I'll try to run it today and see....maybe the switch bypasses it?
What is a fader taper? Does it taper each way from center, then I'd want 5 of those and 1 audio. Let me check the tapers and I will run it and see. Maybe I can hook it into mine and read off the board as probing the din is near impossible.
I got onto that bazooka amp or I would have finished testing the cables and ran it last night.
I can't find any with a switch either, well not yet.
What is a fader taper? Does it taper each way from center, then I'd want 5 of those and 1 audio. Let me check the tapers and I will run it and see. Maybe I can hook it into mine and read off the board as probing the din is near impossible.
I got onto that bazooka amp or I would have finished testing the cables and ran it last night.
I can't find any with a switch either, well not yet.
Apparently my stash of old odds & ends is dwindling...(read: tossed out when I wasn't looking)
I do have a 20k dual volume pot with two switches built-in. One is a momentary that closes when you click the shaft in. The second switch opens when you turn the volume all the way down and click it "off". It's a split shaft, not a D, and about 3/16" or 4mm dia.
As Perry stated, this value isn't critical unless the volume is part of a gain stage. Isn't there a block diagram on top of the unit? If so, that may give you a clue where the volume control is placed.
Tim
I do have a 20k dual volume pot with two switches built-in. One is a momentary that closes when you click the shaft in. The second switch opens when you turn the volume all the way down and click it "off". It's a split shaft, not a D, and about 3/16" or 4mm dia.
As Perry stated, this value isn't critical unless the volume is part of a gain stage. Isn't there a block diagram on top of the unit? If so, that may give you a clue where the volume control is placed.
Tim
Maybe this will help; black box is gain DIN.
Original pots, not the best pic sorry:
Wow that camera works pretty good.
An externally hosted image should be here but it was not working when we last tested it.
Original pots, not the best pic sorry:
An externally hosted image should be here but it was not working when we last tested it.
Wow that camera works pretty good.
Does that help? I still didn't run it, maybe today I can find out what the off switch is for my work area was too messy to work had to clean. Not sure if your control would work Tsmith, I think it opens when on to right. Can get a pushbutton for it but I see they don't give those away....was going to look more for the right one and still need to verify the taper. Those pots are tiny.
Oh Perry thanks for the Radio Shack board suggestion, think I might do that as then can tie the wire to the board that should be a lot better I would think.
Oh Perry thanks for the Radio Shack board suggestion, think I might do that as then can tie the wire to the board that should be a lot better I would think.
If you look at the picture of the PCB, you can see the remote (red/white) wire solder connection is labeled +12V OUT. Therefore, that would be a remote output.
As there is no remote turn on INPUT, the switch incorporated into the volume pot must be the power switch to turn the EQ on.
The switch in my 20k pot would operate correctly, as it would turn the unit on/off at minimum volume. The pot value however, may be an issue. This type of pot is difficult to find without cannibalizing old equipment.
The 555 and GP bipolar opamps ares clues to the PAII's age and simplicity. I think the big key to their magic was simply using a bipolar supply of sufficient voltage for real headroom. Few processors of that era had that feature.
Anyway, it's not immediately evident what role the volume pot plays.
At a glance, it looks like the tl072 is a buffer with gain, the 555 is a vibrator to drive the supply transistors, and the 1458's are part of the actual filter circuit. Although the physical location of the tl072 would be more appropriate for it to be an oscillator for the switching supply.
Simply because the DIN jack is labeled "GAIN", and it's made by Linear Power, I would expect the terminology to be accurate and the pot to be an actual gain adjustment. Therefore, you'd want to stick to 10k.
As far as determining tapers go, the pots need to be measured. Measure each section individually at center, a quarter turn or so off center in each direction, and at extreme. A few readings should give enough information to figure it out.
It appears that if the PCB was removed from the case, you could measure at the solder pins of the DIN jack on the PCB instead of trying to measure inside the plug.
Tim
As there is no remote turn on INPUT, the switch incorporated into the volume pot must be the power switch to turn the EQ on.
The switch in my 20k pot would operate correctly, as it would turn the unit on/off at minimum volume. The pot value however, may be an issue. This type of pot is difficult to find without cannibalizing old equipment.
The 555 and GP bipolar opamps ares clues to the PAII's age and simplicity. I think the big key to their magic was simply using a bipolar supply of sufficient voltage for real headroom. Few processors of that era had that feature.
Anyway, it's not immediately evident what role the volume pot plays.
At a glance, it looks like the tl072 is a buffer with gain, the 555 is a vibrator to drive the supply transistors, and the 1458's are part of the actual filter circuit. Although the physical location of the tl072 would be more appropriate for it to be an oscillator for the switching supply.
Simply because the DIN jack is labeled "GAIN", and it's made by Linear Power, I would expect the terminology to be accurate and the pot to be an actual gain adjustment. Therefore, you'd want to stick to 10k.
As far as determining tapers go, the pots need to be measured. Measure each section individually at center, a quarter turn or so off center in each direction, and at extreme. A few readings should give enough information to figure it out.
It appears that if the PCB was removed from the case, you could measure at the solder pins of the DIN jack on the PCB instead of trying to measure inside the plug.
Tim
Ok I ran this new one today on two amps to check the fader as well, it sounds nice. But, the LEDs didn't work. I hooked up my old one I'm making the cables/controls for and it works the same but no LED on that either. I test and get 11.5v on the LED, but if it is bad it might right? Power is about 12.8v. Do LED have a shelf life? This thing is as-new never installed (the new one and its cables/lights) but they have not made them in years far as I know...unless its a reject. So I guess I need to find the resistor for the LED and figure out what voltage it should run at and get a new LED, or I have some I can scab out of junk amps to try for fun. With its age it is likely a standard LED I would think. Looks like a 1K resistor right behind it might be it. I tried a larger LED and it did not work.
The switch: Why not read the brief manual that came with the new one....it says the switch is to run the trigger for your amps (or look at above pic). Says to wire the whole unit (180ma) to trigger of HU, but use a relay after for multiple amps. I didn't hook it up and it clicks through the speakers when switched...so I think it turns the whole unit off also, and if I used its trigger to the amps it would not click as they would not be on yet. I will test LED voltage for power off.
So I have to check the pot's tapers yet and then get some board to chop up and I should be good, oh and some knobs of course. Then a lot of fumble fiddling with tiny stuff and wires.
It still has the beans, I had an old HU that might be even <2v and I turned the amp gains *all* the way down and the paII all up and it was going loud in the house at 7/8 on the HU. Was trying to see if clipping light came on, it didn't. Then I had to eat dinner.
Yes indeed, it is near impossible to check the DIN ends so I am going to pull the board and test that way. I don't know parts that well, but it sure looks like $20 worth of stuff in there, the whole unit is pretty small. Cute little power supply for sure, after looking at power amps I don't know how else to describe it. The manual states "30v split power supply, up to 5v line output, output buffer preamp w/up to 32db gain, preamp level clipping indicator, amp turn on lead, 150mv-5v input, 4 band EQ, patchback fader." The knobs with the new one are really nice too.
What a nice output to put in a HU.
They used to get $350 for the non remote style, that was more than a 2002 as I recall in the late 80s.
The switch: Why not read the brief manual that came with the new one....it says the switch is to run the trigger for your amps (or look at above pic). Says to wire the whole unit (180ma) to trigger of HU, but use a relay after for multiple amps. I didn't hook it up and it clicks through the speakers when switched...so I think it turns the whole unit off also, and if I used its trigger to the amps it would not click as they would not be on yet. I will test LED voltage for power off.
So I have to check the pot's tapers yet and then get some board to chop up and I should be good, oh and some knobs of course. Then a lot of fumble fiddling with tiny stuff and wires.
It still has the beans, I had an old HU that might be even <2v and I turned the amp gains *all* the way down and the paII all up and it was going loud in the house at 7/8 on the HU. Was trying to see if clipping light came on, it didn't. Then I had to eat dinner.
Yes indeed, it is near impossible to check the DIN ends so I am going to pull the board and test that way. I don't know parts that well, but it sure looks like $20 worth of stuff in there, the whole unit is pretty small. Cute little power supply for sure, after looking at power amps I don't know how else to describe it. The manual states "30v split power supply, up to 5v line output, output buffer preamp w/up to 32db gain, preamp level clipping indicator, amp turn on lead, 150mv-5v input, 4 band EQ, patchback fader." The knobs with the new one are really nice too.
What a nice output to put in a HU.
They used to get $350 for the non remote style, that was more than a 2002 as I recall in the late 80s.Measure the DC voltage across pins 4 and 8 of the op-amps. If the voltage remains high (~30v) with the switch off, the EQ is not powering down.
If you can run audio through it, that would tell you if the switch is shutting down the audio or is simply making/breaking the circuit to the red output lead. If the switch bypasses the EQ, there will be relays or electronic switches to reroute the audio signal around the EQ circuitry.
I'll check maybe later tonight. You have to turn the gain all the way down for off so no audio is heard just before you get there, but the switch clicks in the speakers. I didn't have the remote wire hooked up while testing, the amps were remote off the HU so they stayed on. I have a tiny toggle switch I could use also, but easy to bump depending on where it was mounted.
I removed the board and the switch runs the powersupply. It goes to the remote wire and that .5 ohm resistor with the gray tube on it, there is that diode and a cap then right to two legs on the transformer. It also goes to the 'on' LED through the resistor. The LED both have 100 ohm resistors, one is right behind the din and other across the gain traces. Other side of LEDs to ground. So I need to figure what LED to get for that.
The volume is audio taper, it is ~3 ohm in center of 10K. The rest I have not figured out yet, they show strange readings on the board hooked up and it is so hard to probe the plug and don't have a female cord to chop....I'll try again later or get someone to help me. Maybe I should dig out an analog meter.
I don't see a relay, I can't get sound to come out with it off. I still have to figure out the DIN cables I bought unless they have a standard color coding for the wires....small wires they are.
The volume is audio taper, it is ~3 ohm in center of 10K. The rest I have not figured out yet, they show strange readings on the board hooked up and it is so hard to probe the plug and don't have a female cord to chop....I'll try again later or get someone to help me. Maybe I should dig out an analog meter.
I don't see a relay, I can't get sound to come out with it off. I still have to figure out the DIN cables I bought unless they have a standard color coding for the wires....small wires they are.
The gray tube is covering a small choke (coil) as a filter for the supply. When that piece was made, there weren't many variations in LED's. "Superbright" LED's were unusual. Remove it from the board and check it with a meter like you would check a diode.
Any standard LED will be a fine replacement.
Keep in mind what Perry said early on about the fader, and similar issues could apply to the tone controls. Pots can be made to order, if you have the cash to do so. Read one pot (3 terminal?) at a time. You may find pots for example, that are shorted from the center to one extreme, and tapered from center to the other extreme.
They may have resistors in series or parallel to modify the tapers, in which case you'll have to read them when disconnected.
Given what the manual said about running the unit off the HU trigger, don't expect a relay. It looks like the PAII's supply runs right off the remote trigger lead, and switches that back out to the amps. Back then, remote outputs were typically good for at least 500mA. A relay or transistor switch on the HU's trigger lead would be a good idea.
Tim
Any standard LED will be a fine replacement.
Keep in mind what Perry said early on about the fader, and similar issues could apply to the tone controls. Pots can be made to order, if you have the cash to do so. Read one pot (3 terminal?) at a time. You may find pots for example, that are shorted from the center to one extreme, and tapered from center to the other extreme.
They may have resistors in series or parallel to modify the tapers, in which case you'll have to read them when disconnected.
Given what the manual said about running the unit off the HU trigger, don't expect a relay. It looks like the PAII's supply runs right off the remote trigger lead, and switches that back out to the amps. Back then, remote outputs were typically good for at least 500mA. A relay or transistor switch on the HU's trigger lead would be a good idea.
Tim
I just got help reading the other fader type pots. They go from 0 to 47K on this meter I used and are 24 in the center. However they seem to change fast in the center (near 24) and slow near each end (0 or 47K). Is this a fader taper? They also have a center detent. Then again, it should work fine with a linear taper then right?
.....wait, I checked more and best I can tell half to one side is 10K not 12, but close to half %-wise. I think maybe the way the pots are the end of the travel might fall off the last couple/few K? Is that possible it is just linear?
The pots I tested unplugged as they are on cords with DIN plugs to unit (LEDs are too). I can't get a good reading hooked up, the volume shows roughly 5-10K full travel and 0-10K unhooked so I did them disconnected. (I had tried to test on the board instead of the DIN pins)
I did test the LEDs (both) at the LED (all testing unplugged) and at the DIN, I can't get a reading either place or either polarity on my 20M ohm meter.
Also looked at the board the pots are on, I can see the solder bumps through the tubing and it does not look like any other components are on the board just pot, wires, and ziptie.
Yeah I guess I need like a 500mv switch on the volume. It looks like the switch runs the unit and the remote to the amps.
.....wait, I checked more and best I can tell half to one side is 10K not 12, but close to half %-wise. I think maybe the way the pots are the end of the travel might fall off the last couple/few K? Is that possible it is just linear?
The pots I tested unplugged as they are on cords with DIN plugs to unit (LEDs are too). I can't get a good reading hooked up, the volume shows roughly 5-10K full travel and 0-10K unhooked so I did them disconnected. (I had tried to test on the board instead of the DIN pins)
I did test the LEDs (both) at the LED (all testing unplugged) and at the DIN, I can't get a reading either place or either polarity on my 20M ohm meter.
Also looked at the board the pots are on, I can see the solder bumps through the tubing and it does not look like any other components are on the board just pot, wires, and ziptie.
Yeah I guess I need like a 500mv switch on the volume. It looks like the switch runs the unit and the remote to the amps.
That's close enough. 10% tolerance is respectable on a dual pot. If it's10k at 1/4 turn, and 24 at 1/2 turn or anything even close, it's linear.
Toasts.
Wise observation. PCB mounted pots often have resistors in-tow.
I do not have good suggestions as to where to find replacements. Maybe someone else does? You could also replace pots with resistors for a temporary fix. If you'd like the 20k dual, send me an email.
Tim
If you can find a female mini din connector/cable, it will make checking the pots easier. Radio Shack may have a mini-din cable that you can cut to expose the individual wires. Use alligator clips to connect the meter to the wires. Then you can check the pot easily at several positions to determine the taper, resistance or anything else you need to check. This will also prevent errors from components on the EQ board (assuming you were checking the pots from the bottom of the EQ board).
With the shaft facing you and the terminal down, if the left-most terminals of the volume pot are connected to the RCA shield ground, virtually any pot will work because the pot is simply a voltage divider. An audio taper pot will work better than a linear taper. A pot with relatively low resistance (10k) will produce less noise than one with higher resistance (100K). Cermet pots will be quieter than carbon pots but since there is little gain in the circuit, either will be OK.
What IC are they using to drive the LEDs (LM391x, op-amps...)? If you know what they're using to drive the LEDs, it will make troubleshooting easier.
If your meter has a diode check function, that may work better for checking the LEDs. Is there an IC on the board with the LEDs?
For those of us who have never seen the inside of one of these, a good photo of the entire board may help troubleshooting.
With the shaft facing you and the terminal down, if the left-most terminals of the volume pot are connected to the RCA shield ground, virtually any pot will work because the pot is simply a voltage divider. An audio taper pot will work better than a linear taper. A pot with relatively low resistance (10k) will produce less noise than one with higher resistance (100K). Cermet pots will be quieter than carbon pots but since there is little gain in the circuit, either will be OK.
What IC are they using to drive the LEDs (LM391x, op-amps...)? If you know what they're using to drive the LEDs, it will make troubleshooting easier.
If your meter has a diode check function, that may work better for checking the LEDs. Is there an IC on the board with the LEDs?
For those of us who have never seen the inside of one of these, a good photo of the entire board may help troubleshooting.
I messed with pots (the fader/tone controls) again and they appear to be linear but lag at the very ends of travel.
The power LED goes right off the 12v in to the resistor behind the DIN plug (bottom, left most) and to the LED. The clipping LED goes up/over to that same size resistor across the gain traces and to that IC Motorola NE555N ILPD, I think pin 3...unless I screwed up looking at it. I sent Perry a better pic.
I found those pots at mouser but the volume has no switch, I will look more once I have some time. One tester does have a diode thing on it I have never used Might as well chop the LED off they are no good, but the owner is going to wonder. The seller said it was new to go into a show car and car was totaled and never installed; no answer to why they are dead.
A control cable, LED cable:
Note the cover labels for the DIN plugs:
This is like ampguts!
The power LED goes right off the 12v in to the resistor behind the DIN plug (bottom, left most) and to the LED. The clipping LED goes up/over to that same size resistor across the gain traces and to that IC Motorola NE555N ILPD, I think pin 3...unless I screwed up looking at it. I sent Perry a better pic.
I found those pots at mouser but the volume has no switch, I will look more once I have some time. One tester does have a diode thing on it I have never used
Might as well chop the LED off they are no good, but the owner is going to wonder. The seller said it was new to go into a show car and car was totaled and never installed; no answer to why they are dead.An externally hosted image should be here but it was not working when we last tested it.
A control cable, LED cable:
An externally hosted image should be here but it was not working when we last tested it.
Note the cover labels for the DIN plugs:
An externally hosted image should be here but it was not working when we last tested it.
This is like ampguts!
I needed a mini din cable to make up a plug for a zapco amp. A Radio Shack PS2 Keyboard/Mouse extension cable fit perfectly. The cable end looks identical to the white cables you have. It may not work for the volume if you use a pot with a switch (the wires may be too small to power the EQ), but if you use an external switch, they should work well.
If you want black cables, look for black PS2 extension cables.
Either way, it will be easier than soldering wires to a mini din connector.
If you want black cables, look for black PS2 extension cables.
Either way, it will be easier than soldering wires to a mini din connector.
Ha Ha, I been down that road the faders are all the same and PS2 mouse/kybrd cables...male-male 6' so I can cut in half for two and very cheap to get. One is a Mac serial printer cable (28awg wire) that will be the volume (at compusa), and I forget the last one. All can be found cheap as left over from popular equipment. (& I have more than a few hours into figuring all that out)
True those wires are not good for much current, guess I would have to mod that cable with two larger gauge wires....they can be ugly as cables are not seen....not sure how I would get into the plug area or if I could leave a section small....or give up and use a switch. Well I could put a new plug on that one I guess and wrap the two with it somehow. It says 180ma but that is plus what ever you put on the remote wire unless 28awg is good for that in 3 foot, didn't consider that.
True those wires are not good for much current, guess I would have to mod that cable with two larger gauge wires....they can be ugly as cables are not seen....not sure how I would get into the plug area or if I could leave a section small....or give up and use a switch. Well I could put a new plug on that one I guess and wrap the two with it somehow. It says 180ma but that is plus what ever you put on the remote wire unless 28awg is good for that in 3 foot, didn't consider that.
If you don't mind making a few simple mods, you could use the power switch on the volume control with no danger of damaging the tiny wires. You would use the switch to drive a transistor. Then the transistor would trigger a relay. The relay would power the eq and drive voltage to the remote output of the eq.
I found this, but it does not look like high quality....
http://www.radioshack.com/product/i...t+Type/Potentiometers&fbc=1&parentPage=family
In fact maybe it is not even dual, one would think they could put what the thing is....what is the position of the switch? NO, NC??
http://www.radioshack.com/product/i...t+Type/Potentiometers&fbc=1&parentPage=family
In fact maybe it is not even dual, one would think they could put what the thing is....what is the position of the switch? NO, NC??
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