Phase Linear 2000 troubleshooting

[Coldsmoke]

Florian, I was gonna send your package today but it's a national holiday and the post office is closed.....so it will be tomorrow. I've sent 20-TIS-97's, 20 TIS-93's, 2-4739's, and 1-DC protect board. The extra 97's and 93's are just because....if you have a friend restoring a Moog Synthesizer...you'll be a hero....

AH AH AH Lee, the funniest thing is that we are a couple of lunatics here trying to restore old gears (korg MS series, polysix, old roland beatboxes, etc), with close to 0 skill ... I bet we'll soon see a moog project, and I'll play my part then !

Thanks Lee

 

[Coldsmoke]

Hi Florian
According to the stock PL2000 schematic that I have, R71 and R72 are supposed to be 16K ohms. Looks like some previous owner or Phase Linear ran out of 16K ohm resistors and was improvising?

I bet on the previous owner, he has been messing A LOT with this unit and the WOPL driver board of the 400 (he is responsible for instane for the completely fucked up grounding of the unit...), I can't count the hours that I spent now with your help guys trying to fix this mess...

 

[laatsch55]

AH AH AH Lee, the funniest thing is that we are a couple of lunatics here trying to restore old gears (korg MS series, polysix, old roland beatboxes, etc), with close to 0 skill ... I bet we'll soon see a moog project, and I'll play my part then !

Thanks Lee

Glad I could help.....I have a lot of obsolete stuff. Wouldn't hurt to check if you need something....

Joe is pretty handy with a schematic if need be....

 

[Coldsmoke]

Hello Lee,

I couldn't wait for your IC's to arrive so I tried the unit with the old IC's and, despite a perfect sine response on the scope I can hear a loud hum when I plug the unit to the amp... This is killing me

 

[laatsch55]

Is the amp and preamp both on?

 

[Coldsmoke]

YEs they are

 

[Coldsmoke]

I tested each line input from 0 to 1.23V @ 1000hz and the phono input from 0 to 50mV @ 1000Hz also and checked a perfect response on both outputs of the preamp...
AND the 400 is almost dead silent now with the inputs shorted

 

[gadget73]

So just to make sure I understand here, if you connect the PL 2000 to the scope, the scope says all is right and happy, no noise, hum, hiss, etc right? The PL 400 itself is quiet with the inputs shorted right? But if you plug the two together it makes noise? Exactly what noise, a hum noise or a hiss or something else? Is it dependent on the volume level of the PL 2000 or no ? How about with the level controls on the 400 ?

If its a hum, it sounds like either an open ground at the output jack of the PL 2000 or bad interconnect cables. Could also be an improper ground at the input jacks of the PL 400 I suppose. If you have grounded cords on either (or both) the PL 2000 and the PL 400, that may be it too. Ground loops cause all sorts of nonsense.

 

[Coldsmoke]

So just to make sure I understand here, if you connect the PL 2000 to the scope, the scope says all is right and happy, no noise, hum, hiss, etc right? The PL 400 itself is quiet with the inputs shorted right? But if you plug the two together it makes noise? Exactly what noise, a hum noise or a hiss or something else? Is it dependent on the volume level of the PL 2000 or no ? How about with the level controls on the 400 ?

If its a hum, it sounds like either an open ground at the output jack of the PL 2000 or bad interconnect cables. Could also be an improper ground at the input jacks of the PL 400 I suppose. If you have grounded cords on either (or both) the PL 2000 and the PL 400, that may be it too. Ground loops cause all sorts of nonsense.

Hello Gadget, you perfectly described the situation.
Hard to describe the noise, it is definitely frequencial it coul sound like a groundloop, but very loud even with the volume pot at its minimum.
The cables are fine, these are btw I used to scope the preamp...
Last thing : my equipememts aren't grounded

 

[laatsch55]

OK Florian, by "not grounded" you mean no 3rd prong going in to the wall receptacle??

 

[Coldsmoke]

OK Florian, by "not grounded" you mean no 3rd prong going in to the wall receptacle??

Sorry, I meant not connected to earth yes

 

[laatsch55]

Do you have this "hum" when using another source such as a tuner, LP, CD player??

 

[Coldsmoke]

Do you have this "hum" when using another source such as a tuner, LP, CD player??

Yhe hum appears with or without a source and is the same on the phono and line levels

 

[laatsch55]

OK, you removed the resistor on the on/off switch?

 

[Coldsmoke]

OK, you removed the resistor on the on/off switch?

Yes

 

[Coldsmoke]

And placed a 0.03uF 220V cap there

 

[laatsch55]

Do you have anything else to swap the 2000 out with?

 

[Coldsmoke]

Do you have anything else to swap the 2000 out with?

Yep, I've a mixer hooked to the amp now

 

[laatsch55]

No hum??

 

[Coldsmoke]

No hum??

Nope, it definetly comes from the 2000 ...