Johnny D's 700 Adventure
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Re: Phase Linear 400
this getting to be a pain in the ass, have no way of measure this shit. waste alot of time and money.....going to replace the drivers, then disconnect the latching circuit if that doesnt work Ill try putting in the old board. If no luck going to gut it and use a voltage double and make a push-pull el34 amp out of the chassis.....DONE.
this getting to be a pain in the ass, have no way of measure this shit. waste alot of time and money.....going to replace the drivers, then disconnect the latching circuit if that doesnt work Ill try putting in the old board. If no luck going to gut it and use a voltage double and make a push-pull el34 amp out of the chassis.....DONE.
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Re: Phase Linear 400
Hi John
Some of these old amps have very elusive problems that take a lot of time to work through.
I think you are referring to the original PL700B schematic where it shows +.5 with an arrow pointing to the base of Q13 and the emitter of Q11. If you have zero volts on the output, give or take the normal few millivolts of offset voltage then you should have the bias voltage at this measurement point (~0.35V). If you really measure 0.9V at this point then this means that you have about 3.7A of static current running through the output drivers at idle which will produce a large amount of heat. This is definitely abnormal if that is a real reading you are getting. It could also explain why you are popping a mains fuse at power up if this current is real.
Are you getting this reading on both channels?
Are you able to get the bias current to adjust to the specified 0.300 - 0.400V range on R38?
Hi John
Some of these old amps have very elusive problems that take a lot of time to work through.
I think you are referring to the original PL700B schematic where it shows +.5 with an arrow pointing to the base of Q13 and the emitter of Q11. If you have zero volts on the output, give or take the normal few millivolts of offset voltage then you should have the bias voltage at this measurement point (~0.35V). If you really measure 0.9V at this point then this means that you have about 3.7A of static current running through the output drivers at idle which will produce a large amount of heat. This is definitely abnormal if that is a real reading you are getting. It could also explain why you are popping a mains fuse at power up if this current is real.
Are you getting this reading on both channels?
Are you able to get the bias current to adjust to the specified 0.300 - 0.400V range on R38?
Re: Phase Linear 400
John
Let's check the shared things between the 2 channels in order to rule them out.
First recommendation, ensure the + and - 20V power supply regulators are working properly.
Connect the negative DMM lead to star point ground in your amp.
Plus 20V measurement
Connect your positive DMM lead to the top side of R73R, just to the right of the TO-220 transistor Q30. It is a 10 ohm, 1/4W resistor. This should measure +19.0 to +21.0V if operating properly in your amp.
Minus 20V measurement
Connect your positive DMM lead to the top side of R80, a large 2W resistor just above the board lower mounting stud. It is a 12K ohm, 2W resistor. This should measure -19.0 to -21.0V if operating properly in your amp.
John
Let's check the shared things between the 2 channels in order to rule them out.
First recommendation, ensure the + and - 20V power supply regulators are working properly.
Connect the negative DMM lead to star point ground in your amp.
Plus 20V measurement
Connect your positive DMM lead to the top side of R73R, just to the right of the TO-220 transistor Q30. It is a 10 ohm, 1/4W resistor. This should measure +19.0 to +21.0V if operating properly in your amp.
Minus 20V measurement
Connect your positive DMM lead to the top side of R80, a large 2W resistor just above the board lower mounting stud. It is a 12K ohm, 2W resistor. This should measure -19.0 to -21.0V if operating properly in your amp.
Re: Phase Linear 400
Second recommendation to check.
Ensure the 3 channel to channel interconnect jumpers for sharing power (B+/B-) and ground between the 2 channels are not compromised. Check the teflon tubing insulation and ensure none of it is pierced and touching some unintended component on the board.
The remainder of the shared resources are on the chassis so going through them will take more time.
Are the Zoebel networks on your amp mounted at the speaker binding posts the original ones supplied by Phase Linear? (2 - 10 ohm, 2W resistors in parallel in series with a 0.1uF film capacitor) I ran into a problem on another users amp where some home brew work had been done here by a previous owner and was causing problems with the original PL20 board in the amp.
Second recommendation to check.
Ensure the 3 channel to channel interconnect jumpers for sharing power (B+/B-) and ground between the 2 channels are not compromised. Check the teflon tubing insulation and ensure none of it is pierced and touching some unintended component on the board.
The remainder of the shared resources are on the chassis so going through them will take more time.
Are the Zoebel networks on your amp mounted at the speaker binding posts the original ones supplied by Phase Linear? (2 - 10 ohm, 2W resistors in parallel in series with a 0.1uF film capacitor) I ran into a problem on another users amp where some home brew work had been done here by a previous owner and was causing problems with the original PL20 board in the amp.
Re: Phase Linear 400
Hi Joe
As for the zobel network, have the dc protect board I purchased and has zobel network built on board, I notice that they were 7 ohm ceramic risitors as opposed to the 5 ohm of the original from Phase Linear..I can check the regulator when I get home and will write what I find.
Havent done any thing to it since my last writing.shut it off and left it in fustration...changed every component other than the outputs and drivers. outputs were new when I install, have now way to check the transistors other than diode check, bias I set for 370 at r38 and r39 was 357 on the same channel, dont remember resistor numbers for other channel...but both were vey close to each other.
Hi Joe
As for the zobel network, have the dc protect board I purchased and has zobel network built on board, I notice that they were 7 ohm ceramic risitors as opposed to the 5 ohm of the original from Phase Linear..I can check the regulator when I get home and will write what I find.
Havent done any thing to it since my last writing.shut it off and left it in fustration...changed every component other than the outputs and drivers. outputs were new when I install, have now way to check the transistors other than diode check, bias I set for 370 at r38 and r39 was 357 on the same channel, dont remember resistor numbers for other channel...but both were vey close to each other.
Re: Phase Linear 400
Hi John
So if the bias set properly, it is basically impossible to measure 0.9V at the node referenced on the schematic as the bias resistor is across these 2 points. You should therefore be measuring 370 and 357 mV respectively. Double check this. Will be around later tonight to follow up.
Joe
Hi John
So if the bias set properly, it is basically impossible to measure 0.9V at the node referenced on the schematic as the bias resistor is across these 2 points. You should therefore be measuring 370 and 357 mV respectively. Double check this. Will be around later tonight to follow up.
Joe
Re: Phase Linear 400
Joe you should label the reqiured voltages on the schematic to thier corrospnding point or numbers on your board, make it easier for test without dropping the board to see where the wires are terminated between board and transistors. Just for future. Or link your numbers to the power output stage of the existing schematic..
Joe you should label the reqiured voltages on the schematic to thier corrospnding point or numbers on your board, make it easier for test without dropping the board to see where the wires are terminated between board and transistors. Just for future. Or link your numbers to the power output stage of the existing schematic..
Re: Phase Linear 400
Hi John
The connection numbers on the White Oak board map exactly to the original Phase Linear connection numbers for the PL14 board used in nearly all PL400 amps and some PL700B amps.
Phase changed the numbering when they introduced the PL20 board as they included the bias transistor connections into the bottom row connector lineup versus being up in the center of the board on the PL14. This screwed up universality.
Since the White Oak board is universal, I decided to choose the PL14 standard as that is what the vast majority of amps that Phase Linear produced had installed in them. That is the reasoning behind it.
That said, the connector numbering on the White Oak board is in exactly the same order as the original PL20 order if you omit 4, 10 and 12 on the original PL schematic.
You can mark your schematic as follows to help you debug.
1 no markup required, same
2 no markup required, same
3 no markup required, same
4 N/A
5 mark your original Phase Linear schematic 5(4)
6 mark your original Phase Linear schematic 6(5)
7 mark your original Phase Linear schematic 7(6)
8 mark your original Phase Linear schematic 8(7)
9 mark your original Phase Linear schematic 9(8)
10 N/A
11 mark your original Phase Linear schematic 11(9)
12 N/A
13 mark your original Phase Linear schematic 13(10)
14 mark your original Phase Linear schematic 14(11)
15 mark your original Phase Linear schematic 15(12)
You will note that despite Phase Linear messing with the numbering on the right hand side of their PL20 schematic when compared with the PL14 board, the signal intent from top to bottom on that right hand edge of the schematic is identical. It is also identical to the White Oak schematic, on purpose.
Hi John
The connection numbers on the White Oak board map exactly to the original Phase Linear connection numbers for the PL14 board used in nearly all PL400 amps and some PL700B amps.
Phase changed the numbering when they introduced the PL20 board as they included the bias transistor connections into the bottom row connector lineup versus being up in the center of the board on the PL14. This screwed up universality.
Since the White Oak board is universal, I decided to choose the PL14 standard as that is what the vast majority of amps that Phase Linear produced had installed in them. That is the reasoning behind it.
That said, the connector numbering on the White Oak board is in exactly the same order as the original PL20 order if you omit 4, 10 and 12 on the original PL schematic.
You can mark your schematic as follows to help you debug.
1 no markup required, same
2 no markup required, same
3 no markup required, same
4 N/A
5 mark your original Phase Linear schematic 5(4)
6 mark your original Phase Linear schematic 6(5)
7 mark your original Phase Linear schematic 7(6)
8 mark your original Phase Linear schematic 8(7)
9 mark your original Phase Linear schematic 9(8)
10 N/A
11 mark your original Phase Linear schematic 11(9)
12 N/A
13 mark your original Phase Linear schematic 13(10)
14 mark your original Phase Linear schematic 14(11)
15 mark your original Phase Linear schematic 15(12)
You will note that despite Phase Linear messing with the numbering on the right hand side of their PL20 schematic when compared with the PL14 board, the signal intent from top to bottom on that right hand edge of the schematic is identical. It is also identical to the White Oak schematic, on purpose.
Re: Phase Linear 400
Hi Joe
Stupid me I figured that out when I started poking around to get voltages from components on board...well here is what I found. As you suggested I checked what you wanted me to check, the voltage on the drivers were .3 and regulator is in spec. I couldnt find R23 on your board though. I have phase linear schematic with voltages at alot of the points and checked them all and were good except for one...this is on left and right channel, Q9 to D10 is suppose to be -1.4v, but it is .3v, on the cathode side of D10 is .678, Q5 is connected to the cathode side of D10 and the voltage speced is .7 so that checked out.
I was reading the service manual and they suggest a current sharing test to check for leaky transistor in the output, they say 200hz signal and 53v at output into 8ohm load and then a variac reduced to 80v line voltage...I don't have a variac, is there another way? They say transistor testers dont check for leaky transistor only a load will show voltage drop across emitter resistor, they spec 140mv to 180mv across emitter +/-20% is good.
Hi Joe
Stupid me I figured that out when I started poking around to get voltages from components on board...well here is what I found. As you suggested I checked what you wanted me to check, the voltage on the drivers were .3 and regulator is in spec. I couldnt find R23 on your board though. I have phase linear schematic with voltages at alot of the points and checked them all and were good except for one...this is on left and right channel, Q9 to D10 is suppose to be -1.4v, but it is .3v, on the cathode side of D10 is .678, Q5 is connected to the cathode side of D10 and the voltage speced is .7 so that checked out.
I was reading the service manual and they suggest a current sharing test to check for leaky transistor in the output, they say 200hz signal and 53v at output into 8ohm load and then a variac reduced to 80v line voltage...I don't have a variac, is there another way? They say transistor testers dont check for leaky transistor only a load will show voltage drop across emitter resistor, they spec 140mv to 180mv across emitter +/-20% is good.
Re: Phase Linear 400
Hi John
R23L and R are on the board vertically oriented just above the connection pin labeled 8L and R.
I usually test predrivers and drivers in a matching fixture that I have for that purpose. It measures the Vbe while a controlled collector to emitter current is flowing. I used it to match the RCA410 predrivers that were sent to you.
Hi John
R23L and R are on the board vertically oriented just above the connection pin labeled 8L and R.
I usually test predrivers and drivers in a matching fixture that I have for that purpose. It measures the Vbe while a controlled collector to emitter current is flowing. I used it to match the RCA410 predrivers that were sent to you.
Re: Phase Linear 400
Matching fixture? you talking about a phase linear amp or a transitor loading fixture?
I have sone plans to build one from a schematic I got off the internet...why do you think I have .3v between Q9/D10 when it say's 1.4v? looking at the schematic looks to me that Q7 is suppling D10, but voltages checks fine at Q7..could there be some thing wrong with outputs?
What boggles me is its on the L+R channel...but one channel plays fine by itself until the other channel in added.
Matching fixture? you talking about a phase linear amp or a transitor loading fixture?
I have sone plans to build one from a schematic I got off the internet...why do you think I have .3v between Q9/D10 when it say's 1.4v? looking at the schematic looks to me that Q7 is suppling D10, but voltages checks fine at Q7..could there be some thing wrong with outputs?
What boggles me is its on the L+R channel...but one channel plays fine by itself until the other channel in added.
Re: Phase Linear 400
Hi John
I am not sure I trust the voltages on that old schematic. Most look reasonable but the -1.4V note at the collector of Q9 looks suspicious. I have a couple of board assemblies that I am testing out tomorrow. I will let you know what the voltages are after I measure them off of a board under test.
Hi John
I am not sure I trust the voltages on that old schematic. Most look reasonable but the -1.4V note at the collector of Q9 looks suspicious. I have a couple of board assemblies that I am testing out tomorrow. I will let you know what the voltages are after I measure them off of a board under test.
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), but here's an idea for you - take the DCP out for a quick test to see if the channels bleed still. Fuse the output lines good tho.. quick acting fuse with a low enough amperage - JUST in case.