troubleshooting a Yamaha A-1000

bryblob

Super Member
I have had this integrated amp for a while now and I finally decided to try and fix this. My friend was the previous owner, he said it worked great then one day there was no ouput. All lights turn on, just no output. I got some information from another member here about testing transistors. I desoldered all transistors, pulled the heatsink out and found a few faulty transistors. Also one of the pre-driver transistors tested bad. I found a source for the few transistors I need, they are toshiba 2SC3370 and 2SA1333. The pre-driver that I need is a C3298A, does anyone know where I could find this?:scratch2:
 
you will do better searching for 2sc3298a ..my supplier has them listed but would be too much shipping to you .
 
i am never sure what the other numbers mean ..sometimes its the date and other times its the gain etc .sometimes both . if you look up the data sheets for both you should see the difference .. i have never had a problem ignoring the other numbers .but that's just my experience .
hopefully someone with more info will chirp in .
 
well, I got them today. I took out 2 transistors on one heatsink, and installed the new ones. I got the same ones just on the opposite heatsink out and they don't have the mica insulators mcdeals. Do I need these or can I go ahead and install them without?
 
well, I got them today. I took out 2 transistors on one heatsink, and installed the new ones. I got the same ones just on the opposite heatsink out and they don't have the mica insulators mcdeals. Do I need these or can I go ahead and install them without?

If the new transistors have a plastic backing you don't need them. If they have a metal backing you do need them..
They should be full pack packaged TO -220,s with plastic backs.
 
ok, I guess the mica insulator just didn't come out with the transistor like the other ones, it was stuck to the heatsink instead. I got them all soldered in and everything back together. Powered on and still the same, relay doesn't want to click. Hmm I guess I have further testing but don't what or how...
 
Usually when transistors go south.They tend to take out resistors as well.
 
I have had this integrated amp for a while now and I finally decided to try and fix this. My friend was the previous owner, he said it worked great then one day there was no ouput. All lights turn on, just no output. I got some information from another member here about testing transistors. I desoldered all transistors, pulled the heatsink out and found a few faulty transistors. Also one of the pre-driver transistors tested bad. I found a source for the few transistors I need, they are toshiba 2SC3370 and 2SA1333. The pre-driver that I need is a C3298A, does anyone know where I could find this?:scratch2:

Please list all components you originally found toasted. Just component reference designators.. ie TRxxx,Rxxx Cxxx or Qxxx...:yes:
 
Please list all components you originally found toasted. Just component reference designators.. ie TRxxx,Rxxx Cxxx or Qxxx...:yes:

so far:

(1) 2SA1333
(1) 2sc3370
(1) C3298A

I will do some testing on resistors this weekend, thanks avionic.
 
so far:

(1) 2SA1333
(1) 2sc3370
(1) C3298A

I will do some testing on resistors this weekend, thanks avionic.
Circiut identifiers? ie. example TR401 or Q401
All shorted..
E-C ?
B-C ?
B-E ?
 
I have this unit now, I found 3 cooked resistors and corresponding transistors in the bias circuit to what I suspect is the channel that was fried. It's not a DC offset issue, I tested at the coils and dc offset is under 10mv. There is a short, the trick is to find it. It fires up on a 100w bulb , dims and glows bright again. I hate chasing shorts....grrr. One of the negative supply rail voltages is about half of the positve, I believe that's where the issue is.
 
What I want to know- avionic was going to look at the circuit to see if the unit can be fired up without the outputs- I want to begin with that.
 
Was I...:scratch2: Hell , I don't even remember what I had for breakfast this morning..
 
I do not believe this will come out of prot with outputs removed- there is a transistor from the output side that feeds power to the protection circuit. The bright bulb was the right channel dialed in at 70mv idle, it's now down to 11mv and the bulb is dim. The left channel will not bias, reads 0 so still more digging to do.
 
I do not believe this will come out of prot with outputs removed- there is a transistor from the output side that feeds power to the protection circuit. The bright bulb was the right channel dialed in at 70mv idle, it's now down to 11mv and the bulb is dim. The left channel will not bias, reads 0 so still more digging to do.

What's going on with that "Turbo class A " circuit ?:D
 
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