phase linear 400

gene french said:
second row in....
no dc on outputs....
left offset and right offset set to 0...was off a bit...but well within tolerances
right bias set to 350mv
left bias set to 320mv when pot runs out of adjustment....
i think i will change left and right 909s...to see if it follows the transistors ...
Click to expand...
you have some bad output transistors if it is dragging the bias down.
 
then to top things off...i got a message from my freight forwarder....i ordered over the years all of my wifi smart light switches direct from china....
originally got the first one from amazon...then they quit amazon....so i had to find them and go direct....only ones i could find that put a 3 gang wifi switch into a single box....anyway...i sent the prealert with the invoice and tracking number....only one problem there....they come from china to us with one tracking number from the seller....when it hits the states the item is passed to the usps....where it is assigned another tracking number....i have no access to that....it only shows my china package was delivered to the us...not to the final destination....so of course the forwarder dont know about this either....soooo....i spent about half hour on the computer tracking this down until i found it and forwarded to box correos....
aint life fun....lol
but, it is done!!!
now back to the task at hand....
and good morning y'all...
 
Yeah Gene, I thought the first row checked good after you made adjustments, then the second row had a issue.
If first row checks good, then at this point assume control board is good, the first row is good, and the issue is in that second row. Have fun! Got to make a run to Campbell's Soup, Mmm Mmm Good! Later.
 
another thing i noticed for all of you using amazon, ebay or internet sales...
before i buy something, i leave it in the shopping cart a few days....if time allows....
more often than not...the seller will see it....and send a discount....to finish the sale....
happened on this purchase ... and ebay....very rare on amazon....but, it does happen....
3 gang 3 way smart switches....works on bluetooth, rf, and wifi....
i think some models are back on amazon...but, i am already set up at moes...and a few extra days dont hurt me none...
especially when they give me a better discount....
1653502373820.png
 
put in two different outputs on the left side....
no change....about 320 left bias no adjustment left
right bias normal
both offsets are very close to each other and very close to zero....
did not have to adjust offsets....was 2mv or less...both
left bias would not adjust before it ran out of pot....dont you hate it when you run out of pot....
right bias did not need adjusting....
will do right to left, right to left on all 4 transistors...in case my problem is a driver...
unless there are other suggestions
 
gene french said:
problem followed the drivers....left side bias ok...
right side wont adjust...
hmmmmm....
i only have one more of those...do they have to be matched??
guess i will swap them out until i find the one giving problems...
Click to expand...
No matching required, they just have to be good...
 
gene french said:
set both offsets to zero...
set both bias to 350...
left channel bias pot no longer at the stop...
has two way adjustment from the present position...
will proceed to add one row of 909s
this test was done with only the bottom row of driver transistors...
as per joe and george...
Click to expand...
have you cleaned the bias pots?
and have you wriggled them and check to see if the bias volts changes?


also check First than check again if you have a problem
Also report the Cap - and + dc voltage
and the +15vdc and -15vdc
w Power Off , have you done the short test for output transistor like the manual says?
and you will have to do this every time you install a new row

every time before turning power on you need to look for broken Wires (my break all the time 400 II)
 
MusicSteve said:
What are you measuring?
Click to expand...
this all started with dc on the output left channel....
thats what the meters were on....offset voltages....left and right...before i set them....they were not that far out....
now i really dont know where i am...
upon swapping right to left left to right on the driver transistors....
problem moved to right channel....left channel bias set
both sides show 0v offset...
now the right side wont set bias max 320...end of adjustment ....as the left did before i moved the dri
i had one extra driver sj2741....swapped it in and out....then the bias on the right side dropped to 10mv....and dont move....
but all tests good in my hands....
i am just lost....
i am back down to one row....
bias transistors test good....all of the transistors test good in my hands...but definitely act up when in circuit....
 
gene french said:
this all started with dc on the output left channel....
thats what the meters were on....offset voltages....left and right...before i set them....they were not that far out....
now i really dont know where i am...
upon swapping right to left left to right on the driver transistors....
problem moved to right channel....left channel bias set
both sides show 0v offset...
now the right side wont set bias max 320...end of adjustment ....as the left did before i moved the dri
i had one extra driver sj2741....swapped it in and out....then the bias on the right side dropped to 10mv....and dont move....
but all tests good in my hands....
i am just lost....
i am back down to one row....
bias transistors test good....all of the transistors test good in my hands...but definitely act up when in circuit....
Click to expand...
So mark the Good one w electrical Tape and you have 2- bad ones?
check the transistor type? (weeks ago,,,,, I thought you mixed them up)
You have a Q-comp board? time to recheck everything.

when adjusting the bias pot , one of them stays at 10mv?

looking at the board I see some spots that look open? (could be the camera flash) I would buss out all solder traces , the point to point traces and push a little on the leads for cracked or not solder joints (that's a funny looking board , solder tracks )
I never had a 400 all mine are II boards
 
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