Evening gentlemen, i have dilema.
Friend gave me preamp c-70, not working. Rather than take it apart for spare parts, i started working on it. To some success.
It needed cleaning, dust, rust and mold...
Good news, it has two independent mm and mc sections, lots of loading options, all working.
Headphones output section is working, so it can serve as head amp...plus it has the most over the top bass/treble section.
Not only you have pot for treble and bass, it has a turning frequency pot, and bandwith pot. I thought my sanyo plus preamp had this complicated, this one took it to next level. Off course this section can be bypassed.
Now the bad news. Line level output, which is independent of headphones output, has bunch of burned resitors at one channel.
Its a dc coupled output with complementary transistors. So far i identified A1145 pnp transistor definitely bad. Maybe others.
Here is my dilema. I do not have originals, not even suggested replacements, and even if i succeed fixing burnt channel, would not it result in slightly different sound? Is it worth the effort? I got it for free, i may likely only use it as phono preamp.
Or i could just tap onto headphone output, and be done with it. Granted, not as good as line level signal, but hey, do you know how complicated and stuffed this preamp is? And its their lower model.
I like repairing stuff, the challenge...but do not want to waste time.
Sorry for long post.
Friend gave me preamp c-70, not working. Rather than take it apart for spare parts, i started working on it. To some success.
It needed cleaning, dust, rust and mold...
Good news, it has two independent mm and mc sections, lots of loading options, all working.
Headphones output section is working, so it can serve as head amp...plus it has the most over the top bass/treble section.
Not only you have pot for treble and bass, it has a turning frequency pot, and bandwith pot. I thought my sanyo plus preamp had this complicated, this one took it to next level. Off course this section can be bypassed.
Now the bad news. Line level output, which is independent of headphones output, has bunch of burned resitors at one channel.
Its a dc coupled output with complementary transistors. So far i identified A1145 pnp transistor definitely bad. Maybe others.
Here is my dilema. I do not have originals, not even suggested replacements, and even if i succeed fixing burnt channel, would not it result in slightly different sound? Is it worth the effort? I got it for free, i may likely only use it as phono preamp.
Or i could just tap onto headphone output, and be done with it. Granted, not as good as line level signal, but hey, do you know how complicated and stuffed this preamp is? And its their lower model.
I like repairing stuff, the challenge...but do not want to waste time.
Sorry for long post.
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Not that anyone cares, being preamp junkie, i decided to rapair the preamp. Even ordered original toshiba transistors. Took only 10 days to arrive. I got these, look genuine.
10x 2SA1145-Y TOSHIBA Audio Frequency Transistor, A1145. 6921407465251 | eBay
10x 2SA1145-Y TOSHIBA Audio Frequency Transistor, A1145. 6921407465251 | eBay
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I replaced burned transistor, three resistors, and preamp came to life. Its been making sweet music for few hours, so the replaced transistor is ok with 30 volts per its side. No dc ofset. I believe those transistors are real.
Anyway, still lots to clean there, but its alive.
Its overengineered with too many relays in signal pass, i will likely bypass some.
Cheers everyone.
Anyway, still lots to clean there, but its alive.
Its overengineered with too many relays in signal pass, i will likely bypass some.
Cheers everyone.
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