problems after installing the c4s boards (FIXED)

[wesleyHK]

I’ve been having problems with my reduction after installing the C4S boards.  Prior to that it was running fine with the shunt regulator mod.
All voltages checked out once the c4s boards were installed.  I played it for around 15 mins. and it sounded great, but then it started to have a crackling sound in  the left channel.  Sometimes there’s also the same sound on the right channel.   I switched to another pair of tubes, but still the same problem.

Here’s a rundown  on the voltages and comments.

Input is 222.3vac

Terminal                   vdc
56      115.5
2      68.6
18      84.5-91.4  fluctuates when turned on for a few minutes
26      84.2-91.7  fluctuates when turned on for a few minutes
31      60.0-75.8  fluctuates when turned on for a few minutes

IA      115.0
IB      115.1
OA      105.7
OB      102.6
BA      0
BB      0

MJE5731                   105.8
MJE5731                   102.4  o.k. this morning, but last night it was at 94.6 and fluctuated up to 98.0

At times the led’s on the right board (left channel) flicker and are  slightly dimmer.  Last night on that board the D2 led (BA side) was not lit.  this morning all 4 were,  but the one on D1 1A side was noticeably brighter and the other 3 were slightly on the dim side.

Last night the voltages on 18 and 26 were stable and were at 69.3 and 69.2 respectively.

Please feel free to ask any questions.

Thank you in advance.

Regards,

wesley

[wesleyHK]

since I have not received any reply, I looked into the problem again.  everything seems to relate to a low and fluctuating voltage at the right side MJE5731A transistor.  when the voltage is at a stable 115v, the 4 led's come on and the all the voltages are at spec.  so my guess is that it is the MJE5731A transistor.  I will try to buy one and see what happens  .

[Grainger49]

    .  .  .   At times the LEDs on the right board (left channel) flicker and are  slightly dimmer.  Last night on that board the D2 led (BA side) was not lit.  this morning all 4 were,  but the one on D1 1A side was noticeably brighter and the other 3 were slightly on the dim side. 

I don't have a Reduction or a manual.  But the readings that change from night to morning point to one or more solder joints that are not right.

The first advice is to look at everything and be certain every component is in the right place and orientation for caps, diodes and transistors.

The second piece of advice is to check every solder joint and touch up any that look suspect. 

So... touch up every solder joint around those places where you get different measurements at different times. 

[Paul Joppa]

The center pin of the MJE5731A is difficult to solder to, because it is connected to the heat sink. A working but not quite good enough solder joint there could be the problem.

[wesleyHK]

thanks for the advice guys.

I went over everything and reheated everything (including the mje5731a) on the shunt regulator board.  on top of that, I rechecked everything at least a dozen times.  it was working fine before the c4s boards, so it was a working unit that played well.  I still suspect the mje5731a because sometimes I got a stable reading, and sometimes it went all over the place.  I will see if I can buy one today.  I could have swapped them, but the suspect one was a bit difficult to remove and I don't want to damage the circuit board traces.  it's a cheap part that I think I can source from a electronic parts shop I know.

hoping to get it working later today  .

[wesleyHK]

the part could not be found locally, so I ordered it from Singapore.  I ordered 2 pcs. and they should arrive in 2-4 days time  .

[wesleyHK]

the MJE5713A arrived the next day, I was amazed at how quick that was.  I installed it last night, all voltages were at spec and the LED's lit up evenly.  then played it for around 5 mins. and it was superb, however the crackling sound started up again on the left channel.  I did the voltage checks, and again the MJE5713A (the one on the right side that I changed)  was fluctuating from 85v-95v, so back to square one again.  everything has been checked over and over again, and all the solder joints reheated.  could it be a bad diode on the shunt regulator board?  or a bad cap somewhere?  what would cause the voltage fluctuation at the MJE5713A?

 

[2wo]

How about do the remove/insert the tubes 10X, to clean the pins. Seems to be helping some others and is worth a shot...John

[Paul Birkeland]

Did you end up swapping tubes between channels to see if this behavior follows a tube? 

[wesleyHK]

Did you end up swapping tubes between channels to see if this behavior follows a tube?

i did that and i also tried a new pair of tubes, but to no avail.

[wesleyHK]

How about do the remove/insert the tubes 10X, to clean the pins. Seems to be helping some others and is worth a shot...John

i'm desperate, i miss my opera.  will clean the pins tonight, thanks.

[Paul Birkeland]

There's definitely a loose connection somewhere in your Reduction.

With the amp off, take your needle nose pliers and give all the components on the offending side a gentle tug, then look for movement. 

[wesleyHK]

I check everything and there was nothing loose.

I cleaned the tube pins and sockets.

it played this morning for around 10mins. and started crackling again.  I shut it down.

tonight I turned it on and it played beautifully for 35 mins, then started crackling again...

 

[kgoss]

It sounds to me like the bad connection shows up only after the amp heats up.  I would reheat every solder joint in the amp and see if that fixed the problem.

[wesleyHK]

I re-heated every solder joint on the left channel and that did it  .  I played it for around 3hrs. today and it was crackle free  .  it's embarrassing, I still don't know what joint was at fault.

thank you ken, paul and everybody else that gave me advice, much appreciated.

the reduction is a very significant step up from the two seductions that I own,  it should keep me happy for quite a while  .