined: Sat Aug 02, 2008 11:22 am

Post Mon Sep 08, 2008 5:51 am

Re: TFM-24 problem

Okay, have performed service bulletin and amp is up and running like it's old self. The only minor glitch is one channel is slightly louder than the other. Is this possibly due to slight misadjustment of the bias? It is more noticable at low volume. But I want to thank all, especially Current Limited and BillD for thier help.
Carver C-11, TFM-24, Polk SDA Compacts
"You don't know until you ask"
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ViperZ

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M-400t CUBE

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Joined: Mon Sep 08, 2008 8:11 pm

Location: Toronto, ON, Canada

Post Mon Sep 08, 2008 8:16 pm

Re: TFM-24 problem

Hi all,

I just bought on the auction the TFM-24 with exactly the same problem. This will be my first piece of Carver gear ever :).

Could you guys point me in the right direction - where can I buy the TFM-24/25 service manual and get a copy of SB# TFM-25-2 service bulletin?

Thank you!
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OBI56

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Post Mon Sep 08, 2008 9:19 pm

Re: TFM-24 problem

Welcome to the forum Viperz! Toronto, eh? Montréal here. We have another member located in central Toronto called BigErik; he should be piping in soon.

The TSB should be within the service manual which you can find here:

http://www.servicemanuals.net/ServiceMa ... sults.aspx

It is the same manual as for the TFM-25, the only difference being analog VS LED meters.

If you need technical services, you can contact Anatech in Georgetown as he is probably the only service shop in Ontario that has experience with Carver amps. Otherwise, the best shop anywhere is Rolland at HighTech in Oregon (he is the ONLY place that has original parts in stock)

If you are reasonably proficient with amplifier repairs, the TFM-22/24/25 as well as the 6/15 are just about the only Carver amps that I would suggest you try working on yourself. For any other Carver amp, you should use the services of a techinician who has experience with triac switched Magnetic Field Coil amps as a regular technician has a better than 95% chance of blowing it up by doing what regular technicians do with regular amps (your amp is one of the only Carver amps that does not use a triac switched magnetic field coil instead of a transformer)

Good luck and keep us posted on your progress.
Why let facts or common sense get in the way of your opinions.
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ViperZ

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M-400t CUBE

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Location: Toronto, ON, Canada

Post Mon Sep 08, 2008 9:42 pm

Re: TFM-24 problem

Hello,

Thank you so much for the quick reply. I'll order the service manual ASAP. Will update as soon as the amp will arrive (in a couple of weeks, I guess).
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ViperZ

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M-400t CUBE

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Location: Toronto, ON, Canada

Post Tue Sep 09, 2008 11:01 am

Re: TFM-24 problem

OBI56 wrote:Welcome to the forum Viperz! Toronto, eh? Montréal here. We have another member located in central Toronto called BigErik; he should be piping in soon.

The TSB should be within the service manual which you can find here:

http://www.servicemanuals.net/ServiceMa ... sults.aspx

Good luck and keep us posted on your progress.


All right, I bought the service manual, but TSB is not there. Is there any way to obtain a copy of that service bulletin? Thanks! ](*,)
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OBI56

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SILVER-7 TUBE AMP

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Post Tue Sep 09, 2008 11:57 am

Re: TFM-24 problem

ViperZ wrote:
OBI56 wrote:Welcome to the forum Viperz! Toronto, eh? Montréal here. We have another member located in central Toronto called BigErik; he should be piping in soon.

The TSB should be within the service manual which you can find here:

http://www.servicemanuals.net/ServiceMa ... sults.aspx

Good luck and keep us posted on your progress.


All right, I bought the service manual, but TSB is not there. Is there any way to obtain a copy of that service bulletin? Thanks! ](*,)


OK, did a bit of digging and this is not a TSB but a Technical Modification. It is referenced here in a post by member Current Limited with all the details:

viewtopic.php?f=8&t=5488

Keep us posted on your progress
Why let facts or common sense get in the way of your opinions.
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ViperZ

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M-400t CUBE

Posts: 117

Joined: Mon Sep 08, 2008 8:11 pm

Location: Toronto, ON, Canada

Post Thu Sep 25, 2008 3:11 pm

Re: TFM-24 problem

Interesting... Got the amp, completely inspected and checked it - everything is fine. Hooked it up to a pair of 8-Ohm speakers. Power on, run for over an hour - everything is fine. Hooked it up to a pair of 4-Ohm speakers for about three hours of continuous play - barely got warm - no problems. Now it's running a pair of my Magneplanar MG-II speakers (6 Ohms) without any problems. :-({|=
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ViperZ

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M-400t CUBE

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Joined: Mon Sep 08, 2008 8:11 pm

Location: Toronto, ON, Canada

Post Sat Dec 27, 2008 10:58 am

Re: TFM-24 problem

To resurrect this thread from the dead... and on a bad note... The previous owner of my TFM-24 connected 4-Ohm speaker to the amp in the bridged mode. The amp works perfectly fine up until you raise the preamp level up to ~-20dB, then the speakers start to crackle. I wanted to use it as a subwoofer amp with dual 10" (each speaker is separate 4-Ohm, with separate passive crossover).
I'll start diagnosing it and will keep people updated, if someone cares. I already have all the parts "kit" to replace the resistors with higher wattage ones and to replace the small transistors listed in the other thread (if needed).
It doesn't look like it's worth sending to Bob/Rita for overhaul/repair, since you can get a used TFM-24/25 for 170-200, and the shipping to Carver and back from Canada will cost me an arm and a leg. :(
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OBI56

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SILVER-7 TUBE AMP

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Post Sat Dec 27, 2008 2:43 pm

Re: TFM-24 problem

ViperZ, there are 2 good Carver repair shops in and near Toronto (Anatech who is a member on here) you might want to check out.
Why let facts or common sense get in the way of your opinions.
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