Much appreciated help needed, 5f1 scratch build.

[Sweetsmcdudeman]

I have a scratch 5f1 build that takes the 5f1 schematic and upgraded the PT and the OT to the classic tone 40-18085 & 50-18031 and adds standby switch. The ot has 3 secondary taps and the PT is upright, us and euro voltage, and two HT options(630/550@100ma). I've added the PT specs to this post.

Issue) Current limiter I built works with known good amp but with 5f1 I get no light at all using 100watt bulb. However, I have verified with no tubes present and switch to on position ac voltage where it should be(only using 120v primary taps). This includes 5v rectifier heaters and 6.3v heaters all the way from pilot to V1. My HT are both separately at 333v ac at rectifier(is that normal? I.e. higher than spec of 630?).  With amp in play mode, my 3 b+ DC voltages are at 450v coming out of rectifier to first filter cap. After, first voltage drop resistor I'm at 435v, and after second resistor (third electrolytic) I'm at 305. I can post all voltages from all pins neccecary.

Any help understanding wtf is happening and why would be awesome. I don't just want to play this amp I want to understand it.

[sluckey]

Use a 25W or 40W bulb with a small amp if you want to see a dim glow.

[Sweetsmcdudeman]

Use a 25W or 40W bulb with a small amp if you want to see a dim glow.

Switched to 25 watt and still no dim. Do you have any thoughts on the voltages I posted?

[sluckey]

Your voltages look like there is no lamp limiter being used. Are you sure the lamp is wired correctly?

[Sweetsmcdudeman]

I thought I wouldn't need to limit with 6.3v center tap. I can wire up two resistors and see if that drops it. How does that influence the b+ voltage?

Btw, I've read alot of your replies in other posts, thanks for the help.

[sluckey]

I'm not understanding what you are doing.

Put all tubes in the amp with speaker connected. Just as if you were gonna play the amp. ***EXCEPT*** Plug the amp into the lamp limiter and plug the lamp limiter into the wall. That 25W bulb should have a slight glow. Does it?

[Sweetsmcdudeman]

I'm not understanding what you are doing.

Put all tubes in the amp with speaker connected. Just as if you were gonna play the amp. ***EXCEPT*** Plug the amp into the lamp limiter and plug the lamp limiter into the wall. That 25W bulb should have a slight glow. Does it?

Ok. Sorry I misunderstood.

So I messed around with limiter and it worked. With load connected and all tubes in there is a dim glow. All my voltage measurements are half of what they should be. Should I just proceed without limiter and check voltages and bias?

[sluckey]

It's normal for voltage readings to be low when using the lamp limiter. Since the lamp limiter did not glow brightly it's safe to plug the amp straight into the wall. Then and only then will you have valid voltage readings.

[Sweetsmcdudeman]

It's normal for voltage readings to be low when using the lamp limiter. Since the lamp limiter did not glow brightly it's safe to plug the amp straight into the wall. Then and only then will you have valid voltage readings.

Ok so these are tube pin readings.

V1
1- 359v dc
2- 0v
3- 28v dc
4 - 3.5v ac
5- 3.5v ac
6- 240v dc
7- 0v dc
8- 3v dc
9- 3.5v ac

V2
1- 0
2- 3.4v ac
3- 451v dc
4- 433v dc
5- 361v dc
6- 0
7- 3.5v ac
8- 434v dc

V3
1- 0
2- 453v dc
3- 0
4- 335v ac
5- 0
6- 335v ac
7- 0
8- 453v dc

Does anything jump out as wacky?

Compared with another thread it seems v1 pin 1 is high and my bias isn't showing up properly.

[sluckey]

V1 and V2 voltages are really screwed up. I suggest you double check your wiring.

[Sweetsmcdudeman]

Sluckey,

I spent some time rewiring, triple checking and I definitely found some errors.

I still have no sound but scratchy spots on different sections of the circuit.

I've checked all my grounds for continuity and I'm good.

My voltages are as follows:

B+1 377vdc
B+2
B+3

V1
1 220vdc
2 0
3 1.20
4 3vac
5 3vac
6 187vdc
7 0
8 .87vdc
9 3vac

V2
1 0
2 3vac
3 0
4 260vdc
5 -6.3vdc
6 0
7 3vac
8 18.5vdc

I also saw a thread where you asked someone to check resistance between grounds and specific pins. That checked out well.

It's a scratch build and I'm also really trying to learn here. What da heck am I not getting!

[Sweetsmcdudeman]

I'm also noticing that my capacitors dont seem to be retaining voltage after I turn the amp off.

[sluckey]

V2 voltages are still messed up. I suspect meter reader errors? Pin 3 should be BIG B+.

Pin 5 should be zero volts (no way can it be negative) Maybe you saw -6.3mV which is very close to zero.

Did you use a choke? We need to see some hi-rez pics.

[Sweetsmcdudeman]

Hey Sluckey.

Yeah, I have a new meter and it's really sensitive so I pulled out the old one. Rechecked v2 voltages,
Pin
1 -9.3mVdc
2 3vac
3 403vdc
4 261vdc
5 -9.9vdc
6 -20mvdc
7 3vac
8 17.08vdc

Pictures located in folder here.
https://drive.google.com/folderview?id=15ezGcPHV6ULj3C-IdQe_nE2RdCR2YHPv

[sluckey]

V2 pin 5 is still wrong. Turn power off and measure resistance from pin 5 to chassis. Meter probe directly on the tube socket pin 5. Should be 220KΩ. If not check the wire that goes between pin 5 and that 220K resistor on the board.

[Sweetsmcdudeman]

233k.

I also remeasured
Pin
1 0
2 3vac
3 370vdc
4 328vdc
5 0
6 -
7 3vac
8 20vdc

I have 180vdc coming out of v1b into southside of coupling cap v2. North of coupling cap I'm just getting millivolts.

I'm also getting a really quiet farty guitar signal coming through the speaker.

[Sweetsmcdudeman]

8 watt, with all due respect, I've had a dim bulb awhile back and rectified that original issue.


The tube we are discussing currently is v2 which is a 6v6.

I was understanding my pinout voltages for 12ax7 were ok as I posted above 1 is 220vdc 6 is 187vdc.

That's 220vdc going into the anode of v1a(pin 1) and 187vdc going into anode of v1b(pin 6). I understand that ac is coming in through signal to grid(pin2) out to coupling sending dc to ground and allowing ac to pass on in circuit.

Can we confirm?

As an fyi, I'm using the pinout diagram as it looks from the chassis side of the socket and reading pin number from left to right of "key" .

Are you using a 12ax7? If so the HT 370 should be on pin 1. 328 on pin 6. It should drop once loaded to a lower voltage. If not your power rail may need work.   Its a good thing that you have 0 on pin 5 because if 370 volts hits the heaters I rather suspect you wouldn't have a dim glow, and probably worse. Don't get frustrated yet. It sounds like you may have done SOMETHING correct, or you wouldn't have any noise. Do this. Unplug the amp, set your meter aside for now. Go to the 12ax7 (or whatever tube you are using) tube chart and pinout. Study that, and study your amp. Also the the layout for this amp in el34world library of information is a great easy to read layout. DO NOT power back up until your are certain of the pinout being wired on the tubes. IE pins 4,5 and 9 are heaters, and you should see 6.5vAC or very close. Should be the green wires. Do some more reading on this and how coupling capacitors work (blocking DC). This will help you greatly in the fundamentals. Pin out is different on different tubes, so it is VERY important to know exactly what you are wiring to the pins and why. Then you will begin to understand the signal flow.

[Sweetsmcdudeman]

Thanks. I feel my understanding is very lacking in regard tube data sheets but I'm really studying basic electricity and my math to understand what the heck is going on inside tube etc. I feel like I get signal flow and therefore I can find the measurementa on the pins and the same spots on the board.

Novice concerns I have are:

Possibly the grid stopper for v2 but i get accurateish resistance on pin 5 with power off.

It's a little weird to me that my capacitors are not retaining voltage after powering down. They had been holding a charge until I desoldered to read individual capacitance.

My output tranny. It's not stock but the classic tone one listed above. How the heck do you calculate what resistance you need for the primary? What is it based on? Example, I have 5k and 8k primary and 4 8 16 secondaries. Which one do you use and why, other than just reading a layout that tells me to pick the 8k. 

Yes I misread. My apologizes. I will study your post some more.

[Sweetsmcdudeman]

8 watt,

Using 220k grid and 470 5 watt cathode.

Will check signals when I'm back home.

[Sweetsmcdudeman]

I may have misspoke, I'm cooking a bunch of french food for hungry new Yorkers

Attatched screenshot of my hookup based on robrobinette.com layout.

[Sweetsmcdudeman]

18watt,

Clarify 15.7 watts? Can you also explain how you're checking signal with ac volatge and applying signal?

Yeah, That's the same. Rob's layout's are also cool. So just do some signal tracing, and consider raising that cathode resistor value. I'm figuring 15.7 watts. I think that is high even when considering screen current.

[Sweetsmcdudeman]

I added a link with pictures a few posts back.

 https://drive.google.com/folderview?id=15ezGcPHV6ULj3C-IdQe_nE2RdCR2YHPv

[Sweetsmcdudeman]

Also I really appreciate you taking the time here.

[sluckey]

Those pics are great. Very good detail. But we also need pics that show the entire guts of the amp so we can see where a wire from the board actually connects to chassis mounted components. The number one cause of failure in a new build is wiring error, followed closely by wrong component value.

[Sweetsmcdudeman]

Heard and understood on all fronts.

I'll clean things up asap and repost.

[Sweetsmcdudeman]

I'm going to clean things up and take a gut shot but I noticed something:

On robrobinettes layout there is no grid stopper on v2 5/6, so I don't have one on there. The only 1.5k resistors on his layout are v1a and v1b cathode.

[Sweetsmcdudeman]

Ok. Here's a link for hi res gut shots. I'm still going to clean up my connections and reflow.

In the gutshots you will see one stray grey wire towards v1, that's 16ohm tap which is temp disconnected to run 4ohm test speaker.

I also did a signal check for ac and found some change in ac voltage on r2 but not r1(hi inpunt)I do however hear faint signal in speaker. Going into 1st coupling cap I didn't have ac voltage but coming out I did. I had voltage on pot going in and going out that was effected by the variable resistance. I have upwards of 14 volts coming out 2nd coupling capacitor. I have voltage on the right side of my grid leak and ac voltage on 6v6 pin 5. I also have movement on 6v6 pin 3 both about 5 v.

Also added to google drive folder audio into with phone sitting on top of 8 inch 4ohm speaker. Can't hear it unless up close but sounds bigger on recording.


https://drive.google.com/folderview?id=1-05z4q1ZRQmNLwubNwf6GhPPCcb7_fQl

[Sweetsmcdudeman]

It's on pin5, I have resistance on pin. I can generally check all those wires based on readings on the board correct? I pulled the board a while back to verify and all was as required.

I can't tell cause it's under the board, but the yellow wire that goes to pin 5 v2 needs to be at the junction of your second coupling cap and that 220k. It looks like it may be to ground. I'm sure better eyes will see other things.  For now when you clean up, maybe move those wires under the board back to the top.

[sluckey]

You have a lot of wires that connect to the bottom of your board. Use your ohm meter to verify that the wires go to the correct turret. For example, that wire connected between V2 pin 5 and that 220K resistor. Verify by putting one probe directly on the V2 socket pin 5 and the other probe directly on the correct turret on the board. Should be zero ohms. Verify every wire using this same method. Also, verify any under board jumpers that go from one turret lug to another turret lug.

I want to repeat, "The number one cause of failure in a new build is wiring error, followed closely by wrong component value." We can see the stuff on top of the board, but only you can verify the stuff under the board.

[Sweetsmcdudeman]

I'm following everyone's directions short of give up!

I'm definitely not being lazy about this and already found a 5f1 post where turning amp off and measuring voltages was done.
You don't see solder in lug because I soldered from the other side and was told not to fill it up too much.
On v2:
I have 0 resistance from pin 5 grid resistor and coupling cap. I do have the value of the resistor going from pin to ground side.

I have zero resistance from cathode to cathode resistor. Same as above in regards ground side of resistor with reading of 470ohm.

V1
0 ohm between pin 3 and cathode resistor.

0 ohm between pin 7 and v1b cathode resistor.

0 ohm between grid stopper and pin 2.

0 from pin 7 to pot.

0 from 1 and 6 to respective load resistor.

[sluckey]

found a 5f1 post where turning amp off and measuring voltages was done.

Really? The amp usually has to be turned on to measure voltages.

[Sweetsmcdudeman]

I meant resistance I'm sorry.

found a 5f1 post where turning amp off and measuring voltages was done.

Really? The amp usually has to be turned on to measure voltages.

[sluckey]

Whose layout did you use? Provide link. Did you make the board?

[Sweetsmcdudeman]

Pdf provided via rob robinette. I did make board.


Again while amp off, pin to resistors is 0 ohm. Pin to chassis ground is measuring the actual resistor value.

Whose layout did you use? Provide link. Did you make the board?

Again while amp off, pin to resistors is 0 ohm. Pin to chassis ground is measuring the actual resistor value.

[Sweetsmcdudeman]

My only mod was upright power transformer with multi tap primary and 2 ht values, output with two primary resistances one common and three ohm secondaries, standby option via carling off on on switch.

[sluckey]

I expect to see two wires connected to the tip lug of the speaker jack. Why only one? What does that one wire connect to?

[Sweetsmcdudeman]

Tip connected to yellow 4ohm output secondary.
Ground and sleeve connected to common black from output secondary.

Negative feedback resistor disconnected.

Link below showing what I think you're referencing.

https://drive.google.com/file/d/1-b8bJdx8qidiDK9USe4vO-nCmIqL1GeX/view?usp=drivesdk

I expect to see two wires connected to the tip lug of the speaker jack. Why only one? What does that one wire connect to?

[sluckey]

How are you connecting your speaker?

Check V2 pin 5 voltage again. Hate to harp on that but you have checked it four times and posted four different readings.

This is a divide and conquer test... Turn the volume all the way up. Now use a small bladed screwdriver as a probe and hold it on the middle lug of the volume control. Now touch your finger to the blade of the screwdriver. Do you get a buzz similar (but not as loud) to touching the tip of the plug of a guitar cable that's plugged into a working amp?

[Sweetsmcdudeman]

Update.

Sluckey, I rechecked and rechecked and rechecked pin 5 and I'm at millivolts. I put a screwdriver to middle pin of volume and I definitely had a hum when I touched the metal.

I also decided to wire my output jack to 16ohm and run through my orange 2 x 12. Theres definitely guitar coming through way louder. It's like it plays stronger when I dig in more. There a bit of a high frequency in there. I'll make a recording of it.

Either way, I'm taking 8watts advice and just resoldering everything and moving my wires to top of board. I'm also going to put the grid stopper on v2 pin 5 while I'm at it.

I feel like I just have some bad wiring somewhere but it has been a big help to get feedback and to know that this is not immediately an issue with voltages I have or lack thereof. At least for now.

Of course, if you guys have any idea what would cause the signal to act that way it would be good to know.

I'll clean up the board tomorrow and report back asap.

[sluckey]

That's good news. I'll shut up about pin 5 now. 

Since you get a buzz/hum with the screwdriver test that suggest there's a problem between the input jacks and the volume control. Very few components. Input jacks can be a problem. Be sure you're plugged into the hi jack (the one with the 1M resistor on it). And look closely at the wiring on the jacks and to the 68K resistors. Looks right in the pics but so does everything else that I can see. I really think you're about done. Hang in there.

[Sweetsmcdudeman]

Really!!

Im still going to clean things up in there.

Sluckey, can you explain how that troubleshoot works?

That's good news. I'll shut up about pin 5 now. 

Since you get a buzz/hum with the screwdriver test that suggest there's a problem between the input jacks and the volume control. Very few components. Input jacks can be a problem. Be sure you're plugged into the hi jack (the one with the 1M resistor on it). And look closely at the wiring on the jacks and to the 68K resistors. Looks right in the pics but so does everything else that I can see. I really think you're about done. Hang in there.