TFM-45 Bias,offset,damping adjustment procedure

Not the way I did mine...

Well, help out here, Ed. I'm flying blind to help this guy adjust the bias. You've got one of these fuckers. Get your head into this.

Sorry guys!I didn't mean to get a shit storm started.Bill I did p.m. Ed earlier and he did give me his input also.My fault for posting in addition to the P.M..But thanks ,I appreciate all the input from both of you. I'm not sure I'm clear on Your method either Ed.From what You told me I should test 1 lead of either R94,or R95,relative to Ground?OR test both leads of either R94,or R95 .One would think test points would be clearly marked in the service manual like every other piece of equipment I own service manuals.My first crack at it I assumed the way Bill has suggested was the proper way,but failed to get a proper reading.I'm sorry guys,I'm sure you all know how frustrating it is to have an amp such as this that just needs a little tweak to be perfect,and it fights you all the way.I'm sure it'll be figured out.I still can't believe something so simple has me so flustered.I apologize if I started any hard feelings,my only intentions were to get this operating A-1.(goddamned newbie)Buy the way I see A TFM-45 is bid up to $600 on ebay.Yikes!
Again, thanks for the time and input from everybody,I appreciate it.
Robert

O.K. I finally figured out why I couldn't get a reading Across R94 or R95(top and bottom leads of 1 resistor or the other,ED you were right).Before I powered the amp up again I reflowed the solder joints that looked dull and suspect.The joints on the Bias pots looked very suspect,so I added a bit of solder to these connections.I also used a bit of deoxit on the pots as well.I fired the amp up,and finally,after all the frustration and driving the people who were trying to help nuts,I got a steady reading!In my opinoin I think it was bad connections to the board at the pots rather than the deoxit,but I'm sure the deoxit didn't hurt either.Bias was set at 1.7mv,on 1 side,2.0 the other.I set it to 2.5mv on both boards without a hitch,it holds steady 2.5mv bias with no fluctuation.Rail voltage was a bit high,adjusted to 118v.The damping was off by quite a bit,it was at about .600v on 1 channel and .700v on the other.I set it to 1v on both channels.Perfect.
I put everything back together,hooked it back up and What was it you were qouted as saying Ed? OMFG!!!!!!!!! I believe it was.I'll add a Holy shit to that-absolutely incredible!The fuzzyness in the mids/highs that promted this "whitchhunt" is gone,totally.The amp has much more clean (very clean)usable power,and much more "drive" at lower volumes.I thought it sounded good before,but wow talk about opening things up! I'm gonna keep an eye on and check these settings often,when they're off it really makes a gigatic difference.It was way worth the effort.Now I need another!!
Thank you, thank you ,thank you, guys for all the help.Now I have to figure out how to keep the neighbors from calling the cops!
Robert

Great Robert. Glad to hear you got everything properly adjusted. Your reaction to having everything in spec for this amp 100% mirrors mine. I think the "deteriation" in sound (unique to this amp) is mostly due to the damping adjustment being off...it really kills the sound of this great amp if it not "on". Hence the SB "fix" initiated by Carver to remedy all this....

Now I have to figure out how to keep the neighbors from calling the cops!
Robert

That's easy; you throw a party & invite them all over!

Congrats on your success~

My one neighbor's a 6'7" Deputy Sherriff Who apparently doesn't like Clapton's "from The Cradle"C.D.,Or the Way I play it so I'd rather not!(Yea I'm Kinda F#%$k'd,I got one in the neighborhood,right across the street-and a great big sucker at that!)
Thanks for the encouragement.
Robert

Bias was set at 1.7mv,on 1 side,2.0 the other.I set it to 2.5mv on both boards without a hitch,it holds steady 2.5mv bias with no fluctuation.Rail voltage was a bit high,adjusted to 118v.The damping was off by quite a bit,it was at about .600v on 1 channel and .700v on the other.I set it to 1v on both channels.Perfect.

I would like to do both mine also...
could you take pics??????

please please please

got the manual, but as they say, "a picture is worth a thousand words".......


mbskeam

I have to Do a little work on my CT-17 tomorrow and I'll have My 45 unhooked,So I think I could pop the cover and Give a little "how to" pictorial.I wouldn't want anyone to be as frustrated as I was!Albiet My 45 had a problem that hindered proper testing.After I fixed my bad solder joints it was a very easy adjustment.Bias and Rail voltage were a snap.The dampening adjustment was a snap also,Just a bit more involved,needing a signal at the proper frequency/voltage be fed into the inputs,and an 8ohm dummy load.I'd be glad to help.If your amps have not been serviced for a while you will not believe the improvement after you set them up.I'm listening to 1 TFM-45 through amazing silvers,and the realism is just flat out breathtaking.-and powerful.In my experience very few amps can be both at the same time.(and the ALs still blow my mind)I've been listening to and Rebuilding tube amps/preamps for years and I love the sound of tubes.The TFM-45 sounds more like a tube amp than any solid state amp I've personally ever heard,Even my Mcintosh sucks in comparison.I believe the "dampening"circuit in the 45 is the reason.but it seems when this adjustment is off,it maybe only by a little,it really muds up the sound and destroys the headroom.I about shit the first time I fired it up after the service,couldn't believe it.
Robert

that would be most cool.....

I can fumble my way thru most things...
but I don't want to let the smoke out thats trapped in the parts.....

I don't need the tv experience that I had, "I think I can fix this, it don't look to hard"....
needless to say I bought a new tv. my it RIP...LOL

mbskeam

ps:
if anybody needs info on old Harleys I can do that real good.....

"I about shit the first time I fired it up after the service;couldn't believe it."

Me too!

That why I keep beating this drum whenever any "new" 45 owner pops up here! It's like "ok, Ed we get it!". But as Gunner has confirmed, it's NOT a subtle improvement! And yes, Gunner, the 45 probably DOES have the most "dose" of "tube likeness" of any non-tube Carver amp (Bob himself has confirmed this, I do believe); and this damping adjustment could be the "gate" that opens up that great sound!

Beat that drum Ed,I'll be there with you as Its way more than a subtle improvement.After I read your reply about the "tubeyness"of the 45, I searched around and did find some info backing up your comment about Mr. Carver's confirmation of the "Tubeyness"(silly looking word,fun to type).One of his favorite amplifiers so it seems.Given my fondness for tubes I guess the right amp found the right guy.especially this one,that has most all the updates done.Again thanks for the help,Had I not read your posts I wouldn't have been so quick service mine.
Robert

O.K. Here's what I did in Setting up The TFM-45.Keep in mind I assume no responsibility for Damage to your amplifier or yourself.If you do not know how to safely work inside equipment while powered up,DO NOT ATTEMPT!!!!!!Better off to spend a few hundred bucks and have someone who knows what the're doing in there work on it than risk damaging yourself or your amplifier.I'm not directing this warning to any one specific person,just a general safety concern.

1.Set Rail voltage to 118v [attachment=3]DSC00382.JPG[/attachment]at large red wire on P.S. board,referenced to ground.adjust RP2 on same board.

2.Set Bias to 2.5mv across 5w resistor R94(1 lead of meter on one side of R94 1 lead of meter on the other side of R94)On 1 amplifier board.Repeat for other board.

3.Set Damping.Attach an 8 ohm dummy load to both outputs.I used 2, 20w 8 ohm resistors from radio shack.The amp will be only outputting 1v,so the 20watters will be o.k. for this adjustment.Insert a 2khz 36mv signal to the inputs of the amplifier.Use the signal generator from Higherfi.com and your preamp to get the proper signal if you don't have a dedicated signal generator.Once I got a 2khz signal I adjusted the volume on the preamp for 36mv at the pre-outs.Adjust RP2 on each amp board until you get 1v across the 8ohm load resistor at each output.Keep in mind your pots here may look dif. than mine,as mine have been replaced per damping drift fix at back of service manual.Sorry about the Huge pics!!!I was in the process of figuring out how exactly to post them proper and accidently hit the "submit" button.If anyone has some advice on how to do this,please inlighten me!(I'm just shy of computer illiterate)Robert[attachment=4]DSC00376.JPG[/attachment][attachment=4]DSC00376.JPG[/attachment][attachment=2]DSC00385.JPG[/attachment][attachment=1]DSC00389.JPG[/attachment][attachment=0]DSC00392.JPG[/attachment][album][/album][album][/album][album][/album][attachment=0]DSC00392.JPG[/attachment]

"Insert a 2khz 36v signal to the inputs of the amplifier"

One minor (and pretty obvious typo) correction: should say "Insert a 2khz 36mv signal to the inputs of the amplifier"

Thanks for seeing that!You are correct,Mv is what I meant!The correction has been made.Again sorry for the trainwreck of a post,Just trying to help.I'll figure this pic. posting thing out if it kills me.(like I said,I'm just north of computer illiterate,and not by much!)Robert