a few LED's no longer light up [solved]

[wesleyHK]

  

i finished assembling the reduction yesterday.  the resistance readings tested well except for terminal #31, which did have a reading.  someone here said that  there should be a reading like terminal #2, which means it should be a "*" instead of "OL", which i assume is correct.

i am in hong kong and the voltage at my house is 222V, a bit lower than what my 240v transformer should be getting, so the readings were around 10v lower than what is stated on the manual.  other than that, all the voltage tested correct.

all LED's lit up as they should.

i then listened for around a half an hour, then i got this big cracking sound in the right channel and immediately turned off the system.  i found that the LED was out at A3.  i then resoldered the lead at the tube base center and it was up and running again with no problem.  then i proceeded to do the shunt regulator upgrade in the integration kit.  got the board all nicely soldered up, then put into place, all LED's lit up and the voltage checked out good.  then hooked it up and listened for around 10 minutes and the same crackling distorted sound came back.  then checked under the amp and saw that both LED's in the A socket are no longer lit and also the shunt regulator board's LED at 1A side, D1 no longer lit.  can LED's burn out?  or is there a fault that is causing them to go out?

i was planning on going to the next step of installing the C4S boards when i get this problem solved, but my kit was short 2 pcs. of the 237 ohm resistors, which i have to ask eileen for once i figure out this problem.

if anybody has any ideas of the cause of my problem, i would greatly appreciate it.

regards,

wesley

p.s.  i just reviewed my notes and saw that terminal #2 was 103.3v, so it was a bit high?  what would cause that?

[Paul Birkeland]

Hello Wesley,

Please remove the shunt regulator power supply board and return the Reduction to stock form for now.

It's very difficult to debug your kit when it was never quite working properly from the onset.

Also, no, the LED's won't burn out in any of our lifetimes, but when one goes out, the voltages will be off.

Once you have the amp back to original form, please post the voltage discrepancies that you find. 

[wesleyHK]

hi paul,

o.k., everything back to stock form.

i double checked the resistances and they were all fine.

as for the voltages, most notable are no. 2 and no. 6 terminals.  all others are fine, but a bit low.  all the voltages were higher when i first finished the amp, before playing and getting the cracking sound.

for your info, the input voltage was 225.2V this morning.

2  44.9
4  134.5
6  -0.2
7  68.7
13  68.0
14  68.1
15  68.5
18  69.5
19  69.0
20  68.2
26  69.4
29  133.9
31  67.3
33  6.0
37  6.0
38  9.8
39  4.1
41  4.1
42  9.7
44  165.3
50  149.3
51  149.1
52  165.4
53  165.3
56  133.4
57  133.4
59  149.4
60  149.4

thank you and i look forward to your reply.

regards,

wesley

[Paul Birkeland]

6 is supposed to be 0V.  0.2V is close enough.

Does the voltage at 2 change if you swap the tubes?

[wesleyHK]

after the tube swap it's 47.6V.

[wesleyHK]

 

its alive again, sort of....

i reheated tube socket terminals A4 and A5 and the LED lit back up.  the voltage reading at #2 terminal got back up to spec (69.1V) and it plays fine.  so i left it on during dinner and after dinner i started to get a less crackling sound in the right channel.  looked under it and the LED flickers a bit.  too late to look at it now, but most likely i will add some solder to those points and see what happens.  i did resolder all the points on that tube holder the other day, but i guess it likes to play games...

[Paul Birkeland]

It's generally not always the best idea to just blindly add solder to things.  Eventually, you can add enough solder that your soldering iron will no longer be able to melt the ball, or it may wick into the socket pins and damage the socket.

You have a loose connection, which means a loose part, which means that you need to secure that part (Before soldering!).

One way to find this part is to poke around the area with a wooden chopstick until you find what is loose and causing your issues.

It is actually more likely not to be a connection to the LED itself, but rather to one of the other couple of pins near it.  We often see folks fixate on a dark LED by soldering it until it melts, only to find that it was the wire on the next tube socket pin over that wasn't well connected and was causing the issue in the first place.

-PB

[wesleyHK]

   hi paul,

thanks for the advice, what a great use for a chopstick.  hopefully i can find the fix before breakfast  .

[wesleyHK]

the chopstick poking didn't find anything  .  eventually the LED went out again and poking never got it to light up again.  i decided to clean up a bit since there was some flux splash on the LED, Z5U caps and tube holder, so i used some isopropyl alcohol on a small pc. of tissue paper.    shockinly that did it, the LED came back on and i now have a solid 69V at terminal #2.  so it's playing nicely right now and i am keeping my fingers crossed.

thanks again for your advice paul, i learn a lot from you masters of this hobby  .  i own an extended foreplay and a couple of seductions with C4S mods and they have been working flawlessly for over a decade.  great gear from a fantastic company  .

[wesleyHK]

   it went out again after 1.5hrs of play.  i am going to desolder a few of those joints and make sure i'm getting a good physical contact, then resolder.

[Paul Birkeland]

How's your voltage at T6 when this happens?

If it's some value other than 0, that may help us get somewhere.

[wesleyHK]

it's at zero.

[wesleyHK]

 

it's fixed.  been listening to it for over 2hrs. and it's even sounding a tad bit more livelIier than before, more involving now  .

i desoldered the following points.  then made sure the LED and resistor wires were wrapped around the terminals tightly (which is what i did in the first place), then resoldered everything with just the correct amount of solder.

A3
A4
A5
CENTER TERMINAL
A9

i guess it was a bad solder point somewhere, but i didn't see it  .

when i finished i noticed a booboo.  i accidentily burned the side of one of the 0.01uf caps with my soldering iron.  it was bad enough that i could clearly see the foil.  i don't know if it caused any problem, but the voltage at terminal 13 is normal.  i just taped it up with black electrical wire.  anyhow, maybe i can ask eileen to give me one when i ask her for the 2 resistors that were shorted in the integration kit.

thanks again paul, for the excellent equipment and support  .

[wesleyHK]

   here's a pix of it.

[wesleyHK]

hi paul,

i've been listening to the amp stock for a few days now and it's been fine.  tonight i decided it was time to re-install the shunt regulator upgrade.  once hooked up, all the LED's lit up and then i did the voltage check and it was perfect.  then i unplugged the power cord, turned the top-plate right side up and was ready to hook it up in the system.  just to double-check one final time, i stood it up on the transformer end, powered it up and to my surprise, both LED's on tube socket A and the LED on D1 on the 1B side of the board did not light up.  so now i am back to the same problem i had a few days ago.  i really don't know what to do at this point...