Cory's Phase Linear 2000 Ser II Restoration

[Gepetto]

Brown Dog won't be able to tell you squat about the 2134 innards, they just make adapter boards.

The preamp outputs are NOT working, they just provide an input sneak path of some sort to ground or some other signal path. Have you unplugged all the inputs to the preamp to see if it howls while off but with nothing connected to the input of the preamp?

Have you tried removing C39 and R68 across the AC on-off switch. Remove one at a time and test results

 

[laatsch55]

Now we're getting somewhere!! Where did you find that internal speaker Joe??

 

[calman46]

I will , there is also a small cap across the preamp part on the on/off switch ,its mentioned in the service manual.
FYI there is a 400 on CL http://providence.craigslist.org/ele/4045481836.html

 

[laatsch55]

Good price opn that puppy. Damn clean too.

 

[calman46]

That's it , R68 (33k). Is that resistor for inrush protection? There is a slight turn on thump now . I'll have to put those ceramic caps back on the IC socket 7,11,pins for the upgrade chip.(thinking out loud)

 

[Gepetto]

That's it , R68 (33k). Is that resistor for inrush protection? There is a slight turn on thump now . I'll have to put those ceramic caps back on the IC socket 7,11,pins for the upgrade chip.(thinking out loud)

Glad we narrowed down the offender for you. Now you can enjoy the 2134

 

[calman46]

Can I use it without that resistor? Any idea why It didn't howl with the Rc4136 , thanks

 

[Gepetto]

Can I use it without that resistor? Any idea why It didn't howl with the Rc4136 , thanks

Sure can. That resistor does nothing (but cause problems)

Yeah, the old tech RC4136 did not come alive until the voltage rails were +/-5V for a total of 10V, the OPA2134 comes alive at half that. That resistor was producing some secondary voltage, although small, it was enough to partially power up the OPA2134.

 

[laatsch55]

Dayam!!!! Joe you ARE good.

 

[laatsch55]

Joe, were you an EE in your previous life too??