Right side not working on Extended Foreplay 3

[Paul Birkeland]

OK, now measure the voltage on the metal portion of the transistor closest to the "O" pad with the variable reading.

[Grainger49]

The Voltage checks are as follows:
I = 228v  (when I touched the pin the led that was out lit, as did all the led's on the right board, this state lasted for 5-10 secs)
O = 0v when led's out and 148v when lit
K = 3v led's lit and not lit

I think I was understating the severity of the pops and crackles, they are speaker destroying.

The reading at "I" seems to indicate a solder joint that isn't right.  That is, when there is pressure on it you get conduction.  Did the LEDs go out while you were still taking the measurement?  

I would re-wet all solder joints around this point.

[J Leng]

Rewetted the I joint and no pops for 3hrs, this is the longest it has been silent, also the amp is quieter with less hum.  A tentative thank you guys.

J

[Paul Joppa]

Just another thought - check your power line voltage. With an exceptionally high line voltage, the shunt reg board has been known to get too hot.

[Bribase]

Hi guys

I think I'm having the same problem with my extended foreplay after moving the unit. After setting up things were fine but the second time I fired it up (the next day) I got a lot of pops on the left channel although the music was playing fine. I managed to blow the bass driver as a result of the noise and then the channel gave out. I powered the unit down and took a look at the boards, I noticed that one of the LEDs on the bad channel stayed lit long after the power was off.

The weird thing is I changed to my backup speakers to diagnose the problem today and things seem to be fine again. All the LEDs lit up together and turned off at once when the power was down. Within two hours of playing I got one little pop on the channel but nothing else. I left it on for a couple of hours thinking that the problem might come back once the tubes were fully warmed up but it sounds fine. What do you think guys? Was this just a passing issue from moving my foreplay or symptomatic of a problem that might come back?

Thanks!

[Doc B.]

That very strongly indicates that you have a cold solder joint somewhere. Check the solder pads around the LEDS and R2 on the side that stayed lit after you turned the preamp off, and also check the connections of the wires from the board to the tube socket to make sure everything actually got soldered. If those connections all have solder on them, reheating them all may very well solve the problem.

[Bribase]

Thanks Doc

Just out of interest, what would cause one of the joints to fail? Would moving it be enough to cause the problem? It all doesn't speak too highly of my soldering skills!

B

[Doc B.]

Actually if moving it caused the problem I would guess that it is most likely a joint that was missed altogether at some terminal. That doesn't reflect as negatively on your soldering skill as it does positively on your skill at attaching the lead so it conducts even without solder, which is classic military spec soldering procedure. I recommend a magnifier for inspection.