Cory's Phase Linear 2000 Ser II Restoration

Some good Nichicon KZ's or Silmic II's would probably be just the ticket..
 
Yes I think so . I was reading about the back to back use of electrolytic caps , and this is some of what I found........." The two capacitors rectify the applied voltage and act as if they had been bypassed by diodes.
I think the following describes how the system works.
As I described above, once one capacitor is fully charged at one extreme of the AC waveform and the other fully discharged then the system will operate correctly, with charge being passed into the outside "plate" of one cap, across from inside plate of that cap to the other cap and "out the other end". ie a body of charge transfers to and from between the two capacitors and allows net charge flow to and from through the dual cap. No problem so far.
A correctly biased capacitor has very low leakage.
A reverse biased capacitor has higher leakage and possibly much higher.
At startup one cap is reverse biased on each half cycle and leakage current flows.
The charge flow is such as to drive the capacitors towards the properly balanced condition.
This is the "diode action" referred to - not formal rectification per say but leakage under incorrect operating bias.
After a number of cycles balance will be achieved. The "leakier" the cap is in the reverse direction the quicker balance will be achieved.
Any imperfections or inequalities will be compensated for by this self adjusting mechanism. Very neat."
 
I finished my preamp recap and put in the IC upgrade (matched the pin 1 ) .My preamp howls if its turn off and the amp is on .I shut the amp of first on my other separates . Is this normal ? I am hearing a little hum also ,maybe ground loop . Its not effected by the volume control.
 
calman46 said:
Its the 2.2 uf caps connected + to + number c47/ c49 , c48/c50 .
Click to expand...

After seeing where these are in the schematic, you are much better off with a single or paralleled film cap (polypropylene or polyester) than dealing with electrolytics directly in the audio path. PL did this to save space and $$.
 
calman46 said:
I finished my preamp recap and put in the IC upgrade (matched the pin 1 ) .My preamp howls if its turn off and the amp is on .I shut the amp of first on my other separates . Is this normal ? I am hearing a little hum also ,maybe ground loop . Its not effected by the volume control.
Click to expand...

I would say this is abnormal. What did it do before the recent upgrade work? And what was it that you replaced?
 
It seems to be the the Browndog IC upgrade .I put the original back in and no howl,there is still a little hum that didn't change.
On the electrolytic caps back to back according to that article its more than just money it maybe some kind of protection also. Checkout that excerpt I posted earlier .
 
calman46 said:
It seems to be the the Browndog IC upgrade .I put the original back in and no howl,there is still a little hum that didn't change.
On the electrolytic caps back to back according to that article its more than just money it maybe some kind of protection also. Checkout that excerpt I posted earlier .
Click to expand...

Thanks, we should figure out what you are replacing the originals with in order to find out why the brown dog equipped op amps are howling but the originals did not. Which brown dog module did you use and what op amp did you install on it? What locations in the PL2000 were you replacing these with?

Yes I read the excerpt below before I originally posted. I do not know what protection that this poster thinks is being afforded. It is a way that manufacturers mimic true non polar capacitors with polar type capacitors to save space and $$ and achieve the capacity and voltage rating they need.

If film type non-polar caps were offered in the same capacity (capacitance and voltage rating) in the same physical size and at the same cost as electrolytic caps then electrolytics would not exist because there would be no market for them. The only redeeming qualities of electrolytics are small physical size for a CV rating and low cost. They are inferior in just about every other aspect.

In the location you pointed out in the PL2000, I would be recommending film capacitors.
 
Hi Lee
If you use the Accuphase as a gold standard example, it uses very large size 4.7uF polypropylene non-polar film output capacitor. That will faithfully reproduce a 10 Hz signal into a 6.7K load presented by a power amp.

If we use the PL2000 output stage, with it's effective 1.1uF output capacitor (2 x 2.2uF polar in series) then the PL will only faithfully reproduce 42 Hz into the same load.

Most power amps present a higher input load impedance than this example does, typically greater than 20K ohms.

In the case of a 20K power amp input impedance, the PL2000 will faithfully drive down to 14 Hz and the Accuphase will drive down to 3.3Hz.

5uF non polar polypropylene would be a good choice for the PL2000 output cap.
 
So, is it time to mess with the input impedence on our power amps. Got my Mouser order today?? Did you??
 
And are we gonna have to start stuffing a TO-220 in Q5,Q10??
 
Me too Joe, just got in off an oilspill, not bad but it was still an ass buster.
 
The EOL was on STMicro, I noticed Central was still in production.
 
I used the brown-dog adapter 060601 with OPA2134 chips to replace the original RC4136 .I matched pin 1 to the original it was the same as in the thread photos . It howls with the preamp off and amp on that's strange.
So I can go with a 5uf poly-pro film caps on the outputs (just checking)
 
Yep. It howls with the pre-amp off and the amp on?? That's not strange that's normal.. With the pre amp on and the amp on what happens??
 
The right channel went out and then hum ,thats when I turned off the pre and got the howl so I thought the two might be related . I'm going to test it with the original RC4136 and if all goes well I will try the brown dog again. I also clean the function switch again (may have caused the channel drop)
 
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The background hum I'm getting goes away when the unit is taped(cold solder joint?) .I did re-flow the solder joints on the pots and Jacks, I'll do the switches.
How come the brown-dog howls ? (sorry I couldn't resist) How come the brown dog upgrade IC's howl?
 
Is it a steady state howling when the preamp is off or is it just a temporary situation as the preamp power supplies decay? Important to know.
 
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