Gibsonian's Cherry Pl 700 Ser I, soon to be a PLWO-1000

[Gepetto]

No nothing going on

Interesting Jer, only time it has happened and it happened twice today. Hit the Submit Reply button and it locks up, no hourglass or buffer wheel action. Have to restart web page to recover and upon doing that, the entire message you were sending is gone.

 

[laatsch55]

The auto-save wasn't running??

 

[Gepetto]

autosave on vBulletin??? Not sure that option is available Lee. The web tab crashed and burned, had to restart the web connection.

 

[laatsch55]

Well the one that's available as you type a post, didn't know how far it saved. But if the page went you were definately F&^%$#.

 

[laatsch55]

Still stumbling around in BIAS HELL.......

 

[Gepetto]

what is the voltage across R37, yeah that 150 ohm resistor we talked about earlier...

 

[laatsch55]

.022 mv DC

 

[Gepetto]

Well there is a big symptom of your problem Lee. No drive to the lower predriver is occurring and thus no negative half is on. That should be on the order of 0.60V

 

[Gepetto]

are you getting zero volts across R34L on the control board as well?

 

[Gepetto]

Hi Lee
Unless you hid it real good on me, I do not see the necessary 0.33 ohm R41 on the negative side of the transistor stack. Without this, you will get NO drive to the lower half of the output bridge.

 

[Gepetto]

I looked very closely at the photo you sent me earlier. Did not dawn on me until you gave me that R37 reading.

 

[jbeckva]

Hi Lee
Unless you hid it real good on me, I do not see the necessary 0.33 ohm R41 on the negative side of the transistor stack. Without this, you will get NO drive to the lower half of the output bridge.

I think I see it? The .33's Lee is using are those 1 percenters all gray.

But... the lead going to the base of Q12 looks suspiciously close to the top screw/collector.

 

[jbeckva]

I looked very closely at the photo you sent me earlier. Did not dawn on me until you gave me that R37 reading.

Are you looking at this post (1st pic)?

http://forums.phxaudiotape.com/show...er-I-soon-to-be-a-PLWO-1000?p=60413#post60413

 

[Gepetto]

Lee the socket tulip on Q11 and 14 look like very casual contact as well. Cathode connection of D14 looks like a potentially cold solder joint. Not your problem here but saw that under large magnification.

 

[Gepetto]

Yes I am Jer, the one to the left. That is the one I enlarged.

Lee I am suspicious of those small 0.335 resistors (at least I think that is what it says on them) Some of them have oxidation on the leads that could be preventing proper solder whetting.

Also these cannot be wirewound type resistors. They need to be carbon film, metal film, metal oxide or carbon comp resistors. You cannot stand the potential inductance in this application. The big 0.27 ohm ones look like MO types and are good for this application.

 

[jbeckva]

Yes I am Jer, the one to the left. That is the one I enlarged.

Lee I am suspicious of those small 0.335 resistors (at least I think that is what it says on them) Some of them have oxidation on the leads that could be preventing proper solder whetting.

Also these cannot be wirewound type resistors. They need to be carbon film, metal film, metal oxide or carbon comp resistors. You cannot stand the potential inductance in this application. The big 0.27 ohm ones look like MO types and are good for this application.

Hmm.. I'm seeing the connection to the collector of Q14, but where is the lead going to on Q12? Check it out...

 

[laatsch55]

Ok, checking these out,....

 

[laatsch55]

This what ya mean by wirewound??

 

[jbeckva]

Daggoneit.. why was I thinking from Q14 collector to Q12 base?? That aint right.... it's both collectors

(going to find eye doctor...)

 

[laatsch55]

To the collector Jer...