Ok, first I know that the 4000 gets no love here or with any forum that I have seen. I have a PL4000 I purchased new in 1977. I actually purchased the PL2000 first and took it home tried it and I felt it was noisy so next day I swapped it for the 4000. Back to the present just got it hooked up and every thing seems to work as it should including the auto correlator system and the Peak Unlimiter system, however when the volume control is all the way down there is a low hum (60hz). What would you begin looking to trouble shoot this issue. When any volume is present it is not noticeable. Is this possibly a quirk of this series. Any thought would be appreciated.
PL 4000 issue?
- Thread starter Wayne G.
- Start date
Hey Wayne,
The 4000 has a lot of innovative designs incorporated in the design of this preamp. I have one and the are quite the looker. One of the downfalls of this preamp are the lack of support of the motherboard. What happens is when you remove or install a daughter board it tends to flex the mother board causing fractures of the solder joints. Another is the choice of connectors used for the daughter board - mother board interface. These have little contact surface so probably not the best choice. One other issue that I'll note is the ass ton of electrolytic capacitors used in the design. I think this amp can be improved - just don't know what the final product would be. I like this preamp and the only thing I've done to mine is to clean the pots and reflow the solder joints on the motherboard.
Ok - with that said you should check your power supply first as this is the most likely cause of your 60 or 120 Hz hum. Hum is not normal so check your supply first. The caps are aging and they would be suspect along with the rectifier circuit. Do you have an oscilloscope or a meter?
Keep us posted and photos are always welcome.
The 4000 has a lot of innovative designs incorporated in the design of this preamp. I have one and the are quite the looker. One of the downfalls of this preamp are the lack of support of the motherboard. What happens is when you remove or install a daughter board it tends to flex the mother board causing fractures of the solder joints. Another is the choice of connectors used for the daughter board - mother board interface. These have little contact surface so probably not the best choice. One other issue that I'll note is the ass ton of electrolytic capacitors used in the design. I think this amp can be improved - just don't know what the final product would be. I like this preamp and the only thing I've done to mine is to clean the pots and reflow the solder joints on the motherboard.
Ok - with that said you should check your power supply first as this is the most likely cause of your 60 or 120 Hz hum. Hum is not normal so check your supply first. The caps are aging and they would be suspect along with the rectifier circuit. Do you have an oscilloscope or a meter?
Keep us posted and photos are always welcome.
The PL4000 looks great but suffers from some design issues as Dennis points out.
It is a single power rail design rather than a split rail design which forces the use of a lot of coupling caps to move from gain stage to gain stage. It also means that the gain stages suffer from low PSRR (power supply rejection ratio).
The single positive regulator is a crude shunt regulator design using a zener diode to regulate the output voltage. This regulator will allow some level of AC ripple through, especially when the filter capacitors used in the regulator circuit are old and ineffective. When you couple this and the low PSRR above, that equals 60Hz hum.
The connectors to the mother board were tin plated and oxidize over the years leading to intermittent connections. I have a PL4000 and that is what plagues me all the time. I finally broke down and ordered the gold replacement connectors to mitigate that shortcoming. I have to find a block of time to install them now.
It is a single power rail design rather than a split rail design which forces the use of a lot of coupling caps to move from gain stage to gain stage. It also means that the gain stages suffer from low PSRR (power supply rejection ratio).
The single positive regulator is a crude shunt regulator design using a zener diode to regulate the output voltage. This regulator will allow some level of AC ripple through, especially when the filter capacitors used in the regulator circuit are old and ineffective. When you couple this and the low PSRR above, that equals 60Hz hum.
The connectors to the mother board were tin plated and oxidize over the years leading to intermittent connections. I have a PL4000 and that is what plagues me all the time. I finally broke down and ordered the gold replacement connectors to mitigate that shortcoming. I have to find a block of time to install them now.
Guy's thanks for the reply's. For the fist time in since it was purchased I removed the cover and cleaned the volume control pot and the selector
switch with Deoxit F5 and Deoxit Fader F5 which took care of the horrible scratchy volume control. I do not own an oscilloscope and my soldering
skill is not as good as it should be however, I do know where to begin - I did suspect the hum probably originates in the power supply. Thanks
again I will keep you posted.
switch with Deoxit F5 and Deoxit Fader F5 which took care of the horrible scratchy volume control. I do not own an oscilloscope and my soldering
skill is not as good as it should be however, I do know where to begin - I did suspect the hum probably originates in the power supply. Thanks
again I will keep you posted.
I have one of these as well. It's not as bad as you may have been lead to believe OTOH, it has it's quirks, which the others have touched on. Mine was outputting DC on one channel when I got it due to a bad cap, so I recapped the entire thing (electrolytic only). Mine is not in service right now, but lacks any noticeable hum. Almost every cap I changed was out of spec, most by a large amount. I'm not talking about inside the 20% tolerance, but way out on some.
Oddly, the LED on the unlimiter works backward, but the unlimiter itself works correctly.
I haven't looked closely, but this may be of interest. I think it applies to our 4000's also- been a while since I looked.
http://home.onemain.com/~jvandyke/id9.html
Also, if you don't have a Haako de-solderer or similar, and intend to recap, do yourself a favor and get one of these...MUCH better than bulb or wick.
http://www.parts-express.com/ecg-j-045-ds-45-watt-desoldering-iron--372-202
Joe, can you share your source and maybe a part number for the jacks if it's handy? I know...lazy. What can I say?
Oddly, the LED on the unlimiter works backward, but the unlimiter itself works correctly.
I haven't looked closely, but this may be of interest. I think it applies to our 4000's also- been a while since I looked.
http://home.onemain.com/~jvandyke/id9.html
Also, if you don't have a Haako de-solderer or similar, and intend to recap, do yourself a favor and get one of these...MUCH better than bulb or wick.
http://www.parts-express.com/ecg-j-045-ds-45-watt-desoldering-iron--372-202
Joe, can you share your source and maybe a part number for the jacks if it's handy? I know...lazy. What can I say?
Sure
Phase Linear standardized on the 10pin and 6pin versions of the Molex KK series 0.156 pitch connectors. If they needed a wider connector, they just used 2 or more of these 10p or 6p connectors.
Mouser part numbers shown below.
Male 10p straight header with lock, gold = 538-26-61-4100
Male 10p straight header without lock, gold = 538-26-48-2101
Male 6p straight header with lock, gold = 538-171813-1006
Female 10p right angle receptacle, gold = 538-09-48-3105
Female 6p right angle receptacle, NON gold = 538-09-48-1064 (they have no stock in gold for this receptacle)
Engineering cheat sheet of locations is below.
Phase Linear standardized on the 10pin and 6pin versions of the Molex KK series 0.156 pitch connectors. If they needed a wider connector, they just used 2 or more of these 10p or 6p connectors.
Mouser part numbers shown below.
Male 10p straight header with lock, gold = 538-26-61-4100
Male 10p straight header without lock, gold = 538-26-48-2101
Male 6p straight header with lock, gold = 538-171813-1006
Female 10p right angle receptacle, gold = 538-09-48-3105
Female 6p right angle receptacle, NON gold = 538-09-48-1064 (they have no stock in gold for this receptacle)
Engineering cheat sheet of locations is below.
Last edited:
Sure
Phase Linear standardized on the 10pin and 6pin versions of the Molex KK series 0.156 pitch connectors. If they needed a wider connector, they just used 2 or more of these 10p or 6p connectors.
Mouser part numbers shown below.
Male 10p straight header with lock, gold = 538-26-61-4100
Male 10p straight header without lock, gold = 538-26-48-2101
Male 6p straight header with lock, gold = 538-171813-1006
Female 10p right angle receptacle, gold = 538-09-48-3105
Female 6p right angle receptacle, NON gold = 538-09-48-1064 (they have no stock in gold for this receptacle)
Engineering cheat sheet of locations is below.
View attachment 13892
Phase Linear standardized on the 10pin and 6pin versions of the Molex KK series 0.156 pitch connectors. If they needed a wider connector, they just used 2 or more of these 10p or 6p connectors.
Mouser part numbers shown below.
Male 10p straight header with lock, gold = 538-26-61-4100
Male 10p straight header without lock, gold = 538-26-48-2101
Male 6p straight header with lock, gold = 538-171813-1006
Female 10p right angle receptacle, gold = 538-09-48-3105
Female 6p right angle receptacle, NON gold = 538-09-48-1064 (they have no stock in gold for this receptacle)
Engineering cheat sheet of locations is below.
View attachment 13892
Thanks Joe.
I didn't read closely enough. I thought you meant the RCA's. I'm guessing that they're probably pretty standard, but I haven't looked. Pretty sure I'm placing a Mouser order for work soon, and like to get in on the free shipping I get that way. Not important.
My MoBo connectors are in good shape, but this is still good info to have up on the board.
I didn't read closely enough. I thought you meant the RCA's. I'm guessing that they're probably pretty standard, but I haven't looked. Pretty sure I'm placing a Mouser order for work soon, and like to get in on the free shipping I get that way. Not important.
My MoBo connectors are in good shape, but this is still good info to have up on the board.
Joe, speaking of RCA jacks, I know the jacks on the rear of the 4000 are not the greatest. A recent sale of a 4000 on eBay had been refurbished
by a Bill Green (Circle Stereo) in Texas and it appears he replaced the board mounted jacks with jacks that mount on the rear panel? Another shop
told me this can't be done? Have you seen this done before?
by a Bill Green (Circle Stereo) in Texas and it appears he replaced the board mounted jacks with jacks that mount on the rear panel? Another shop
told me this can't be done? Have you seen this done before?
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Joe,
Thanks for the inputs. The connector replacement would be an excellent upgrade for this preamp.
It seems that the power regulator could stand to be upgraded. Have you given this any thought - I know you have but wanted to ask. Maybe another daughter board with modern components could be a possible solution.
Thanks for the inputs. The connector replacement would be an excellent upgrade for this preamp.
It seems that the power regulator could stand to be upgraded. Have you given this any thought - I know you have but wanted to ask. Maybe another daughter board with modern components could be a possible solution.
- Joined
- Jan 14, 2011
- Messages
- 75,335
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
Dear Nav Linear ,
I answer you here about PL 4000 restoring .
Probably I was lucky twice , because the mother boards into the two my father's PL4000 are O.K.
At this point I have the doubt that this well known problem is related to the version of the mother
board (there are two versions ) , but I'm not sure , of course .
Any way a complete recap was necessary in both samples . ( at least 80 caps ) .
This replacement is critical and it's necessary to have a desoldering station to do a good job .
I also replaced all the RCA connectors in one sample because they breaks after 25/30 years and I
used some good connectors as spares for the other .
For deoxing switches I used Philips Contact Cleaner .
I also found false contacts on the relay for switched outlet. ( sand paper #1000 and deox )
I added two 12 kOhm resistors in series to aux outputs in order to obtain a 6dB attenuator
when you use PL 400 , because the output level is too high and PL 400 has no input attenuators .
My hifi guru ( specialist in PL and Carver service ,etc. ) helped me very much in this operation .
Ciao
Marco
I answer you here about PL 4000 restoring .
Probably I was lucky twice , because the mother boards into the two my father's PL4000 are O.K.
At this point I have the doubt that this well known problem is related to the version of the mother
board (there are two versions ) , but I'm not sure , of course .
Any way a complete recap was necessary in both samples . ( at least 80 caps ) .
This replacement is critical and it's necessary to have a desoldering station to do a good job .
I also replaced all the RCA connectors in one sample because they breaks after 25/30 years and I
used some good connectors as spares for the other .
For deoxing switches I used Philips Contact Cleaner .
I also found false contacts on the relay for switched outlet. ( sand paper #1000 and deox )
I added two 12 kOhm resistors in series to aux outputs in order to obtain a 6dB attenuator
when you use PL 400 , because the output level is too high and PL 400 has no input attenuators .
My hifi guru ( specialist in PL and Carver service ,etc. ) helped me very much in this operation .
Ciao
Marco
Sorry NavLinear ,
I have forgotten to say that I replaced the RCA connectors with an other type ,
so two short wires are necessary to connect these connectors to the mother board .
I also suggest to short phono 2 input ( generally not used ) with two male plugs shortened
to prevent autoscillations , because original PL connector are self shortening .
Ciao
Marco
I have forgotten to say that I replaced the RCA connectors with an other type ,
so two short wires are necessary to connect these connectors to the mother board .
I also suggest to short phono 2 input ( generally not used ) with two male plugs shortened
to prevent autoscillations , because original PL connector are self shortening .
Ciao
Marco
Ciao Marco,
Thanks for sharing what you did for upgrades regarding the preamplifier. Is this the first of the series - the quad preamp with the joystick? In a previous post one of the Phoenix members (Gepetto - aka Joe) replaced the board and mother board connectors as the original ones have a tendency to corrode over time.
If you have any photographs of the modifications that you'd like to post we'd be grateful to see them.
Nav
Thanks for sharing what you did for upgrades regarding the preamplifier. Is this the first of the series - the quad preamp with the joystick? In a previous post one of the Phoenix members (Gepetto - aka Joe) replaced the board and mother board connectors as the original ones have a tendency to corrode over time.
If you have any photographs of the modifications that you'd like to post we'd be grateful to see them.
Nav