Kenny Nelson's WOPL 400 conversion.

[laatsch55]

Pullede the DC protect relay and Voila' no bad sinewave, no oscillation, clean and green to 300 into 8.


YEE HAW!!!!!!

 

[Gepetto]

Was not aware that a DC protect was in this unit Lee

 

[laatsch55]

Joe, when the relay drops out it grounds the output to output ground. Now when the relay pulls in, thiose contacts are awfully close, could there be some induction of RF from the coil or bleed thru from the proximity of the contacts??

 

[laatsch55]

20 or so posts ago you said you thought it would wind up being a ground loop or a local ground problem....well there ya go....

 

[laatsch55]

Starting to make sense, cause as the voltage and current got stronger the output got dirtier........

 

[Gepetto]

Unlikely that it is a relay issue Lee, relays have been around a long time and work in tougher environments than this as you can attest. But don't rule anything out until you and Don get to the bottom of whatever is going on

 

[laatsch55]

Does ot make sense to ground the outputs when the relay drops out??

 

[laatsch55]

Well I had the horns on idle during most of the night and was getting feedback through the AC to the big tunebox from the test bench. As i brought up the input voltage on the 400 he screech in the horns got louderf, cut the input to the DUT, screech disappeared. Figured it was RF, but now that I think about it, it was feeding back into the AC. Don's 400 board has a DC input and 2 from the unrectified side of the secondaries. Could be wire discipline on my end too, have to check that out too.

 

[Gepetto]

Does ot make sense to ground the outputs when the relay drops out??

The best approach is to just open the circuit, like a fuse does

 

[Gepetto]

Lee
It appears you may have inadvertently been testing the 2N1304/5 protection circuit on this amp

 

[Gepetto]

Joe, when the relay drops out it grounds the output to output ground. Now when the relay pulls in, thiose contacts are awfully close, could there be some induction of RF from the coil or bleed thru from the proximity of the contacts??

Hopefully the ground that you are talking about is the chassis star point ground (the one that goes to pin 5 on the PL14_20 board) and not the signal ground that goes to pin 2.

If it is going to the one that attaches to pin 2 then it is all starting to crystalize on why you blew out the R2 resistors multiple times.

Nothing should be attached to the pin 2 board ground except the RCA jack shells and both of these RCA jacks should be confirmed as fully isolated from the chassis ground.

 

[laatsch55]

No Joe, The output rail that the DC protect board interrupts. The NC contacts ground the output rail to the speaker ground.

 

[laatsch55]

Lee
It appears you may have inadvertently been testing the 2N1304/5 protection circuit on this amp

That occured to me also.

 

[laatsch55]

Lickety Split LIVES!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[Gepetto]

Great to see it is back from the dead Lee.

 

[laatsch55]

Half dead anyway. Now to Gibsonians. Gotta wortk awhile though....

 

[jbeckva]

Hey Lee check yer email... tell me what you think, eh?

 

[laatsch55]

I did jer, and you are an absolute, F^%$#@! Genius!!

 

[laatsch55]

Kenny, the cabbage case should have just hit Gibsonians house to deliver Cathy. It will then head to Jer's to bring Poppa's 700B home then Lickety Split will be headed home. Enjoying it thoroughly while it's here though.

 

[laatsch55]

The IC on the original DC protect board evidently is toast as i have no relay drive action. Am populating another Dc board to put in before we send it home to Kenny. Had some factory Zoebels hacked in to isolate the problem. The IC----a----C1237HA is not in stock at Mouser.