12002: 2" OT

[Roe]

mains grounding should be at least an inch away from PT in order to awoid humming and noise

[vanhalen5150]

I have some MiniWatt .1uf 400v capacitors. I'll give you a good price vanhalen5150

Sweet. I'll PM ya Art!

[vanhalen5150]

mains grounding should be at least an inch away from PT in order to awoid humming and noise

I think it looks pretty close because of the bracket but I'll check on that. Thanks.

i've seen some pics of amps use the PT mounting screws as grounds. Never heard them however.

[vanhalen5150]

Going with top loaded lead wires. Found this wiring for the inputs on a SDM layout. There is a wire(black on top) conecting the grounds, however I'm wondering if using the two bottom grounds to lug #1 could create a ground ddloop of some kind. Seeing as though there would be only one jack being used I cant see it....right?

[vanhalen5150]

.

001.JPG (157.46 KiB) Viewed 1607 times

002.JPG (174.65 KiB) Viewed 1607 times

003.JPG (241.36 KiB) Viewed 1607 times

[vanhalen5150]

.

004.JPG (250.26 KiB) Viewed 1606 times

005.JPG (269.11 KiB) Viewed 1606 times

006.JPG (193.72 KiB) Viewed 1606 times

[vanhalen5150]

.

007.JPG (190.81 KiB) Viewed 1606 times

008.JPG (245.7 KiB) Viewed 1606 times

010.JPG (233.15 KiB) Viewed 1606 times

[vanhalen5150]

.

011.JPG (255.45 KiB) Viewed 1606 times

012.JPG (282.23 KiB) Viewed 1606 times

013.JPG (294.53 KiB) Viewed 1606 times

[vanhalen5150]

.

014.JPG (282.15 KiB) Viewed 1605 times

015.JPG (246.54 KiB) Viewed 1605 times

016.JPG (178.54 KiB) Viewed 1605 times

[vanhalen5150]

Started up with preamp tubes in. Got 3.0 AC on the heaters.
Switched to DC and got a bias reading of about -67 with the switch midway.
V1 pin 1 reads about 550vdc. Big voltages all around.
Only V3 shows signs of life.


Wouldn't be any fun if it worked right away.

[Tone Slinger]

Hey Shannon, why did you shield the 820 before the v2 .68uf, as well as the resistor after it ?

[vanhalen5150]

Hey Shannon, why did you shield the 820 before the v2 .68uf, as well as the resistor after it ?

The one after was because of the Lemco sitting underneath. I had to set the one before up pretty high in the amp and had read somewhere to do that in that specific arrangement.

[Strat78]

The resistor between the V3 PI inverter grid resistors is too high, it should be 470 (yellow, purple, brown).

[vanhalen5150]

The resistor between the V3 PI inverter grid resistors is too high, it should be 470 (yellow, purple, brown).

Yup your correct guy. I have a 470K not a 470 ohm in there. I could have looked at that a few times and still made the same mistake because your brain keeps telling you it was done correctly the first time. I'll change that out tonight and see what happens. I'll have to check everything else as well before hand. High res pics seem to show more mistakes on the soldering joints than your normal eye can see. I reduced these pics by 50% and picked out a few soldering joints that may be suspect down the road. The bad thing about top loading everything is the amount of solder on some of the turrets. George's boards really are not for this as they should have higher lugs for such.

I keep telling people to post pics to troubleshoot....but they don't listen.

What happened to all the chassis Metro did runs of the past year? Bookends?

Thanks dude.

[vanhalen5150]

Changed to 470 ohm resistor. Heaters are 3.0 vac. Bias resistor at diode is 104 vac. Bias is -45.

No DC voltage at pin1 v1 to v3. Only v3 tube glows. Switched tubes, no change.