2 Resistance checks failed [resolved]

[smodtactical]

At terminals 22 I am reading 4-6 ohms and it should be closer to 0 (my other 0 readings are coming out at 1.4 ohms on my meter).

At the red RCA Jack I am reading 83 kOhms (should be above 90 kohms).. the black RCA jack is reading 94 kOhms.

Any idea what specific joints are faulty? I guess I can resolder the red jack but what about terminal 22, nothing is connected to it.

Would appreciate your help, thank you!

 

[Paul Birkeland]

I don't think you should power up this amp just yet.

While the resistance measurements that you're posting aren't a problem, there are major issues in your build.  Many of your component leads are untrimmed and sticking out in random places.  Most of the wires I see have too much of the jacket stripped off and this will cause problems.  The green wire that's going to A9 with the bare butt joint making it longer just isn't OK.  If that touches the chassis plate, you'll destroy the power transformer. The red wire going to the volume pot has so much jacket stripped off that it can touch the chassis plate, which will short out the right channel. One of your UF4007 leads also looks like it might be touching the chassis plate, which could also damage the power transformer.  Many of the wires and components look like they are just slipped through the terminals and then soldered.  It's important to attach these connections first so they don't slip around after soldering (this also lets you get the jacket of the wires much closer to the terminals).

Most of this could be cleaned up with a little time.  The green twisted pair of wires may just need to be replaced, and it's a good idea for this twisted pair to rest against the chassis if at all possible.

 

[smodtactical]

Hey Paul thanks. Ok will have to do all this work on another day as put so many hours into this over the past 2 days so need a break. Sucks about these issues and its my fault, my first build ever.

Is there any way to wrap/insulate the green wire so i dont have to de-solder it and replace the whole thing?

Also you think my resistance measurements are ok ?

 

[smodtactical]

Hey Paul just did some clean up of all the long leads I could find. Updated pic attached. Thanks.

 

[smodtactical]

Oh shoot upon re-testing terminal 6 is reading infinite when it should be 0 ohms. Damn it.

 

[smodtactical]

Some more pictures of terminal 6

 

[Paul Birkeland]

I still see a bunch of leads poking out around terminals 1-5.  The center post of the 9 pin socket doesn't look to be soldered too.

There's too much jacket stripped off the white wire going to B4.  If the bare part touches B5, bad things will happen.

What DC resistance do you get from the connection of the red wire at the headphone jack to ground?

It may be a decent idea to order up a fresh wire bag and some LEDs to have another shot at this.  The wire routing matters (which wires are on top of which, where wires run under terminal strips rather than over, etc), the amount of jacket that should be stripped off of each wire is also pretty important as well.

 

[smodtactical]

DC resistance from redwire at jack to ground lug is 30 Mega ohms (infinite I guess).

Center post on 9 is soldered for sure it just looks weird at that angle. I'll try to trim the leads further.

And again to be clear I cannot use electrical tape to insulate the exposed wires?

 

[Paul Birkeland]

Electrical tape would be a good plan.

What is the DC resistance to ground of the middle outer terminal on the headphone jack (The one at the same level as the one where the red wire lands, but on the other side of the jack).

 

[smodtactical]

40 Mega ohms

 

[smodtactical]

Paul I found out the problem with terminal 6. I accidentally cut the connection between the outer middle and lower headphone terminals for some reason (I think I thought they were long leads and just snipped them). So I soldered a wire between them at now terminal 6 reads 1.4 ohms just like all my other '0 ohm' terminals.

So now the only issues left are the terminal 12 reading 4-6 ohms and red RCA jack reading 83 kOhms. I wonder if thats ok ?

 

[smodtactical]

This is the latest version of my work. I tried to clean up more leads and trying to desolder and push through some of the wires so there was less exposed wire.

 

[Paul Birkeland]

With a little electrical tape on the green wire, you could give firing that up a shot.

 

[smodtactical]

Ok will try.

I guess the red RCA is ok since its within 10-15% of DocBs range.

But the terminal 22 is measuring 32 ohms right now.

 

[smodtactical]

On my discord one of the engineers told me to tighten the ground lug and I did it and now its 1.4 ohms at terminal 22! Yes!

 

[smodtactical]

Ok the tubes are glowing but my voltages are way off. Terminal 1 and 2 are both under 1 volt. I think i have it set right on the meter, the V with a line and 3 dots.

Not sure if the 2 tiny leds are supposed to light up that are attached under the 9 pin socket but they arent.

 

[smodtactical]

The red leds are  now lit!

1) 83 V
2) 172.8
3) 0 V
4) 173 V
5) 75 volts
6)  0 V
7)  107 V
8)  0 V
9)  102 V
10)  0 V

 

[smodtactical]

Its working! Thanks so much Paul for all your help. I am shocked with how quiet the background is... I can't hear any noise at all.

 

[smodtactical]

By the way paired with 800S I am really liking it! Nice smoothness and richness.

 

[Paul Birkeland]

For the terminals on the power transformer with nothing connected to them, the transformer screws will need to be nice and tight for them to show proper resistances.