He he, I always have a dozen or so in various states of repair. To that add in a few motorcycles and a car or 2 as well.
It was way more chaotic when we had an offer on our house and they were wanting this and that ... now that that is past and we're not moving cos the sale fell through, I am going to dedicate more time and energy into it.
Not to mention I opened a few altec drivers and managed to put em back together and have most of my finger skin intact and they made sound ... if its working - it will be messed with, if its not working, it'll be messed with.
Cool.
Srinath.
It was way more chaotic when we had an offer on our house and they were wanting this and that ... now that that is past and we're not moving cos the sale fell through, I am going to dedicate more time and energy into it.
Not to mention I opened a few altec drivers and managed to put em back together and have most of my finger skin intact and they made sound ... if its working - it will be messed with, if its not working, it'll be messed with.
Cool.
Srinath.
I'm sure you've heard the saying "If it ain't broke don't fix it", the other version of this saying is "If it ain't broke I haven't worked on it yet". 
I too have a ton of projects in the works, usually by the time I get them they've been "messed with" so I usually strip them to the bare chassis and start over. I have shelves full of stuff, GAS, SUMO, Luxman, Dynaco, Heathkit. But since my everyday job is repairing old crap I just don't feel like working on my own crap.
Craig
I too have a ton of projects in the works, usually by the time I get them they've been "messed with" so I usually strip them to the bare chassis and start over. I have shelves full of stuff, GAS, SUMO, Luxman, Dynaco, Heathkit. But since my everyday job is repairing old crap I just don't feel like working on my own crap.
Craig
This amp was marginal but on the right side of the line between dead and working. But now that I modded it, it crossed that line, and seems to keep going.
OK so now that I have looked @ Q112 that sparked and it tested bad and more - left side - R135 and R153 were burnt.
It also had C505 top touch one of the legs of D409.
Still looking ... they feed Q107 - that was on the upgrade list - I may have it dead, might as well replace all the usual suspects list before putting juice to this I think.
Cool.
Srinath.
OK so now that I have looked @ Q112 that sparked and it tested bad and more - left side - R135 and R153 were burnt.
It also had C505 top touch one of the legs of D409.
Still looking ... they feed Q107 - that was on the upgrade list - I may have it dead, might as well replace all the usual suspects list before putting juice to this I think.
Cool.
Srinath.
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The Carvers with the Mag power supplies are a challenge in three ways. First the power supply is different and not "plug and play" if it's bad. Second is the power supply is tiered, more circuitry than a normal amp. Lastly and the biggest PITA is the mechanical layout, not very service friendly at all. The Carver cube is a real PITA. Once you understand the circuitry #3 is still in the way.
Every time I get one with TO-3 output and commutator transistors it's almost guaranteed some, if not all, of the commutator transistors will be bad. The real challenge is if you don't have the correct test equipment. The xsistors will test fine with a DMM on diode test but on an analyzer they are dead, won't do anything.
I got lost following your repair and haven't chimed in. Mooly should get you through it.
Craig
Every time I get one with TO-3 output and commutator transistors it's almost guaranteed some, if not all, of the commutator transistors will be bad. The real challenge is if you don't have the correct test equipment. The xsistors will test fine with a DMM on diode test but on an analyzer they are dead, won't do anything.
I got lost following your repair and haven't chimed in. Mooly should get you through it.
Craig
OK I have those Q125 and 126 a plenty. These are supposedly known trouble makers.
I also have replacement upgrades for 107, 108, 109 110, 117, 118, 119, 120.
However I dont have Q111 and Q112.
I believe these are to shut the amp down in case of thermal runaway.
Would I blow up more stuff if I powered up the amp without the Q112 in - Its bad, Q111 is OK.
Thanks.
Srinath.
I also have replacement upgrades for 107, 108, 109 110, 117, 118, 119, 120.
However I dont have Q111 and Q112.
I believe these are to shut the amp down in case of thermal runaway.
Would I blow up more stuff if I powered up the amp without the Q112 in - Its bad, Q111 is OK.
Thanks.
Srinath.
Q112 can be shorted out between C and E. On a working amp, doing that would reduce the output stage current to zero. It would all work as normal but with a little crossover distortion.
(Remember I mentioned the other day that I would make the amp "safe" to work on and part of that was by shorting Q112)
(Remember I mentioned the other day that I would make the amp "safe" to work on and part of that was by shorting Q112
)OK Q112 can be shorted. So the amp works like its in "overheated" mode -
My Q112 tested as bad in my transistor tester. I cant even tell which is C, B or E - its saying "bad component" - Need to check the pinout diagrams for it.
I have done so much crap to this amp I'm barely remembering what happened. Which is why I use this as thread my reference.
Anyway for now I need R135 and R153 (both of which I dont have) and all the other little transistors which I do have.
I have googled it - and found very little relevant info.
What is a "Common mode condution prevention" transistor.
This amp uses Q125 and 126 - 2sc2240 - as those. But it also uses those in the preamp board (which is why I ordered it and have some extra + the ones out of the preamp board which test good).
Thanks.
Srinath.
My Q112 tested as bad in my transistor tester. I cant even tell which is C, B or E - its saying "bad component" - Need to check the pinout diagrams for it.
I have done so much crap to this amp I'm barely remembering what happened. Which is why I use this as thread my reference.
Anyway for now I need R135 and R153 (both of which I dont have) and all the other little transistors which I do have.
I have googled it - and found very little relevant info.
What is a "Common mode condution prevention" transistor.
This amp uses Q125 and 126 - 2sc2240 - as those. But it also uses those in the preamp board (which is why I ordered it and have some extra + the ones out of the preamp board which test good).
Thanks.
Srinath.
Q112 is essentially just a vbe multiplier seen in any amp. I'm really surprised the transistor is faulty tbh, there is not much fault wise that could see it off (other than shorts or mishaps like that).
Q126, I'd spotted those earlier but not really given them any thought. Never seen anything quite like that tbh, and how effective they are I wouldn't like to say. It looks like they take the place of conventional resistors across B and E of the outputs (which do the same job, reducing cross conduction and speed up the turn off of the output transistors. Cross conduction is when both output transistors "linger" in an on state following what should be a rapid turn off (say when squarewave testing or at high frequencies) and the result is both pass substantial current causing heating and a reduction in efficiency.
Q126, I'd spotted those earlier but not really given them any thought. Never seen anything quite like that tbh, and how effective they are I wouldn't like to say. It looks like they take the place of conventional resistors across B and E of the outputs (which do the same job, reducing cross conduction and speed up the turn off of the output transistors. Cross conduction is when both output transistors "linger" in an on state following what should be a rapid turn off (say when squarewave testing or at high frequencies) and the result is both pass substantial current causing heating and a reduction in efficiency.
OK I tested all the power transistors.
Q127 and 129 tested bad, like a pair of resistors and as a capacitor. Both are left side.
Q125 and 126 both test good.
I am still looking for bad resistors and everything else, I'll do all the usual suspects and then worry about powering it up.
Cool.
Srinath.
Q127 and 129 tested bad, like a pair of resistors and as a capacitor. Both are left side.
Q125 and 126 both test good.
I am still looking for bad resistors and everything else, I'll do all the usual suspects and then worry about powering it up.
Cool.
Srinath.
I'm using this one -
Graphical Transistor Tester Capacitor ESR Inductance Resistor LCR Meter NPN PNP | eBay
In fact its showing hFe and Vf on the graphic they have on it now. What is that Vf ? I am not really sure looking at the pin outs of the transistor on google.
This one my favorite yet, I've tried 3 of em so far, the first one died when I did an in circuit test of something and that may have had a cap in the circuit, that discharged and killed the tester. The second one I screwed up soldering the first one's leads to and it wasn't a very good fit.
On this I have leads I modified from the first one, but I clip it on and test it and I remove transistors electrically from the circuit, but dont have to get em out.
This one when you test something that has capacitance like this dead Q127 it goes into a self test mode - which I think means its got some type of protection circuit.
Cool.
Srinath.
Graphical Transistor Tester Capacitor ESR Inductance Resistor LCR Meter NPN PNP | eBay
In fact its showing hFe and Vf on the graphic they have on it now. What is that Vf ? I am not really sure looking at the pin outs of the transistor on google.
This one my favorite yet, I've tried 3 of em so far, the first one died when I did an in circuit test of something and that may have had a cap in the circuit, that discharged and killed the tester. The second one I screwed up soldering the first one's leads to and it wasn't a very good fit.
On this I have leads I modified from the first one, but I clip it on and test it and I remove transistors electrically from the circuit, but dont have to get em out.
This one when you test something that has capacitance like this dead Q127 it goes into a self test mode - which I think means its got some type of protection circuit.
Cool.
Srinath.
Everyone of the transistors I am suspecting are either in usual suspects in the trouble shooting document, or scheduled to be tossed in the upgrade I embarked upon.
They say start with a working amp, trying to repair this amp via an upgrade is hard.
I'd say - start with a working amp, and by the time you do the first step of the upgrade it will be dead, then continue the upgrade and it will work again.
I hope.
Cool.
Srinath.
They say start with a working amp, trying to repair this amp via an upgrade is hard.
I'd say - start with a working amp, and by the time you do the first step of the upgrade it will be dead, then continue the upgrade and it will work again.
I hope.
Cool.
Srinath.
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