Which is a better power supply transistor?

[jkrokenberger]

Which is a better power supply transistor? D44VH10 or 2N6487? I have a stick of the 2N6487's and would need to order the D44VH10's. Application is DC-DC SMPS in an automotive amplifier, specifically an MTX BTA2100.

It's a fairly rare and desirable piece and I'd like to put the best parts in it. I've replaced the electrolytics with Nichicon VX in the PS and FG in the audio. I've verified the repairs and function with a single pair if the 2N6487's in the PS and want to button it up but if the D44VH10's are worth the expense and wait I will order them instead of just finishing it up with the 2N6487's.

Please let me know which is the better part for the application. You guys here have more experience than I do so I'd like a professional opinion.

Thanks!

 

[schiirrn]

Now that you have started exchanging parts randomly the MTX is still rare but not that desirable anymore.

 

[wg_ski]

It may seem to work, but the proof of the pudding would be what happens at high power. The D44 series are fast, and more importantly have very low Vce(sat) and are relatively free of quasi-saturation effects (beta drop at low Vce). The 6487s may have significantly higher conduction losses, even if they are “fast enough”. Do you get full rated power out of the amp, and is heating reasonable at full power?

 

[jkrokenberger]

I have not made any full power tests. The original devices were 2N6488, I fitted a 2N6487 on each side to verify the repairs to the drive circuits were good. I used original parts in the drive circuits.

I know the 2N6487's are "fit for duty" but I would like to use a better component for the power devices as I intend to keep and use this amplifier. Very few of these were made and even less survived through the years.

 

[davidsrsb]

SMPS are especially hard to do substitution as the original design will have been tuned for transistor capacitance etc.

 

[JMFahey]

I would like to use a better component

I understand amplifier is currently working fine but you intend to "improve" it by using "better parts"?

Sorry but design (improving implies at least partial redesigning) does not work that way, this is not "a bunch of parts" but a complex *system* , where parts interact in a given way, chosen and tuned by original designer.

Introducing a "better part" may very well lead to a "worse System", as was hinted above.

 

[wg_ski]

If 2N6487/8 parts were used originally, that would indicate that the original design was done by brute force. They are slow and hungry, but robust. There is generally nothing wrong with that approach, up to a few hundred watts.

 

[jkrokenberger]

Thank you for the replies and information! I was looking for the advice of experience.