BUF03 equivalents

[tubenut]

Hi all

I seemed to have had 1 or 2 AD BUF03 buffers fail on my Theta DS Pro Basic 2 DAC output stage. As many of you may know, these are now obsolete and so are the BUF04 pin equivalent.
I have been thinking of trying the BUF634 from Burr Brown but these have a possible DC off set of 100 mv vs 1mv on the BUF04.
It is a DC coupled ouput stage and I am not sure if my ECI 3 is DC coupled or not. I would obviously prefer to avoid the possibility of a highish DC offset.

Does anybody have any suggestions for a replacement, or how I may make the BUF634 work. (could one trim the off set?) BUF03/4 has a specific set of pins for this.

Regards
Guillaume

[mlloyd1]

first question - do you know why the BUF03 units failed?
We wouldn't want to replace them to have the same problem

May want to look at discrete designs to replace?

mlloyd1

[Kochkurov Maxim]

You may use AD843. This opamp in unity gain mode sounds like BUF03. BUF634 sounds worse than BUF03 and AD843

[Ola]

What about BUF04?

[markp]

Originally posted by mlloyd1
first question - do you know why the BUF03 units failed?
We wouldn't want to replace them to have the same problem

May want to look at discrete designs to replace?

mlloyd1

The usual cause of a BUF-03 failure is heat due to a high rail voltage, that is above 15volts. A discrete design would have to go a long way to beat the BUF-03, they were excellent.

If you search, you can find a unit or two still on the shelf.

[dtm1962]

Any opinions on BUF634 good or bad would be appreciated!

[Praudio]

get some BUF 03 new, if interested send me a private email.

[kmtang]

My friend has a Theta DAC which employs two BUF03 for the last buffer output stage. The right channel failed. I bought two BUF03 IC from the PRAudio. My friend passed this IC to a repair shop and get it done. After few weeks time, the DAC failed the right channel again. I asked my friend I can take it home and take a look at it.

After checking the data sheet and signals around the BUF03, the +/-15Vdc are good. There's signal at the input but nothing at the output. The DC at output seems good. Then, I had the IC replaced with the spare one. It started working good. Then, I noticed that there's one 100uF 25V tantalum capacitor at the -15Vdc bypass changed color from yellow to dark brown. I had it removed from circuit board and measured the capacitance. It read 0uF and there's burning sign at the side. I had it replaced with a 10uF tantalum in parallel with a Sanyo 100uF 20V OS capacitor.

By the way, the BUF03 has a small heat sink at the top. I added some heat transfer compound before putting in the circuit board. I hope the DAC will keep working from now. The temperature at the IC is around 45 deg C.

Merry Christmas and a Happy New Year.


Johnny