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Replacing 2N3055/MJ2955
Replacing 2N3055/MJ2955
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Old 23rd April 2011, 12:42 PM   #1
jazko is offline jazko  United Kingdom
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Default Replacing 2N3055/MJ2955

Good day, I have a NAD 2030 amp with one channel down, I was wondering if I can replace the transistors (MJ2955/2N3055 (all four)) with MJ21195/6 ? What should I look for to know whether transistors are interchangeable?
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Old 23rd April 2011, 01:49 PM   #2
lineup is offline lineup  Sweden
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I think better in this case to take MJ21193/4.
Myself use replacement TIP2955/TIP3055 in my simulator.
It is not much to gain to use faster devices. Try to make it as similar as possible.
This will avoid a mismatch in quality. And work the best.
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Old 23rd April 2011, 01:57 PM   #3
jaycee is offline jaycee  United Kingdom
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If this is the NAD amp where there are no emitter resistors, you will need to add them or it will not be thermally stable. 0.33 ohm 3W resistors will work.
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Old 23rd April 2011, 02:26 PM   #4
jazko is offline jazko  United Kingdom
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jaycee there are emitter resistors with the values you mentioned.

lineup I can find MJ21195/6 pretty easy, so I suppose I can use them? I know it is a bit of an overkill
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Old 23rd April 2011, 03:55 PM   #5
jaycee is offline jaycee  United Kingdom
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ok, i couldnt remember which NAD amp just used plain old 2955/3055 with none
To be honest yes, the MJ21195/6 should be fine, even MJ15024/5 will be good

One thing NAD often do is use fixed resistors for bias. You may have to change that as the biasing will be different on the newer transistors. If there's a pot, then you're fine
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Old 23rd April 2011, 04:24 PM   #6
indianajo is offline indianajo  United States
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MJ15015 and 16 datasheet refers to the 3055-2955 spec. They have a higher Vceo and an actual SOA, not as big as 21195. I got my On Semi versions for $1.28 each from farnell (newark in USA). Depending on layout, you might have to put 10-20 pf across the B-E leads to prevent oscillation, especially on the MJ15016 which has ft of 4 mhz. The MJ15015 ft is .8 mhz.
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Old 23rd April 2011, 04:27 PM   #7
jazko is offline jazko  United Kingdom
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Yes, unfortunately no pots are present, but I think I'll be alright.

Thank you
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Old 23rd April 2011, 05:54 PM   #8
wg_ski is offline wg_ski  United States
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If there is no bias pot, you want something close to the original 3055/2955. MJ21195/6 would *work*, but the bias would need to be adjusted if possible. MJ15015/16 are much closer to the Moto/ON 3055 (only slightly larger die with the same layout and processing) so the bias should be closer to correct without adjustment. The extra 10-20 pF cap trick may be needed regardless of what type is used if they are not the originals.
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Old 11th June 2011, 12:01 PM   #9
logawamania is offline logawamania  Indonesia
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Hi all, I have same situation with zacko...
I will try to use TIP2955/TIP3055


Btw... I'm sorry for bad english
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Old 11th June 2011, 03:02 PM   #10
big jim is offline big jim  England
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Hi there are no emitter resistors in the 2030 amplifier
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