Johan's Phase Linear 700B Fully Comp Conversion

[laatsch55]

More Gov't involvement...nothing stopping you from building a cement themed house....other than money of course. Get the gov't involved and it will get more expensive...

 

[jbeckva]

The yellw bias + for the positive led, the yellow bias- for the negative lead, got mini grabbers or just straight leads?? And I agree, if the bias was at 160 mv, it probably sounded like shit...

Hold on there ... It should be yellow bias + and grey OUTPUT for the - lead. Bias - to Bias + is going to give you double the reading because bias - is measuring across the 10 ohm on the negative side. Adjusting for 380 there is going to actually give you half the bias voltage required.

Or just like he had it with one on the bias TP on the PL14, the other on the output.

 

[jbeckva]

View attachment 14043

Johan had the correct connection here. High side to the bias TP (which is just measuring across the 10 ohm on the positive half), low side to the output (the other side of the 10 ohm).

 

[Northwinds]

northwinds.....every time I see you nickname,I think of HAWKWIND.....remember that band?....way back....lol...

Hell yeah I dig Hawkwind, I have all their early lps still

 

[Northwinds]

............??

Lemmy Kilminster was the bass player for Hawkwind and went on to form Motorhead, a total biker get drunk and get punched in the face band

 

[laatsch55]

I'll check that on the Pig Jer.

 

[laatsch55]

You are absolutely correct Jer!! On each side of the 10 ohm resistor shows 160 mv or so..Where does your pot wind up, on yours? I've got the Pig adjusted up , will monitor heatsink temp.

 

[laatsch55]

That's why my THD & N's were high...I'll put the Pig on the AP at 160mv and run a qick scan and bump it up and run another one..

 

[Skynyrd77]

No rest for the wicked eh!!!back at it already lol.

 

[laatsch55]

Um.....yep, glad that mystery is solved... THD & N figures are great.....nothing wring with the AP...just the operator..

 

[laatsch55]

THD & N figures are more than doubled when adjusted like I had it....Good catch JER!!!!! I feel stupidddd....


Good way to start the day...

 

[laatsch55]

Johan!! Adjust it like you did , then give it a listen...

 

[laatsch55]

All owners of previously adjusted amps have been notified of low bias issue and how to cure it...thankfully it was just on the fully comp models...

 

[Skynyrd77]

All owners of previously adjusted amps have been notified of low bias issue and how to cure it...thankfully it was just on the fully comp models...

Glad you caught it before mine. My dumb ass would of prob had to send it back for that. As I know how to do nothing to a amp except abuse it!!!

 

[jbeckva]

You are absolutely correct Jer!! On each side of the 10 ohm resistor shows 160 mv or so..Where does your pot wind up, on yours? I've got the Pig adjusted up , will monitor heatsink temp.

Gotta look, but a little on the "high" end. It still has a few mV to go tho...

Glad ya found the issue! Yeah, the -bias TP (I think.. Joe correct me...) is just as a double check where the reading across the 10 ohm on the positive half SHOULD match the reading across the negative (neg lead to -bias, pos lead to "output"). A "balance check", if ya think of it that way.

 

[johan1212]

Lemmy Kilminster was the bass player for Hawkwind and went on to form Motorhead, a total biker get drunk and get punched in the face band

what was that vinyl with 1 side was 1 single track...?...loved it...very astrospace ambiance...

 

[johan1212]

ok...lee....to make it clear for a non tech dude.....reajust bias on the backplanes(what I did)...or on the board and and positive of protection board(speaker)..?..pos probe to board....neg probe to protection board....correct?..

so when i was reading 160mV between board and speaker,it was wrong bias?...sorry....a bit confused..

 

[laatsch55]

Yes, I was wrong Johan.... Positive test lead to the DRIVER BOARD bias test point , negarive lead on the positive speaker post , set bias to 385mv...

 

[laatsch55]

Gotta look, but a little on the "high" end. It still has a few mV to go tho...

Glad ya found the issue! Yeah, the -bias TP (I think.. Joe correct me...) is just as a double check where the reading across the 10 ohm on the positive half SHOULD match the reading across the negative (neg lead to -bias, pos lead to "output"). A "balance check", if ya think of it that way.

Yep, positive and negative bias should be within 10%...let's not sugar coat it Jer, it was a SEVERE blonde moment...

 

[johan1212]

ok.....warming up.....am sure it will be perfect now....give me like 1 hour.....happy that this forum helped so much....wow...thanks a lot to all here...am excited to finaly hear it nicely...see you in 45 minutes....YYYEEESSSSS>>>>