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Old 7th February 2002, 11:40 AM   #1
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Default Transistor replacements

Hi!


The following transistors belong in a Luxman power amp:

∑ 2SC 1775 A
∑ 2SA 896
∑ 2SC 805

Can anyone suggest where to find them or likely replacements?

Where can I get their specs? Would it be wise to use replacements?

The Luxman manual says it's alright to use replacements, as long as specs are the same.



Carlos
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Old 7th February 2002, 12:22 PM   #2
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Default circuit

Sorry again.

This is the first time I attach a circuit here, and I got a message that the image was too big.

Let's hope this time it goes through.



Carlos
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File Type: gif lux5m21.gif (30.2 KB, 1739 views)
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Old 7th February 2002, 06:34 PM   #3
Geoff is offline Geoff  United Kingdom
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Carlos

The 2SC1775A is a Hitachi device and the datasheet should be available on their website. So far as I know, it is still current and should be readily available.

According to my databook, the 2SA896 and 2SC805 were made by Sony. I'll email you the specs that I have. A Google search indicates that there are a number of (surplus?) suppliers listing these devices.

Geoff
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Old 7th February 2002, 06:38 PM   #4
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Thanks for posting this, I haven't seen it before.

They seem to have left off the output coil in parallel
with the resistor shown.
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Old 7th February 2002, 07:28 PM   #5
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Default Coil

My apologies again.

Yes, Nelson. There's an output coil in parallel with the 10R/5W resistor at the output. There's no coil value specified on the Luxman circuit.

On that drawing I didn't put it, as I had done it just for my personal use. My mistake.

The input is also a small pcb, where a cascode differential is used. Nothing fancy. The hybrids were sold as such by Luxman, some having FETs and later types only bipolars, if I am not wrong. It doesn't use any DC servo or feedback cap, and it's quite stable. You set DC offset and you're done. There's a DC protection although.

Model was 5M21 and construction just great. A bit old (around 18 years) but still hold its teeth.

This amp belongs to a friend of mine, and we are thinking of cloning it with better pcbs and parts. The original boards were phenolic, and I think fiber boards would already be an improvement.

Quality passive part replacements already bettered things. But I think dual mated transistors might improve things a bit more on the first stages. May that be so?

Some comments I got was that the circuit is probably Kaneda's.


Carlos
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Old 2nd March 2002, 05:43 PM   #6
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Hi!

I'm back again with more inforamtion on the Luxman amp. Here's the complete 1st stage for you to see.

We could find out what the hybrid piggy-back consists of. In fact there seems to be a problem with one of the input dual FETs on one channel.

Could find the FET part at Audio Lab, reasonably priced.

The trimming pot at the input was unusual for me. I wonder if a trimmed FET wouldn't work better as CCS at the input instead of a plain resistor.

Comments?


Carlos
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Old 2nd March 2002, 05:47 PM   #7
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Default Updating circuit

Hi!

I'm back again with more information on the Luxman amp. Have a look at the complete 1st stage.

We could find out what the hybrid piggy-back consists of. In fact there seems to be a problem with one of the input dual FETs.

Bought the part at Audio Lab, reasonably priced.

The trimming pot at the input was unusual for me. I wonder if a trimmed FET wouldn't work better as CCS at the input instead of a plain resistor.

Comments?


Carlos
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Old 2nd March 2002, 09:44 PM   #8
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Default Re: Transistor replacements

[QUOTE]Originally posted by carlmart
[B]Hi!


The following transistors belong in a Luxman power amp:

∑ 2SC 1775 A
∑ 2SA 896
∑ 2SC 805

Can anyone suggest where to find them or likely replacements?

Where can I get their specs? Would it be wise to use replacements?

The Luxman manual says it's alright to use replacements, as long as specs are the same.

HERE IS MY SUGGESTION

Transistors of many types are available at:

http://www.ceitron.com/

Web site prices are

2SC1775 at $ .27 each
2SA896 at $1.45 each
2SC805 at $3.65 each

I hope this helps. Use the original part numbers when ever possible to avoid problems or call backs. I have used this company lots of times and they provide excellent service.

John Fassotte
Alaskan Audio
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Old 3rd March 2002, 09:25 AM   #9
tvi is offline tvi  Australia
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Data For NEC <font face="symbol">m</font>PC63H
<table width="75%" border="1" cellspacing="0" cellpadding="4">
<tr><td > Spec </td> <td > Typ. </td> <td > Min. </td> <td > Max. </td> <td > Note </td></tr>
<tr><td > V<sub>GS</sub> (V) </td> <td > -60V </td> <td > - </td> <td > - </td> <td > - </td> </tr>
<tr><td > I<sub>A</sub> </td> <td > 10m </td> <td > - </td> <td > - </td> <td > - </td> </tr>
<tr><td > P<sub>D</sub> (W) </td> <td > 0.25/ch </td> <td > - </td> <td > - </td> <td > - </td> </tr>
<tr><td > I<sub>GSS</sub> (A) </td> <td > - </td> <td > - </td> <td > -1n </td> <td > -20V<sub>GS</sub> </td></tr>
<tr><td > I<sub>DSS</sub> </td> <td > - </td> <td > 1mA </td> <td > 18mA </td> <td > 10V<sub>DS </sub></td> </tr>
<tr><td > V<sub>GS(off)</sub> </td> <td > - </td> <td > -0.3V </td> <td > -4.2V </td> <td > 10V<sub>DS/</sub>10<font face="symbol">m</font>A I<sub>D</sub> </td> </tr>
<tr><td > gm </td> <td > 4mS </td> <td > 2mS </td> <td > - </td> <td > 10V<sub>DS</sub>/1mA I<sub>D</sub></td> </tr>
<tr><td > Cis </td> <td > 6pF </td> <td > - </td> <td > - </td> <td > 10V<sub>DS</sub> </td> </tr>
<tr><td > Crs</td> <td > 1p6F </td> <td > - </td> <td > - </td> <td >10V<sub>DS</sub> </td> </tr>
<tr><td > <font face="symbol">D</font>V<sub>GS</sub> </td> <td > - </td> - <td>-</td><td>60mV</td><td > 10V<sub>DS</sub>1mA I<sub>D </sub></td> </tr>
</table>


Regards
James
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Old 5th March 2002, 11:08 AM   #10
ppl is offline ppl  United States
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Do you Have a source for the upc63H i have a Technics amp that uses this and Would like to get Replacemets in case i ever need them But i gess I could always stuff a Match Jfet 2N Pair in a pinch
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