TFM-45 Whistling

My TFM-45 is now having big problem. It whistles loud (hear from speakers) when turn on, and some times it whistles on and off during playing. What is wrong with my TFM?

Does it happen when you have your preamp off? Might be a bad feed from the pre.

Maybe it's just happy!
Sorry; have not experienced that with mine.

Does it happen when you have your preamp off? Might be a bad feed from the pre.

Yes. It happened when preamp is off.

Helpless, so studied service manual. Suspect whistling was due to damping of amplifier board (not sure what damping means). Slightly turn RP2 pot in clockwise direction, no more whistling . So-called damping pot drift.

Now, I know why there is Service Bulletin # TFM-45-4. Should I carry out this modification?

I'd certainly realign the amp. You want your channels in balance. Turning any pot changes things.

Helpless, so studied service manual. Suspect whistling was due to damping of amplifier board (not sure what damping means). Slightly turn RP2 pot in clockwise direction, no more whistling . So-called damping pot drift.

Now, I know why there is Service Bulletin # TFM-45-4. Should I carry out this modification?

If you aren't comfortable or capable in doing the work yourself, you might want to send it to Bob & Rita's shop for a complete going over.

viewtopic.php?f=4&t=7093

It's been my experience that until that service bulletin mod is made for the 45, you will continue to have this damping adjustment issue (and will need to re-adjust it ~ every several months). I did mine; it is a little challenging what with the circut board traces being pretty fragile/thin. Make sure you get a 500 ohm (I believe - check!) pot (used to replace the "baseline" higher value pot) that has the exact same "footprint" as the one you are replacing (on both channels of course). Mine were not; I ended up having to run jumper wires from the new pots to where they go to the components (bypassing the circut traces and holes that did not align). But should be pretty easy if you have the right based pot (also need to add a resistor as well).

Wasn't this adjustment just adding a fixed resistor and a lower valued pot for the higher valued pot, or was there more to it than that?

Yes, that's all (to the "fix" to make it less sensitive to pot changes). The "adjustment" is to tweak this pot 'til 1 V across speaker terminals with 8 ohm load when 35.5 mv input signal @ 2000 hz is applied to amp. As I mentioned earlier, it appears like someone (Rolland?, most likely) did this "fix" to my/FrankieD's 42 by elimanting the pot altogether and replacing everthing with resistors (evidently valued s.t. you get the required 1 V at speaker terminals with 8 ohm load and with the required 2000 Hz input). This "fix" also appears to work just fine and I have had no "damping adjustment" issues with this 42. It sounds very perfect (and balanced)!

Yes, that's all (to the "fix" to make it less sensitive to pot changes). The "adjustment" is to tweak this pot 'til 1 V across speaker terminals with 8 ohm load when 35.5 mv input signal @ 2000 hz is applied to amp. As I mentioned earlier, it appears like someone (Rolland?, most likely) did this "fix" to my/FrankieD's 42 by elimanting the pot altogether and replacing everthing with resistors (evidently valued s.t. you get the required 1 V at speaker terminals with 8 ohm load and with the required 2000 Hz input). This "fix" also appears to work just fine and I have had no "damping adjustment" issues with this 42. It sounds very perfect (and balanced)!

I have got my 45's pots fix. But there is a big switch off/on thump on the right speaker.
When switching on, I can see that the speaker woofer bounce forth once rapidly. But when turning it off, the woofer bounce forth slowly, returning to original and then it's slowly sucking deep to rear position, finally returns to original position! What is happening!? Capacitor started fail to perform? Which one?

Please help me.

Hello,
I'd set all the voltage adjustments in the amp according to the service manual first.At least then you'll know that being out of adjustment is or isn't the problem.I've found this amp very sensitive to these adjustments,just a little off makes huge differences.I couldn't believe the change in sound after setting it up.It was like focusing a camera.
I know in my 45 there were a bunch of cold solder joints on the amp boards,mostly around the Bias pots,the pots them selves were dirty and needed a bit of contact cleaner.Both problems made the bias pot on 1 channel non functional,not allowing voltage across R95,R94.It caused a very funky distortion in the mids/highs at low volume,that dissapeared at higher volume.Just putting a screwdriver in the slot of the pot made bias voltage cut in and out,but when the screwdriver was removed I lost voltage across R94,R95 all together.I know you didn't mention a problem here but I just wanted to throw it out there,as I had this problem with mine.
Also I think there is a service bulletin in the service manual that adresses the thump your experiencing.I know my amp has the "thump correction" installed and doesn't make a peep out of the speakers (audible or inaudible)at power on or off.That mod I believe involves adding/removing components on the power supply board.Check and see if this fix was done to your amp.But like I mentioned I'd first set the voltages as the service manual instructs,The amp can't function correctly if not set correctly.
Good Luck!!!

Hi gunner64,
I am a layman but try to repair personally. I have only analogue multitester, the indicator move to left side not able to get -2.5v across R94 follow your method in viewtopic.php?f=4&t=11490&start=15
The rail voltage is set to about 118v anyway.

Please guide me. Thank you.

reverse the leads on your test if you need to read negative voltages

I could set idle current on left side on R94. But right side is dead no reading. I followed gunner64 way, re-solder the pot and re-check, but still obtain no reading. What's the problem?
My 45's internal looks like this: