Dougs Stout beginnings

[lego4040]

Okie dokie on pics. I got multicap in as well, maybe tomorrow I can finish. I have some wires to sockets, pots & the gain pot, oh I want to wire the 1ohms in so I can read the tubes.

[sluckey]

Much better. But your aspect ratio has changed from the original pic and that distorts the true pic. You misinterpreted Doug's limitations. "1024 pixels wide and 800kb" does not mean 1024 pixels wide by 800 pixels high. It means 1024 wide and keep the file size below 800KB (kilobytes).  When you resize or crop your pictures you can specify 1024 as the width, but don't specify a height. Instead, keep the original aspect ratio. Then resistors will not look very skinny or fat. They will look just like the original pic, only smaller.

If you ever resize a pic of your wife and change the aspect ratio such as the width is much greater than the height, she'll explain it to you in different terms!   

Anyhow, now I'm beginning to see what you are doing.

[Willabe]

If you ever resize a pic of your wife and change the aspect ratio such as the width is much greater than the height, she'll explain it to you in different terms!   

                                  

[lego4040]

Ok I hope I read schem correct. I removed the 470k in between .022uf and 47k(V1 P6) and added the 500k pot. That's the yellow and whit wire you see on board and next pot is it wires to pot

[sluckey]

See pic... This is how to replace R14 with a gain pot.

FYI, the red arrow pointing at C6 is the famous Stout error. The bottom end should be connected to ground. Doug won't tell us if the error is intentional. The amp works either way.

[lego4040]

So that gain pot is wired like a volume control. I wired mine like a trimmer resistor, turn clockwise and resistance goes up. Here is how I did it. I reset and pot works correctly, am I wrong? My understanding was that should pot fail it can't go past it's rating

[lego4040]

I fired it up with the poor man variac and all is good. 480vdc on the plates and that's as far as I got, schems didn't have volts readings and I have 6v6's. I ran outta time and left shop. Odd thing is I had no sound when I hooked up guitar but I was expecting that, I gotta go back and check inputs and rest

[sluckey]

480v on the plates. That's gonna be one hot little amp... for a little while!

I really didn't think that little PT would put out that kind of voltage.

[lego4040]

Tisssszzzz, hot little B isnt she   I know I have to really look at wiring when I have a period of time. Thanks for the neg ground lift, I can take some readings I'm the afternoon and get them posted

[sluckey]

Deadly hot for those tubes.

I have that same Allen TP25 in my 5F10 Harvard fixed bias 6v6 amp. I only have 387V on the plates. I believe you may still have a dangerous B+ problem, or your meter is lying.

What is a poor man's variac and do you have 480v on the plate while using it? I hope you're not talking about a household lamp dimmer?

[lego4040]

Not a dimmer, oh no. It's a current limiter actually, light bulb thingy. When you power up it goes dim, if it stays bright then you have a wiring error in amp. I figured it was still to much, back to drawing board

[sluckey]

Are you sure about the wiring of that bridge? PT red wires go to the AC terminals. Plus terminal connects to filter caps. Negative terminal connects to nothing. PT Red/Yellow wire connects to chassis. PT Orange is not used in this amp. PT Yellow wires are not used.

I suppose if your PT is putting out 350-0-350 (unloaded) AC to the rectifier, then your unloaded B+ would be 495V. I would also expect that to drop considerably when the tubes warm up. It may all be correct. If so, you will likely need that 300Ω resistor between the bridge positive terminal and the first filter cap.

I just checked the voltages in my Harvard. The TP25 is delivering 345-0-345 to a NOS 5Y3 tube. Voltage at the first filter cap is 390V. The amp is fully warmed up and loaded for these readings.

[lego4040]

Ok Steve I have my PT wired like this: red pair to bridge, red/yellow to chassis ground. Red/green not used. Orange is to chassis ground( you weren't using yours) should I lift it off and cap? Green pair to lamp/ heaters. Green/ yellow to chassis ground. Yellow pair not used since I put in solid state. I had this in amp in amp with this PT before. I will put this between DC positive and 40uf cap and see where it drops to. Also verified I have input jacks wired wrong, need to fix

[DummyLoad]

IMHO, you have the wrong PT for this application. see PSUD2 plots below. i estimated the load currents. the 367V is estimated NL voltage of the B+ winding. the 115ohm source Z is based on readings that steve provided. last sim is with the 330ohm resistor inserted. the load current is an estimate.


--pete   

[lego4040]

Steve I added the 330ohm between bridge and cap, didn't really do much. I got 470 on the plates, A:470 B:470 C:419 D:410. I am gonna either have to buy different tranny or go to tube rectifier. I don't want to have to buy anything else for this project. Tube rec next. Will post results

[DummyLoad]

is that with tubes installed?


--pete

[lego4040]

Yeah, I just disconnected the solid state and hooked up the tube rectifier. I got the plates down 450 and the abcd's down as well. I guess I'm getting a new PT

[lego4040]

Readings with tube

[lego4040]

Would anyone know the Hammond transformer that would work here? I can get it thru work and order two. Use it for another project.

[sluckey]

The 290CAX is a good choice, electrically speaking. Use the 275-0-275 taps. Compare the physical dimensions to your TP25 to see if it will fit the existing holes.

     http://www.hammondmfg.com/pdf/EDB290CAX.pdf

The PT in your AC-15 is another good choice if you don't mind covering the big cutout in your chassis.

It's not Hammond, but Doug's 18W PT is another good choice if it fits the chassis. The physical dimensions are listed.

[lego4040]

I can get these for nothing from my supplier. I can't do it all the time but I got a ok today

[lego4040]

Ordered two Hammonds from my supplier. Gonna get other one out monday

[sluckey]

I measured my TP25 this morning. Looks like that 290CAX should just drop in.

[lego4040]

Thanks for doing that Steve, I'll take the PT out and reinstall the bridge rectifier. What would I use that PT for then. Maybe I put it on the Buy sell trade page

[sluckey]

What does Allen say it's for?

[DummyLoad]

Thanks for doing that Steve, I'll take the PT out and reinstall the bridge rectifier. What would I use that PT for then. Maybe I put it on the Buy sell trade page

same thing. drop in a pair of 5881 or EL34 w/ a 4K load: vibrolux OT. more power! ugh! ugh! ugh!


--pete

[lego4040]

Well the PT came with his 5F1+ kit. I was running the amp with a 5881 and two 12AX7. But I'm down with Steve's next build if he does it, a tweed Princeton Reverb!! I'll build that in a heartbeat.  Maybe I can use it there

[DummyLoad]

that PT was designed to kick the tweed champ/princeton/harward up a notch with a 6L6GC/EL34/5881 & tube recto. allen sells the OT compliment: the TO11C/TO11S


--pete

[lego4040]

I have the TO11 and the choke that comes with that set. I put the TO11 in a box and on the shelf for later usage. I was putting out about 12 watts with his 5f1+. When you mentioned 4k load, you were referring to the OT for the Vibrolux? I'm still a newbie with all this amp tech stuff

[sluckey]

I just looked at your voltage chart!     

You either have a bad meter, are measuring incorrectly, or there are some serious wiring errors in that amp. Please recheck. Whenever you get some believable voltage readings on ALL tube pins, your high B+ may be acceptable also.

[lego4040]

Well a wiring error is believable but it did check out with the current limit bulb tester. I can order those washer thingies Doug was making on his 3d printer if he has them, so I can put the EL's in them that the build calls for. Doug you selling those 8pin to 9 pin spacer tube sockets, I'll email him

[sluckey]

EL84s will not hold up to the kind of voltages you are reporting. Please just recheck and post voltage readings for all tube pins. Don't really need a picture. Just type the numbers.

[Ken Moon]

Many of the other voltages are way off also, like the readings of about 300VDC on the preamp cathodes - this should be about 2 volts!

Please be careful - when I see voltage charts like this, I worry that the readings are not being done in a safe manner.

I saw a young man get shocked badly testing a big tube Tek oscilloscope when I was about 20 years old. He lost his arm. That's why I harp a lot on safety.

This is not to insult anybody - but consider taking those voltage readings again, and make sure your DMM is set on DC Volts, and the Negative lead is connected to circuit common, like the negative side of the power tube cathode bypass cap, or right on the lug of a star ground.

And please put one hand in your pocket whenever probing a live circuit with the other hand. This will eliminate the current pathway through your heart muscle if you get shocked, and it only takes about 100mA to kill you 

[lego4040]

Oh I'm being safe, one hand testing always draining, etc.......  I will take PT out, take 6v6 sockets out and find those spacers. I will recheck the board wiring and all.  Those volts are to close to the cap 500v ratings and I don't want problems.

[lego4040]

Hmmmmm, I pulled out PT and make a test board. I have 350-0-350 AC, and close to 700 together. when hooked up to bridge I get anywhere from 650-700dc. When I hooked it up to 5y3 I got only 350dc? That ain't right! 350*1.2 should get me around 420. I made sure all connections where right, I may have killed tube rectifier with those high volts, you think it's time for a new one

[sluckey]

Hmmmmm, I pulled out PT and make a test board. I have 350-0-350 AC, and close to 700 together. when hooked up to bridge I get anywhere from 650-700dc. When I hooked it up to 5y3 I got only 350dc? That ain't right! 350*1.2 should get me around 420. I made sure all connections where right, I may have killed tube rectifier with those high volts, you think it's time for a new one

Both of your meter readings are meaningless.

You are measuring voltage wrong on the bridge. Black meter probe needs to connect to the PT center tap which you have connected to a PT bolt. Then positive probe connects to plus terminal on the bridge. ***CONNECT NOTHING TO THE NEGATIVE TERMINAL ON THE BRIDGE***. If I were you I'd just cut the negative lead off flush with the body of the bridge so you will leave it alone. 

Same goes for measuring voltage with the tube. Black probe to PT bolt, red probe to pin 8.

One more thing... You don't need a new tube. The voltage from the 5Y3 is not low. You must put a filter cap between pin 8 and that PT bolt before your meter will quit lying to you. Likewise, you need to use a filter cap on the bridge to get a correct meter reading. I suggest putting a 100K to 220K resistor across the filter cap so it will discharge when you unplug the power. Otherwise, that cap will bite you.

EDIT... There's nothing wrong with that PT other than the fact that David Allen advertises it as 310-0-310 but in fact the one he sold me is 345-0-345 and the one he sold you is 350-0-350. That PT is just not a good choice for the Stout.

[lego4040]

Ok Steve here it is once more as per your instructions. Third picture is how I hopefully connected the gain pot, ccw resistance decreases and vise versa. My Free PT is a week from me and I'll gotta give Doug some more business

[sluckey]

Don't you love it when stuff works like you expect it to? 

As for the gain pot... That's the brute force way to do it. It'll work. I showed you the elegant way to do it.

And if you want a fatter sound, here's what I'd do...   

[lego4040]

 

[sluckey]

Glad you can recognize my sic humor. You also got the point, right?

Here's the elegant method in layout format...

[lego4040]

Took a second but I got it, on your more elegant way you wouldn't be connecting to the 47k anymore. Reason?

[sluckey]

Look closely. It's still connected to the left end of that 47K.

[lego4040]

Where? The .022uf was in series with the 470k and went up to 47k, it also teed over and went to the .01uf. You wired the pot where the line connects to the .01 but eliminated the wire up to 47k. The wire on right side to the 47k hasn't changed changed. I still haven't had my two cups of coffee so I could be sleeping still

[sluckey]

Fingered it out yet?

[lego4040]

Ooo, Oooo Mr Koter, the gain pot leg 1going to ground

[sluckey]

Good boy Vinnie! You can have an A in 'picture lookin' or two beers for lunch or sleep with Julie tonight. Your choice.   

[Ed_Chambley]

What is the purpose of the "gain pot".  Does it lower the gain to get a cleaner signal?

[lego4040]

yes, it lets you dial in voltage input to next stage I believe is how it was explained

[DummyLoad]

wired as is it keeps the gain stage connected to the top of the pot AC load constant like the 470k r does. now you get to vary how hard you slam the LTPI.

--pete

[lego4040]

Made all my changes, wired as per Steve. Just need to hit send and my parts are ordered from here. I have two Hammond 290CAX on the way, got em free   I just watched some videos on the 1968 Marshall SuperLead and oh boy would that be a nice amp to drive the neighbors crazy