First Build Problems

[Zacwah]

So im doin my first build and its all done.
All the ohms check out apart from terminal 7.  it either has no reading or its up and down and gets know where near the 2.9k ohm.
I did the volt test and its reading 230-240 volts on terminals 1,2,4,5.
The tubes glow But there is no sound and when i plug stuff in i get a little zap. Like if i touch the rca connetors and the headphone jack.
gone over the manual numerous times

Will post photos now

 

[Zacwah]

Pics

 

[Zacwah]

The LED's did work but they don't now.

 

[Doc B]

If things keep changing regarding how the amp operates, a good place to start is to reheat all of the solder joints. There might be a cold joint that looks OK, that might actually need a little persuasion.

 

[Zacwah]

Voltages.
1- 90v  220v
2- 170  231
3-   0    228
4- 170   231
5-  90   230
6-  0    2.2
7- 100   231
8-  0    230
9- 0     230
10- 0    2.2
11-0     230
12- 0
13 170  232
14-0     230
15-185    230
20-0     9
21

a1-90  230
a2-0     0
a3-1.5  230
a4-0    230
a5-0    230
a6-90  230
a7-0    0
a8-1.5  230
a9-0    230

All the B's are 230 bar b8 b7.

i'm not sure whats goin on but thinking something is touching the wrong terminal. Also with terminal 8 and 11 with current does that mean the plate is live too??

 

[Doc B]

OK, sounds like something is not grounded. Is this a recent purchase, or have you had the kit for a while? The reason I ask is there were some corrections to the manual in the early days of the kit being shipped. Here is a link to those:

http://www.bottlehead.com/smf/index.php/topic,657.0.html

If it is a more recent purchase, the manual should be correct and it sounds like it might be a miswire, where something that should be attached to ground isn't. Best bet is to run thru the instructions one more time and see if something got missed. It's easy to miss a step, I've done it myself - more than once!

 

[Zacwah]

Its a recent purchase. Will run through the manual when i get the chance. Would it matter if the Socket A screws and Ground Screw is painted?

 

[Noskipallwd]

ZacWah,
I noticed you have the back side of your top-plate painted. You might want to check and see if you are actually grounded to it. Just test for continuity between the plate and your bus wire. If not, you want to scrape paint from underneath all components grounded to the plate. Don't know if this is the problem but can't hurt to check.
Just noticed in your signature you own a Schiit Valhalla, I own one as well. I think you will be very happy with how much better the Crack sounds, good luck.

Cheers,
Shawn

 

[Doc B]

Its a recent purchase. Will run through the manual when i get the chance. Would it matter if the Socket A screws and Ground Screw is painted?

We don't run signal ground through the chassis plate, just the wiring. So the circuit should be grounded in terms of signal and power supply ground even if the chassis is painted, and the voltages should read OK. The safety ground screw should be in mechanical contact with the chassis, and the toothed washer should cut through the paint for safety's sake, but even if it isn't making chassis contact the circuit should still work.

Maybe try looking at the connections of all of the black wires. What I can see from the photo looks OK, but I can't really see every terminal.

 

[Zacwah]

There was a few joints i resoldered. No change with voltages.. But did notice if i earth to terminal 12 and test the ohms on terminal 7 i don't get an ohm reading.. but if i earth to the safety ground and test terminal 7 i get a reading of 2.9kohm.

Also after about an hour of being switched off I get zapped off the potentiometer. If I earth on the inside terminal farthest from the chassis and then positive on the top of the potentiometer it reads about 100v.

 

[Laudanum]

Looking at your pics, I see some wire insulation burnt (by the iron it looks like)  and some wire leads not trimmed.  You may want to visually check those areas.  Make sure there arent any untrimmed wire or component leads touching adjacent terminals or leads.  Also make sure the conductors of neighboring wires arent making contact due to damaged insulation. 

 

[Zacwah]

Still no luck after doing the manual again. Have attached some pics of what the terminals look like now.. Probably been staring at it for to long. If the red led don't come on anymore would it be a good idea to buy some more?

 

[Doc B]

The case of the pot having 100VDC on it suggests two things - one, that it is not sitting at ground potential (which it should be since it is in contact with the chassis plate) and two, that the power supply voltage is not being bled off by the 270K ohm bleeder resistor.

Sounds like maybe there is still a missing ground connection somewhere around the power supply. Possibly a miswire or a loose wire. Some of the solder joints still look kind of blob-ish rather than being a smooth fillet. Are you using a solder station, or a plug in style iron? Might need a bit higher temp setting if you are using a solder station, or maybe a bigger iron if you are using a plug in iron.

 

[Zacwah]

So after a few months of hiatus i decided to give this another crack.
I re-soldered most of the connections and now the chassis isn't live!

The valves heat up.
There is no sound and the LED's don't work. Are those 2 symptoms connected??
I have ordered some more LED's and will give them a go.

 

[Grainger49]

When I saw your post this morning it looked like a new post.  So I read the first post and immediately was concerned that you were shocked by the headphone jack.  Then I saw that the underside of the chassis was painted.  You want to unscrew all the screws that are not insulated and sand/grind off the paint where everything is attached to the top plate.  The headphone jack has a signal ground on it that ties to chassis ground at terminal 3. 

Also, scrape clean the underside at one corner and attach your meter there.  take all your resistance measurements there.  It will verify that you have a proper ground.  I have listed all Crack grounds in a post and will find that and copy them to here.

Yes, if the LEDs don't light up the driver tube is not on.  That keeps any sound from getting to the output tubes.

The LEDs are not easy to read.  Try checking them with your meter before installing them.  Your meter might have a diode checking position.  Once you see how they work install them upside down so you can see that the silver edge is toward the grounding point (IIRC in Crack that is the center pin of the tube socket). 

 

[Zacwah]

Ok so i installed the LEDS and sanded underneath the screws. The LEDS lit up but there was no sound.
When i unplugged everything i got a zap from the Right RCA jack ( Plate is still Live (im waiting about 15 minutes after powerdown before i do anything.))
So i decided to do OHM test. Ohm's are fine apart from T7, T9, B3 and B6 i don't get a reading from them if i ground off terminal 12, But i do if i ground of the chassis earth (Sometimes).
I plugged it back in and noticed the LEDS didnt come on. Then they flashed then came back on and stayed on about 2 minutes after power up. I took the voltages and everything was live. 170-220v

I'm getting a reading from T11 and T17? Surely that can't be normal with the Fiber shoulder washers?

 

[Grainger49]

Getting a zap from the RCAs is wrong.  This indicated that there is voltage where it should not be. The RCAs should have no internally generated voltage.  It receives a very small, and unnoticeable AC voltage from the source.

Where else were you touching when you received the shock?

 

[Zacwah]

Pretty sure i was tightening up the fastener on the RCA so that and the centre pin of the RCA.

 

[Grainger49]

If you were tightening the RCA jack with one hand where was your other hand, holding the chassis?  Was it plugged in and on?  I'm trying to get a handle on this.

 

[Zacwah]

Unsure on my other hand.
Waited 10-15 mins after power down to touch it.
Before I get a zap the plate reads 190v. And after I get the zap the plate is 0v
But when I get 190v off the plate the RCA jacks read negative 160v.

Will be away over the weekend so when I get back I will go over the manual and check all wires and connections.