B+ being pulled down - looking for suggestions

[SLW]

I just finished building a 5E9A.  I put the 5Y3 in it and powered it up using a lamp limiter.  It looked good.  I measured 420VDC.  I put the rest of the tubes in and powered it up again.  This time the lamp glowed.  I measured 300VDC.   I started pulling tubes and measuring.  With the two 6V6's pulled and all of the preamp tubes installed the lamp is dim and B+ is back up. 

A little background about the build.  This is built into my test chassis.  I have built several amps in this chassis.  The PT is the unit that Mr Hoffman sells as a replacement for the bassman / super reverb.  I built a new board for this test.  I copied the fender layout except the 68K resistors are on the input jacks and I have 470 screen resistors on the board.  The heater string uses two 100ohm resistors and follows the modern convention.  The OT is a vintage unit (from a radio) that I got from a member here.  I have not used the OT before.

I quickly checked all the connections to the 6V6 tube sockets and found no errors.  I have questioned the OT.  Can an OT malfunction in a way that would pull the B+ down?  Are there any other suggestions for things to check?

Thanks
SLW

 

[sluckey]

I just finished building a 5E9A.  I put the 5Y3 in it and powered it up using a lamp limiter.  It looked good.  I measured 420VDC.  I put the rest of the tubes in and powered it up again.  This time the lamp glowed.  I measured 300VDC.   I started pulling tubes and measuring.  With the two 6V6's pulled and all of the preamp tubes installed the lamp is dim and B+ is back up.

That's perfectly normal operation when you have a light bulb (big resistor) in series with the amp. Time to put the limiter under the bench and plug straight into the wall.

[SLW]

I will do it and report back.

[SLW]

It works great. I just spent thirty minutes playing it. Thanks for kicking me along.    What I was seeing makes perfect sense when I stop and think about it.  I guess I am still very conservative with tube amps.  I am nervous about burning up a transformer.  When I tinker with electronics and blow up a ten cent part I don't think twice about throwing it away.