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TFM 15 still needs to be fixed.


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I have rebuilt two of these in the past. I can read a schematic; but, that as far as I can go in trouble shooting. I checked the idle currents and reset them. The speaker relay looks like it is working; but, that is only by observing it make and break. I am looking for advice as to the next check points down the signal path. Are there any components that would be immediately suspect? If I remove the board, it probably can facilitate looking at the solder joints on the back and checking each component.

All suggestions about the amp will be considered.

Thanks,

Papajoe

 

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I think you would need to confirm that there is continuity through the relay to really know if it is working or not.  It may look like it is closing but you don't know if it is making a clean contact.   Find a spot on the trace before and after the relay for the right channel.  Power the unit up with nothing connected and once you hear the relay click you can check for continuity on the right channel with your multimeter.  I always connect the amp to a dim bulb tester when doing stuff like this just in case the probe moves due to unsteady hands and causes a short.

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After the relay click, turn it up really loud, for a second. If the sound "breaks through", you know you have a relay contact problem.

 

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Balok- Since the traces on the TFM15 circuit board are only reachable after you remove the board from the chassis. There is no way to activate and test continuity.  Plain and simple, does anyone have a list of all the components needed to rebuild a TFM 15? I understand that the speaker relays are hard to find. Has anyone tried to build a replacement board that will takes its place.  If not, I know that some of the members really like to be given a challenge.  Here's one.

Papajoe

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With a little finesse you can often pop the case off the relay and check it from the topside.

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Posted (edited)
16 hours ago, Papajoe said:

Balok- Since the traces on the TFM15 circuit board are only reachable after you remove the board from the chassis. There is no way to activate and test continuity.  Plain and simple, does anyone have a list of all the components needed to rebuild a TFM 15? I understand that the speaker relays are hard to find. Has anyone tried to build a replacement board that will takes its place.  If not, I know that some of the members really like to be given a challenge.  Here's one.

Papajoe

You can find a speaker relay on eBay. Thats where I just bought mine a few weeks ago and if you cant find one let me know. I have one. Like I said before, the pins are not an exact fit so you have to finesse it in there.  I also have other relays that you can change the coils out if you feel like doing some delicate work. 

Edited by Rob
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Posted (edited)
On 7/7/2021 at 7:18 PM, Papajoe said:

Balok- Since the traces on the TFM15 circuit board are only reachable after you remove the board from the chassis. There is no way to activate and test continuity.  Plain and simple, does anyone have a list of all the components needed to rebuild a TFM 15? I understand that the speaker relays are hard to find. Has anyone tried to build a replacement board that will takes its place.  If not, I know that some of the members really like to be given a challenge.  Here's one.

Papajoe

 

Oh ya.  Sorry Papajoe i forgot you can't remove the bottom.  If you look at the schematic, you can probably find whatever component comes in front of the relay and probe that along with the speaker terminal to check continuity.  I'd say it is better to try to solve the problem first and then you can do a "rebuild" after if you want.

Edited by Balok
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