5f1 Help Needed - DOA

[martinman]

Hi Everyone,

I'm soo disappointed that my build didn't turn out. This is my 3rd project so far after a successful mission 5e3 and 84 design. It's a weber kit with Heyboer trannies. I'm following the weber 5f1 layout. My first problem: The Heyboer didn't come with a wiring specification, but going by the weber diagram (I realize that the color coding is different) and the web, I was able to come up with this:

Green: Pilot Light
Black/White = Primaries (black to power cable, white to fuse)
Yellow: Rectifier pin 2 & 8
Red: Rectifier pin 4&6
Red/Yellow = Center Tap ?? currently taped off
Orange: Ground (some type of funky hum reducer / Faraday cage from what I was reading)

Big Question #1: I'm not quite sure what to do with the red/yellow. I suspect that it isn't used so I just have it tied off (again, this is a guess based on gut feel).

Big Question #2: There were not distinguishing marks on the green wires coming out of the PT. There was same writing on both wires. Does order matter when connecting them to the pilot light? When connecting the pre and power tube pins I drew a black line down the green cloth wire so I could keep everything straight. However, there doesn't seem to be a way to match these up to what comes out of the PT...

Here are some voltage readings:

Rectifier pin:
4: 301v
6: 290v
2: 5.42v
8: 0v (yes, zero)

6V6 pin:
2: 3.1v
7: 2.3v

Obviously something is wrong...

Furthermore, I get 0v across all the caps on the main board. This should be a pretty easy one for all of you. BTW, the 6v6 and 12ax7 are warm to the touch, the pilot light is on and the fuse is still intact.

On a side note: I'm quite disappointed with the weber kit. This is my first purchase from them. I had to open up a few holes on the chassis so the grommets would fit, a few missing parts, speaker jack is terrible, cabinet tolex isn't the best job, the rectifier is some type of crazy copper cap that I haven't seen before (was assuming a regular 5y3 or something similar). And finally, the non existent docs for the Heybour! Oh well, lesson learned. My 5e3 and '84 projects went swimmingly.

Thanks everyone!
Mark

[Mandopicker]

RED-YELLOW is the C.T. and must be grounded. Use a power transformer bolt.

Try that. First..there may be other things after you solve this.

Good luck and don't shock yourself.

[martinman]

Thanks Mandopicker! Yep, that was it! But... After 5 minutes of playing at various volumes, the fuse went. I played on 2 separate occasions for a total of 5 minutes each. The first was just a test a low volume, then cranked it up, tried the 2nd input, and then went back and forth. The dry run worked perfect with my strat.

Then I took out my les paul and did the same thing. After about 5 minutes of playing I heard this fizzle and then the light went out. Wouldn't you know it.. the fuse blew. I tell ya, this thing sounded beautiful while I was playing. I had it cranked up to 12 and there was almost no noise. It's total silent (which surprised me!). My 5e3 isn't this quiet.

Where do I go from here?

[JoeM]

Just a long shot, but do you have a 5Y3? I had a Copper Cap from Weber that would cause my amp to blow the fuse, but the amp otherwise worked fine. (Using a 5U4GB). No CT for the green wires? (Green/Yellow)

[martinman]

JoeM: it's one of the copper caps.

No CT for the greens on the Heyboer.

Believe me, I would much rather have gone with a traditional tube rectifier, but this is what the kit came with. Is the 5U4GB a direct replacement for the copper cap?

If it was something with a connection, wouldn't the fuse blow right away? The amp was just sitting there when it blew after 5 min of runtime - I wasn't touching it... just playing through it.

[Mandopicker]

Any gut shots...particularly the rectifier and output tube wiring areas? This could help us all out.

[martinman]

So, I had a 5Y3GT rectifier laying around and another 2w fuse. I put them in the 5f1 and it works *perfectly*. I just got done playing for about an hour on lower volume. (not sure if volume could be the variable here?).

I also poked around inside (after draining the filter caps of course) and moved the pilot light terminals away from eachother a little more. They were not touching, but I suppose there could be arcing? Not sure, so I moved those apart a little more.

Perhaps the only issue is a very slight intensity variation on the pilot light. I'm not sure if I would have even noticed it without the back off (the bright white light shining on the insides). There is no periodicity to it. Just goes from what I would call 'normal' to just about a hair dimmer and then back to 'normal'.

I'll get those pics tomorrow and you guys can check it out.

[RWood]

Is there some sort of artificial center tap for your 6.3V filament circuit? Like two 100Ω, one from each leg of the filament to ground? Or if not to ground, to the cathode of your power tube? If not it needs one, since you said there was no CT for the filament from the power transformer.

[martinman]

Here are some snaps I took of the insides:

https://picasaweb.google.com/mschund...eat=directlink

I'm afraid there is limited docs on the heyboer... Very frustrating. I followed the weber layout and it didn't have anything in the way of 100ohm resistors...

Most of the reading that I've done suggests that the heyboer is a generic transformer that can be used on a variety of builds. Additionally, from what I understand, it also runs hot.

More discussion here:
AX84.com - The Cooperative Tube Guitar Amp Project

[RWood]

Don't despair, you are closer than you realize. And you're learning some things you didn't know.

Seems to me that this situation has arisen because the Weber schematic shows one of their own PTs that does use a center tapped filament, but what they provided was a Heyboer PT that does not have one. Yes, it would have been nice if they told you this, etc, but many kits out there are not paint-by-numbers and may require some research and some online posting, which is exactly what you're doing so that's fine. And like I said you will learn some things you didn't otherwise know that will help you in future builds.

For a PT without a centertapped filament supply there are several things that can be done; there is no single right way to do it and you are free to try any or all of them. The filament does need some reference to ground, though, in order to keep it happy (and not overheat and ultimately short that winding). In my opinion, the easiest way to accompish this is by using two closely matched 100Ω resistors, one from each leg of the filament supply. I do this right on the power tube socket, and instead of going to ground, I go to the power tube's cathode, pin 8. This "elevates" the reference 15 - 20 volts above ground and may keep AC noise from the filament circuit from mixing in with signal ground. So what I do is simply solder one of the 100Ωs from pin 7 to pin 8 of the power tube socket, and solder the other 100Ω from pin 2 to pin 8. That's it.

Starlooper's got a great picture of this in his thread!

Other builders like a variable control over the amount of resistance on each leg, so they'll use a 100Ω or 200Ω 2W potentiometer, one leg of the filament circuit to each of the outside tabs, and the center tab (the wiper) goes either to ground or to the power tube cathode (if elevation is desired) or to an elevated point off the B+ supply, separate from the power tube and filtered. AX84 has some excellent examples of this. What you end up with when using the pot is a hum balance control, and you set it wherever on the scale you hear the least amount of hum.

As I said, there are lots of ways to do it. Once you do one of these your Champ will be singing happily. If not, come back and let us know why!


RWood

[martinman]

RWood: Awww man - that's huge!! I really appreciated your post.

I'll try the 100ohm method -- and I have the resistors. 1/2w should be ok, right?

Also, i'm trying to correlate why the amp still works w/o the CT filament ground. I suspect that it might eat power tubes (and also damage things in the long run?)

[RWood]

Glad to help

1/2w should be ok, right?

I prefer 1W carbon films or the metal oxides like were in that picture - they looked like 2W.

Running the amp without the filament CT doesn't bother the power tube, but it eventually burns out that winding on the PT.

Rwood

[JHow]

...i'm trying to correlate why the amp still works w/o the CT filament ground...

I always thought Valve wizard had a good explanation of this stuff.

The Valve Wizard

Check out the full-wave two-phase article (link) and then look at the "bridge rectifier" one as well.

[martinman]

I prefer 1W carbon films or the metal oxides like were in that picture - they looked like 2W.

Running the amp without the filament CT doesn't bother the power tube, but it eventually burns out that winding on the PT.

Rwood

That's 100ohm.. not 100K ohm *sigh* gotta open the patient again.

I reread your post and was going to report back -- glad I read through more carefully. Boy I sure an giving this PT a workout! Will the 100kohm damage anything?

I have 100 1/2w metal oxides that I'll use in place of the 1w for now. I'll have to order the 1w.

[JoeM]

I dont think I've ever seen anything over 1/2W for the 2 100 ohm resistors for the filament winding. The only time I've seen them burn out is when a power tube shorted.