vibrolux issues

[Bugman3183]

Hello all, I just put together a 5e11 using the schematic and layout provided here .  I fired it up for the first time and all I'm getting is a lot of rhythmic pops through the speaker.  I have double and triple checked all my connections and am at loss as to what the problem could be.  I must admit I don't know anything about oscillator circuits and although it's not notated on the schematic I am wondering if the tremelo Jack  should have a ground reference.  Any help on this subject would be greatly appreciated.  Thanks.

[sluckey]

I am wondering if the tremelo Jack  should have a ground reference.

The tremolo works without a ground on the jack. You turn the tremolo oscillator off when you put a ground on the tip of the jack.

[Bugman3183]

Ok, thanks.  I'll Keep searching for what the problem may be

[eleventeen]

Are you saying you get ZERO audio through the amp? Just your pops? Are the pops affected by the setting of the "speed" & "depth" controls?


We'll need some voltage readings to help you better. You have the ground end of the bias rectifier connected? If that doesn't mean anything to you, what voltage do you measure on either 6V6 pin 5?

[sluckey]

You have the ground end of the bias rectifier connected?

I don't know what that means either???

[Bugman3183]

Just took some readings and I have 370v on 6v6 plates and 140v on pin 5 with depth control all the way down, and at max it's at 154v.  Also notice the pops get faster as the depth control pot is turned.

[Bugman3183]

Also, no guitar signal, just the pops coming through the speaker

[eleventeen]

POSITIVE 140-154 volts? Your 6V6 tubes would be cherry red hot and probably cooked good. Bias diode installed backwards.





If the ground side of the 56K & the 25/25 u was disconnected from ground, bias would be way way negative and the 6V6 tubes would probably  be cut off.

[Bugman3183]

I have the diode cathode (side with grey band) pointed toward the 6.8k resistor.  Is that backwards?  The 56k ous grounded.

[eleventeen]

That's backwards! That will produce a positive voltage where the schematic shows -31 volts. It quite possibly will have blown up the 25/25 cap, which is no big deal, cheap part. It will be interesting to see if your 6V6's survived. By all rights, with +140-150 volts on the control grids, Pin 5's, they should resemble Chernobyl.





               Was that wrong?

[sluckey]

I have the diode cathode (side with grey band) pointed toward the 6.8k resistor.  Is that backwards?  The 56k ous grounded.

No. That's correct.

[Bugman3183]

Either way I directed the grey band I'm still getting the popping sound through the speaker.  My voltages are all over the place.  Most of my wiring is under the board, so I'm gonna take the board out and re-check the connections.  Afterwards, I will give a full account of voltages, but to be clear the grey band on the diode should be facing the 6.8k resistor?

[eleventeen]

Sluckey is right, I was wrong. [costanza] I misread you, I apologize. Diode band towards the 6.8K


You cannot allow +big volts to live on your 6V6 pin 5s. The voltage there has to be negative relative to the cathodes of those tubes. Otherwise those tubes will burn up, and fast. You can troubleshoot the amp as it is, but I would pull out your 6V6 tubes. *If* you had +140 volts on the 25/25 uf cap in the rectifier circuit, reverse polarity, that cap is probably fried.


I see no rational way you could end up with +140 on your bias feed, unless the .25 u/400 v cap connected to the first 12AX7 plate, the trem oscillator, is very very leaky, or shorted. Even w/the bias diode reversed (and it is not) your + volts should not be that high.

[Bugman3183]

Thanks.  I'll pull them out when I take the new readings.  I'm gonna pull the board out and make sure I have all the connections going to the proper places.  Well report back tomorrow evening

[Bugman3183]

Great news guys!  I made some changes on the amp, and now I'm getting a guitar signal through the speaker.  Unfortunately, I'm getting a lot of hum as well (more like a hum than a buzz).  I'm thinking it's a grounding issue.  Currently I have a faux center from the power tube to the cathode of v2 pin 8.  +51v's so it seemed feasible.  I didn't use shielded cable to input jacks since it's not a high gain amp I didn't feel it was necessary.  I was thinking of maybe grounding node #2 with preamp instead of power amp to see if that would make a difference.  I have 360v b+,  -41v for the bias(same on 6v6 pin 5).  Another problem I'm having is, even without the foot switch in the Jack I'm still getting vibrato if pots aren't at to zero.  I must say, even with hum the vibrato is simply glorious.  I'm super excited to be moving in the right direction.  Any help on this situation would be greatly appreciated.

[sluckey]

Another problem I'm having is, even without the foot switch in the Jack I'm still getting vibrato if pots aren't at to zero.

That's how it works. Read reply #1 again.

[sluckey]

Currently I have a faux center from the power tube to the cathode of v2 pin 8.  +51v's so it seemed feasible.

DON'T DO THAT! REMOVE IT BEFORE SOMETHING BAD HAPPENS.

Just because you see +50v written on a schematic or measure it somewhere in a circuit does not mean that point is available to be used for anything. V2 pin 8 happens to be the cathode of the cathodyne phase inverter and there is also guitar signal on that pin.

And what does "faux center from the power tube" mean? I assume you're talking about elevating the filament circuit. If so, just connect one 100Ω resistor between pin 2 and pin 8 of a 6V6, and connect another 100Ω resistor between pin 7 and pin 8 of that same 6V6. If you have your filaments wired IAW the original Fender layout you'll also need to remove the ground from pin 2 of each 6V6 and connect pin 8 of each 6V6 directly to ground. Then cut the jumper between pins 2 and pins 1.

Maybe your hum will decrease/disappear when you do all this.

[Bugman3183]

Thanks Sluckey.  I meant to post "faux center tap". I appreciate the help.  I'll make these changes this evening after work and report back.

[Bugman3183]

Hey fellas, been working on the amp since I got home today. I implemented the changes sluckey suggested and the hum decreased a bit.  Upon further inspection I noticed a couple of stands of wire that connected the grid of v1 b to the plate v1b.  Took care of that and now hum is non existent.  I do still have a couple of questions though.  The foot switch does not effect the tremelo at all, whether  on or off the sound remains the same. I also wanted to know if there is a way to make the lowest speed setting slower.  And the last problem I have is that I used a string of five 5v zeners on the center tap to ground in an attempt to lower the b+, and it actually went up by 8v.  They were positioned with the band pointed towards ground.  I've done this before and it worked in previous amps that I have built.  Please excuse my ignorance, this is my fourth build and all the others were cathode biased without tremelo so it seems there's a learning curve here.  I appreciate all the help and any suggestions on how to remedy the remaining issues.  Btw:  note have 368 b+ and I'm trying to get it down to 340.  Not only because that what the schematic says, but I also have a pair of 6v6g's that I would like to try in this amp, which apparently are happy with the lower b+ and screen voltages.  Thanks.

[sluckey]

The foot switch does not effect the tremelo at all, whether  on or off the sound remains the same. I also wanted to know if there is a way to make the lowest speed setting slower.

All the footswitch does is puts a ground on the jack. That ground will kill the trem oscillator. Use a gator clip lead to ground the tip of the FS jack. If that kills the trem then the footswitch ain't wired right. If it doesn't kill the trem then the jack is not wired correctly to the board. For a slower speed replace one of the .01µF caps that the footswitch connects to with a .02µF cap.

And the last problem I have is that I used a string of five 5v zeners on the center tap to ground in an attempt to lower the b+, and it actually went up by 8v.  They were positioned with the band pointed towards ground.

The zeners are installed backwards. Turn them around.

I'd just completely remove the zeners. Look at the 'Notice' on the schematic. It says voltages shown are +20%. 368 is only 8% higher than 340. Don't worry 'bout it. I'm running 420v on a pair of 6V6s in my DR.
 

[Bugman3183]

Thanks a lot sluckey,  I'll try those changes this evening.  You've been extremely helpful, I really appreciate it.

[Bugman3183]

Alright, I increased the on cap to.02 in an attempt to slow down the speed of the vibrato.  While doing so fooling around on the guitar I noticed that the controls don't work as expected.  The depth pot seems to act as a master volume.  Turned to zero I get no sound from the amp.  Tone acting as speed pot. When checking my connections it appears that the schematic doesn't match the layout.  Especially as it applies to the speed pot.  Admittedly, I'm no expert with schematics, but there seem to be some discrepancies between the layout and schematic.  I followed the layout.

[Toxophilite]

For myself, initially
I found the layout much easier to follow as it showed things as they looked in the amp


The schematic shows connections with often no regard for distances, paths taken or comparative placement of components, thus it often looks like it's depicting something different.


However it usually is the best to follow, and there probably isn't (if any) too much of a discrepancy between them. It likely just appears that way


Use them both together as there is the odd thing that layouts aren't as good at depicting as the schematic


Sometimes I would build with the layout ,then double-check and trouble shoot with the schematic

[Bugman3183]

I'm using the 5e11 schematic and layout.  On the layout it shows the right lug of the speed pot connected to .03 cap from v1b plate and 100k to ground on wiper with nothing on left lug.  Schematic shows left lug of speed pot connected to junction of .01+.02 caps,100k to ground on wiper and nothing on right lug.  And I don't even see the .03 from the v1b plate on the schematic.  Actually v1b plate has a .25mfd cap on it, whatever that means.  I guessed at value and used a .02 cap.  As it stands I'm at a complete loss as to how fix current problem with amp.

[Willabe]

I'm using the 5e11 schematic and layout.  On the layout it shows the right lug of the speed pot connected to .03 cap from v1b plate and 100k to ground on wiper with nothing on left lug.  Schematic shows left lug of speed pot connected to junction of .01+.02 caps,100k to ground on wiper and nothing on right lug.  And I don't even see the .03 from the v1b plate on the schematic.  Actually v1b plate has a .25mfd cap on it, whatever that means.  I guessed at value and used a .02 cap.  As it stands I'm at a complete loss as to how fix current problem with amp.

The .02 and .03 caps, 1 is of the 2 is a misprint, you can use either 1, the larger value, .03 will slow the speed down a little.

The .25mfd is probably a misprint too, but I think either would work just fine. I'd probably go with a .1 there. (Your guess was off by a factor of 10, they mean 0.25mfd = 1 quarter of 1 micro farad, 0.1 = 1 tenth of 1 micro farad. Most guys here use   uF = micro farad.)

Wire up the speed and depth pots as in the layout drawing.

(I believe the schematic is correct for the 2 pots but you need to be able to see in your mind,

1. Which way turning the pot moves the wiper towards either end lug in the electrical schematic. 

2. That when you look at a pot from the back, in the layout drawing, you need to be able to see which way the pot's wiper goes, ie, towards which end, the O end/ground or the X end full up.

Take a pot put a knob on it hook up your meter on resistance, put 1 lead on the wiper and the other on 1 end of the pot, rotate the pot, watch meters resistance until you see how it works. Tip; look at Fender layout drawings, volume pot ground ~ O end ~ is always on the pots back side left. I still need to have a pot in my hand when I draw up a circuit.)         

[sluckey]

Please post the schematic and layout you are looking at. The one I'm looking at shows the schematic and layout to be in total agreement as far as the V1B trem circuit is concerned.

[Willabe]

Here's the 2 I looked at, shows the caps like he said;

http://el34world.com/charts/Schematics/files/fender/Fender_VIBROLUX_5E11.pdf

Another typo; V1b plate R is 100K in 1 and 220K in the other.

[sluckey]

That's not an original Fender schematic. Someone botched that. The layout is a 5E11 but the schematic is a 5F11. Look at this instead...

http://el34world.com/charts/Schematics/files/fender/Fender_vibrolux_5e11_schem.pdf

[Willabe]

Should we have Doug get rid of them to avoid further confusion?

[sluckey]

I'm not concerned. People just gotta take more notice of what they are looking at. I spotted that error in about 15 seconds. It's in big, bold type at the top of the page. That same error is in the Aspen Pittman series of schematics.

There are a lot of those schematics in the library. They are cleaned up originals and I think they have value. Whoever did that 'clean' series simply mismatched the layout and schematic when they assembled the pdf.

There are plenty of similar errors in the original Leo schematics/layouts too.

[Bugman3183]

Well, I moved all of my below board connections above  board to be sure everything is correct and replaced the 500pf cap between tone and volume. And no change in my situation.  Officially out of ideas.

[sluckey]

Did you build your own board? If so, did you use a 5E11 or 5F11 layout? You gotta match the layout to the schematic. I did not study the two layouts enough to tell if there are differences other than the component values.

It's time to show us some hi-rez pics of what you have built.

[Bugman3183]

I purchased board from did
Doug.  5e11

[sluckey]

I don't think Doug makes a 5E11 board. All I see listed is a 5F11 and the schematic/layout linked on his for sale page is correct for a 5F11.

[Bugman3183]

You are correct. 5f11 board, but I was using 5e11 layout and schematic.   The eyelet positioning is the same between the two with only a few component value changes between the layout

[sluckey]

I was hoping the boards would be the same. But according to your reply #23 you are comparing a different schematic and layout. That's causing the confusion about component values. Just forget 5E11 and use the 5F11 layout/schematic listed on the same page where you bought the board. Make sure all component values match 5F11.

I don't even remember what the original problem is with your amp but I'll bet it's a wiring error. Hang in there. Still need to see some hi-rez pics.

[Bugman3183]

Unfortunately I don't have the ability to post pictures.  Using crappy phone (no computer currently) .  Problem is the depth control acts as a master volume.  Turned to zero there's no sound from amp.  Tone control acts as speed control.  I've moved all of my below board wires above board to be sure of correct wiring.  I've replaced all of my tone stack components with new ones to eliminate the prospect of a faulty cap/resistor.  There's only three changes needed to convert to the 5f11 layout.  Two caps and one resistor (I believe).  So I'll change those and see what the results are.  Probably not until tomorrow though.  I get up extremely early for work and have been fooling with this thing all afternoon.  I'll let you guys know how it turns out tomorrow.  Thanks.

[shooter]

depth control acts as a master volume

Can you measure the "-31v" at the junction of the 2 bias R's of the 6v6s, while the meter is hooked up, adjust the depth pot and see what the bias range is.  I admit I don't know what "normal" should be, just guessing from the schem that somehow you're dialing the PA tubes to cutoff?

[sluckey]

Just took some readings and I have 370v on 6v6 plates and 140v on pin 5 with depth control all the way down, and at max it's at 154v.  Also notice the pops get faster as the depth control pot is turned.

The only way to get 140v or 154v on pin 5 would be if the coupling cap between V1B plate and the DEPTH pot is shorted either due to a faulty cap or a wiring error.

[Bugman3183]

B+ is 368v. Depth pot on zero= -41v   on max???????  My meter is just jumping around like crazy between -36 and -56v.  That's with all other pots on zero

[Bugman3183]

I'm currently getting  -45v on 6v6 pin 5

[Willabe]

That same error is in the Aspen Pittman series of schematics.

Dave Funk's book, 5E11, both the layout and the schemo match each other and are the same as the good 5E11 pair you posted the link to in Doug's library. But the 5F11 pair are messed up, 1 shows .02 the other shows .03 caps and V1b 220K plate looks like it was changed with white out and both are rewritten as 100K.   

[Willabe]

Sluckey's right, it has to be wired wrong.

Here's the best way I know how to double check a newly wired amp;

http://el34world.com/Forum/index.php?topic=17701.0

So depth pot acts as a MV, tone pot acts like a speed control, what does the speed pot do?

[Bugman3183]

Hello all,  I finished changing the components over to the 5f11 schematic values and replaced one of the signal caps on the board and now the  amp is performing perfectly.  I'd like to thank everyone for helping me get this thing up and running.  Thus far I'm very happy with it.  Very cool little amp!  Thanks again.