Wayne's BA 2018 linestage

[6L6]

Are Q9 Q14 (and their 2nd channel mates Q19 Q26) the proper devices? Those are the odd ducks in the row. I cant tell from the photos, could you double check that please?

 

[Russellc]

Just soldered in the teeny J fets on the new store board. Much easier this time.
I smeared just a coating of solder on to the single pad side, held Jfet in place with 6l6 scotch tape method. Worked perfect!

Once in place, heat on the single tab on solder coated tab sticking it in place. Over to other side and solder down the two remaining tabs. Then a touch on the initial tab.

The new solder was perfect for this, melted fast and flowed easily making this chore much easier.

One of the Q4 feet looks like I better take a second look, solder melted super easy and just flowed over the pad and tab. Sometimes I notice soldering looking worse in pics...

Russellc

 

[audionut]

When will the store have Wayne's Pre Amp kits again??

Thanks

 

[Russellc]

Wow! that was quick!

Russellc

 

[Dennis Hui]

Yes, that was quick. I guess that means there will be many happy builders.

 

[Russellc]

I just checked the store, parts kit appears to be in stock, boards are out however.

Russellc

 

[PJN]

Had the chance to check out my board.

BPD,

Q8 gets hot, but Q10 doesn't. The voltage across R13 is 2v.

6L6,

Q9 is KSC1845
Q14 is KSA992
Q19 is KSC1845
Q26 is KSA992

The same as shown on the silkscreen.

Thanks for the help.

Paul

 

[wayne]

What are the voltages across R11 and R12 and the junction of the two referenced to ground? Any Dc across R19?

 

[BDP]

Had the chance to check out my board.

BPD,

Q8 gets hot, but Q10 doesn't. The voltage across R13 is 2v.

6L6,

Q9 is KSC1845
Q14 is KSA992
Q19 is KSC1845
Q26 is KSA992

The same as shown on the silkscreen.

Thanks for the help.

Paul

2 volts across R 13 is good. 13 ma

The voltage across R11 and R12 on my boards were 0.3 volts

 

[Jason]

When will the store have Wayne's Pre Amp kits again??

Thanks

Parts kits are in stock, PCBs went out of stock 7 days ago. Following up on this, I can see PCBs have been sitting with our 3PL for several weeks but they seem to have forgotten about the work order lodged to turn them into shippable products. I've just sent them a gentle reminder, which should mean they will be back in stock in a "couple" of days.

 

[RainfallSky]

I need some help troubleshooting my build. I'm using the board from the store and powering it using a ultraBIB psu set at +/- 20 vdc @ 200 mA. When I power up the LEDs do not light and Q8 and Q20 get very hot.

I installed the leds so that the cathode(short leg) was towards the flat side on the silkscreen.

It is configured as a line stage using the digikey BOM in this thread (KSC1845, KSA992, 2SK209BL) I have double checked all the transistors to make sure the correct ones are in the right spots, they are.

I double checked all of the resistors and they are the correct values shown on the silkscreen with the exception of R6 and R36 which read 894R and 929R respectively instead of 1.5K, but since they are in parallel with P1 that should be OK.

I have cleaned the board and checked it for shorts and cold joints under magnification and found nothing.

I have attached pics of my build so that hopefully someone can see what I'm missing and point me in the right direction.

Thanks,

Paul

Maybe LED still end up being reversed.

 

[PJN]

What are the voltages across R11 and R12 and the junction of the two referenced to ground? Any Dc across R19?

Hi Wayne,

The voltages across R11 is 4.9v.
The voltage across R12 is 4.9v
The voltage from the junction of R11/R12 to the is 8.9v.
No DC across R19

Q8 got very hot during testing and may have given up the ghost,. Now Q10 is getting very hot. I'm starting to wonder if I got some bad devices from digikey.

Paul

 

[PJN]

Maybe LED still end up being reversed.

I've got a few red LEDs laying around I'll try swapping new ones in to see what happens.

 

[wayne]

Yes try new Red LEDs and test them on a meter first. Most meters the red lead is + on diode test. So the red test lead goes to the long side leg.

 

[PJN]

Doh, I was able using a battery to verify that despite my best efforts I still installed the LEDs backwards. Will any red LEDs suffice, the old LEDs don't light so well once I removed them. I have some kingbright LEDs that measure at 1.6v using the diode test on my dmm.

 

[Gaz2613]

Got my boards back from the fab house and they look spot on! Slides nice a neat into the Hammond enclosure with plenty of room for the Linestage PCB. This is my spare one. I already have a Linestage built and ready to go. Just need to build this power supply and make sure everything checks out.

 

[PJN]

Things are looking up, I powered up with the LEDs just inserted but not soldered, LED lights, nothing gets hot and was able to adjust offset to 0 my. I also replaced Q8. Now I need to assemble it all and give it a listen. Thanks all for your help.

 

[Gaz2613]

Sounds like you've sorted the problem. Great work!

 

[PJN]

Just got it hooked up and it's playing music. Letting it break in on my garage system before I give it a serious listen, but sounds very clear.

 

[gary s]

Gareth, what model Hammond enclosure have you used?