phase linear 400 voltages change

[laatsch55]

That's probably best. A Phase 400 is really difficult to learn on.

 

[changdangnz]

L channel is less sound than R channel

Lee got an issue with L channel sound. It's a PL400c PCB. How can i adjust it ?

 

[laatsch55]

The only thing that is adjustable is DC offset and bias. Neither one makes sound less or more. You have some other problem.

 

[changdangnz]

yeah , i just play on my new PL400 bought from US. I got 2 already but 1 i was make a blow fuse . Another one is still fine and very great condition. I just play a new PL400 then i just hear a sound on left speaker is not really equal to Right speaker . to measure a DC offset is that i just put a lead on speaker out put ???

 

[laatsch55]

Yep. Positive lead on positive speaker post. Negative lead on negative speaker post. Nothing on the inputs.

 

[R1200S]

Here's a very good thread on Audiokarma on how to test diodes and transistors. Scroll down to post #11.....


http://www.audiokarma.org/forums/showthread.php?t=43186

Speaking of testing transistors.... can anyone recommend any of the $30 transistor testers that are on eBay? I know they're cheap and made off-shore but the price is right.

 

[changdangnz]

dc offset adjustment

Been doing dc offset measure And i can see a left channel value is keep moving up and down not stay on 1 value. Right channel was fine. Lee , do i need to replace Q1 and Q2 on PCB on left hand side ?

 

[laatsch55]

What are the numbers from your measurements?

 

[laatsch55]

Speaking of testing transistors.... can anyone recommend any of the $30 transistor testers that are on eBay? I know they're cheap and made off-shore but the price is right.

Got a link to one?

 

[changdangnz]

Out put transistor measure

Lee , may I ask you about value of out put transistor ? I try to test a blow fuse amp out put transistor and I got a value about 2.6 to 3.0 mV . Is that ok ?

 

[laatsch55]

To make sure there are no other circuit influences in your test , remove the output and perform the standard transistor test.

 

[changdangnz]

DC OFFSET VALUE

Right channel is -131.4mv and left channel is about -132.0mv

 

[laatsch55]

Replace Q1,Q2,Q3,Q4.

 

[changdangnz]

Finally I got about less 50 mV for both channel. But left channel number value keep jump up and down not stay on what I been set. Right channel is okay stay on

 

[laatsch55]

On the amp with the PL400C board that has adjustable DC offset?

 

[changdangnz]

Yes , it had adjustment dc offset.

 

[laatsch55]

The reason the DC offset is not steady is probably the potentiometer being old and dirty. That's not THE ONLY thing it can be, just the most probable. What are the bias measurements.

 

[R1200S]

Lee , may I ask you about value of out put transistor ? I try to test a blow fuse amp out put transistor and I got a value about 2.6 to 3.0 mV . Is that ok ?

Here's a link for transistor testers overall:

http://www.ebay.com/sch/i.html?_fro...r+tester.TRS1&_nkw=transistor+tester&_sacat=0

Here's a couple of specific units:

http://www.ebay.com/itm/12864-LCD-T...-MOS-NPN-US-/131539364479?hash=item1ea05b6a7f

http://www.ebay.com/itm/NEW-Transistor-Tester-Diode-Triode-Capacitance-ESR-resistance-Meter-MOS-PNP-NPN-/141296318232?hash=item20e5eab718

Thanks Lee

 

[laatsch55]

Now that's a cool meter. How low capacitance will it measure?? Granted for 30.00 what can a guy expect, but in most cases it will answer a lot of questions we ask....

 

[R1200S]

Now that's a cool meter. How low capacitance will it measure?? Granted for 30.00 what can a guy expect, but in most cases it will answer a lot of questions we ask....

Thanks Lee, No idea how low they'll measure but I'll check before I buy one and compare that to specs on some Fluke units to see where these things shake out. Beats buying a another meter if it'll do what we need.