First Champ build. Need a turret board and help.

[1gonecat]

I'm a beginner I have been reading a lot about single ended tube amps. I have 90% of the components needed but still lack a turret board. I looked here but none for 5 Watt Champ amps. Any one know were to get one under 20 bucks? Watts tube audio has them. Any good?

  Power transformer is a Weber W022772 center tapped. Output transformer is a ClassicTone 40-18030 4 and 8 ohm. They will be installed inside a Valve Junior Head.

Thanks
Gene

[sluckey]

eBay has plenty for under $20. Watts is OK but pricey.

[kagliostro]

Doug has a service dedicated to custom boards


http://hoffmanamps.com/php/TurretBoard/TurretBoard.php


K

[1gonecat]

Checking on ebay they have a few from China with turrets for under 10.00 dollars.

Also looking at fiber boards. Is one better than the other?

[kagliostro]

Also looking at fiber boards. Is one better than the other?

OH Yes, but who can say without the board under hands ?

K

[HotBluePlates]

Most fiberboard will absorb moisture and become conductive eventually. But it may take you 40-50 years to run into that problem.

Other than that, it's mostly an issue of preference.

[1gonecat]

Just ordered this on eabay. Fiber Circuit Board for Fender 5E1/5F1 Tweed Champ w/ Brass Eyelets and two 9 pin tube sockets to directly attach to the vj chassis. For the tubes I'm using a 12ax7 and an EL84.

Edit: Correction: A 12ax7 and a 6V6GT 9 and 8 pin.

[1gonecat]

Getting started. I need a 2 diode rectifier also for my center tapped tranny. Are the 3 22uf 450v ok or should I put the 47uf in front? What should be my next step?

[sluckey]

I need a 2 diode rectifier also for my center tapped tranny.

You're not going to use a tube rectifier? If not, use a couple of those 1N4007s.

Are the 3 22uf 450v ok or should I put the 47uf in front?

Those 22µF caps are fine for the AA764 Champ. But your board is for a 5F1 and that uses a 16µF and two 8µF caps.

What should be my next step?

I believe you have the power resistors on the wrong side of the board. They should be moved to the left side (as seen in your pics) so they are connected to the positive side of the filter caps.

I would gather up ONLY the parts needed for this build and clear the bench of all that stuff that is not needed. Then load the components on the board. Don't forget the jumpers.

[1gonecat]

I have a clear work bench. This is my table to pick out the resistors and caps that I need. So the caps I have will not work for this board? I can get the proper caps. See I thought I could use what caps I have and change the resistor values.

[sluckey]

You can use those caps. They'll work 'better' than the original values. But the amp may sound a bit different than the original.

Keep the resistor values the same as original.

[HotBluePlates]

You also may want to dry fit the board to the chassis and see if the layout makes sense.

Fender put the board in the middle of the chassis, with tube sockets mounted on a side of the chassis. The Valve Junior puts the sockets right in the middle of the chassis. You do not want your circuit board to be over top of the sockets, at least with the type of boards you're using.

[1gonecat]

I am going to 1/4 turn it or horizontal. It will be 2" from the tubes and not over the transformers. It has clearance and should work but I won't know for sure until I install it.

[eleventeen]

In the category of "What should be my next step?"

I would say to perform ALL your drilling and metalwork, including figuring out the method by which you're going to get the power transformer wires to the underside of the chassis, which typically means providing some means of grommeting the hole or placing a sleeve of some kind over the bundle of wires. It's considered good practice to be sure you have de-burred the holes so that they do not cut into the insulation of your transformer wires AND to provide either a protective grommet in the hole OR, to find some kind of plastic hose or tubing to go around those tranny wires. That means the hole for those wires has to be bigger than the diameter of all those wires bundled together. Same goes for selecting a location for your output transformer, with as always, some consideration for where those wires will emerge on the underside of the chassis relative to where you plan to mount your parts board.

You don't want, for example, to be drilling a largish hole through the chassis with your parts board mounted and in the way of possibly being damaged from your drilling. You don't want to be filing away at something and crunch your input jacks or your fusepost or a tube socket. You don't want to be filing away and cut through some insulation somewhere.

The other thing I myself would probably do would be to make two pieces of wood, say 1" x 4" x 10-12" and temporarily screw them to the top of the chassis so that they act like stabilizing "wings" that both hold the chassis steady as you work on it, AND, compensate for the height difference between the output and power transformers. Otherwise you'll have this small thing that wants to scoot out from underneath you and/or it will be lying on a slant all the time you work on it.

But the more you have (only) a hand drill versus a drill press (and you didn't say that, I am just assuming) the more important it is to get all your drilling and reaming and rounding off done before you install fragile electronic sockets and switches, etc;

Next, populate your parts board, paying VERY careful attention to how your electrolytic caps are positioned and thus polarized. If you need to provide some other place to mount your rectifier diodes, then that is typically a terminal strip.....make sure you have a mounting hole drilled for same.....in the area of the power supply, NOT near the input/preamp area (eg; the small 12AX7 tube) Given that it's a lot easier to solder the wires that connect to your parts board on your bench rather than mounted inside the chassis, make the solder connections for those "lead off/lead on" wires to lengths of hookup wire. You will cut those wires to fit their desired lengths once your parts board is mounted.

[1gonecat]

My holes are drilled and I have the grommets. I need to position my rectifier now and drill a holes for the terminal strip and the tone pot. I am using the existing holes on the vj chassis for the transformer wires. The power transformer is used so I may have to extend the wires as they were cut already once. When I get it layed out I will take a pic. This is some great info. Thanks all.

[eleventeen]

From your pix: (and forgive me if I am only getting a partial view of things; if you have these things solved, then they're solved.



The power trans, does that get a big rectangular cutout, or is it mounted on those little angle brackets? You for sure want to get that rectangular hole happening if that's the plan, that's a lot of metal to move & cut. If not, if the wires are going to be "feed-thru and the tranny mounts pretty much as it is pictured....I would *try* to get the wires on the other side, the perimeter side of the chassis. There is no rule that says you have to have all the wires going through only one hole, they do not care. That means you can drill much easier, smaller holes, smaller grommets. BUT > I don't see the chassis thru-holes for the tranny wires in your pix.


The spacers/standoffs for your parts board appear to partially cover up the footprint of the tube sockets if those are what you plan to hold up your parts board. That's a potential issue as I believe someone else said. You can maybe get away with it if you are very precise with your soldering...but it makes troubleshooting tough. AND...if you are not very adroit with soldering iron, and they DO cover the sockets and you don't want to change that in terms of mechanical layout, then instead of soldering your pigtails to the parts board and leave the ends hanging, I would solder them to the tube sockets instead and leave the ends hanging, for later connection to the pts board. Make sense?


Make sure the mounting holes in your parts board match the spacers. Yeah, I know, dumb. But if you don't check, then you have to do metalwork with parts mounted on the chassis that you'd rather not have.  Are you absolutely sure the parts board is right side up? In other words, you are not loading it up with parts upside down?


Just trying to give you the benefit of mistakes I (and possibly many others) have made. 


Looks like you'll have to extend a few tranny wires. Most people use heatshrink, of course. I like to first place a length of jacketing from some kind of cable, in other words, a plastic tube, and put heatshrink over that. IOW, double insulated. Not entirely necessary, just cautious with them high volts.

[1gonecat]

I am going to work on the chassis today. Very interesting things I have not thought of. I am going to use my own stand offs and remove the existing ones. I was thinking of something like this or I can turn the p t around and use the back two holes or extend the wires to use all 4 holes.

[eleventeen]

In principle, we would like to avoid having those power supply caps near the preamp tube. That's my biggest comment in this post.


If you are going to have to extend the power tranny wires, it makes little or no difference whether you extend them 4" or 8"; I know I said I would prefer to have them enter the chassis nearer the perimeter, and I would. This makes almost no difference...it's one of those things that you do to try for a 1% improvement in noise and if you do 4 or 5 of those...though I *do* see your 12AX7 has no shield. (another 1% thing, but also an item of tube retention if the chassis is hung upside down.


Any chance you can rotate your parts board such that it lies along the back panel, parallel to the line of the tube sockets? Prefer.


You *probably* do not need to remove the existing spacers if you use and drill for new ones that are taller than the old ones. Save you some metalwork and potentially some ugly holes when you go to drill them out. Those old spacers are not necessarily of zero utility...you may find yourself needing another small terminal strip somewhere down the line or wanting to bundle some wires in a nylon cable-clamp and since they are tapped, you could screw a screw into one of them and mount the term strip on one of them. This is less of an issue in such a simple amp, but in a more complex one, sometimes those things might come in handy.

[1gonecat]

I turned the transformer around to use the holes in the back as I reposition the board. I can flip the caps and put the power side out and the ground buss against the back of the chassis.

[eleventeen]

Nice! MUCH better!


You will of course trim back those leads on the power resistors that connect from ecap-to-ecap. And....where they go under the board and bend and get cut off...point them towards the inside of the board so the sharp points are away from the chassis. Just good practice.


You will probably use the holes in the parts board to mark the locations for your new spacers. When you mark those holes, see if you can get a thin shim (temporary) between the edge of the board and the back inside of the chassis---in other words, see if you can leave 1/16" or 1/8" space there while not having the other long side of the parts board impinging on the tube socket(s). Like a popsicle stick. This will give you a little bit of slop on your hole placement which is good. Also gets the B+ a teeny bit further away from the chassis. Always good.


I see your tube socket hold-in screws are tapped. Ideally, there should be lockwashers on those or lock-tite or locknuts. Not absolutely necessary...but supposedly this is a guitar amp and it's in a cabinet that vibrates and those do not vibrate tighter---they vibrate looser.


You're looking good.

[1gonecat]

I have some lock-tite I will use then. Should I turn the caps around leaving the B+ on the inside of the chassis instead of it being on the back "wall?" I have a shield for the 12ax7 and will install it then also.

[eleventeen]

No preference on turning the caps around.


In one sense, it's maybe a teeny bit safer to have the B+ hard to touch with your fingers = up against the back wall, OTOH, for the REST of the circuit, assuming the grounds are all on one side of the board, the same side as the e-cap grounds, do we want the signal grounds closer to the tubes (meaning, the signal points are closer to the tubes) or closer to the back wall?


Kind of a tossup.

[1gonecat]

Ah, good idea. I am installing the board now but it just got too hot in my workroom. I need to go to the hardware store and get some screws for my standoffs anyways but the holes are drilled. When lengthening my wires should I just twist them together then shrink wrap them? Rarely have I done this and usually drop a bit of solder on them before shrink wrapping.

 My tools and parts drawer is full of things for rebuilding guitars. That is rapidly changing now.

[1gonecat]

I changed the layout. This will be easier and less noisy I hope. I am going to go with 5w resistors on the B+ rail as advised by Don. Also still need to add the 25uf cathode bypass cap.

[1gonecat]

I built this too.

[John]

The most important build of all! Cheers to ya. 

[EL34]

I stock champ turret boards on this page


http://hoffmanamps.com/MyStore/catalog/parts12.htm


I have a complete one with all the parts on the board for $38 on the

http://el34world.com/Forum/index.php?topic=17375.0

[1gonecat]

Thanks! Those turret boards look like the way to go. Next build I will get one then.

 One thing I would love to know how to do is to find useful power and output transformers in "junk yard" devices. To know if the old ones will be useful or not in terms of volts and such just by looking at them. You never can tell what you may find at sales and flea markets. The most expensive part of building smaller tube amps are the transformers for me. Finding workable used ones cheap is key.

[terminalgs]

One thing I would love to know how to do is to find useful power and output transformers in "junk yard" devices. To know if the old ones will be useful or not in terms of volts and such just by looking at them. You never can tell what you may find at sales and flea markets. The most expensive part of building smaller tube amps are the transformers for me. Finding workable used ones cheap is key.

Getting difficult to do.

99% of scrapped trannies are for SS devices.. The PTs are worthless to a tube amp.

Next up, the 1% of tube trannies scrapped: these are old phonographs, the odd Japanese hifi , tape recorders, organs, and sometimes test equipment.

3/4s of which will have an undersized PT.

That's not to say you can't find the odd gem...

[PRR]

> useful power and output transformers in "junk yard" devices

The only for-sure PT+OT pairs will be Audio Amplifiers.

Keep the WHOLE thing together: PT, rectifier, OT, power tubes. While you can change power tubes to other similar-size devices, and maybe change rectifier, the connections work like they are and usually can't be modified. And you'll never sort-out multiple impedance taps without a clue.

In my experience, quarter-decent audio amplifiers are pretty rare in general junk-yard searches. I did score a 9W 6L6 PA amp once. But my most recent "find" is a transformerless (death-trap) 1.1 Watt radio. And the 'power' tube in it is rare and would cost $22 to replace (I could whack the socket hole and run 50L6 in it for $8).

Large radios from the 1930s, especially with 6F6 or 6V6, are possible conversions and are sometimes found in rough condition and negotiable price. Anything 50L6, 35L6, 35C5, 35A5, etc are death-traps and hardly worth making-safe due to low output and low-low quality.

[1gonecat]

I see. Well it was a thought. 

  As a beginner I watch these videos of techs building small amps with spare parts. Heck, one guy made his own fake center tap on an old transformer.

[sluckey]

I like converting Hammond organ reverb amps to guitar amps. You basically just add a guitar preamp to the Hammond amp and you have a nice guitar amp. I've used the AO-39 and AO-44. The AO-35 and AO-43 are also popular. The iron is good quality. Lot's of those four models on eBay all the time.

Old juke box amps and PA amps are another good source for good iron.

[EL34]

Dukanes , Bogens and Stromberg carlson are good candidates also

[1gonecat]

I went back to look at the video. The pt was off an old rf signal generator that had been trashed he said. He said he could tell by the wired tubes that it used  and therefore was able to map it.

[1gonecat]

Should I use the brown 120v or the blue 125v to the power light/switch?  The red/yellow Center tap I will ground to the chassis too.

[sluckey]

I would use the blue 125v.

[eleventeen]

On the topic of salvaging trannies....it's indeed pretty much the case that you need to find an actual amplifier before you find something useful for an amp....this is assuming your find is a tube something or other, like a record player. On occasion, such a carcass will yield a SE 3-5 watt OT. Usually the chassis is not especially convenient---it will be cut away or open ended, which I guess would be OK if you plan to place the thing into a cabinet.


The other thing is that people do not give away their old junk the way they once did. Anything from the 50's in now an "antique" so a silly little record player, they want $75 for. Leave alone.



*Very occasionally* a SS transformer can be voltage doubled to a usable level for tubes. But at the same time, such a power tranny is VERY unlikely to have a 6 volt heater winding. I recent got such a transformer....but I later found out that the three 40-50 volt windings were "nested"---they were all the same winding, with taps. Thus I could not connect separate windings in series for 300+ volts out of a doubler.


In general, I would have to say that your time and effort is better spent working your normal job and buying the stuff you need new. However I WILL say that dead solid state amps sometimes furnish appropriate cabinets for zombie-like reuse as homes for tube projects. Sometimes you get a usable speaker; the reverb cans are unfortunately the wrong impedance.