BIG problems

[Michael F]

TIME OUT

We are spinning our wheels here. Can we agree on:

1. PCB wire color code, Red>Collector, Black>Base, Brown>Emitter

2. 2N3415 pin out. Looking at FLAT side, pins on the bottom =ECB

3. Looking at picture posted, the Left Channel is wired properly, the Right side is not.

 

[laatsch55]

Correct.

 

[Michael F]

Correct.

Alright, so would that mean that the 2n3415 are the wrong devices? Should I put the original 2n3403s back in?
BTW, thanks for your patience

 

[laatsch55]

The 3403's are barely adequate for the job but better than the 3415's. What we do is split the P-Strap of the old 3403's and put a 2N5088 in there, bolt the p-strap back together, and add a drop of epoxy on the top of the tranny to help in heat transfer and keep it kept. The 3403's wiill be OK to get things straightened out but for ultimatre reliability go with the 2N5088's.

 

[laatsch55]

And thank you for your patience.....

 

[Michael F]

The 3403's are barely adequate for the job but better than the 3415's. What we do is split the P-Strap of the old 3403's and put a 2N5088 in there, bolt the p-strap back together, and add a drop of epoxy on the top of the tranny to help in heat transfer and keep it kept. The 3403's wiill be OK to get things straightened out but for ultimatre reliability go with the 2N5088's.

OK, I`ll put the 3403s in to see what happens. I don't recall the pinout though (here we go again )

 

[laatsch55]

Same pinout.

 

[Michael F]

2N3403`s back in, voltages dropped a little, about 150mv all around, but still cant get below .400 volts anywhere except Right channel R38 which comes in at .352 with trimmer fully counter clockwise.

 

[laatsch55]

Is that the channel you put the 1K in place of the 470??

 

[laatsch55]

And remember 350-400 is doable. What do you have for offset now?

 

[Michael F]

Is that the channel you put the 1K in place of the 470??

No, original resistor was put back into place.

 

[Michael F]

And remember 350-400 is doable. What do you have for offset now?

The lowest bias #`s are:
Left R38 .421
Left R39 .430

Right R38 .352
Right R39 .478

Keep in mind this is with trimmers fully counter clockwise (1:00 position) where they originally were just past the halfway (7:00) position

 

[laatsch55]

Is this with the 3403's ort 3415's?? When you short outputs the bias transistor often times becomes the walking wounded. They took a hit in the gain department when they didn't have much to begin with...

 

[laatsch55]

Mike, what is the DC offset at the speakere terminals??

 

[Michael F]

Is this with the 3403's ort 3415's?? When you short outputs the bias transistor often times becomes the walking wounded. They took a hit in the gain department when they didn't have much to begin with...

That's with the 3403, does that mean they too are FOOBAR?

 

[Michael F]

Mike, what is the DC offset at the speakere terminals??

Offset is a respectable .09 and .04

 

[laatsch55]

Yes , when you can't dial in the bias they are foobarred.

 

[NavLinear]

Yes , when you can't dial in the bias they are foobarred.

I hate to correct your technical terms but it's FUBAR.

Something everyone should see:

During WWII the U.S. Army created animated shorts that included "Three Brothers" and "Private Snafu Presents Seaman Tarfu In The Navy" feature the characters Private Snafu, Private Fubar, and Seaman Tarfu.

 

[Michael F]

I`m about to place an order for 2N5088s for Q6 from Digikey, is there anything else I should replace while I`m at it?

 

[laatsch55]

Yeah, a White Oak Rev "D" board, a White Oak LED light board,. .......ETC.....Seriously, Mike, what else do you need?? I can throw some 5088's in the cool FaboNav bracket in with the board. How is the 410 driver situation??