phase linear 400

Sunnbobb

Sunnbobb

Journeyman
#4,442
Joined
May 25, 2023
Messages
195
Location
Mount Vernon, WA
Tagline
Bikes, baseball and big amps.
#4,442
Just wondering if anyone has a single meter clamp for the analog meter on a 400 they could sell me. I just picked up a unit. The meters were loose, and the clamps scattered throughout the chassis. 3 of them that is. the 4th one is no where to be found.
 
Sunnbobb

Sunnbobb

Journeyman
#4,445
Joined
May 25, 2023
Messages
195
Location
Mount Vernon, WA
Tagline
Bikes, baseball and big amps.
#4,445
Here is one for the brain trust.
I picked up a PL400 with the pl14 board.
It had a blown line fuse, and the rail fuses were fine.
I replaced the blown fuse and hooked up the DB tester and the Variac, the DBT lit up very bright, and there was no voltage to the meters or the filter caps.
I checked each output transistor, and all 4 tested fine.
I then took out the rail fuses, and fired it up again. The meter lights worked fine, and the Filter caps had good voltage (80+, variac wasnt all the way up) and the DBT did not light up.
I then put the Left rail fuse in, meters lit up, filter caps charging. I then pulled that fuse and put the Right rail fuse in, and again, ights on, filter caps charging. Put both rail fuses back in, the DBt lit up and the filter caps were not charging.
So, any ideas were to check next?
Thanks for your time in this!
 
Gepetto

Gepetto

Administrator
Staff member
#4,446
Joined
May 15, 2011
Messages
13,906
Location
Sterling, MA
Tagline
Old 'Arn Enthusiast
#4,446
Sunnbobb said:
Here is one for the brain trust.
I picked up a PL400 with the pl14 board.
It had a blown line fuse, and the rail fuses were fine.
I replaced the blown fuse and hooked up the DB tester and the Variac, the DBT lit up very bright, and there was no voltage to the meters or the filter caps.
I checked each output transistor, and all 4 tested fine.
I then took out the rail fuses, and fired it up again. The meter lights worked fine, and the Filter caps had good voltage (80+, variac wasnt all the way up) and the DBT did not light up.
I then put the Left rail fuse in, meters lit up, filter caps charging. I then pulled that fuse and put the Right rail fuse in, and again, ights on, filter caps charging. Put both rail fuses back in, the DBt lit up and the filter caps were not charging.
So, any ideas were to check next?
Thanks for your time in this!
Click to expand...
Possibly a shorted to chassis transistor case in column 1 or 3 where column 1 is near the transformer.
 
Sunnbobb

Sunnbobb

Journeyman
#4,451
Joined
May 25, 2023
Messages
195
Location
Mount Vernon, WA
Tagline
Bikes, baseball and big amps.
#4,451
Ok, so I removed the transistors from Row 1 and row 3. DBT did not light up. I reinstalled Row 1, DBT still did not light up. I installed the bottom transistor in row 3 and the DBT lights up. I took it out, and installed the second transistor - DBT still lights up. I can put all the transistors in row 3, and as long as I don't install the hold down screws, everything is fine. If I install a hold down screw on any transistor in row 3, the DBT lights up. I don't see any damage or crossed wires on the inside of row three. hmmmm. so close.
 
Gepetto

Gepetto

Administrator
Staff member
#4,452
Joined
May 15, 2011
Messages
13,906
Location
Sterling, MA
Tagline
Old 'Arn Enthusiast
#4,452
Sunnbobb said:
Ok, so I removed the transistors from Row 1 and row 3. DBT did not light up. I reinstalled Row 1, DBT still did not light up. I installed the bottom transistor in row 3 and the DBT lights up. I took it out, and installed the second transistor - DBT still lights up. I can put all the transistors in row 3, and as long as I don't install the hold down screws, everything is fine. If I install a hold down screw on any transistor in row 3, the DBT lights up. I don't see any damage or crossed wires on the inside of row three. hmmmm. so close.
Click to expand...
Well you found it then, You have a screw to chassis short going on under the right channel heatsink assembly. Time to take it off and find some broken sockets underneath it...
 
Sunnbobb

Sunnbobb

Journeyman
#4,455
Joined
May 25, 2023
Messages
195
Location
Mount Vernon, WA
Tagline
Bikes, baseball and big amps.
#4,455
Took the cooling fins off, cleaned everything, there is no damage to the sockets in row 3. The weird thing is if I put any of the screws holding the transistors in row three, the DBT lights up, a single screw anywhere along the row, lights up the bulb, yet row 1 is fine.
 
Last edited:
Sunnbobb

Sunnbobb

Journeyman
#4,456
Joined
May 25, 2023
Messages
195
Location
Mount Vernon, WA
Tagline
Bikes, baseball and big amps.
#4,456
And another twist/clue. If I take out all of the row 4 transistors, and install all of the row 3 resistors, the DBT doesn't light up. Then, If I reinstall one or any of the row 4 transistors, the DBT lights up.
 
Gepetto

Gepetto

Administrator
Staff member
#4,457
Joined
May 15, 2011
Messages
13,906
Location
Sterling, MA
Tagline
Old 'Arn Enthusiast
#4,457
Sunnbobb said:
And another twist/clue. If I take out all of the row 4 transistors, and install all of the row 3 resistors, the DBT doesn't light up. Then, If I reinstall one or any of the row 4 transistors, the DBT lights up.
Click to expand...
Are any of the transistors you removed shorted Collector to Emitter? Did you check them while they were out?
 
Sunnbobb

Sunnbobb

Journeyman
#4,460
Joined
May 25, 2023
Messages
195
Location
Mount Vernon, WA
Tagline
Bikes, baseball and big amps.
#4,460
mlucitt said:
Replace the RCA B05 transistors with RCA 410 or RCA 66546 (they are the same device, just a newer number). I have them if you need them. PM me.
Click to expand...
This amp came with four 66546's as output drivers on the bottom row, and the rest of the transistors were B05's. of which 3 were bad. I have a set of 10 15025's I'd like to use, I need two more. I have removed all the B05's.. I tested the 66546's, installed them, and the DBT is behaving. Now I need to populate the rest of the transistors. Thanks for the offer!
 
You must log in or register to reply here.
Top