Hey guys,
So I have a Phase Linear 300 Series 2 here on the bench,symptoms were no output,and no output relay 'click'.
I opened it up and quickly noticed some burned resistors in both channels,a zener shorted in one channel,and a pair of the outputs shorted in the other channel.
So,long story short,I have one channel working with the original outputs,etc.
These output transistors are 2SB706A and 2SD746A,which are no longer made. I did source some on the 'net,but at $30 each,I think we'd be better off to just replace them all with something new (better/cheaper).
Which brings me to my main question, What would you suggest as replacements?
Quiescent rail voltage is +/-64V,or so,and there are two pairs of outputs per channel.
So far on my post-it note I've jotted down,
MJL4281A/4302A
MJW21193/21194
MJW21195/21196
Does anybody have a favorite,or a part they'd like to add to the list?
Second question: What should these amps be biased at?
At first check,there was no bias. I've got the working channel idling at about (7.5mv/0.33R) ~20ma/device,or so?
I have a schematic that I've tweaked to match what I have in front of me.
http://i199.photobucket.com/albums/...dio stuff/Phase Linear 300/PhaseLinear300.png
I'll attach the original PL300 (non-series 2) PDF to this post.
So I have a Phase Linear 300 Series 2 here on the bench,symptoms were no output,and no output relay 'click'.
I opened it up and quickly noticed some burned resistors in both channels,a zener shorted in one channel,and a pair of the outputs shorted in the other channel.
So,long story short,I have one channel working with the original outputs,etc.
These output transistors are 2SB706A and 2SD746A,which are no longer made. I did source some on the 'net,but at $30 each,I think we'd be better off to just replace them all with something new (better/cheaper).
Which brings me to my main question, What would you suggest as replacements?
Quiescent rail voltage is +/-64V,or so,and there are two pairs of outputs per channel.
So far on my post-it note I've jotted down,
MJL4281A/4302A
MJW21193/21194
MJW21195/21196
Does anybody have a favorite,or a part they'd like to add to the list?
Second question: What should these amps be biased at?
At first check,there was no bias. I've got the working channel idling at about (7.5mv/0.33R) ~20ma/device,or so?
I have a schematic that I've tweaked to match what I have in front of me.
http://i199.photobucket.com/albums/...dio stuff/Phase Linear 300/PhaseLinear300.png
I'll attach the original PL300 (non-series 2) PDF to this post.
Hi
I would go with MJ15024/25
I installed 15024 at my 700b and it is ok. Don't go with some ultra modern and ultra fast devices because of oscillations.....Maybe you will be forced to install some b-c caps to the outputs.....check with scope.
Bias...hm Probably something from 30-50mA should work but again I would check it by scope.....
Regards, Taj
I would go with MJ15024/25
I installed 15024 at my 700b and it is ok. Don't go with some ultra modern and ultra fast devices because of oscillations.....Maybe you will be forced to install some b-c caps to the outputs.....check with scope.
Bias...hm Probably something from 30-50mA should work but again I would check it by scope.....
Regards, Taj
Are those TO-3 transistors? Do they come in TO-3P?
I need TO-3P(TO-263),TO-247,or similar.
Also,I will go dig up the Lynx. Thanks for the input guys,keep it coming!
Hey Taj,
Here's a pic of the original (shorted) transistors.
I'm not quite sure what this package style is,curiously these have 2 Collector leads. With a bit of lead-bending I think I can get some TO-263/TO-247 transistors to fit.
http://i199.photobucket.com/albums/...ted Audio stuff/Phase Linear 300/PICT0001.jpg
Here's a pic of the original (shorted) transistors.
I'm not quite sure what this package style is,curiously these have 2 Collector leads. With a bit of lead-bending I think I can get some TO-263/TO-247 transistors to fit.
http://i199.photobucket.com/albums/...ted Audio stuff/Phase Linear 300/PICT0001.jpg
Oh my God....vintage....uh
There you will have a lot of mechanical work to repair it.....
Those MJL21193/94 should work fine. They are not too fast and will handle at least so much of current, power,voltage.......
Maybe there you can stick in some big plastic units from San Ken too but it is probably not worth.
You can find MJL ON Semi units cheap there in the US.....and those are excellent devices.
Of course you must replace all transistors at both channels to get same performance...and re adjust idle current....
Maybe than you can make some sot of metal plates with 2 holes to mount new transistors if you want to avoid making new holes.....
Best regards, Taj
There you will have a lot of mechanical work to repair it.....
Those MJL21193/94 should work fine. They are not too fast and will handle at least so much of current, power,voltage.......
Maybe there you can stick in some big plastic units from San Ken too but it is probably not worth.
You can find MJL ON Semi units cheap there in the US.....and those are excellent devices.
Of course you must replace all transistors at both channels to get same performance...and re adjust idle current....
Maybe than you can make some sot of metal plates with 2 holes to mount new transistors if you want to avoid making new holes.....
Best regards, Taj
stay close to relatively slow transistors or as close o the original ....too fast transistors will take you to oscillations... opposite might do the same ....replace the op amp with something too fast with slow outputs ....
point is that beyond speed considerations be sure that construction pcb and layout of the amp will not support F1 speeds
at this age of course you need to take a look at all small electrolytics... you need to verify that local stabilization of the low voltage of the IC is working properly and efficient enough .
Finally depending on the year of make and model there is a chance that the legend used resistors that drift from original value if exposed to excessive heat or moisture ... check carefully that also its critical ...
Kind regards
sakis
point is that beyond speed considerations be sure that construction pcb and layout of the amp will not support F1 speeds
at this age of course you need to take a look at all small electrolytics... you need to verify that local stabilization of the low voltage of the IC is working properly and efficient enough .
Finally depending on the year of make and model there is a chance that the legend used resistors that drift from original value if exposed to excessive heat or moisture ... check carefully that also its critical ...
Kind regards
sakis
Hey guys ive been working in this amp, but mjl21193/4 are relatively expensive in my country
how about 2sc52900/a1943 i have lots of these transistors.
also ive been thinking about tip35c/tip 36c
would some of these transistors work?
As far as I can see you guys are chasing ghosts.
Once the components are "USED" their parameters are gone forever, unless you have the original data and recordings you will never, ever, make it as it was original.
Even with the scope, you see a line on the screen, nothing more, all this back and forth is useless.
Just replace the bad parts all together and mostly the CAPS and make sure the replacements are within the voltage specs so will not blow up.
From what I could see on the schematic your supply is 70Vdc, any MJ will work, first of all they are up to 200v-250v, second you replace all of them so glitches and oscillations should not happened, old components are susceptible to that, maybe that it blow up in the first place.
Think about it.
Once the components are "USED" their parameters are gone forever, unless you have the original data and recordings you will never, ever, make it as it was original.
Even with the scope, you see a line on the screen, nothing more, all this back and forth is useless.
Just replace the bad parts all together and mostly the CAPS and make sure the replacements are within the voltage specs so will not blow up.
From what I could see on the schematic your supply is 70Vdc, any MJ will work, first of all they are up to 200v-250v, second you replace all of them so glitches and oscillations should not happened, old components are susceptible to that, maybe that it blow up in the first place.
Think about it.
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