Tapco Juice J 2500 slave amp, 2007
 

Anyone fmiliar with these ? One ch down but nothing visibly or rhinally
amiss inside. Not powered up at all , just cold exploring at the moment.
Is there output relays lurking under the main board? Triac crowbar ccts on
the o/ps ?

Tapco Juice J 2500 slave amp, 2007
 

Would any Mackie amp be similar?
Comes apart easier than it looks, not one large board, 2 sparated pcb and
heatsinks. Still nothing seen amiss so presumably false protection, at least
no microcontroller seen. Plenty of SM under the pcbs but analogue seemingly.

Tapco Juice J 2500 slave amp, 2007
 

Hopefully Mackie M 1400 will be similar enough , NJM13700 and LM311 instead
of LM338 for muting and supervision

Tapco Juice J 2500 slave amp, 2007
 

How do American repairers get on with PbF boards, not marked as PbF. Is
there an overlay codification meaning PbF or LF ? Has anyone collated
together what USA makers + models for what 21C years definitely had PbF or
definitely had leaded solder? Or putting it another way , what is the
probability of any China manufacturer using leaded solder in 2001/ .../2007/
.... ?
This amp made in China in 2007, for USA, exported to UK. Balance of
probabilities from appearance, indentation test etc is probably PbF.
Yet again faced with repairing a "fully working" but intermittant failure
PbF amp
However much tugging and twisting on input and output and pot boards cannot
get either channel to fail, as user contact there, most likely failure
areas. Closely inspecting all boards - no bad-contact solder found. So far
powering to 75 percent mains, noting some mid-amp signal AC and DCs , as
nothing useful out there on this amp. Before upping the mains (may of course
cause a protect failure in one ch from that) . And before seriously
attacking the main amps with engraver tool and nylon bolt as tip ,
monitoring large dummy loads with attenuated phones, to try and make a
failure.

Tapco Juice J 2500 slave amp, 2007
 

Wanging everything with engraving tool + nylon bolt eventually elucidated.
Loss of ch 2 , no prob on its i/p board, due to bad mono/stereo/bridge slide
sw on the ch1 i/p board.
Unusual DC rails for the SMD opamps , will go on my tips files for anyone
else confused by this.
One operates from -113V and -101V supplies and the other 40V and 55V, same
for both ch

Tapco Juice J 2500 slave amp, 2007
 

A right pain to desolder, double sided thin board, thin traces, tiny pads ,
plated thru holes and PbF solder. 19 inch rack amp but with unnecessary
miniature complex asymmetric switch impossible to find replacement for, 4
pole,3 way, but only 8 of the 16 pins used here. "re-soldered" with copious
flux before hot-air desoldering because of extra PbF temp . Not contacts
corrossion it would seem. I suspect sloppy phosphor bronze contact
carrier/slider in outer metal shell, will rebuild with 0.5mm hard PTFE strip
padding out one side to stop it flopping about, and cleaning contacts.
Maker YSC logo and also DC stamped on the outer.

Tapco Juice J 2500 slave amp, 2007
 

there is a potential safety issue with these.
On reassembly make sure the mains switch crimp connectors are pointed
downwards, easy to have bent them up to nearer normal straight rearwards, in
moving wires and boards about.
If straight out , then the plastic of the crimp will get squashed into the
edge of the pcb with nearest track just 1mm away from mains connection.