Failed glow test [resolved]

[Suger]

Good evening.

May I ask for some advice? I have started building my first MonAmour and am at the Glow test step, and, sadly, I only partially passed it. The 5670 glows, but not the 2A3. I guess I must have a faulty soldering somewhere in the circuit from the transformator to the socket, but a non-expert inspection didn't reveal any obvious flaws. Voltage between B1 and B4 is very low (in the 0.2V range), which doesn't seem normal, obviously. But I don't really know what values I'm supposed to find where to help me identify the likely culprit.

Any help would be very much appreciated!

 

[Paul Birkeland]

Can you post some build photos?  This is likely something we can spot since there isn't a ton built out in your amps at this point.

-PB

 

[Suger]

Of course. Here you go. It's probably something as stupid as "have you checked that the printer is actually plugged in" or "you've wired the wrong plug"...

Many thanks for the help.

 

[Paul Birkeland]

You need more solder and a lot more heat to get good joints.

If the MBRF diodes are not mounted flat against the chassis, they will overheat and blow.  I see at least one of them is mounted at an angle and that will absolutely lead to a failure.

If you take photos from maybe an extra foot away, your camera should be able to capture more objects in focus. 

The black jumper on your power transformer looks to not be soldered on one end.

https://www.youtube.com/watch?v=EN16Pi7pcfk

 

[Suger]

Many thanks. I'll (re-)watch the video, correct all of these things and let you know.

 

[Suger]

Sorry for the long silence, but I got stuck away from home by Covid. Anyhow, back at MonAmour.

A couple of updates, which might mean very bad news for me. First, the diode that wasn't flat against the chassis was actually mounted upside down. I know, awfully stupid. I hope I didn't destroy everything by doing that. Anyhow, I've now turned it the right way up.

Second, as a side, I realised that I had soldered the drain wire of the 9 pin socket wire to 9L instead of 8L. This is now corrected (although probably unrelated, as the 5670 lamp passes the glow test).

Third, I've redone many of the solders. Prior to that, I had a small resistance (c. 50 Ohms) between B1 and B4. Now, the circuit is fully continuous, which, I hope, is a good thing, and about 8V going through the circuit (whether I test at B1-B4 or at H3 to terminal 8).

But still no glow that I can see. Three questions, though:

1 - There is a capacitor. Does it needs to charge before the lamp glows (in which case, I might not be waiting long enough).
2 - What voltage should I have in that circuit? Do I still need to check for wrong soldering?
3 - Is it possible that I may have killed the capacitor?

Any other suggestions?

Sorry to be such an oaf.

 

[Paul Birkeland]

If you put your meter probes on terminals 1 and 4 on the 4 pin socket, what DC voltage do you measure?

 

[Suger]

DC I get 4V.

 

[Paul Birkeland]

How about with at 2A3 in the socket?

 

[Suger]

2.4V

 

[Paul Birkeland]

Those two data points tell me the 2A3 is glowing.  It's not a very bright glow, so you may need to turn the lights down a bit to see it.

 

[Suger]

It is glowing indeed. Faintly, and I thought it was the relfection of the red writing on the lamp, but it's glowing.

Many thanks for your patience.

P.S.: much better after nightfall!

 

[Paul Birkeland]

If your intuition is to come here when you're not sure about something, that bodes well for the rest of your build.

-PB