Champ 5F1 with vibrato

[txstrat]

When moving the OT closer to the PT, did you take care the windings are in an angle of 90 degrees to each other?
Anyway, when you get the least hum close to the input, what the heck.
On of my first amps had the OT in the same place. Worked out well.

[dinkotom]

Thanks for fast reply!
Yes, OT is at 90 degrees to PT.
I'll try it with OT at the input. I forgot to mention that I don't have anything installed in the chassis yet except PT, so I hope the hum will stay where it is now...

[theunrulychef]

I just built one with the OT on the input side because of space issues. I kept the wires on the outside of the chassis (read this in a post about unconventional OT placement a few weeks back). It's dead quiet & sounds great. It's nice & balanced to pick up too.

[dinkotom]

Good, I was just about to ask where to run those wires...

[dinkotom]

Since this amp is going to be a mix of layouts and I don't have the original fiberboard (my parts board is mounted on 5mm spacers), I'll need a little guidance about where to place some wires - what would be better: to run the B+ wire for preamp and signal wire to power tube grid over or under the parts board? Any other wires I should be concerned about (vibrato section)?
Grounding: I don't have the brass plate, so I could use buss wire (soldered to pots backs and ground lug on input jack) for all preamp grounds and PT lugs for all other grounds. Would that be OK?

[dinkotom]

I forgot to ask, is 5mm space between chassis and board enough, should I put some kind of insulation under it or another blank board?

[theunrulychef]

I didn't use the standard layout either - the pre-made eyelet or turret boards are too rich for me so I've started using the $6 terminal boards Weber sells. I used shielded cables for most of the under board runs. I ran a straight solid wire along one side of my board to supply power to the preamp, so it's not running directly over any components & any wires that cross are at 90 degrees.

As for grounding, I know many people say it's not the best setup, but I've had pretty good luck with the buss bar on the back of the pots so far. I have the filter caps & tranny grounded at the same point as the buss bar.

I would think 5mm is enough. I'd think your biggest worry would be if you filled up a solder connection with so much solder that it actually bridged to ground, but 5mm would be quite a bit of solder

[dinkotom]

thanks, I guess it'll turn out OK, just had to make sure that I don't have to unmount the board and rewire, I already had to alter a lot of things on the chassis since I started, which didn't turn out as neat as it should have, all due to my impatience and lack of pre-planning. I'll post some pics next week, I hope there's nothing beyond repair (input jack too close to the chassis, speaker jack too close to the board and tubes, vibrato jack too close to tubes, everything too close to everything, etc..)
Edit: and there should be a tutorial for noobs on how to bend those nice looking cloth-covered solid-core green filament mofos - I spent at least 3 hours working on heater wires the other day, twisting, bending, pushing, pulling and cussing, trying to do the neatest job I could, and they still look frayed and scrambled as a rat's nest. This amp already has that original 50's vintage vibe to it and it's not halfway finished...

[dinkotom]

What would be a correct fuse value for 220V AC from the wall? I've read/heard somewhere that a half value of the original fuse for 110V should be used.

[tubeswell]

I use a 1A - 2A slo blo for a 5F2A from 240VAC mains

[dinkotom]

I use a 1A - 2A slo blo for a from 240VAC mains

Is that correct, it's 3/4A on 5F2A schematic?

[dinkotom]

Just looked at some schems for export amps, I guess it doesn't matter, values are the same regardless of VAC.

The build is near complete, it looks sorta ok after all, the first fire-up will be tomorrow (after a check acc. to P. Ruby), hopefully nothing goes terribly wrong.
My main concern is still OT placement as headphone test was done without any circuit wired in. Trannies are home made, they don't have end bells - could this cause any hum/oscillation? If so, what could be done to fix it?

[dinkotom]

Is Sovtek 5Y3 OK to use for rectifier?

Edit:Ok, I just found it's not a real 5Y3

[tubeswell]

End bells are usually just for looks. Does the PT have a shield?

In regards to the sovtek 5Y3, you can always put one or more 5W 9V-15V reverse-biased (anode/banded ends pointing to ground) zener diodes in series with the centre tap-to-ground off the High Tension winding, in order to bring down the B+ if you think that rectifier doesn't drop enough voltage. But I'd wait until you fire it up and see how much B+ you get first.

[Bruce / Mission Amps]

Is that correct, it's 3/4A on 5F2A schematic?

I'd also use a 1 amp slo-blo or a 1 amp MDL fuse.