So Close...Yet So Far [resolved]

[anthonynchandler]

Greetings from the Great North!

I finished my wonderful soldering journey with the Moreplay only to find myself at the dreaded voltage problem on the final page. I thought I would post a cry for help based on my Resistance and Voltage Checks first before posting images, as the numbers may tell more than photos for now.

I passed the Power transformer test. I passed the glowing 6v6 test. I passed the Raw B+ voltage test. My numbers for those were spot on.

For the resistance Check the main incongruencies with expectations were:

Terminal 9 - OL
A5 1.94
A6 OL
B5 - 215
B6 - Ranges

Voltage Check DC

Terminal 1.  -1.2V
Terminal 4  - 0.1
Terminal 6 - -1.2
Terminal 11 -1.1
Terminal 14  - 0.1
Terminal 16 -  -1.1

I should note that I did try the Moreplay in my system (I was not sure if I was just messing up with the multimeter and was off by 1000 or something) and there is nothing. As per my reading of the "rules on p.58 I could proceed with the voltage check. I wore rubber boots and had a hand in my pocket [with Alanis Morissette playing on my phone].

Any thoughts before I go through the entire circuit tomorrow? I thought my solder points were good, and I think my capacitors are in the right directions.

So close...many thanks.

Anthony

 

[hmbscott]

On your resistance test, terminal 9 should read 10k ohm, and that it reads OL suggests your vol pot red lead isn't connected to terminal 9. Its not clear to me if that would cause all the other issues.

Actually the A6 resistance also should not read OL either, that implies it's not connected to anything. For the A&B 5&6 pins I recommend setting your ballence pot at about the middle of it's range. You should then read values like 40-60k ohms, and A5 & A6 should be almost the same and B5 & B6 should be almost the same. If yoou don't get that there's a wiring issue there too.

 

[Paul Birkeland]

I should note that I did try the Moreplay in my system
Any thoughts before I go through the entire circuit tomorrow? I thought my solder points were good, and I think my capacitors are in the right directions.

Definitely don't try to use a piece of gear you know isn't working in your system, as that can cause lots of damage to other components and you aren't really learning anything by doing this. 

Can you post some photos of your build?

 

[anthonynchandler]

I am attaching a selection of images which might help if I connected something in the wrong place. Everything seems attached properly, but I could be wrong. Absolutely my mistake to attempt a hook up without 100% measurements being proper. I thought that with the passed tests on the previous checks I may have simply been measuredly those points incorrectly. My mistake.

What I found strange was that the misreadings both seemed to be off of the tube sockets in the same spots for both A and B.

Anyway, any help offered is greatly appreciated.

Anthony

 

[anthonynchandler]

More

 

[Paul Birkeland]

What DC resistance values do you get across the three lugs on the lower level of the volume pot?

 

[anthonynchandler]

Black lower - 0 with beep
Middle lower lug - 0.900
Red - OL

 

[Paul Birkeland]

How about the other level of the pot?

 

[anthonynchandler]

Hi Paul,

Black Upper- 0 with beep
Middle Upper  lug - 0.904
White Upper - OL

I went over the diagram and found that the C/D on the selector switch were in the wrong place (blame my eyesight on that one - so hard to see those letters). So I fixed that and then went back over any questionable solder joints.  No changes on the readings on Resistance for 9 (still OL) and the A5/B5  and A4/B4 remain incorrect.

Now does the orientation of the larger film resistors affect anything. I have the print facing the opposite direction to the tube sockets.


Thanks,
Anthony

 

[Paul Birkeland]

Can you send me a link to the meter you're using? 

If it's not an autoranging meter, you may need to go up on the resistance scale to resolve the 10,000 Ohm reading.

 

[anthonynchandler]

Sure. It is a Klein Tools MM300. 
https://www.kleintools.com/catalog/multimeters/digital-multimeter-manual-ranging-600v

It is manual ranging

 

[anthonynchandler]

Paul,

Okay...when you mentioned the multimeter I changed how I was measuring the circuit for resistance and was able to get the proper numbers except forB5/B6 which seemed to range a bit, but is definitely not clear like the A side.

When I now measure voltage, all of the numbers are perfectly within the ranges posted.



A.

 

[Paul Birkeland]

If the voltages are OK and you swapped the wires on the selector switch, then you could attempt to use the preamp again.

 

[anthonynchandler]

Okay. Voltages are all okay. I also found the problem with the B tube socket: a tiny end of the resistor on the balance was touching the metal on the balance knob. So now I get the correct reading on that.
I have all readings correct for resistance and voltage.

But...no sound at all when plugged into a system.  I get tube glow, I get no sound. I tried using different amps and sources in the different places, but nothing.

What fun - ha ha ha.

 

[Paul Birkeland]

Are you confident that your cables are in the correct RCA jacks?  If all the voltages are good, it'll be something pretty simple like this.

 

[anthonynchandler]

Yes. I am, BUT let's confirm in case I am not.
The inputs are the three sets of RCA jacks. I have tried using different jacks from the three with both a phono pre output and a connection from my iPhone.

The outputs have been tried going  to either an AudioLab 6000A (as power amp) or two DIY Nelson Pass Amp Camp monoblocks out to Klipsch Heresy IV speakers.

The system works without the Moreplay.

Am I missing something obvious? I try different outputs, move the balance and the volume and the selector.

 

[Paul Birkeland]

Can you check the resistance between the black (whichever you'd like) wire on the selector switch and the white wire?  How about black and red? 

Your meter won't support signal tracing, but finding a meter with a 2V AC scale isn't super tough, and that can be used to figure out where things are dropping out. 

Based on both channels not working properly, I'd be suspicious of wiring issues around the selector switch and balance pot.

Come to think of it, I looked back at your photos and didn't see anything showing the balance pot wiring, so posting a couple of pictures of that could be helpful.

 

[anthonynchandler]

Certainly. Give me a moment and I will photograph the two sections.  I tried different tubes to troubleshoot, and then just switched through all of the jacks with all of the combinations. I figured that if it was something like one sloppy solder point then I would get some signal somewhere.
Photos and results of metering will be incoming.


Thanks

 

[anthonynchandler]

The resistance between black and white is 77
Black and red is 66.

 

[Paul Birkeland]

Something we have seen happen now and then is CAT5 getting overheated and the individual wires end up touching when the jacket melts away. 

This would appear as 0 resistance on the upper or lower middle lugs on the volume pot with the volume pot turned all the way up, or 0 resistance across the outer pairs of lugs on each level of the balance pot.