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Marantz 2230 amp transistor replacement question

Chris __R

Chris __R

Well-Known Member
Hi all,

Upfront note: I am very new to diagnosing signal path problems. That said, I am in the process of diagnosing a 2230 and have located at least one potential issue on the P750 amp board using a handheld oscilloscope.
The very first transistor in the signal path, H751, appears to be bad - 1kHz tone sinewave is clean at the base but distorted at the collector - so I am planning on replacing that one on both boards as it is quite accessible.
However, the rest of the board is difficult to access without desoldering a fair amount of wires to pull it out. Rather not do that.

My basic question is: there are three other transistors that are similar to a 2N3440 - the round kind of which I have never replaced. Are these types any less susceptible to failure than other types of transistors? With the first transistor seemingly bad, it's difficult to measure things downstream and I'd rather not shotgun replace everything if I don't need to.

Does anyone have any suggestions/thoughts?
Thanks!
Chris
 
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The 2SC945 is the original in the H751 spot. The 2N3440 is not the right tranny for that spot according to the Schematic.
1790902834920.png
My chart says you can use any of these KSC2383 / KSC1845 / KSD1616A or the KSD945C where the Suffix C means center collector .

You should see what your 2SC945 orientation is.

for now you can test the other channels H751 and see if that one behaves the same.
If it seems good then swap it over and see how it behaves in the new location.

Athanasios
 
Nashou66 said:
The 2SC945 is the original in the H751 spot. The 2N3440 is not the right tranny for that spot according to the Schematic.
View attachment 3848437
My chart says you can use any of these KSC2383 / KSC1845 / KSD1616A or the KSD945C where the Suffix C means center collector .

You should see what your 2SC945 orientation is.

for now you can test the other channels H751 and see if that one behaves the same.
If it seems good then swap it over and see how it behaves in the new location.

Athanasios
Click to expand...
Thanks! - I was going to order some KSC945s from Digikey for H751 but I was more wondering about the transistors downstream - I think its the H752 - that are the different style. But for now I might take your advice and swap the channels on H751 to see what happens. The left channel does not distort.
 
Chris __R said:
Thanks! - I was going to order some KSC945s from Digikey
Click to expand...
Make sure you order KSC945C - the C designation is the center lead is collector, which is same as original part. If you don't use the C suffix, you get parts with base in the center and you have to twist leads around, And there is no physical difference if you look at them...
 
sregor said:
Make sure you order KSC945C - the C designation is the center lead is collector, which is same as original part. If you don't use the C suffix, you get parts with base in the center and you have to twist leads around, And there is no physical difference if you look at them...
Click to expand...
Great - thank you!
 
sregor said:
Make sure you order KSC945C - the C designation is the center lead is collector, which is same as original part. If you don't use the C suffix, you get parts with base in the center and you have to twist leads around, And there is no physical difference if you look at them...
Click to expand...
Steve - looks like Digikey only has those with base in the center - even with C as a suffix. Unless I'm not searching properly. I can deal with that...
 
Nashou66 said:
The 2SC945 is the original in the H751 spot. The 2N3440 is not the right tranny for that spot according to the Schematic.
View attachment 3848437
My chart says you can use any of these KSC2383 / KSC1845 / KSD1616A or the KSD945C where the Suffix C means center collector .

You should see what your 2SC945 orientation is.

for now you can test the other channels H751 and see if that one behaves the same.
If it seems good then swap it over and see how it behaves in the new location.

Athanasios
Click to expand...

avionic said:
Click to expand...
We both showed it at mouser ;)

Nashou
 
To clarify - the C comes right after the 945 - (even the spec sheet says it unclearly) so KSC945Cxxxx The rest of the numbers are HFE group and packaging - TA is on a tape. The Korean manufacturers do the same thing with the KSA733, don't know of any others of the top of my head.
 
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