One thing I would do is to disconnect the power supply, if it is possible... replace fuses and see if it can run witout anything connected... It would be a good time to measure some voltages.. a cheap multimeter will do... also google how to do a diode test on transistors...
Now for the part that will save you hours of head scratching, remove transistors one by one, do diode test, resolder if good, mark transistor as tested, do next one...
Now for the part that will save you hours of head scratching, remove transistors one by one, do diode test, resolder if good, mark transistor as tested, do next one...
I removed all the transistors and did a diode test and found one 2sc3902 and one 2sd1047 blown. I'm still waiting for the parts to arrive.
I noticed there are three opamp in the machine, 2 opa2134pa and 1 opa2604ap. Will it work if I change them to LM4562 or will there be any sound difference? How about changing the capacitors to black gates? Or any suggestion on how to modify this amp?
Thanks,
Kevin
I noticed there are three opamp in the machine, 2 opa2134pa and 1 opa2604ap. Will it work if I change them to LM4562 or will there be any sound difference? How about changing the capacitors to black gates? Or any suggestion on how to modify this amp?
Thanks,
Kevin
Hi Kchu
Good that you now know which transistors are blown, replace only those ones together with their complementary, that is if the transistors you purchased are complementary.
Big gains can be had from rotels in upgrading the preamp. Those ICS are what destroys the sound of these amps competing against some of the best here. I personaly have bypassed the preamp on my old 972 and and with a change of compensation this amp can kick a lot of *** compared to some very expensive gear and diy designs here, and at very low cost. But having a preamp is sometimes a practical thing, depends on how you wanna use the amp.
Let me get schematic then ill tell you a little more. But yes a change to better opamps will improve sound but youll have to spend quite a bit more to get better ICs. Those Ics are good mid to low hifi chips, ive heard good things about lm4562 maybe they are better and can be drop in replacements. Ive used ad826, ad 827 ad828 with very good results but these cost about 3 times more than the regular opamp.
What no blackgates, in your Amp?????, mine which is a 12 year old model only have blackgates, Maybe they only used them in certain critical positions like for decoupling inputs.
Im talking out of my head, let me download the schematics and have a look.
Alex
Good that you now know which transistors are blown, replace only those ones together with their complementary, that is if the transistors you purchased are complementary.
Big gains can be had from rotels in upgrading the preamp. Those ICS are what destroys the sound of these amps competing against some of the best here. I personaly have bypassed the preamp on my old 972 and and with a change of compensation this amp can kick a lot of *** compared to some very expensive gear and diy designs here, and at very low cost. But having a preamp is sometimes a practical thing, depends on how you wanna use the amp.
Let me get schematic then ill tell you a little more. But yes a change to better opamps will improve sound but youll have to spend quite a bit more to get better ICs. Those Ics are good mid to low hifi chips, ive heard good things about lm4562 maybe they are better and can be drop in replacements. Ive used ad826, ad 827 ad828 with very good results but these cost about 3 times more than the regular opamp.
What no blackgates, in your Amp?????, mine which is a 12 year old model only have blackgates, Maybe they only used them in certain critical positions like for decoupling inputs.
Im talking out of my head, let me download the schematics and have a look.
Alex
The Ics you mentioned, are the preamp section, they use opa2604 and opa2134. These are mid to low fi quality opams, but its difficult to tell you what to use as diffrent people have diffrent tastes and opamps sound very diffirent. Ive recently tried a discrete opamp from PMA in the threads here which i very much like the sound of, but you need to have electronic knowhow to make such a conversion.
So i suggest you try the lm4562, ad826 ad825 and i can give you a very long list of good audio opamps if you want to try.
The lm4562 is cheap so i suggest you try that first, i dont know what they sound like but some here say they are very good, i prefer discrete opamps. I ve used ad826 with good effect which is a very lively sounding opamp but i like rock music which suits it.
On the amp side check if capacitors c614 c616 and c606 and c604
are of the polistyrene type. Earlier models were and these are critical to good sound.
Ill have another look at your pics to see what components used as there are gains to be had in upgrading some of these.
Are black gates used in position c601 and c607????
Alex
So i suggest you try the lm4562, ad826 ad825 and i can give you a very long list of good audio opamps if you want to try.
The lm4562 is cheap so i suggest you try that first, i dont know what they sound like but some here say they are very good, i prefer discrete opamps. I ve used ad826 with good effect which is a very lively sounding opamp but i like rock music which suits it.
On the amp side check if capacitors c614 c616 and c606 and c604
are of the polistyrene type. Earlier models were and these are critical to good sound.
Ill have another look at your pics to see what components used as there are gains to be had in upgrading some of these.
Are black gates used in position c601 and c607????
Alex
Hi Alex,
The C614, C616, C606, and C604 are polystylene capacitors. What do you recommand to change them to?
Some of the electrolytic caps are TK and some are Rubycon. C601 and C607 are Rubycons. BTW, what are the two cards beside the two big caps are for? C601 and C607 are on one of the card. Will changing these caps to Black Gates NX benefit. What about changing the electrolytic caps in the opamp area?
Does Rubycon=Black Gates?
Thanks,
Kevin
The C614, C616, C606, and C604 are polystylene capacitors. What do you recommand to change them to?
Some of the electrolytic caps are TK and some are Rubycon. C601 and C607 are Rubycons. BTW, what are the two cards beside the two big caps are for? C601 and C607 are on one of the card. Will changing these caps to Black Gates NX benefit. What about changing the electrolytic caps in the opamp area?
Does Rubycon=Black Gates?
Thanks,
Kevin
I was just checking if quality has been kept the same, dont change them, better quality only if you change to teflon caps and these are extremely expensive.
Rubycon are the manufacturers of the black gates, however they do also make other caps which are not blackgates. Have a look on those caps whether they specifically say blackgate, on the net theres plenty of pics. Usually Rotel used the standard and C version of these caps *black with gold writing on it* which are very good already, although they claim nx to be better, cant help you there i have not tried. Maybe there is some gains to be had with nx but not that much. C611 should also use a blackgate. This is what i meant by those amps being very well built with some of the best components.
On each one of those cards is the diffrencial and the vas section of the amp. If you look on schematic its the first block on the amp section and its marked as X-1294003 and x-1294002
Rubycon are the manufacturers of the black gates, however they do also make other caps which are not blackgates. Have a look on those caps whether they specifically say blackgate, on the net theres plenty of pics. Usually Rotel used the standard and C version of these caps *black with gold writing on it* which are very good already, although they claim nx to be better, cant help you there i have not tried. Maybe there is some gains to be had with nx but not that much. C611 should also use a blackgate. This is what i meant by those amps being very well built with some of the best components.
On each one of those cards is the diffrencial and the vas section of the amp. If you look on schematic its the first block on the amp section and its marked as X-1294003 and x-1294002
Changing those will then make a difference, i will look at schematic and let you know the most crucial positions. They can be purchased from here
http://www.acoustic-dimension.com/blackgate/bgmain.htm
Alex
http://www.acoustic-dimension.com/blackgate/bgmain.htm
Alex
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