phase linear 400
- Thread starter gene french
- Start date
I don't want to hijack this thread, but I have a similar question and this thread is fresh... So here comes the hijack.
I am currently giving my first 400s1 8 fin the full WO treatment. I gutted the old boards and wiring and assembled the new boards. I have completed the instruction set up through the beginning of the start up procedure. Rail fuses are removed, no transistors are mounted, control board is still out and all wires from the driver board are wrapped (12 on the bottom plus 3 bias). I plugged in the amp and started to slowly increase voltage on the Variac to 60VAC with no transistors mounted and both rail fuses removed. The DBT bulb stays lit. It never dims. Where could my short be? What should I check first? I thought this was going to be an easy check of my Xformer voltages, but I had to shut her down before checking anything.
Is my transformer shot? Do I need to have the rail fuses in? Should I have already installed the bottom row of output transistors? I'm hoping I'm doing something wrong/out of order and it's not my Xformer.
Thanks in advance for any suggestions.
Adam
I am currently giving my first 400s1 8 fin the full WO treatment. I gutted the old boards and wiring and assembled the new boards. I have completed the instruction set up through the beginning of the start up procedure. Rail fuses are removed, no transistors are mounted, control board is still out and all wires from the driver board are wrapped (12 on the bottom plus 3 bias). I plugged in the amp and started to slowly increase voltage on the Variac to 60VAC with no transistors mounted and both rail fuses removed. The DBT bulb stays lit. It never dims. Where could my short be? What should I check first? I thought this was going to be an easy check of my Xformer voltages, but I had to shut her down before checking anything.
Is my transformer shot? Do I need to have the rail fuses in? Should I have already installed the bottom row of output transistors? I'm hoping I'm doing something wrong/out of order and it's not my Xformer.
Thanks in advance for any suggestions.
Adam
I assume you have the rectifier wired to the transformer output? If so you may have it miss-wired or it's bad. Or, do you also have the storage caps hooked up, is polarity correct?
The transformer output stranded wires connect to the rectifier and the solid wires to the copper bus bar.
If you replaced the rectifier with new, compare the wiring indexing with the old, one solder lug is offset to index.
If indexing looks good, check cap polarity. B+ is at the top cap lug. Coming down, next is - at the copper bar, then + for the bottom cap, then B- at the bottom. Storage cap polarity must be correct.
If everything looks good, test by disconnecting the caps, then rectifier. If problem persists, then it's time to check the cord, main fuse holder, and pull the transformer and cradle to check for shorts.
Sending this and I'll look for a photo of rectifier index wiring.
The transformer output stranded wires connect to the rectifier and the solid wires to the copper bus bar.
If you replaced the rectifier with new, compare the wiring indexing with the old, one solder lug is offset to index.
If indexing looks good, check cap polarity. B+ is at the top cap lug. Coming down, next is - at the copper bar, then + for the bottom cap, then B- at the bottom. Storage cap polarity must be correct.
If everything looks good, test by disconnecting the caps, then rectifier. If problem persists, then it's time to check the cord, main fuse holder, and pull the transformer and cradle to check for shorts.
Sending this and I'll look for a photo of rectifier index wiring.
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i think....(i know, its dangerous for me to think...)...that being said...i believe...
the c8 being backwards drastically changed the bias...and after a few seconds the bias ran away frying the outputs...
today i will check all diodes and transistors on the 400c board....i did check q6...which seems to be ok...
again...totally my error...no one to blame but myself...
the c8 being backwards drastically changed the bias...and after a few seconds the bias ran away frying the outputs...
today i will check all diodes and transistors on the 400c board....i did check q6...which seems to be ok...
again...totally my error...no one to blame but myself...
Thanks guys. I appreciate the suggestions. Bridge rectifier is brand new. I copied the wiring from previous. It didn't have the snubber caps before, so I added those new as well. I double checked bulk capacitor polarity on install. It's tough to see in the attached, but they are +/-, +/-.
I'll remove the capacitors from the equation and try again.
I'll remove the capacitors from the equation and try again.
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yes, the bright bulb went away after all of the outputs were removed....and i changed the fuses....bulb tester returned to normal...
there were 5 shorted/open junctions on the outputs...
i need to check the .22 ohm emitter resistors on the back plane...to make sure they are not open....i had two bad ones on the sx restoration...it also fried one final...i changed them all...
i need to check all of the diodes and resistors on the driver board....i have a feeling something there is damaged....i need to be methodical and patient...i always document what it do... with pics...for reference...
this is one reason i am waiting for finishing the wopl upgrading....i would hate to know that an error, which i make plenty of, just cost me all of my new boards and outputs....i want to have a stable platform and know more about the carver amps before i proceed....for now i want to reproduce the 400 i fell in love with in the 70s...just because that is what i want...when i know more and am more familiar with the 400....i will proceed....it is not a function of money....yes, i do watch my finances... but, i can afford to pretty much enjoy my hobby.... maybe i will keep the 400 as stock and safe as possible and get joes 700b recommendation for the full all out upgrade....one kick ass amp...as i progress i can make better decisions...
i want again to thank all who have helped me along this journey....i am very appreciative....and i do enjoy reading and learning more...
take care....this is a nice forum!!!
gene french
there were 5 shorted/open junctions on the outputs...
i need to check the .22 ohm emitter resistors on the back plane...to make sure they are not open....i had two bad ones on the sx restoration...it also fried one final...i changed them all...
i need to check all of the diodes and resistors on the driver board....i have a feeling something there is damaged....i need to be methodical and patient...i always document what it do... with pics...for reference...
this is one reason i am waiting for finishing the wopl upgrading....i would hate to know that an error, which i make plenty of, just cost me all of my new boards and outputs....i want to have a stable platform and know more about the carver amps before i proceed....for now i want to reproduce the 400 i fell in love with in the 70s...just because that is what i want...when i know more and am more familiar with the 400....i will proceed....it is not a function of money....yes, i do watch my finances... but, i can afford to pretty much enjoy my hobby.... maybe i will keep the 400 as stock and safe as possible and get joes 700b recommendation for the full all out upgrade....one kick ass amp...as i progress i can make better decisions...
i want again to thank all who have helped me along this journey....i am very appreciative....and i do enjoy reading and learning more...
take care....this is a nice forum!!!
gene french
I threw my DBT together last night same way. 3/16 extension cord, sliced the jacket, pulled the hot, wired in switch to lamp socket back to hot, soldered and wrapped. Done.
I suspected my DBT was at fault (because it couldn't POSSIBLY be my wiring
) so I pulled out an old Denon AVR and tested it. Light dimly illuminates and then turns off fairly quickly. DBT works :-/
I suspected my DBT was at fault (because it couldn't POSSIBLY be my wiring
) so I pulled out an old Denon AVR and tested it. Light dimly illuminates and then turns off fairly quickly. DBT works :-/
Yep, 5-AGX fuses for the B+/B- rails were removed (actually the unit had 8 amp fuses in... I already ordered 5's). Only the main fuse was left in place (also an AGX-8).
Caps and rectifier look good to me. Side note, the power cord was cut and someone wired in a toggle switch. I replaced the cord with a 2 conductor 16 awg.
Caps and rectifier look good to me. Side note, the power cord was cut and someone wired in a toggle switch. I replaced the cord with a 2 conductor 16 awg.
