Ron's Carv M1.5T Recap

[jbeckva]

Thanks for the info, Ron. We'll know more when the new caps come in today and I'm able to get back to it.

 

[Northwinds]

Thanks Jer, just trying to help track down whatever lead I can to make your job a little easier. I am glad that at least he hears it also with the same amp!

 

[jbeckva]

Hmm...

So the new ones are 5900's, up from 4800's. Also I adjusted the 122vdc up from 111 volts. Listening ... seems a little strained on the vocals. Gotta check the bias.

Maybe we'll stick with the originals...but I hate that 8708L datecode on 'em!

Will give it a real good shakedown this weekend and see what's on the scope with the sig gen.

 

[laatsch55]

Ron, that post from the AK'er sounds like he knows his shit....

 

[Northwinds]

Ron, that post from the AK'er sounds like he knows his shit....

He does seem pretty knowledgeable. He says he is working for the only repair shop that was "blessed" by Bob Carver whatever that means???

This mental image came to me when he said that... I could see Bob doing the sign of the magnetic cross outside the shop to great fanfare complete with a choir of triac angels

 

[laatsch55]

That's some funny shit right there...

 

[Northwinds]

Jer, did you get those D9's thumping lastnight with the old biggun's?

 

[jbeckva]

Jer, did you get those D9's thumping lastnight with the old biggun's?

Getting ready to swap 'em now...

 

[jbeckva]

Joe I sent ya the manual. Bias adj you would think be straight forward, but I can't believe the current read is 0v... are they saying have the signal applied above it, and that is what I need to do first?

 

[Gepetto]

Joe I sent ya the manual. Bias adj you would think be straight forward, but I can't believe the current read is 0v... are they saying have the signal applied above it, and that is what I need to do first?

What bias adjust Jer? This amp does not have one. Also does not have a THD rating. Not surprised.

 

[laatsch55]

OH????? Jer, do you have a distortion instrument?? May have to reroute that bugger to AP-ville on the way to Ron.

 

[Gepetto]

OH????? Jer, do you have a distortion instrument?? May have to reroute that bugger to AP-ville on the way to Ron.

You can't fix what was designed in Lee

 

[Northwinds]

What bias adjust Jer? This amp does not have one. Also does not have a THD rating. Not surprised.

Joe, if there is no THD rating, what is the rating they give mean??? (IM Distortion 0.15% SMPTE)

I'm starting to get a queasy feeling in my stomach, like I made a huge mistake and traded my rarest Beatles lps away for a pile of junk

 

[laatsch55]

You can't fix what was designed in Lee

I'm aware of that Joe. i was thinking a few hours on the analyzer and most of these questions will be answered...



Ron, if it was a pile of crap Jer would have heard that. He hasn't, he said it's very close to WOPL sounding, cool your jets, you're ok.

 

[Gepetto]

Joe I sent ya the manual. Bias adj you would think be straight forward, but I can't believe the current read is 0v... are they saying have the signal applied above it, and that is what I need to do first?

Jer you set the idle current on this amp. Adjust RP1 so that you achieve 4mV measured across R87 which is near the output stages of the amp, should be a large 5W cement resistor.

 

[orange]

Joe, if there is no THD rating, what is the rating they give mean??? (IM Distortion 0.15% SMPTE)

I'm starting to get a queasy feeling in my stomach, like I made a huge mistake and traded my rarest Beatles lps away for a pile of junk

IM-Intermodulation (crosstalk is another way to think of it)

0.15%- Pretty low

SMPTE-Society of Motion Picture and Television Engineers, a film and television standards and practices membership organization, one of the most prominent.

In reality, there is always some form of harmonic distortion inherent in a reproduced signal but overall (Total Harmonic Distortion) it can be reduced so as to be imperceptable to the listener. The less that it crosses over into the other channel(s) the better as it would be obvious that IM would introduce unwanted harmonics into the adjacent channel and therefore add to THD.

 

[laatsch55]

Steven, IM distortion has bnothing to do with crosstalk, but I understand your reference to it. IM distortion, as Joe said the other day reflects an amps ability to keep up with a change in frequency. A standard IM test conforms to the DIN and SMPTE standards. The standard call for a low frequency tone to be mixed with a high frequency tone at a 4:1amplitude ratio. The signal is then sent through the device under test. Next the low frequency tone is filtered out and the high frequency tone is sent through an AM demodulator. After bandwidth-limiting to 700HZ, the de-modulated signal is measured.This is IM.It is measured as a percentage or db difference between the amplitudes of the high frequency tone and the demodulated remainder..

 

[jbeckva]

Jer you set the idle current on this amp. Adjust RP1 so that you achieve 4mV measured across R87 which is near the output stages of the amp, should be a large 5W cement resistor.

That's what I did, it measured around 0 even before adjustment. But further above that step it states to drive the amp to 1 vRMS. Not sure if that should be applied while adjusting the bias.

 

[Gepetto]

That's what I did, it measured around 0 even before adjustment. But further above that step it states to drive the amp to 1 vRMS. Not sure if that should be applied while adjusting the bias.

No, at full idle Jer. No input. 4 mV is pretty close to zero so check your meter scale.

 

[jbeckva]

Well HMMM... so I put the old caps back in, adjusted everything.. now it can't handle any current past barely a watt... shit.

Going to be getting one of these for myself next week, early. I want one to compare with...