voltage imbalance with my speedball

[Agweeks]

I have installed the first board of the speedball, only to find that the voltage at OA reads 42v and 72 at OB.  I've reflowed, or in some cases cleaned and resautered, the connections all the way back to both tubes for that side of the amp.  Still it reads the same.  Any suggestions? 

Thanks in advance.

AGW

[Paul Birkeland]

Can you post a photo of your board?  I would bet you have a PN2907 installed backwards.

[Agweeks]

I have to use my phone for photos. Sorry for the delay.

[Agweeks]

I just retested the voltage and it now measures 57v on OB but still 42 on OA. Both below the range of 60-90v the manual says the circuit requires.

IA reads 185v and IB 184.5v. B-BA reads 0v.

Thank you in advance for your help. I really appreciate you.

AGW

[Paul Birkeland]

Are the LEDs on the socket illuminating?  Was the amp working properly prior to installing the Speedball?  Can you post a photo of the bottom of the PC board?

It's important not to make any guesses at this point, but rather to collect a complete set of information.

[Agweeks]

All leds light up. Amp worked fine before. Attached is the photo

[Paul Birkeland]

All leds light up.

For every joint on the bottom of that PC board other than the ones for the LEDs, reheat them with your soldering iron until the solder melts, then count to ten.

The LEDs lighting up tell me that your tubes are glowing and that the board is passing some current.  The really low plate voltage in combination with the illuminated LEDs tells me that the amount of current passing through is very, very low, which is almost always a solder joint issue. 

[Agweeks]

I have re-soldered every point on the board except the leds twice.  I even reflowed all the joints on that side of the amp circuit.  the volts are now up on the OB side.  It reads 64V.  The OA side reads 41V. 

AGW

[Paul Birkeland]

So this is some good evidence that solder joints are an issue, and the improvement demonstrates the need for a lot more heat.

What is the wattage rating of your soldering iron?

[Agweeks]

I have a new Vastar iron that I ordered.  I have it turned all the way up to 8.  When I did the board though, I used the finest tip that came with it.  I had a hard time getting it hot, as I now recall.  I'm now using the larger tip. 

AGW

[Paul Birkeland]

OK, that looks like a 60W iron.  You want it cranked up all the way for sure. 

[Agweeks]

Well I have soldered and resoldered everything on the board. 

The voltage on the two outside legs of both Q2A and Q2B are 181V.  The center leg on Q2A is 40v.  The center leg on Q2B is 57V.  That seems odd to me. 

AGW

[Paul Birkeland]

I would go ahead and give the LED solder joints on the board a bit of reheating as well.  Looking at the images again, I can see at least one LED joint that isn't all the way flowed.

[Agweeks]

As we discussed over the phone, I have a broken LED's on the 9 pin tube socket.  I've ordered more from you guys. 

You mentioned that I could temporarily create a jumper?  From where to where would I do so?

[Paul Birkeland]

Just a piece of wire to connect A3 and A8.

-PB