Dx Blame MKIII-Hx - Builder's thread

[evette]

Hey crispycircuit it,s about time you build your amps. Evette

 

[meanman1964]

Rudi,
I'm a little concerned regarding your heatsinks cause the fins are horizontal and not vertical did you measure the temperature yet?

 

[BMW850]

Hi Patrick,

This will give no problems because these heatsinks are only for testing.
And the heatsinks are very big and heavy and they were cheap 😉

Regards,
Rudy

 

[AndrewT]

BMW is intending to stand the heatsinks upright so that they become:
Tower Amplifiers.

 

[BMW850]

The countdown has begun 😉

Everything is ready now, waiting for my comrade who check everything also and then the plug in the mains
I have put on the trimpot 1000ohm I hope that my 25 watt lightbulb is enough, I have tested this 25watt lightbulb also with the 2000Va torroid and everything works fine.
Still a few photos ...

Regards,
Rudy

 

[AndrewT]

set the Vbe multiplier trim pot to maximum resistance.

This sets the Vbe multiplier voltage to minimum.
The result of this initial and temporary setting is that the output stage draws near zero current.
The main current load is now the front end voltage amp stage and losses in the PSU.
I have never used lower than 40W for the bulb tester.
25W may allow successful startup and go dim. It may not go off. The purpose of the bulb is to prevent damage due to wiring errors.
Do not try to bias the output stage with a bulb tester in place.

 

[sandbasser]

BMW850 - Amp looks great!

Question: why do you have the electrolytic caps tie-wrapped together???

Thanks for sharing your work,

 

[BMW850]

On the negative side we measure 3 volt constant over the 100R resistor.
On the positive side we measure also 3 volts, then the 100R resistor runs hot then rise to 12 volts, then we switch the power supply off.

We also have a heavier lamp 40 watt tried that also helped nothing
the light bulb tester has been removed because the trimpot does nothing.
No smoke, no smell, what's wrong?


Regards,
Rudy

 

[BMW850]

We see differences in the schema and the print screen.
Schema is MJE 15030 and on the print screen we see MJE 15032.
I used the MJE 15032 is this good?

Regards,
Rudy

 

[evette]

The amp such still work perfectly regardless of what transistor you have in that position,,I would check elsewhere on your board bad soldering cold solder joints or a wrong resistor someplace or a bad capicator...Evette

 

[evette]

In your photo I don,t see the litte jumper that should be in front of mje15031 is this the completed board? Evette

 

[evette]

Please post a photo of the board that you are testing. Evette

 

[BMW850]

The MJE 15030 is another brand

Regards,
Rudy

 

[BMW850]

Hi Evette,

Here you see the picture from the board I am testing.

BMW850 - Amp looks great!

Question: why do you have the electrolytic caps tie-wrapped together???

Thanks for sharing your work,

Hi Ray,
Now you can see why I am using tire wraps, the caps don't fit

Regards,
Rudy

 

[evette]

Hello Mr. Rudy I don,t know who makes that mje15033 I don,t believe thats a real on semiconductor,,If You needed those transistors I,ve Would have send you real ones. Evette

 

[BMW850]

Evette,

I mean the MJE 15030 is another brand.
Please send me real ones, perhaps the MJE 15030 is the one is bad

Regards,
Rudy

 

[evette]

Hello Mr. Rudy Didn,t I send you With the output transistors a matched set of mje15030/mje15031 for free.Are you sure I didn,t send you the correct amount? Evette,,Ps In any case I send you the Matched pre-drivers with all the other ones again.

 

[evette]

Also I don,t know this other brand of transistors your referring to. Evette

 

[BMW850]

yes, but the MJE 15030 for the small heatsinks I order here in The Netherlands also 2x MJE 15030

Regards,
Rudy

 

[BMW850]

Hi Evette,

Maybe it is better to renew all 10 driver transistors (stereo) for matched pairs.What do you think?

Regards.
Rudy

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