princeton reverb build

[Garycbet]

started to post this on another section but realized that it should be here.

here was the building setup.  i used the mounting holes in the chassis and just screwed them into some 1x8

[Garycbet]

here is a pic of the faceplate.

[Garycbet]

well got her together checked, double checked, triple checked.  amp came on into standby them powered up no tubes?  no smoke or sparks but also no high voltage.  very frustrating.  the heater wires have about 7 volts at the lamp.  high voltage out of the transformer measures about 650 volts.

pin 5 at the power tubes shows -35 volts.  this is really frustrating.  Got to tired to work safely around the amp so ill hit it again tomorrow.  I see no reason though why this is happening.  oh well ill get back at it tomorrow with fresh eyes.

(might have been premature but I put an equal value resistor in parallel with the bias range resistor and the negative voltage went to -70 volts.)

[sluckey]

You must have the rectifier tube plugged in to get any high voltage dc.

[EL34]

I am not sure why you think something is wrong??

Put the tubes in and do DC voltage checks


After the components are all installed and the wiring is complete, that is 

[Garycbet]

Ok that's what I thought.  But it was very late and the tube bias instructions say that you should test for the presence of high voltage with the tubes out.  Which I took to mean that it should be there.  I'm awake now.  Tubes it and she sings sweetly.  about 25 am of current

[EL34]

Ok good deal.

I was not sure you even had the parts on the board yet
The picture at the top shows a bare board with no parts

[Garycbet]

here are the final build pics (minus cabinet of course).  This was really easy.  Doug lays everything out wonderfully.  so well infact I really didn't need to dig into the schematic much.  the build becomes visual.  which is bad when like me you are supposed to know what your are doing.  It can make you too lazy when the power is connected.  LOL  In my haste i dropped the normal "one handed" troubleshooting method that i always preach to my employees and got bit by the mains power.   I inadvertently let one hand rest on chassis and the other just touched the hot at the fuse housing.  I put things away and waited till i was rested and fresh.  I know better than that.   

Anyway.  The base build went together and now that its alive.  I tweeked some of the values to make it slightly more aggressive than the standard design.  (just my preference and maybe not very noticeable) also i adjusted for a wider bandpass on the tone control.  once again not necessary.

[EL34]

Looks good from here


You did a nice neat job wiring it up
 

[Willabe]

Very nice! 

[Garycbet]

went a little ocd on the build.  Got some small parts organizers for all the components.  Then I got a seperate one just for one Amps worth of components.   When all the bins are empty the amp should be together.  Kept me from wasting time sorting through parts that got mixed up and made sure that all the parts were in easy reach at all times.  Best 9.00 I ever spent at harbor freight.  It also keeps you working "cleanly".  Also I double checked the values while sorting just incase.  I have owned quite a few amps in the past and the one I just built is way more quiet.  (Just can't get over that)

Defiantly ready for the next build.

[Garycbet]

The paduk faceplate was an old piece of scrap that was just to narrow for a freatboard.  I liked the copper leaf but could not make the volume, treble, etc. labels to come out right so at the moment I'm using a very thin piece of birch ply that you can get from your favorite hobby store and water transfer decals.  Layers of shellac and sanding go over that then a final couple of topcoats laquer and its on to the cabinet.

 For that I plan to go with a head cabinet with a seperate 2x10 speaker enclosure.  I'll post pics when I get that done.

So far ive put in a solid 12 hours of build time.  Looking at another 6 for the cabinets.  Hopefully I can be totally complete by the first week of October. 

[Garycbet]

 

major setback in the build.  ive been playing the amp for the last couple of days and it has been awesome.  went out today nothing.  then after a min or so it gave out a loud bass tone.  i turned the amp back to standby. looked everything over and then turned the amp back on.  no sound.  after about thirty seconds i tried to adjust volume and it made some high pitches then sounded like it was trying to communicate with aliens.  i shut it off and checked the current across the 1ohm resistors on the power tubes.  tube on the left is 23ma  tube on right is 4. 

guess ive got some troubleshooting to do.  sure wish i knew what changed.

[mresistor]

One tube could have went bye bye...  it happens. The reason I say that is because it just happened to me with my HPR. Tunred it on, and it went BLAM crackle pop...  and then worked fine. Turned it on next time and it did the same only worse, this time I was watching the 6V6s and saw one of them flash over when the HV was applied. Tested them and both were weak and in the bad area. 
Check your voltages on the tube sockets and make sure they are all good and try another set of tubes.


Your HPR looks real nice and tidey inside. Nice work. Looks great with those little Xicon caps and was probably a bunch easier to populate the board. Mine was a nightmare to populate as I used orange drops, and a couple of Mallory 150s.

[Garycbet]

OK its done and sounds really awesome.

[Fresh_Start]

I love that brown tooled leather like covering!

Chip

[drew]

Very nice.

It seems like a lot of guys are building Princeton Reverbs lately.