Princeton Reverb Startup - Reverb Issues [update]

[BetterOffShred]

So I just recently built a Princeton Reverb clone using Edcor iron, and I've run into a problem I haven't experienced before.

[15 watt bulb lamp limiter is being used]
2A slow blow fuse installed -has not blown


I installed a solid state rectifier toggle using the below Robinette clip design, and with the SS selected everything works fine and the xformer generates 420V or so at the A node B+

So swapping to tube recto and installing a 5U4GB .. no voltage at the A node at all (DC)  so I basically removed the SS wiring and unhooked the node from the board so it only would be charging the cap and still no voltage.  I disconnected the 5V heater leads and measured those and get 4.3V through my 15W lamp limiter. The HV taps clearly work because it'll hit 420V B+ through the SS..

I have a few 5U4G and tried multiples and no luck there. 

Is the lamp limiter prevent enough current from passing to actually run the tube heater?  With everything disconnected but a single cap on the B+ output of the tube it should be Ok to test with a higher wattage bulb or no bulb? The bulb stays glowing brightly, but the tube doesn't glow.  I should point out that the SS scenario only works with the tube removed which makes me think the current may be the problem.

Not sure what else to check at this point.
Any ideas?

The attached pic shows the HV taps to the tube, and then the 5v taps and the B+ to one node of the cap, nothing else is hooked up at all. The SS wiring has been removed.

[PRR]

The lamp should be "bigger" than the amp. A Princeton (how many were there?) is 60-80 Watts. 15W is far too small. I'd use a "100W Halogen" (really 90W).

[BetterOffShred]

Ah marvelous. I suspected I had too small of a bulb but I had searched around a bit and never really saw a reference list. 

The Princeton Reverb is supposed to be about a 20W amp with 2X6V6 - I did try all this with a 40W appliance bulb and had the same result

Thank you so much! I'll go get some new bulbs tomorrow and report back

[BrassElephant]

Ah marvelous. I suspected I had too small of a bulb but I had searched around a bit and never really saw a reference list. 

The Princeton Reverb is supposed to be about a 20W amp with 2X6V6 - I did try all this with a 40W appliance bulb and had the same result

Thank you so much! I'll go get some new bulbs tomorrow and report back

20W audio output is not what you're looking for here. You want to reference the power consumption. In this case 60W-80W as PRR says. 100W bulb should be perfect.

After first power up with all tubes installed, if the bulb doesn't light up like 4th of July, you can put it away and power up like normal. After any changes to the circuit, soldering, etc, I always hook up the LBL again to check for a dead short again. But like the first time, if no fireworks then I put the LBL aside.

[BetterOffShred]

Also I should apologize for this thread, looking around afterwards there's numerous threads that address this very question. 
My bad.

[pdf64]

Bear in mind that the 5U4 heater is 15W, so even if the power transformer was 100% efficient, a 15W LBL bulb would be somewhat bright.

[BetterOffShred]

Thank you. Yes I realized it was high draw, but not that high! 

I have to wait till tomorrow get a 100w bulb sadly!

[BetterOffShred]

Update:

The 100W bulb allows the rectifier tube to work now and it's generating 435V of B+ at the A node.  The bulb does not light up at all even with the initial current inrush. 

I will continue startup and report back!

[BetterOffShred]

I have successfully got it going and it sounds marvelous. However I have a couple more questions if anyone will have a look.

Do both RCA jacks for the reverb need to be "grounded" to the chassis or should I be using the isolation washers on the input jack?

Does anyone have a drawing of a TRS cliff style jack used for trem and reverb (6 lugs) ?

My trem works and is strong but the verb does not, though I realized I don't have a shielded cable in my stomp switch for the reverb, and I think my switching in the Cliff jack may be .. jacked up .. 

Anyway thanks for looking

[sluckey]

Do both RCA jacks for the reverb need to be "grounded" to the chassis?

yes

Does anyone have a drawing of a TRS cliff style jack used for trem and reverb (6 lugs) ?

see attachment

My trem works and is strong but the verb does not, though I realized I don't have a shielded cable in my stomp switch for the reverb, and I think my switching in the Cliff jack may be .. jacked up .. 

You don't need a footswitch for the trem or reverb to work. The cable for the reverb must be shielded. Trem does not need to be shielded.

     https://i.ebayimg.com/images/g/ikEAAOSwHnVg3KXj/s-l1600.jpg

[BetterOffShred]

Thank you for all this information. I ended up just having the tank plugged in backwards. 

I also ran my reverb wire up through the switch and put the 220k to ground off the tip. 

The amp sounds great and the reverb is very nice, I had a 3 spring mojotone.

It's also pretty much noise free.  Obviously not a lot of gain happening but still I'm happy there's no hiss or hum.

Had to change the baffle cleats a little to get the speaker baffle where I wanted it so once that is all finished up I'll post a clip

[BetterOffShred]

One more question:. Will using 3 conductor shielded wire be Ok for the trem/verb remote stomp? I was planning on a dedicated ground wire, and then the shield obvs grounded at the jack end. Does the verb wire need to be shielded from the trem wire or is it ok for them both to be in a shield wrap?
Thanks for looking

[sluckey]

Does the verb wire need to be shielded from the trem wire?

Yes. That reverb cable is the most sensitive wire in the amp. Even more sensitive than your instrument cable.

Hoffman used to sell the same cable used by Fender...

[BetterOffShred]

Yes I had seen this wire in older posts though it's no longer available. 

I'll keep looking for a suitable replacement.

[sluckey]

An alternative that I have on my Sunn dual footswitch is Belden shielded twisted two pair cable. It's about 1/4" diameter. Each conductor has its own shield.  If you know some FAA techs, or communications techs you can probably get lots of free 20" long pieces. There are literally thousands of feet of this stuff in an Air Traffic Control Tower.

[BetterOffShred]

I'm torn because I love building stuff myself, but that $49.95 dual stomp with a TRS connector is looking pretty nice...

Yeah I'll inquire with some of the relay techs at work and see if any double shield stuff is available.  Thanks again

[BetterOffShred]

Here is a pic of the finished amp.

Built a cab from Pine, mojotone 3 spring reverb, GE NOS 12AX7s and a NOS 12AT7, Reflektor 6V6's.  Jensen JCH 12/70 I got super cheap, but it sounds fantastic.  I used mostly red drop caps and 1W-3W metal film resistors.  Modded the trem with some .02 caps and a 68k max speed resistor, and dropped the 1M at the oscillator filter to 330k to make it deeper, or so I'm told.

I'll record a clip soon here.