Sony TA-E88 Fet Replacement Problem

[zedrider]

Hello

The above device is used in the buffer and line stages of a Sony TA-E88 pre-amplifier, one of them has gone , i have searched all over for one and cannot find any.

I tried replacing the fet with 4 2SK30a fets which worked but not very well, i could not get "0" volts between the two sources of the fets.

So

I am wondering if anyone knows where i can find one these or has some that would be willing to sell to me or knwos of a way around the problem, i have uploaded a jpeg of the circuit showing the original fet in circuit.

Thanks
Gary
http://www.btinternet.com/~swlthr/ebay/IT500.jpg

 

[jan.didden]

Hi Gary,

I own one of these per-amps, unfortunately I have no spares. But did you try to adjust the balance with Rt301? I would expect that that is necessary even when replacing them with the original IT500's.

Another option would be to buy a bunch of fets that come close and select a matched quad.

Jan Didden

 

[zedrider]

Hello Jan

Thanks for your reply.
Yes i have tried setting the offset voltage with the pre-set but i cannot get less than 300 mv dc on the output, if try the working It500 from the other channel it works.

Gary

 

[jan.didden]

You could try two pairs of two matched fets, or two pairs of two in a single package.

Wait, did you try to swap the individual fets of the four you have used? There must be a combination that lets you get to zero, I would think.

Jan Didden

 

[zedrider]

This is a problem, i do not know how or where to buy matched fets, i know sony used to make matched pairs in a 6 pin package (2SK97) but i cannot find these either.

Fets are not my thing when it comes to understanding them.

Gary

 

[tvi]

The were made by ge/intersil, I have a data sheet somewhere.

Either HP or Tektronics used them, but using an in house numbering system, If I can find it I will post the cross reference.

Regards
James

 

[zedrider]

Hello James

Thanks for that, could be worth a try.

Gary

 

[jan.didden]

No, they were definitely packaged in a SONY marked package. I have a source that still had similar chips for a TA-N88. I bought all their stock of it, 6 pieces.
I will call them next week for this, small chance buth worth a try.

Jan Didden

 

[zedrider]

Hello jan

Thanks for that, the ones i have in my pre-amp are just marked "IT500" followed by a date.

Just out of interest, some of the tantalum capacitors failed in this pre-amp, which what i think caused the fet to blow, so i changed every single tantalum cap for a stargetz audio grade electrolytic capacitors, not only did this solve some of the problem but it improved the sound aswell, making the sound a little richer and the soundstage wider.

Gary

 

[zedrider]

<<<<No, they were definitely packaged in a SONY marked package. I have a source that still had similar chips for a TA-N88. I bought all their stock of it, 6 pieces.
I will call them next week for this, small chance buth worth a try.

Jan Didden


__________________
/ The brain is logical - the mind may not be>>>

Tell me Jan

what sort are the ones you have for the TA-N88?

Gary

 

[jan.didden]

Bingo!

My source apparently has 2SK97's, but there's no price, I'll have to call Monday.
Anyway, in the -88 schematics there is a general picture showing 4 fets in one package, but all the detailed schematics show 2 in a package (6 pin DIL), so I think that's the ones? Or is the one in your preamp actually a package with 10 or 12 pins?

Jan Didden

 

[zedrider]

Hello Jan

My fets are 4 fets in one 6 pin DIL package

hmm sounds promising

 

[zedrider]

Bingo!

My source apparently has 2SK97's, but there's no price, I'll have to call Monday.
Anyway, in the -88 schematics there is a general picture showing 4 fets in one package, but all the detailed schematics show 2 in a package (6 pin DIL), so I think that's the ones? Or is the one in your preamp actually a package with 10 or 12 pins?

Jan Didden

The 2SK97 is two fets in a 6 pin DIL package but the IT500 is 4 fets in a 6 pin DIL package

 

[jan.didden]

Right, on the buffer amp it's the IT500, on the mainboard it's two 2SK97's, on the REC OUT buffer it's an IT503. They all are used in quite similar circuits though. Are you using the REC OUT buffer? If not, you could try Q501 (IT503).

Jan Didden

 

[zedrider]

Hello

I have tried the IT503 aswell and it works, but i do use the record out on this pre-amp for my tape machines.

So the fets you might be able to get are the 2SK97s, then possibly two of these would do the trick, i can wire them the same as the IT500

i see you have the service manual for this pre-amp aswell.......it makes life a lot easier 😀

 

[jan.didden]

Yes...
I'll contact you next week.

Jan Didden

 

[zedrider]

ok jan

Thanks for your time

Gary

 

[Elso Kwak]

It500

Hi zedrider,
According to Linear Systems the IT 500 is equivalent to their LS844. I guess they mean two of these. Of the latter you can download the datasheet here:
www.linearsystems.com
Maybe the U440 or 2N5912 will work.😕

 

[zedrider]

Hi there

these look very interesting, they appear to have only two fets in them (the it500 has four), but they could still be used, i have sent them an email asking about price and availability.

Thanks very much

Gary

 

[zedrider]

The were made by ge/intersil, I have a data sheet somewhere.

Either HP or Tektronics used them, but using an in house numbering system, If I can find it I will post the cross reference.

Regards
James

Hi James i have had an email back from Tektronics saying that they cannot cross reference the Fet number with there's so if you can find that numbering sheet that would be great
Thanks
Gary