Aleph P Rev. 1.7

[Ignatz]

I am having some teething problems with the Aleph 1.7 on my Proto Board.

I have had it running for the last couple of days.

It perfectly handles the following:
1.95 kHz square wave
976 Hz square
488 Hz square
900 Hz sine

I have not tried any other signals because of the following.

If I put R48 and R63, which are 221K0 into the circuit, it starts to oscillate.
I have re checked my layout and I think it is correct; however I can not use the 221K resistor which I think provides a little feed back.

I used Hitachi 2SD667 NPN and Hitachi 2SB647 PNP to replace the ZTX450 and ZTX550.
The readings on the IRF mosfets from ground to drain are as follows:
21.6 volts DC on Q17
25.6 volts DC on Q16
25.6 volts DC on Q15

Only the IRF9610 require heat sinks as everything else runs mildly warm with the exception of R58, R56, R71 and R68, which run quite hot.

Over all it runs much cooler than the BZLS.

Has anyone else experienced the problem of oscillation using R48 & R63?

 

[JoeD]

Ignatz
On my circuit Q17 is about 10 volts DC.
No componants seem warm. None are Hot.

I believe no Heatsinks are needed. NP Aleph P service manual page 12 shows componant layout. These transistors do not apear to have Heatsinks.

I do not have equipment to run tests so I can't help you there, but it sounds fabulous.

 

[Jens]

Ignatz

I have no oscillation problems, R48/63 are in - use ZTX450/550.
Get the following voltages (GND/D):
Q15 = 25.3
Q16 = 25.3
Q17 = 8.7(!)
I don’t need heat sinks even on the 9610s (54° Centigrade).
R56/58/68/71 are absolutely cool.

Jens

 

[Ignatz]

Thanks JoeD and Jens for your information it is greatly appreciated. Maybe the Hitachi NPN and PNP devices are not equivalent to the Zetex or I have a layout error.

I think I will get some Zetex devices from Digikey.

Is the reason to have 3 10uF caps in parallel on the out puts to minimze the ESR? Or is there another reason for this, as this must make fc very very low.

Thanks

 

[nar]

Aleph P oscillations

Nelson stated to isolate the drains taken for output with a little series resistor,100R or so.

If doesn't help,check for the layout and especially if the gate resistors 221R are not too far from the gate on layout.The closer the gate resistors,the best.