Hi,
My amp got stolen (CMI Bass Lead 100😡) and a friend of mine gave me the Fender FM212r that he had stored for years without working.
I check it out and I realize that one of the power transistors, Q20, was shorted. Thinking that could be the effect and not the cause of the problem, I checked the circuit further and I pull out some other transistors that could cause problems (Q6, Q7, Q11, Q12, Q13, Q15, Q18, Q19 and Q21)and I found that one of the bias transistors, Q14, has some leakage and also the Q12.
Is not that easy to find this transistors here in France, so, does anyone knows some alternatives by heart before I start comparing datasheets?
I also want to replace the correspondent pair of the defected transistors. So I'm looking for alternatives for the 2SC3263, 2SA1294, 2SD1857, 2SB1236, 2SA103 and for the 2SC2383.
When I open the amp I realize that the components are really bad quality. For example, for the input and tone they used the TL072 op amp, I guess it's not that bad. But for the the preamp they use the BA4580 which is a very noisy op amp. Do you think if I replace them with less noise op amps it will get a little better?
Do you think if I recap with better quality caps the power supply, the input section, the pre amp, clean channel, power amp section and output, would I get better results? The filter caps on the power supply are Nichicon's, but all others are low quality.
I know that I don´t know the sound of this amp and it will be better to fix it first and then do some changes. But I just want to hear what you guy's have to say.
I only use the clean channel, all the effects come from pedals.
Thanks in advance,
Bru
My amp got stolen (CMI Bass Lead 100😡) and a friend of mine gave me the Fender FM212r that he had stored for years without working.
I check it out and I realize that one of the power transistors, Q20, was shorted. Thinking that could be the effect and not the cause of the problem, I checked the circuit further and I pull out some other transistors that could cause problems (Q6, Q7, Q11, Q12, Q13, Q15, Q18, Q19 and Q21)and I found that one of the bias transistors, Q14, has some leakage and also the Q12.
Is not that easy to find this transistors here in France, so, does anyone knows some alternatives by heart before I start comparing datasheets?
I also want to replace the correspondent pair of the defected transistors. So I'm looking for alternatives for the 2SC3263, 2SA1294, 2SD1857, 2SB1236, 2SA103 and for the 2SC2383.
When I open the amp I realize that the components are really bad quality. For example, for the input and tone they used the TL072 op amp, I guess it's not that bad. But for the the preamp they use the BA4580 which is a very noisy op amp. Do you think if I replace them with less noise op amps it will get a little better?
Do you think if I recap with better quality caps the power supply, the input section, the pre amp, clean channel, power amp section and output, would I get better results? The filter caps on the power supply are Nichicon's, but all others are low quality.
I know that I don´t know the sound of this amp and it will be better to fix it first and then do some changes. But I just want to hear what you guy's have to say.
I only use the clean channel, all the effects come from pedals.
Thanks in advance,
Bru
All transistors are available from Mouser or RS or Farnell Element 14 etc.
TL072 is a good op amp! Don't waste your time replacing them. The 4580 is a good op amp as well.
Only replace the faulty semiconductors otherwise you will be in trouble with unexplained fault conditions.
Your 2SA103 is actually a 2SA1013 (Q12).
TL072 is a good op amp! Don't waste your time replacing them. The 4580 is a good op amp as well.
Only replace the faulty semiconductors otherwise you will be in trouble with unexplained fault conditions.
Your 2SA103 is actually a 2SA1013 (Q12).
First, thanks for your answer.
I've miss spell the 2SA1013.
Before I a made this thread I've checked Mouser, Farnell and RS. Of all the above mentioned transistors I could only find the 2S3263 at Farnell and the 2SC2383 at Mouser. That's why I asked for alternatives.
I agree with you, the TL072 its a good op amp, I use it in modules for analogue synths. But the BA4580 I think it is to noisy.
Like I said, I'll only use the clean channel, so the op amps that matters are the U1, U6 (the two TL072) and U5.
I've miss spell the 2SA1013.
Before I a made this thread I've checked Mouser, Farnell and RS. Of all the above mentioned transistors I could only find the 2S3263 at Farnell and the 2SC2383 at Mouser. That's why I asked for alternatives.
I agree with you, the TL072 its a good op amp, I use it in modules for analogue synths. But the BA4580 I think it is to noisy.
Like I said, I'll only use the clean channel, so the op amps that matters are the U1, U6 (the two TL072) and U5.
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No, you're right, it's not. I don't know why, but for years had this belief that it was without rechecking the datasheet. My mistake,. Thanks for the notice!
As for the transistors, I found this store Dönberg Electronique - Composants électroniques et équipements who has them.
And don't know if the amp have another problems, I'll change the faulty transistors and see what happens.
If I get noise after I think I'll first pull out Q4, C11, U4 and R60, to completly isolate the clean circuit,. If it works I won't be losing more time with it because I only use the clean channel.
Thank you all for your answers, I'll post again with results.
As for the transistors, I found this store Dönberg Electronique - Composants électroniques et équipements who has them.
And don't know if the amp have another problems, I'll change the faulty transistors and see what happens.
If I get noise after I think I'll first pull out Q4, C11, U4 and R60, to completly isolate the clean circuit,. If it works I won't be losing more time with it because I only use the clean channel.
Thank you all for your answers, I'll post again with results.
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