I blew out a couple output transistors on my PL400, what next?

[rollcentre]

Everything is the same on both sides except connection 10 and 9


10L is .375
10R is .032

9L is .960
9R is .499

 

[George S.]

Prior post #59 you mentioned D3 and D4. Looks like you have a resistor in D4. Might want to verify this is correct. Can't help any more, on the road with phone.

 

[George S.]

Oops post #50.

 

[George S.]

Hmm, the board you show in post #27 is same way. Guess a resistor subs for a diode to make the board quasi complementary.

 

[rollcentre]

Also, you haven't populated the complementary output portion of the control board have you? Looks like every component has been stuffed (complementary and quasi) unless I'm missing something. When I build a control board the first thing I do is fill component locations I won't be using with solder so I don't inadvertently stuff them.

Thanks George. I'm thoroughly perplexed now.
I've been double checking the quasi BOM, and went back and looked over the baggies that had the optional full comp/ quasi parts to make sure I actually put in the quasi parts. It appears I did. I Reflowed all the solder joints on that side, and cleaned up the top of the board with ipa.

I just ordered a optivisor, I can see more details in the picture of the control board than the actual board in my hand.

 

[Gepetto]

Solder bridge between D1R cathode and D2R cathode? Check it out carefully with magnification. Your photo seems to show that when I blow it up.

 

[mlucitt]

Solder bridge between D1R cathode and D2R cathode? Check it out carefully with magnification. Your photo seems to show that when I blow it up.

Either that or a cat hair...

 

[Gepetto]

Either that or a cat hair...

That cat has strange hair...

 

[George S.]

Looks like the fault. Good example of why magnification is important, especially for old guys like me.

 

[rollcentre]

Well that's embarrassing lol.


Joe you nailed it. We're back on track. Bias is now in range.

Thanks!!!

 

[mlucitt]

That one is going into the Strange Problems and Solutions Folder

 

[rollcentre]

I got both amps hooked up to my Infinitys and they are rockin'. I gave it the gusto last night and they REALLY sound nice

The LED boards are very cool. I love watching the meters dance while on the most sensitive setting. The dimmer comes in handy to get the brightness in both amps to match. One amp has Jewell meters and the other one has Dixon meters, the Jewell ones have a darker tint. I can dial them in to look identical.

Thanks for the help fellas you guys rock.



I have the fans installed and blowing on to the back wall, is there any reason not to go ahead and put the metal strips that cover the output transistors back on? Would that help or hurt the thermal bias tracking with the fans?

Also, would there be an any advantage to putting a 14ga power cord on these? I have some 14ga non polar power tool cords I bought earlier for them with some heyco bushings. I can get it to work if I take a little material off the inside of the bushing. Jw if it would be worth the effort.

 

[George S.]

Personally, I'd leave the cords as they are now until your ready to go FULL WOPL! At that point install a IEC socket as Mark L. showed me and I documented in the WOPL building section. I installed my sockets after doing a full WOPL. Would have been better and much easier with a stripped chassis.https://forums.phxaudiotape.com/threads/iec-power-cord-socket-in-a-400-wopl.9624/

 

[George S.]

Oh, and last month I stripped down a PL Pro 700 to fully WOPL this coming winter. Same size power cord as both of my 400s came with from the factory. I'd wait and do it right.

 

[WOPL Sniffer]

That cat has strange hair...

View attachment 51697

Hmmmmm, soldering on the component side?????

 

[laatsch55]

Have you read his explanation of the matchup tendencies in a stock amp? Wopl archives...

 

[laatsch55]

Oh yes, I certainly do. Grew up in Riverside. Cal in the sixties..