doggy said:
My heart is breaking but don't let that fact stand in the way to build something with that massive supply.
/Hugo 🙂
They're really made for 8 ohm speakers, and most speakers today are 4 ohms.
The transformer VA and filter cap size is sized for 8 ohms, and there isn't really enough heatsinking for 4 ohms. The meters are slow, and show nothing of meaning for music.
They do bring USD$200+ on eBay, and a set of outputs and drivers for one channel run less than $20.
You could use it as a mono amp for sub use.
The transformer VA and filter cap size is sized for 8 ohms, and there isn't really enough heatsinking for 4 ohms. The meters are slow, and show nothing of meaning for music.
They do bring USD$200+ on eBay, and a set of outputs and drivers for one channel run less than $20.
You could use it as a mono amp for sub use.
Hi djk,
You're down on these amps for some reason. I see most spkrs as 8 ohm still except for car use - or am I out of touch ? - possible!
The VA and filter size is probably more than adequate for normal dynamic range music unclipped - typically a fifth or less of the peak RMS capability. Indded, when the bean counters take over they actually do the product a favour by cost cutting appropriately (hopefully) and making it available to a larger population. Why should people pay more for something that has no extra benefit. It's only poor design that needs stiff supplies!
Cheers,
Greg
You're down on these amps for some reason. I see most spkrs as 8 ohm still except for car use - or am I out of touch ? - possible!
The VA and filter size is probably more than adequate for normal dynamic range music unclipped - typically a fifth or less of the peak RMS capability. Indded, when the bean counters take over they actually do the product a favour by cost cutting appropriately (hopefully) and making it available to a larger population. Why should people pay more for something that has no extra benefit. It's only poor design that needs stiff supplies!
Cheers,
Greg
I call any speaker that the DCR measures above 5R6 an 8 ohm load. When the DCR measures less than 4R I call them a 4 ohm load.
Yes, the one pair of main filters are barely adequate (6800µF) for a stereo amp for 8 ohms running off 60hz.
The newer opamp driver version does sound a bit better, but still is no great shake.
I've fixed too many to remember fondly.
Kind of hard to find some of the germanium transistors in this thing (yes, I did say germanium).
The newer version has a way cool, accurate LED meter. The old meters were for looks.
It's a love/hate deal with these things.
Yes, the one pair of main filters are barely adequate (6800µF) for a stereo amp for 8 ohms running off 60hz.
The newer opamp driver version does sound a bit better, but still is no great shake.
I've fixed too many to remember fondly.
Kind of hard to find some of the germanium transistors in this thing (yes, I did say germanium).
The newer version has a way cool, accurate LED meter. The old meters were for looks.
It's a love/hate deal with these things.
Good morning, An old design; I wonder how it would sound with newer electros, double the capacitance to about 12000 mfd. per rail and snubber these caps?
Is there a current diy design that can use this 75 volt per rail?
Is there a current diy design that can use this 75 volt per rail?
Hi Doggy,
"Is there a current diy design that can use this 75 volt per rail?"
I have one coming, just have to prove it up. Symmetrical diff'l with modulated cascode, comp MOSFET out and R2R.
Soon.
Cheers,
greg
"Is there a current diy design that can use this 75 volt per rail?"
I have one coming, just have to prove it up. Symmetrical diff'l with modulated cascode, comp MOSFET out and R2R.
Soon.
Cheers,
greg
Phase Linear Model 400 Series 2 Repair Question
I loaned my PL 400 Series 2; when I got it back it had blown protection fuses. Three output transistors (using the service manual procedure) showed as bad (shorted). I had used it the day before loaning without problems.
The outputs are relatively cheap (ON 15024) ... about $5 each. Would it be worth just changing all of them on the bad channel, or is there a good possibility that other parts are bad? Last time it was serviced it had only bad outputs, but that was back in 1988.
I did take it to a recommended local service outlet, but they don't agree with all the service bulletins regarding transistor substitutions, and I really don't know if they know what they are doing. They say six outputs are bad, though. They want to use NTEs. My old really good service tech is out of business.
My thinking is to try changing them all and sending it to a Phase Linear expert if that doesn't work, unless someone here has some hints otherwise.
Thanks,
Richard Wagoner
(PS: I tried to do this as a new subject, but the forum would not let me. Is replying here OK?)
I loaned my PL 400 Series 2; when I got it back it had blown protection fuses. Three output transistors (using the service manual procedure) showed as bad (shorted). I had used it the day before loaning without problems.
The outputs are relatively cheap (ON 15024) ... about $5 each. Would it be worth just changing all of them on the bad channel, or is there a good possibility that other parts are bad? Last time it was serviced it had only bad outputs, but that was back in 1988.
I did take it to a recommended local service outlet, but they don't agree with all the service bulletins regarding transistor substitutions, and I really don't know if they know what they are doing. They say six outputs are bad, though. They want to use NTEs. My old really good service tech is out of business.
My thinking is to try changing them all and sending it to a Phase Linear expert if that doesn't work, unless someone here has some hints otherwise.
Thanks,
Richard Wagoner
(PS: I tried to do this as a new subject, but the forum would not let me. Is replying here OK?)
You should replace them all with new MJ 15024.. You could chance it with just the ones you know are bad but they probably would end up blowing the new or the old transistors.
I would look for another tech. Anyone experienced in audio wouldn't even consider the NTE's. The 15024's are easy too find and you could probably replace all of them for the price of 6 NTE's.
With the outputs going you should look further back in the amp for other damage.
I would look for another tech. Anyone experienced in audio wouldn't even consider the NTE's. The 15024's are easy too find and you could probably replace all of them for the price of 6 NTE's.
With the outputs going you should look further back in the amp for other damage.
lubbie said:
Thanks for the reply. I ended up opening up a new thread, so to keep from tying up the boards, I'll copy this over to http://www.diyaudio.com/forums/showthread.php?s=&postid=1281757
I picked up the amp today. They found the same bad output transistors; at least they did want to change all 6 rather than just the bad 3. They said they checked everything and that the outputs were all that was bad. I don't necessarily believe them. Interestingly, they switched one of the driver transistors with an output transistor on the "good" channel.
Now ... should I buy MJ15024, or would the MJ21196 be a good upgrade? (supposedly more able to dissipate heat).
I put the new caps in my Phase Linear 200 series 2. I realize its a smaller amp but it has considerable more power with the new caps. I upgraded to 35,000uf. <-- Thats not a typo. I have used my meter and have caught it at 226w rms. Thats peak short term rms but thats alot of power for for a 120w rms rated amp. The new caps made a huge difference in the highs and the lows mids became clearer and more musical.
In the last production runs of the series II amps the drivers were the same as the outputs. Also they switched to full complimentary.With some work it is possible to convert to full comp. I've done it a few times for customers. I've had amps that were not stable with NEC's but worked fine with 2119X's.
I'd wonder about any tech who thinks he's smarter than the factory service bulletins. You don't write a bulletin based on one or two repairs.
I'd wonder about any tech who thinks he's smarter than the factory service bulletins. You don't write a bulletin based on one or two repairs.
The amps will work fine with the MJ15024's and the amp will be stable and that is the number one consideration in my opinion. Stay clear of ECG and NTE parts. The amplifier is nothing special and has no magical sound as its so so. Fix it and Ebay it is what I would do and then look for something that is fully complimentry in design and you will be further ahead.
Quote:
I put the new caps in my Phase Linear 200 series 2. I realize its a smaller amp but it has considerable more power with the new caps. I upgraded to 35,000uf. <-- Thats not a typo. I have used my meter and have caught it at 226w rms. Thats peak short term rms but thats alot of power for for a 120w rms rated amp. The new caps made a huge difference in the highs and the lows mids became clearer and more musical.
Sounds like you ran it with one channel driving a load. The amplifier's power rating is with both channels driving a load. Your 35K filter cap size will not raise the power output of the amplifier enough to see any great measurable difference. Highs and mid lows more clearer and musical? Sounds like your original filter caps were in bad shape. One has to be careful when oversizing the power supply caps because this causes strain on the bridge rectifier and in some cases will result in one having to build or purchase a soft start circuit.
Quote:
I put the new caps in my Phase Linear 200 series 2. I realize its a smaller amp but it has considerable more power with the new caps. I upgraded to 35,000uf. <-- Thats not a typo. I have used my meter and have caught it at 226w rms. Thats peak short term rms but thats alot of power for for a 120w rms rated amp. The new caps made a huge difference in the highs and the lows mids became clearer and more musical.
Sounds like you ran it with one channel driving a load. The amplifier's power rating is with both channels driving a load. Your 35K filter cap size will not raise the power output of the amplifier enough to see any great measurable difference. Highs and mid lows more clearer and musical? Sounds like your original filter caps were in bad shape. One has to be careful when oversizing the power supply caps because this causes strain on the bridge rectifier and in some cases will result in one having to build or purchase a soft start circuit.
as with any high power amp, you want to check the beta of the output devices. some amps require a beta of LESS THAN 75 or 100. this is to minimize common mode conduction. MJ15024/25 specs are 50-150 for beta. with NTE devices, you are probably getting relabeled 15024/25's, BUT possibly not within spec.
the problem of common mode conduction (pass through) in the output stage, plus instability with long (capacitive) speaker cables was the Achilles' heel of the PL amps. this earned them the nickname of "flame linear". operating the amp with long speaker cables would cause oscillation, which would then cause common mode conduction, and there go some output devices.
again NTE's definitely a NO-NO!.... treat NTE's as a spare tire... enough to get you back on the road, but not anything you want to put mileage on.
the problem of common mode conduction (pass through) in the output stage, plus instability with long (capacitive) speaker cables was the Achilles' heel of the PL amps. this earned them the nickname of "flame linear". operating the amp with long speaker cables would cause oscillation, which would then cause common mode conduction, and there go some output devices.
again NTE's definitely a NO-NO!.... treat NTE's as a spare tire... enough to get you back on the road, but not anything you want to put mileage on.
unclejed613 said:
MJ15024's are able to tolerate common mode conduction better than the original PL909's. Adding the missing RL filter to the output of the amp will enable it to deal with capacitive loads.
The *real* reason for the nickname was because when it did fail, sometimes people on the dance floor thought it was part of the pyro. I've seen sparks fly out of the vents a foot in the air. And that's what happens when you bypass the rail fuses, which would nuisance-blow constantly if you didn't.
i've seen the results of the pyro.... at least PL amps are repairable once this happens, unlike Acoustic Controls model 370 bass amps. once those go, they're done. rebuilt a 370 for a friend 3 times, replacing all of the silicon and burnt resistors, etc... each time, only to have the amp instantaneously self destruct upon reaching 60 volts on the variac. since then i have talked to other techs who had the same thing happen. PL amps seem to be repairable (usually) but sometimes by bridging solder wick or bus wire across holes in the board. i once saw a PL amp that had blown a hole through the top of one of the output devices right over the emitter pin.
unclejed613 said:
uncljed613
I'd like to ask you a few questions concerning common mode conduction without hijacking this thread. If you're available please email me.
jleaman said:
The LED power meter was the best part of the PL400 S2. I've never found one single piece of documentation on the LED driver chips. However, it is possible to make a similar LED meter with 3914's (yes, the linear driver, not the log version) in Dot mode. You need to stack 4 of them. and use a simple peak detector for the input signal. The app notes on the 3914 give all the info you need. For the final finishing touch, the clip indicator, you need a 555 configured as a one-shot to stretch the pulse on the top LED indicator, and put 4 LEDs in series or parallel on the output of that. It looks eerily similar to the PL power meter.
I have a pdf of the display schematic, board layout and theory. It's too large to post here. Anyone who wants it can email me.
Phase Linear 400 rebuilds
Just completed the rebuild and re design of a pair of Phase Linear 400s. The first is the earlier version with meters but has the upgraded heat sinks and the second is the later version with the bar graph and level controls.
I use MJ15003/ MJ15004 for both outputs and drivers. The +/-82v of rail doesn't scare these devices as their Vceo is way higher than the 160v rails. I grade all devices for voltage beardown before installation and the addition of a base emitter turn off resistor raises the effective Vceo well above 160v anyway.
The older 400 was converted to a fully complementary output stage. I modified the differential pair (and used better devices) to have a constant current source for the diff tails and degenerated the diff pair for better stability and lower open loop gain. Threw out those terrible VI trannies and used high current TO92L devices.
The input resistor was changed from a 10K to a 2K to lower the pahse shift ay higher frequencies.
The VAS stage was changed to also have a constant current driver instead of the simple bootstrap system PL was so fond of.
The amplifier was stripped and completely rewired as Phase Linear did a bad job of wire routing and grounding. Their "cure" for some of their bad grounding was to join the RCA grounds to the right channel speaker ground. Lots of crossotalk and noise with their method. All gone woth proper grounding.
Installed Tiifany RCAs and new binding posts with thicker posts and all gold plated stuff here. Looks cool of course.
Stability issues were easily taken care of by installing base stopper resistors on the drivers on the PCB. Added base stoppers to each output device and changed all emitter resistors to 5w metal oxide types.
Had to change the bias circuit to take care of the 6 base-emitter junctions in the output stages. Track pretty well with increased heat sink temperature.
Changed the power supply caps to 12,000mfd 80v parts (Anyone need I have hundreds in stock)
The amplifier was completely rewired.
THD was acceptable at less than 0.05% at any power level from 1w to 210 watts per channel at all frequencies from 20Hzx to 20KHz as measured with an Audio Precision System One.
The newer 400 has the LF353 front end. Basically did all what I did to the older 400 and replaced the LF353 with an OPA2134.
The amplifier has been completed rewired as well.
Anybody have the schematics of the meter driver circuits for the newer 400?
If so can you send to me at "zedaudio@aol.com
Steve Mantz
Zed Audio Corp.
Just completed the rebuild and re design of a pair of Phase Linear 400s. The first is the earlier version with meters but has the upgraded heat sinks and the second is the later version with the bar graph and level controls.
I use MJ15003/ MJ15004 for both outputs and drivers. The +/-82v of rail doesn't scare these devices as their Vceo is way higher than the 160v rails. I grade all devices for voltage beardown before installation and the addition of a base emitter turn off resistor raises the effective Vceo well above 160v anyway.
The older 400 was converted to a fully complementary output stage. I modified the differential pair (and used better devices) to have a constant current source for the diff tails and degenerated the diff pair for better stability and lower open loop gain. Threw out those terrible VI trannies and used high current TO92L devices.
The input resistor was changed from a 10K to a 2K to lower the pahse shift ay higher frequencies.
The VAS stage was changed to also have a constant current driver instead of the simple bootstrap system PL was so fond of.
The amplifier was stripped and completely rewired as Phase Linear did a bad job of wire routing and grounding. Their "cure" for some of their bad grounding was to join the RCA grounds to the right channel speaker ground. Lots of crossotalk and noise with their method. All gone woth proper grounding.
Installed Tiifany RCAs and new binding posts with thicker posts and all gold plated stuff here. Looks cool of course.
Stability issues were easily taken care of by installing base stopper resistors on the drivers on the PCB. Added base stoppers to each output device and changed all emitter resistors to 5w metal oxide types.
Had to change the bias circuit to take care of the 6 base-emitter junctions in the output stages. Track pretty well with increased heat sink temperature.
Changed the power supply caps to 12,000mfd 80v parts (Anyone need I have hundreds in stock)
The amplifier was completely rewired.
THD was acceptable at less than 0.05% at any power level from 1w to 210 watts per channel at all frequencies from 20Hzx to 20KHz as measured with an Audio Precision System One.
The newer 400 has the LF353 front end. Basically did all what I did to the older 400 and replaced the LF353 with an OPA2134.
The amplifier has been completed rewired as well.
Anybody have the schematics of the meter driver circuits for the newer 400?
If so can you send to me at "zedaudio@aol.com
Steve Mantz
Zed Audio Corp.
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