My bread board

[Willabe]

Well I have made some progress but I'm still thinking about a few things.

I wired the 9 pin sockets for 12.6v.

Here's a few pictures;


            Brad   

[jojokeo]

looking good so far, (looks like fun to have one)

[Willabe]

I bought some meters from Weber some years ago for future projects like this and dug them out. I'm not sure how to hook them up.

I have 2x100mV large, 2x200dcmA small, 2x100dcmA small and 2x1000dcv.

I'd like to use the large, their easy to read, not sure if I have the room thou, 100mV for bias current, 1 for each tube. (I don't see myself building any 4x power tube amp. If I do I could always put in a couple of switches to change between tubes.)


1. The large dcv meters, do I just put them across the 1 ohm K resistor, + to K?

2. I'd like to use the smale 200dcv meter to monitor the power tubes plate (A) B+, so I hook up the + on the meter to plate B+ and the meter - to ground?
 
3. And I think I should put in a switch to lift the + connection on the K and A meters when playing through the amp after biasing it?

4. Should I fuse the meters? If yes, how?
           
                         Brad   

[Willabe]

looking good so far, (looks like fun to have one)

Thanks Jojo.        I get the feeling that after I work with it some I'll want to make some changes. 

I want to play around with some things without cutting/drilling out a chassis and face plates.


              Brad   

     

[jojokeo]

I want to play around with some things without cutting/drilling out a chassis and face plates.
     

Over the years at various times I've just used existing chassis, iron, sockets, and pots into various designs and/or experiments. This is where turret boards can be nice but eyelets actually can be easier/faster.

[jojokeo]

1. The large dcv meters, do I just put them across the 1 ohm K resistor, + to K?

2. I'd like to use the smale 200dcv meter to monitor the power tubes plate (A) B+, so I hook up the + on the meter to plate B+ and the meter - to ground?
 
3. And I think I should put in a switch to lift the + connection on the K and A meters when playing through the amp after biasing it?

4. Should I fuse the meters? If yes, how?

I'm sure PRR, Sluckey, or HBP have specific answers but how I've used them in the past on things: since voltage readings should be only taken/used across various points like a volt-ohm meter you're only worry would be not to exceed the voltage scale reading you're planning on applying them too. On the ammeter(s) you would definitely fuse in-line with a fuse rated no higher than the highest scale reading. Following these simple "rules" and you should be fine.

[Willabe]

Thinking out loud;

I really want to use the analog meters I have for the bread board to monitor voltages and current in different circuits and save my hand held meter for what ever else I might want to check. Since it's test bed for circuits it's makes sense to me to have these in place and not have to keep moving the hand held meter probes around to different parts of the circuit that I know I need to keep an eye on. I will also be able to just glance up and take a look at a few important parts of the circuit at once. 

And, as I don't have multiple meters, and even if I did, these will always be set up in place and I'll have no extra meter leads/alligator clips to deal with, plus their way less expensive to have multiples of.   

So, I was trying to figure out how to mount the analog meters and I remembered that I have a compass/circle cutting arm for my Dremel that will cut holes as small as 3/4" and up to 12".

It will take a few try's on some scrap to get the size adjustment correct but I think it will work.   

I have some 1/4" plywood that I think will work or I might use some 1/8" fiberglass board.

The problem is the trim skirt on the meters is pretty small, so the meter will have to fit pretty tight so I can still use the mounting holes on the trim skirt to bolt it in place. If the meter hole is just a little too big the mounting bolts hole will cut into the meters hole and weaken the meters mounting to the panel.

Then I have to figure out where and how many switches I need. I'll need at least 2 power switches, 1 for the main PT and the 2nd for the 9 pin tubes heater PT. And I want a stand by for the main B+ PSU.

For the Carling switches I'll have to either enlarge the holes in the angle iron with a step bit or depending on where I need to mount them, I might need to make/find/buy different mounting brackets.  I don't see the whole picture yet as far as layout.

I do have some fuse blocks that I stashed away for a build like this and I need to incorporate them in the PT's and OT, both primaries and secondary's.


                          Brad      

[PRR]

> a switch to lift ... meters when playing through the amp...?

No. Watching the meters while using/abusing the amp is a KEY development tool.

When building your race-car, do you disconnect the tachometer before you drive it?

With self-bias power stages, you expect current to rise 0% to 20% from idle to FULL wail.

Fix-bias MAX power stages may double or triple their idle current when you smack them good.

Any sudden or large deviation from the trends is a sign of trouble.

Large power amps (more than 2*6V6) will exceed 100mA at full power. You got a 100mA meter. Add a shunt for large currents. A small resistor across the meter to divert some current. Get any darn amp running <100mA. Say 88mA. Now tack 1 or 2 Ohms across the meter. You want the value which makes the meter say 44mA (half of the total). Or any reasonable multiplier: big 6L6 amps can suck over 250mA, so a 3X multiplier (29.3 indicated on 88mA actual) may be useful.

[Willabe]

Ahhh, Ok, thank you PRR.

(Oh, put the current meter in the - return leg.)

         
                   Brad     

[Willabe]

I'm sure PRR, Sluckey, or HBP have specific answers but how I've used them in the past on things: since voltage readings should be only taken/used across various points like a volt-ohm meter you're only worry would be not to exceed the voltage scale reading you're planning on applying them too. On the ammeter(s) you would definitely fuse in-line with a fuse rated no higher than the highest scale reading. Following these simple "rules" and you should be fine.

Ok, makes sense, thanks Jojo.


                 Brad     

[kagliostro]

If you have a spare voltmeter my council is to use it as to keep under control G2 voltage


this may be useful in general and very useful if you use power tubes that requires a very  lower G2 voltage respect to plate voltage


(EL500 - EL504 - GU50 - 6DQ6 ........)


Franco

[Willabe]

Ok, thanks K, I'll keep it in mind.


                Brad     

[jjasilli]

Blundered into this article on how to wire & use panel meters:  http://sound.westhost.com/articles/meters.htm

[Willabe]

Hey, thanks jjasilli!


             Brad     

[Willabe]

Got some more done.

The dcv current meters board, for the power tubes cathodes came out pretty good using the Dremel router/compass arm.

I'm still trying to figure out how I want to make a few common circuit separate modular boards that I can plug in and not have to use the barrier strips.

I have some different barrier strips and fuse blocks laying around that I want to use up, pics below. I have more of both, single, doubles, triples, 4x, 5x and 6x.

I included a rough layout schematic for the bread board.

Here's a couple of pics and drawings.


               Brad     

[Willabe]

I'm working on the bread board and I have a few questions.

1. In the drawing PRR posted, the current meter is hooked up the the PT secondary CT?

2. To get the current meter's needle to swing correctly, on the back of the meter, there are 2 terminals, 1 has a + sign, so...... then the - (negative) meter solder tab, should be soldered to the ground end of where the B+ filter cap/PT CT meet with the B+ negative rail? (Look at my drawing below, I'm not saying this very well.)

3. To fuse the current meter the fuse goes before the meter?

4. Can I hook up the B+ negative rail to ground from anywhere along the negative B+ rail without affecting/bypassing the current meter?

I'm thinking all the B+ current has to come from ground and go through the CT.   

Thanks        

[vibrolax]

This is a great thread.  I wonder if it could be preserved in the "Amp Tools/Tech Tips" section?

[Willabe]

Maybe, if I ever finish it!   

Dummy Load, with Richard, (board zilla?) and Silvergun (Let's build a bread board and Son of bread board) have great threads on the bread boards they built.  (Their threads would be included in with mine if we put it in favorites?)     

Do a search. If you use the search button on the top left, that search lets you enter a members name with the search, works better for some searches.   

[HotBluePlates]

1. In the drawing PRR posted, the current meter is hooked up the the PT secondary CT?

PRR will have to confirm, but I see the current meter after the first filter cap, negative side connected to 1st filter cap -, positive side connected to the ground lead of whatever comes next (probably a screen filter cap - and output tube cathode R ground lead).

The current meter is not between the CT and the 1st filter cap ground, but after the 1st filter cap ground. Otherwise, you'd also be measuring big charging current pulses going into that cap.

2. To get the current meter's needle to swing correctly, on the back of the meter, on the 2 terminals, 1 has a + sign, that goes before the B+ filter cap/CT ground connection? Or the negative side of the meter goes to the CT going to the PT. (Look at my drawing below, I'm not saying this very well.)

In accordance with the above, meter "-" side to CT/1st cap "-"/Ground, meter "+" side to 1Ω cathode resistor "common"/2nd filter cap "common".

3. To fuse the current meter the fuse goes before the meter?

It would seem like "6 of one, half-dozen of the other" since the fuse and meter are in series. Maybe PRR has a reason for a preference of which side of the meter gets fused.

4. Can I hook up the B+ negative rail to ground from anywhere along the negative B+ rail without affecting/bypassing the current meter?

No. Sorta...

If you have a 3-wire power cord, with the 3rd wire connected to chassis, PT center-tap and 1st filter cap ground, then that's "(Chassis) Ground". You need all output tube current to flow through the current meter, so the stuff to the right of the meter in the drawing which would normally be "grounded" are all connected to a "common" buss. The fuse and the meter complete the path to chassis ground. If you didn't do this, output tube cathode current could flow through the chassis instead of the meter, probably failing to produce a reading at all.

If you don't want preamp tube current measured in the same 1 meter, then preamp filter caps and common buss could be connected via a wire from the preamp common buss to the power cord ground/1st filter cap ground/PT CT. That would be a 2-legged star to chassis ground.



BTW, thinking of "circuit ground" or "circuit common" as something separate from the chassis ground and the power cord 3rd-wire helps you envision how to lay out an amp for a ground-lift switch. Pretend your chassis was all plastic and you couldn't bolt a ground wire to it; you could still have a wired circuit common (all filter cap - leads, PT CT, all circuit 0v returns), which functions effectively at completing the circuit. You'd only get buzz due to lack of a grounded metal shell shielding the circuit from picking up noise in the air....

[HotBluePlates]

If you have a spare voltmeter my council is to use it as to keep under control G2 voltage

And G2 voltage in relation to G1 voltage is what sets the idle current. I suppose you could ignore G2 voltage if you always have a choke-filter G2 supply node and assume G2 is roughly-same voltage as the output tube plate (in other words, lacking a separate variable G2 supply voltage or not using some of the schemes to keep G2 well below the plate, as in the Standel amps or some 6550 amps).

[Willabe]

Thanks for the reply HBP. 

I thought about this and I think I understand what your saying.

I'm going to try it like in the drawing below.

Edit; Added OT.

[Willabe]

I've made some good progress, I stacked the B+ DCV and mA current meters with some zip ties and weather stripping to save some space and tilt them back a little to see them, new pics below;

[Willabe]

B+ power switch and mounting bracket;

[Willabe]

I can see the 2 meters very well even though they are small, their tilted back just right and B+ DCV on/off is well in reach;

[Willabe]

 

[Willabe]

More;

[Willabe]

I ditched the din rail and bolted the 8 pin relay sockets down to the plywood.

[Willabe]

You can see the nice tilt back I have on the B+DCV and mA current meters.

[Willabe]

Looking at the back/side of the power tube K current meters. I installed 2 octals so I can play around with PSE;

[Willabe]

3 rows of EU style 600dcv barrier strips for the 9 pin sockets;

[Willabe]

19 is from the back;

[Willabe]

3 speaker jacks and barrier strip for OT secondaries;

[Willabe]

Last;

[Willabe]

I need to do a few more things;

1. Hook up the power tube heater wires to the 8 pin power tube relay sockets.

2. Hook up the dual 3AG fuse holder to the power tube K current meters.

3. Hook up and fasten down a few B+ star grounds, the B+ -A- node ground wire to the ACV 'in' barrier strip where the safety ground wire is, hook up the B+ -B- node ground wire to the B+ -A- node ground and the pre amp ground node to the -B- node ground.

4. Solder/wire up the speaker jacks to the OT secondary barrier strip.

5. Fasten down the EU style barrier strip, with wood screws, that goes between the power tube sockets and the power tube K current meters.

6. Install/solder up the input jack.   

[Willabe]

I moved the B+ stand by switch so it's after the B+ DCV and current meters so I can keep an eye on the 1st B+ filter cap at turn on. 

[Willabe]

Here's the link for where I started this, has more good info and more pictures;

http://el34world.com/Forum/index.php?topic=18922.msg194284#msg194284

[Willabe]

I finished up all the wiring. 

I hooked it up > variac > lamp limiter > IEC input box, power switch/150vac meter/fuse > Hammond torid 12.6 heater PT.

No smoke, set the variac to 120vac, and I'm getting 13.3vac on the heaters (pins 4/5) with 6x 12A_7's installed. The PT say's; 12.6vac @ 1.19A. 

I have some zener diodes 12v/1w here, can I use a pair of those to knock down the heater acv to 12vac?

If so, will they be noisy?

And to hook them up, 1 to each leg, banded side to leg other end of the zener to ground?

Or am I better off getting a couple of resistors to run is series with the heater leads? If so what value to knock  the 13.3vac down to 12.6? As it is now I have all 6 sockets filled to draw the max current I can. If I can knock it down some I wont have to keep all 6 9 pins in all the time.   

[sluckey]

You can't connect the zeners like you're suggesting. Just crank the variac down a bit more.

[Willabe]

Here's a couple of pics of the underside. I ran a few wires underneath to keep the top side clutter down.

I'm trying to use up some things I bought over the years on this. So I to help protect the under carriage wire runs I used some of the spaghetti tubing I got from AES along with some 1/4" plastic clamps. To get the clamps to hold tight, I used 2 and 3 different sizes of tubing nested inside of each other. 1 full length and 1 or 2 more short pieces just the width of the clamps. Worked very well.           

[Willabe]

You can't connect the zeners like you're suggesting. Just crank the variac down a bit more.

Can't, then the main PT will be low.

Hmmm......... maybe I can because the main PT will be under used on it's heater wind too. Might kill 2 birds with 1 stone. 


 

[jojokeo]

Looking real good Brad. Won't the heater voltage drop a bit once you get a load going? What are you going to build first?

[Willabe]

Thanks Jojo. 

I put in all 6, 9 pins to load it.

I think what Sluckey suggested will work.

[sluckey]

Ain't no thang! It's only 5.56% high.

[Willabe]

What are you going to build first?

It's time for me to find out about Champ amps! Some love them some not so much. 

Then I'm going to use the champ set up on the board to see if that Gibson GA55V's (true pitch shift) vibrato works. (Gibson's schematic could be wrong.)

Then the Gibson/Vox AC15/30 vibrato. 

Then maybe mix Sluckey's Warbler vibrato with the Gibby vibrato, run them in series. 
 
Then a 1 tube verb.

Then.........     

[Willabe]

Ain't no thang! It's only 5.56% high.

Yes, but that's with all 6 pre amp tubes in. 

I could just leave them in with nothing else hooked up to them to keep the same current draw? 

[sluckey]

There are lot's of things you 'could' do. You could use a dedicated variac just for the filaments. You could wire the tubes for 6.3v. But it's just a breadboard and in the end it still ain't no thang! 

[Willabe]

But it's just a breadboard and in the end it still ain't no thang! 

Very true. 

Ain't no thang! 

[Willabe]

Sluckey I want to make a little substitution box loaded with several K bypass value caps.

I have a few C&K 2P/6T rotary switches.

I thought I could wire it up like your tone switch for your Vox AC15.

You tied all the caps together on 1 side and also tied that side to 1 of the in/out poles, why? To stop pops when switching? 

[sluckey]

and also tied that side to 1 of the in/out poles, why?

No particular reason other than I wanted to. It serves no purpose. My switch is a MBB so popping is not an issue.

[Willabe]

No particular reason other than I wanted to. It serves no purpose.

  ??????

What about why you tied all the positions together on 1 side?

Must be a reason for the extra work.