Music Man RD-50s - Why So Many Output Section Issues?

[turk 182]

following with interest as in the past have struggled and lost to an RD50....

 

[MusikalienATX]

following with interest as in the past have struggled and lost to an RD50....

Hope it helps, these things are kinda "special", but as Mr Enzo likes to remind us, it's just a guitar amp and it can be fixed.

Is the problem with yours in the output section too?

 

[MusikalienATX]

RD-50 Internal Fuse Protection!

It looks like MM did add some fuse protection to the RD-50 export models...

So far I've found photos of three separate units in three different countries with the same setup, all Rev A export models, so it's pretty certain this was a factory setup. Also notice that the external fuse value is screen printed as 2A (vs 3A on the domestic builds) and the internal fuse values are identically marked on labels inside the units.

 

[MusikalienATX]

When all else fails... read the directions!

I didn't notice before that the MM documentation included the power input configurations for different markets (attached). Apparently only the Scandinavian countries warranted the extra fuse protection?

Also note that they changed to Type-T slo-blo fuses for Rev B.

 

[ahankinson]

If it’s red plating your voltages should be out of whack. Have you checked them? Have you checked your coupling caps for excessive DC leakage?

 

[MusikalienATX]

If it’s red plating your voltages should be out of whack. Have you checked them? Have you checked your coupling caps for excessive DC leakage?

Thank you! Right now I'm sure I have a blown driver transistor but I need to check components upstream to figure out why. Coupling caps certainly could be a cause, I'll check them all...

I'm still convinced that there's a common cause to a lot of the problems people seem to have with these transistors and related components.

 

[turk 182]

eh, i could be wrong but i once thought that it came down to the difference in the interval of time that a tube vs transistors ability to live with a burst of high frequency noise on the supply line and live....

 

[mozz]

Music Man Amps Discussion Forum: JE1692 Substitutes

 

[MusikalienATX]

eh, i could be wrong but i once thought that it came down to the difference in the interval of time that a tube vs transistors ability to live with a burst of high frequency noise on the supply line and live....

That's an interesting angle I hadn't thought of - not sure how to test the theory though. Maybe I should use a filtered AC power supply just to be safe?

 

[MusikalienATX]

Music Man Amps Discussion Forum: JE1692 Substitutes

Thanks, I hadn't seen that one, more to consider! For starters I'm gonna try the MJE 15030s that Mr. Enzo recommended based on good performance in some Peavey designs, and on Sr. Fahey's awesome deep dive analysis... Music Man RD-50 Driver Transistor Conundrum - Music Electronics Forum