First attempt: 5F2A, Advice appreciated.

[spsimmons]

Hi all,
I have a Behringer V-Tone 110 that I bought (not working) from a guy for $20. I figured that even if it never worked, $20 wasn't a bad price for the Jensen 10/35 that came in it. Predictably, I did not get it working. The problem seemed to be in the main control module. In any case, I didn't really want a V-Tone 110 enough to start replacing the modules. I do, however, think it would be REALLY cool to have a Tweed Princeton. With that in mind, I ripped all the guts out of the Behringer and ordered a 5F1 kit from Triode along with the extra parts I need to make it a 5F2A.

I have a couple of questions as I get started.

First, is there anything out of that Behringer that would be worth keeping. For instance, the transformer or power amp module? I have no reason to think there is anything wrong with either of them. Or, should I just trash the whole thing?

Second, the Behringer chassis is a good bit bigger than you'd ever need for a Princeton. I understand that these amps can be pretty sensitive to layout. Is there anything that I should keep in mind while fitting it to this larger chassis? Is the extra space good for me, or should I try to keep things pretty tight?

Is there anything else I should keep in mind during this build (besides not electrocuting myself)?

I was very pleased when I got the parts from Triode to find that the new transformer fits perfectly in the old tranny's hole. Less metal work, yay!

Thanks, Shannon

Here are some pics of the donor amp.

[loudthud]

Since Behringer doesn't like to let out schematics or spare parts, I'd keep the old parts with an eye for selling them at a later date. As far a layout goes, the 5F2 is not real fussy except for how ground is connected. Just try to keep things arranged from input - preamp - controls - output stage - power supply.

[spsimmons]

Update: Just got my chassis work done. Ready to move on to the electronics. Unfortunately, Triode shorted me a couple of parts. They didn't send my 2 octal sockets, and also left out one of my 16 uf capacitors. Bummer. I robbed a couple of octals from an old organ chassis I had laying around, but I don't have any filter caps. Hopefully one of the repair shops around town has an extra that they'll sell to me. I don't really want to have to wait until a shipment gets here from Triode.

[spsimmons]

Then again, maybe I can run the amp without that 16uf cap? It's one of the few differences between the Champ and the Princeton. I don't really understand what it does in that position.

[nickb]

Then again, maybe I can run the amp without that 16uf cap? It's one of the few differences between the Champ and the Princeton. I don't really understand what it does in that position.

Two 16uF caps are used to reduce the hum from the power supply. With only one it's going to hum more than it should, that's all.

[spsimmons]

Ok, so I'm 95% complete. I'm still missing one of the 16uf filter caps and the 25uf cap between pin 3 of the pre-amp tube and ground.

I deviated from the grounding scheme on Triode's layout drawing. They showed the mains ground on one PT bolt and everything else grounded to a different PT bolt. I grounded the mains at a point right as it enters the chassis (This is where Behringer had the mains grounded, and I re-used the IEC socket). I grounded the center taps together near the front corner of the PT. Everything else is grounded at one point just below the inputs and tone/volume knobs.

I was pretty slow and methodical with the build, so hopefully it'll fire up and run. One worry that I have is that leads from the turret board to the other components are sometimes a little long, especially those going to the 12ax7 socket. Is this likely to cause problems?

I built a light bulb limiter as well and have bulbs of 15w, 25w, 40w & 60w. Should I start with the 15w/no tubes, then 15w/rectifier, then 15w/all tubes and then step up the wattage of the bulbs? Is there a better way?

I'll attach some pics, let me know if you see any red flags!

[spsimmons]

Hooray, the Princeton lives! I'm still waiting for two capacitors, but couldn't resist starting it up anyway. I'll just install them when they get here.

My first impressions:

It's much quieter than I expected. Since it's missing one of the filter caps, some of my leads are on the longish side, and I was kind of winging it with my grounding scheme I expected a good bit of hum. Surprisingly, it's almost dead silent.

It's not as loud as I expected, definitely a bedroom amp. I did go with the 15w OT, so I may convert it to run a 6L6 for a little more volume.

It's also not as dirty as I expected. Even with the guitar (Epiphone Dot) and the amp cranked, the distortion is fairly mild and pleasant (obviously subjective).

I took readings of all my voltages, but can't find a really good resource for what they should be. Opinions?

With all tubes in:

Sovtek 5Y3GT

pin 2: 423v
pin 8: 423v
pin 4: 342vac
pin 6: 342vac

JJ 6V6 S

pin 2: 3vac
pin 3: 407v
pin 4: 362v
pin 5: 0
pin 7: 3vac
pin 8: 23v

JJ ECC83 S

pin 1: 189v
pin 3: 2v
pin 4: 3vac
pin 5: 3vac
pin 6: 188v
pin 8: 2v
pin 9: 3vac

Do these seem off? I'll post these readings in "debugging" too.

[spsimmons]

Here's a link to my debugging thread: New 5F2A, not sure voltages are good.

And some pics of the amp finished: