Beepre voltage question

[Jamus]

One more observation that might help. Now the LEDs on the B sides of both C4S boards are very dim compared to the A sides of each board (when I first turn it on all 8 lights are strong, then the B sides dim).

When I first completed the build a few weeks ago I'm certain all 8 lights remained bright. Then a few days ago I noticed just 2 lights would dim after the unit warmed up. Now it's both channels, 4 LEDs. "A" side LEDs remain bright.

[Jamus]

How much would it cost to replace both PC boards?

[Paul Birkeland]

Cool heatsinks tend to indicate that the 300B's aren't drawing any current. 

When you have 5-ish volts on the non-ground end of the 10W resistors by each 300B socket, that let's us know that the 300B's are drawing current and heating up.  This should be sufficient to draw plate current, but your high voltage at OB and cool heatsinks tell us that no plate current is being drawn by the 300B. 

This is further complicated by the fact that both channels exhibit the same problem. 

Rather than buying new boards, it might be a good idea to have a second set of eyes look over your build.  This can be accomplished through the repair service, or by posting your approximate location and hooking up with a fellow Bottlehead builder who can have a look under the hood.  A few people have even had their significant others check their work with success.

-PB

[Jamus]

Thanks PB. I was reflowing all terminals on the boards and ended up with a solder blob bridging across 2 leads on a PN2907A transistor. After trying unsuccessfully to remove the blob from this tight spot I ended up pulling the transistor off the board.

After cleaning it up I proceeded to break it trying to reinstall it. The problem is there was still residual solder in each hole that was a complete PIA to remove. I'm afraid the board may be shot because of those efforts. Picture below, notice you don't see those nice shiny metal collars around the 3 holes where the transistor belongs. Will those still conduct?

[Paul Birkeland]

Yeah, that board is kaput.  You can contact replacementparts(at)bottlehead(dot)com about replacement boards/parts. 

-PB

[Doc B.]

To avoid this in the future pick up a vacuum solder pump, the type with a plunger. They are inexpensive and work well for clearing liquefied solder from pad holes so you can more easily remove and replace components without board damage.

[mcandmar]

This stuff works great too, it will suck up solder like a sponge  http://www.mouser.ie/ProductDetail/Plato/1810-5F/?qs=%2fha2pyFadugWAcSf2iQEFtymdo91GCxIBSLwI45ystI%3d

[Jamus]

Thanks all. The thing that kills me about this is there was nothing wrong with this transistor until I started mucking around looking for the bad connection. I can fix this but I'm still no closer to fixing the voltage issue. With a Kaiju on order I'm feeling the pressure to get this finished. I'm thinking I should just send this in for service. Should I rebuild the board first or send as is?