Princeton Build Chronology Complete and in Cab

[Ed_Chambley]

I am adding a bias vary tremolo.

Sorry,my fault Ed, that's the trem the bias/balance wont work with.

I forgot you were going with a bias-very trem.

(But sluckey's working on something that I'd bet will work.)

                             Brad      

No problem man.  I've got an amp build going and I know it is going to be cool as hell.  It is taking some time, but I have everything and have tested the dual pot on the intensity.  It works very well.  I hope when i finish wiring it up it works as well.  I am trying to build one where I do not say I wish I would have done this as well.  It will probably take me another month to finish, but when I am done I will have a Princeton with a mid and NFB, 2 10 in tweed and 2 single 12's in blond extension.  The 4 ohm will be the only Ceramic Vintage 30.  A Princeton with a vintage 30 and mid up around 14k sounds very vox like.

I have been gigging with a blackface fender twin for years when doing the country thing.  Blues is Super Reverb.  I am not a big fan of blues, but a gig is a gig. 

[Ed_Chambley]

Put power to her the first time tonight.  Since I am using a 50v bias tap, my resistor is too large 22k.  I am reading -16vdc past the diode.  What voltage should I be trying to get?   Rectifier tube only one in.  I get 417 on the plates.

I am using mini pots, 27kl and not getting any adjustment on no the screens which is pin 3 on a 7c5.  I am not familiar with these pots and I believe this where the problem is.  Should the Diode hook to the wiper the resistor hook to 3 and the cap hook to one.  This is not the way I currently have it.

Right now I have the diode to 1, the cap to 2 and the resistor to 3.  I assume you cannot swing the bias unless the wiper is receiving the bias voltage.

Everything else is checking out.  I have gotten tired so it is time for questions.  Experiment do not go well when I am tired.  This is by far the best looking build I have ever done and I do not want to muck it up.

[HotBluePlates]

The Princeton Reverb schematic shows -34v with 400v on a 6V6 screen. If I were you, I'd shoot for -35v at the mid-point of your bias pot's travel.

I am using mini pots, 27kl and not getting any adjustment on no the screens which is pin 3 on a 7c5.  I am not familiar with these pots and I believe this where the problem is.  Should the Diode hook to the wiper the resistor hook to 3 and the cap hook to one.  This is not the way I currently have it.

Right now I have the diode to 1, the cap to 2 and the resistor to 3.  I assume you cannot swing the bias unless the wiper is receiving the bias voltage.

If I read you right, your bias pot is set up like Hoffman's AB763, which is perfectly fine. At least, that's how your schematic from earlier in this thread is drawn; cap/bias output at the wiper.

I dunno why your bias voltage isn't changing when you adjust the pot. The trem circuit from your schematic drawing seems suspect: only one of the pair of 250k pots is connected to the output of the trem circuit, so only one side of your output stage would get the trem. But you might not have actually wired it that way in your amp, since you're using a dual-pot. Either way, sorting out the bias is issue #1.

[Ed_Chambley]

Looks as if I need to drop down to around 10K resistor for bias range.  That should get me much closer.  The dual intensity pot is connected to the .1 cap via 1 wire, but through both solder lugs at the pot.  There are 2 bias caps.  Each is connected to lug 1 front and back.  The 220k bias resistors are separate and connect to the wiper (lug2) of the intensity pot front and back.

Both sections of the bias are connected just past the diode using an underboard jumper.  I'll check to see if I am getting a voltage swing tonight by disconnecting the wire leading to the cap.  That should eliminate any question about the proper wiring of the pots.

What is weird is I am getting -41vdc on the screens, but cannot adjust it.  Something is amiss.  This is not possible with -16 reading at the diode.  I'll have a new look tonight.  Probably just got something tangled up as I worked on the amp about 2 or 3 hours past time to give it a break.

[Willabe]

What is weird is I am getting -41vdc on the screens, but cannot adjust it.  Something is amiss.

Screen grid should be a + voltage, close to the plates voltage and not adjustable.

The control grid, grid #1 gets the -bias.

You either have the names mixed up or it's wired up wrong at the 7C5 tubes socket.

My GE book says, pin #6 is control grid (grid #1) and pin #3 is screen grid (grid #2).


                        Brad     

[Ed_Chambley]

What is weird is I am getting -41vdc on the screens, but cannot adjust it.  Something is amiss.

Screen grid should be a + voltage, close to the plates voltage and not adjustable.

The control grid, grid #1 gets the -bias.

You either have the names mixed up or it's wired up wrong at the 7C5 tubes socket.

My GE book says, pin #6 is control grid (grid #1) and pin #3 is screen grid (grid #2).


                        Brad     

Yep, that is one of the problems.  Nothing should be hooked to screen, Correct?  Also, I have the master volume wired to the wrong side of the caps and resistors.  Tonight I am going to remove the master and change to pin6.

Another question, I have the choke connected in the B+ rail from 470 Ohm 3 watt to the next one.  Basically in-between the 2 control grid resistors.  Thinking there is some resistance in the choke should I move it up so it is connected to 1k 3w resistor then to the 470 3 watt?

[HotBluePlates]

The screen is pin 4 of your normal 6V6.

Yes, you'll need a B+ node attached to it, or you output tube will pass very, very little current.

[Ed_Chambley]

Guys, getting confusing.
7C5
1-Heater
2-P, Plate
3-G2 or Screen Grid
4-NC
5-NC
6-G or Control Grid
7-K, Cathode
8- Heater

6V6
1-NC/Glass
2-Heater
3-Plate
4-G2 or Screen Grid
5-G1 or Control Grid
6-????????
7-Heater
8-K, Cathode

Now I have what is pin 4 on a 6V6 connected to Pin 3 of the 7C5, so this is correct.  I have a 1k5 resistor inline from the OT wire and shrink wrapped and connected to Pin 2 of the 7c5, the plate.

I do not see where this is wrong as the schematic shows a connection to pin 4 of the 6V6.

Should I connect the 1k5 resistor from pin 6 to pin 2 to pickup the Control grid and then connect my lead from the OT to pin 2, the plate.

[Ed_Chambley]

What is weird is I am getting -41vdc on the screens, but cannot adjust it.  Something is amiss.

Screen grid should be a + voltage, close to the plates voltage and not adjustable.

The control grid, grid #1 gets the -bias.

You either have the names mixed up or it's wired up wrong at the 7C5 tubes socket.

My GE book says, pin #6 is control grid (grid #1) and pin #3 is screen grid (grid #2).


                        Brad     

The Schematic shows the 470 ohm resistors connected to pin 4 of the 6V6 which is the Screen Grid (G2) not the Control Grid.  The only connection of Pin 5, the control grid (G1) is when people install grid resistors.  Maybe I am reading it wrong, but pin 4 of a 6V6 is pin 3 of a 7c5.

Let me know if you agree.

[sluckey]

I have a 1k5 resistor inline from the OT wire and shrink wrapped and connected to Pin 2 of the 7c5, the plate.

Why??? The plate should only have a wire from the OT connected.

Should I connect the 1k5 resistor from pin 6 to pin 2 to pickup the Control grid and then connect my lead from the OT to pin 2, the plate.

That will destroy your tubes.

You really, really, really need to draw out what you are building, especially since you have changed to 7C5s. Maybe this simple drawing will help you unravel some of this.

[Ed_Chambley]

I have a 1k5 resistor inline from the OT wire and shrink wrapped and connected to Pin 2 of the 7c5, the plate.

Why??? The plate should only have a wire from the OT connected.

Should I connect the 1k5 resistor from pin 6 to pin 2 to pickup the Control grid and then connect my lead from the OT to pin 2, the plate.

That will destroy your tubes.

You really, really, really need to draw out what you are building, especially since you have changed to 7C5s. Maybe this simple drawing will help you unravel some of this.

I do have it drawn out.  I made some mistakes.  In your drawing you have the cathode going to ground.  I have them going back to the board to the 1 ohm resistor which is grounded.  Same thing?

[sluckey]

I do have it drawn out.

Please share with us. It's so much easier to troubleshoot when we have an accurate schematic to follow. You have deviated too much from stock PR for us to keep your changes in our heads.

In your drawing you have the cathode going to ground.  I have them going back to the board to the 1 ohm resistor which is grounded.  Same thing?

Yes

[Ed_Chambley]

Here is the layout.  I am using those bias tips on the back.  I have never used them when connecting to a board, only when I connect them to ground.  Should the wire from the ground one simply attach to the ground side and the red one connect at the cathode.

I am still learning to draw schematics, but I can do layouts.  I do not have the master on here or the nfb pot or the middle control.

[Ed_Chambley]

Schematics are confusing to me.  Like this one.  I have always seen a pot like this.  I do not have a great background in electronics, but I am reading and attempting to draw schematics, but when I see them I do not know what goes where.

I have downloaded many schematics and have actually begun understanding them some.  In time I will.

See, you guys seem to know when the zig zag is a resistor and when it is a pot.  To me they both look like resistors unless someone actually wrote out 1Ma or B1M or even 1kl or 1M pot.  I am beginning to figure it out tho.

[Ed_Chambley]

There is an error in the first upload.  I have G2 connected to pin 4 and should be pin 3.  Here it is corrected.  Have not had a chance, but I found the wiring error.

I still would like to know the best way to hook up the bias tips. I have 3 on the back of the amp.  One black and 2 red.  Should the black go to the ground side of the 1 ohm resistors and the red hook to each cathode?

Also, I have never used a small reverb tank, but I have one that requires a dwell (3 spring).  Are the larger ones better to use?

[sluckey]

I still would like to know the best way to hook up the bias tips. I have 3 on the back of the amp.  One black and 2 red.  Should the black go to the ground side of the 1 ohm resistors and the red hook to each cathode?

yes

[Ed_Chambley]

I still would like to know the best way to hook up the bias tips. I have 3 on the back of the amp.  One black and 2 red.  Should the black go to the ground side of the 1 ohm resistors and the red hook to each cathode?

yes

Thanks Huckleberry.

[fdesalvo]

Here's how I did mine - the ground is now at the PT main ground lug (thanks, Steve).

I still would like to know the best way to hook up the bias tips. I have 3 on the back of the amp.  One black and 2 red.  Should the black go to the ground side of the 1 ohm resistors and the red hook to each cathode?

[Ed_Chambley]

Here's how I did mine - the ground is now at the PT main ground lug (thanks, Steve).

I still would like to know the best way to hook up the bias tips. I have 3 on the back of the amp.  One black and 2 red.  Should the black go to the ground side of the 1 ohm resistors and the red hook to each cathode?

Very neat looking.  I like it.  Thanks.

[fdesalvo]

Thanks - I looked at a few implementations of the idea and I believe this style was from an SLO clone.  I like the orientation of the tube sockets, as well.  Made it really easy to run the heaters and the tube alignment keys point straight out back, so it's easy to change tubes by feel if you have to do it on a dark stage.

[Ed_Chambley]

I have gotten the dual bias working.  It is sort of interactive, but I expected that.  Still no problem separate voltages on the control grid.   In the Screens I have 389v and 417 on the plates.

I have a problem.  I have not spent much time with it yet, but v4b has no voltage.  All the voltages look good until this area.  Could just be a bad tube, but it get its voltage from the B+ as far as I can tell. I have 223 on the plate of 4va.  Nothing on pin 6-7-8.

I can hear pops as I check voltages so I getting close.  I will get all the voltages later today and post them.

[sluckey]

I have gotten the dual bias working.  It is sort of interactive, but I expected that.

It's interactive with what? Each other? ie, if you adjust one pot it affects the voltage on the other pot?That should not be. If it's interactive with something else, like cathode current thru the output tube, please explain.

Could just be a bad tube, but it get its voltage from the B+ as far as I can tell. I have 223 on the plate of 4va.  Nothing on pin 6-7-8.

Not likely a bad tube. More likely a wiring error or bad solder joint, or bad resistor. V4 pin 6 (plate) gets its B+ thru a 56K to the B+ rail at the junction of a 18K 3W and a filter cap in the can. Should be pretty easy to locate this problem.

BTW, you have your choke in the wrong place. The choke is meant to replace that 1K 3W resistor. Just move the left choke lead over to the right side of the 1K 3W. Then remove the 1K 3W. Be sure you have a jumper between the 1K 3W and the 18K 3W.

[Tyrannocaster]

Ed, it's looking great. I wish my stuff looked half as nice. I only get by because I can play reasonably well and it fools a lot of people into thinking the amp is good. 

[Ed_Chambley]

What I meant by interactive is they are on the same connection after the diode.  I did not split the bias tap to individual diodes.  For instance, if I turn one pot a great deal with my MM connected to the Control Grid v5 I will get a swing from about -22 to -50, bump to bump in the other pot is centered.  If I leave one pot wide open the other control grid will read about -17 fully closed.  Both fully closed are -22 and both fully open are -50.  Centered they are both around -35.

The pots are 25kl and each one will pass more current than provided by the bias tap.

I assumed this is caused by one of the pots when fully open is using enough current to cause the other to drop.  This only happens at full turn.  If you put both pots in the center and turn them oh say 20volts, the other one will not change.

With no resistor prior to the diode I get -46 vdc.  I was thinking if I use too much of that current on one pot, the other one would have to drop as there is nothing left for it.  These are only readings at the Control Grid with no load.  I put the tubes in for a very short time to darken the room and check to make sure all the tubes were heating up.  The tubes I use, like I mentioned, are very old and I only use them for checking new builds.  If I kill one, no big deal.

Would it be better to split the bias tap and individualize each bias section?  Right now I just have an underboard jumper.  It is shown on the drawing as on top.

[Ed_Chambley]

Ed, it's looking great. I wish my stuff looked half as nice. I only get by because I can play reasonably well and it fools a lot of people into thinking the amp is good. 

Funny thing, you don't even need an amp to play well.

[Ed_Chambley]

Not likely a bad tube. More likely a wiring error or bad solder joint, or bad resistor. V4 pin 6 (plate) gets its B+ thru a 56K to the B+ rail at the junction of a 18K 3W and a filter cap in the can. Should be pretty easy to locate this problem.

[/quote]
No voltage at the end of the B+, that is the problem.  I remember now that you mentioned this.  When I was taking readings of the B+ Rail I did not get a reading there and forgot to go back and recheck it.  It may be a bad resistor, but I always use steel wool on the leads and measure each before installing.  I guess that does not insure it did not go bad once current was applied. I can always use the one I remove to change the choke position.

[sluckey]

I was thinking if I use too much of that current on one pot, the other one would have to drop as there is nothing left for it.

The amount of current thru the pots is fixed. It does not change as you crank on the pots. The voltage across each pot is the same. The only thing that changes is how much voltage you pick off with the wiper to send to the tube grid.

The only thing I'd change about your bias circuit would be to add an additional filter cap. Connect it from the anode of the diode to ground. This will give you a two pole filter that will greatly decrease the 60hz component on the bias supply, making the dc voltage much smoother.

[Ed_Chambley]

I was thinking if I use too much of that current on one pot, the other one would have to drop as there is nothing left for it.

The amount of current thru the pots is fixed. It does not change as you crank on the pots. The voltage across each pot is the same. The only thing that changes is how much voltage you pick off with the wiper to send to the tube grid.

The only thing I'd change about your bias circuit would be to add an additional filter cap. Connect it from the anode of the diode to ground. This will give you a two pole filter that will greatly decrease the 60hz component on the bias supply, making the dc voltage much smoother.

What size cap?  I assume polarity consistant, negative to anode and positive to ground.  So basically it is just adding another filter stage prior to the bias circuit.  I've got some sprague 50uf/100v.  That too much?  I have many others, just not any 47uf/100's.  Never used them until this build so I only bought 2.

Question 2: What is the - voltage should I have after the diode?  With no resister at all it is a -46.  HBP said to get the Control Grid at -35 with the pots centered and that is what I have with no resistor.  Should I put a small value there as protection or will the diode suffice?

#3:  I usually do not use a 12AX7 in a tremolo circuit, normally a 12ay7.  I know fender tube chart has 7025/12ax7.  It being bias vary will will it benefit from the stronger tube?  I find with the roach, the clicking is not near as obvious with the 12ay7.  When I get it working well I have some true 7025 I will put in.  Not being familiar with the Bias Vary I was just wondering if subbing tubes causes problems or if it is the same, just preference.

Oh yea, thank you for the assistance.

[sluckey]

I've got some sprague 50uf/100v

That's fine.

Should I put a small value there as protection or will the diode suffice?

What value resistor do you have between the diode and the PT?

I have some true 7025 I will put in

I wouldn't waste a true 7025 on a trem oscillator or PI.

[Ed_Chambley]

I've got some sprague 50uf/100v

That's fine.

Should I put a small value there as protection or will the diode suffice?

What value resistor do you have between the diode and the PT?

I have no resistor.  I have clamps to stub different one in. The pt is direct to the diode.  I am at -46, but with the bias trim pots centered I have -35 on the Control grid of the tubes.  That's what I was asking. should I put something like an 18 ohm, 1 watt.  It seems as tho what the bias tap and the combination of the bias circuit is sufficient to get a good bias adjustment swing.  I am not certain.  I guess I will do the usual and hook up my meter once I get proper voltages and watch the bias.  if it climbs too high, turn it off and raise the resistor value or vice-visa. 

That is why I asked what the voltage should be just past the diode.

[sluckey]

You're feeding the diode from a low voltage bias tap, right? Put a 470Ω 1W between the PT and diode just like fender did on their AB763s. And put the cap in that I recommended. Now with no tubes in, recheck the bias voltage swing on the output tube grids. What do you have?

[Ed_Chambley]

It is jumping around.  Turn the speed know all the way up the swing is -17 to -60 which seems pretty good.  Something wired wrong with the tremolo.

[sluckey]

It is jumping around.  Turn the speed know all the way up the swing is -17 to -60 which seems pretty good.  Something wired wrong with the tremolo.

That's what bias vary trem does.

Now, pull the trem tube Vee4 and repeat the bias voltage test. What's the range?

[Ed_Chambley]

The tube was not in it.  The only tube in it is the rectifier. I took some voltage readings earlier and found some things that seemed strange.  I figure I \'ll give them to you.
v1
1-203
2-0
3-1.34
6-202
7-0
8-1.41

v2
1-409
2-.013
3-7.77
6-409
7-.013
8-7.77

v3
1-287
2-0
3-0
6-297
7-0
8-0

v4
Speed knob all the way up 1-240
Speed know on o jumps
2-jumps vary small voltage and the voltage is negative when speed know turned up -1.33
3-.7 stable with speed know all the way up
6-297
7-0
8-0

v5
2-417
3-417
6- Negative 35

V6 Same

At this point I did not have the additional cap.  Had an 18 ohm, 3 watt resistor between the pt and diode.

Had the bias on both power tubes at 25ma bias with the plates at 417.

I know there is something going on, so I pulled the tubes and began reviewing the wiring.

Where it sits now is where you last said.  Additional cap. no tubes except rectifier.  It seems the speed pot is working backwards.  I would think the higher your turn it the more the bias jumps.

[sluckey]

In that case, you have some major wiring issues.

[Ed_Chambley]

Just finished retracing.  Nothing.  I was hoping to find a wire or 3 wrong.  No such luck.  I have the 3meg pot.  It should be reverse which means it should read 3 meg off and go to zero as you increase.  It does..  The resistor changes it some, but that is the general idea.  Correct?

The only things I have done different is I added a wire from the bass lug repacing the 6k8 resistor with a pot.  Wire to left lug and 3k3 resistor to ground.  I bypassed the NFB resistor and connected it to a wiper of a pot 10kl then to the high tap on the ot.  That is the only things which are not wired the same.

When I removed the crossline MV should I have separated the bias resistors from the .1 cap?   Sort of at a loss here.  I have made many wiring errors, but thoroughly checking them I always find them.  One at a time, mark the sheet and wire.  I have 6 different color sharpies on this amps wiring and 6 marked up sheets.

I made one bad mistake right at the beginning.  I connected the end of the B+ to the ground leading to the inputs and through the pot bus.  That is why I had no voltage on v4b. but I have checked all the parts and they seem fine.  I guess I am going to have to disassemble and begin again checking each part, but the only parts that got the B+ were input jacks and pots and they check out.

What else could have happened? 

[John]

I made one bad mistake right at the beginning.  I connected the end of the B+ to the ground leading to the inputs and through the pot bus.  That is why I had no voltage on v4b. but I have checked all the parts and they seem fine.  I guess I am going to have to disassemble and begin again checking each part, but the only parts that got the B+ were input jacks and pots and they check out.

No e-caps anywhere in that path?

Also on your voltage readings (I'm not looking at the schem so forgive me if this sounds stupid) your V2 voltages are much higher than V3. Doesn't seem right?

[sluckey]

your V2 voltages are much higher than V3. Doesn't seem right?

V2 is the reverb driver. It's voltages should be much higher than V3 voltages. However, V3 pins 3 and 8 should have similar voltages to V1 pins 3 and 8. Zero on those pins indicates a problem.

I connected the end of the B+ to the ground leading to the inputs and through the pot bus.  That is why I had no voltage on v4b.

OK, so what are V4 voltages now? Are the bias pots still working OK and giving a good range of bias voltage to the output tube grids?

EDIT... added the below comment...

When I removed the crossline MV should I have separated the bias resistors from the .1 cap?   Sort of at a loss here. 

No. That's how the negative bias voltage gets to the output tubes' grids. The crossline mv had to be removed. You went to a lot of effort to separate the grids for dual bias. That crossline would have just tied them back together.

[John]

V2 is the reverb driver. It's voltages should be much higher than V3 voltages.

''

So am I forgiven? 

[Ed_Chambley]

V2 is the reverb driver. It's voltages should be much higher than V3 voltages.

''

So am I forgiven? 

Man, I forgive you.  I appreciate you being involved.  I am going crazy with this.

[sluckey]

None needed. Now go to the board and write 100 times, "I will look at the schematic." 

[Ed_Chambley]

your V2 voltages are much higher than V3. Doesn't seem right?

V2 is the reverb driver. It's voltages should be much higher than V3 voltages. However, V3 pins 3 and 8 should have similar voltages to V1 pins 3 and 8. Zero on those pins indicates a problem.

I connected the end of the B+ to the ground leading to the inputs and through the pot bus.  That is why I had no voltage on v4b.

OK, so what are V4 voltages now? Are the bias pots still working OK and giving a good range of bias voltage to the output tube grids?

EDIT... added the below comment...

When I removed the crossline MV should I have separated the bias resistors from the .1 cap?   Sort of at a loss here. 

No. That's how the negative bias voltage gets to the output tubes' grids. The crossline mv had to be removed. You went to a lot of effort to separate the grids for dual bias. That crossline would have just tied them back together.

Ok Steve, those readings were taken after I correct the ground issue.  Here is the way it went.  I had no voltages on v4b and knew I had a wiring issue.  Flipped on the amp to take readings.  B+ rail seemed low as I moved from lug to lug.  When I reached the last one it was 0 after the 18k resistor, before it it was 190.  I touched the resistor and it was fire hot. Bam, here is the problem.  Looked and said shit because I saw the ground bus connected.  Pulled the plug.  Clipped the wire and connected it where it should be.
Pulled the resistor, checked out.  Back in rechecked wiring again completely.  Found one error on v2.  Cross wire not connected, one of them.
Then I put an 18ohm 3 watt resistor between the Bias tap lead and diode.  At this point I had not done any of the things you suggested about the bias, I had just moved the choke.  Got steady reading at the control grid, but only with the speed know wide open.  This is when I took the readings.  Since these readings I put in the added filter cap, negative from anode to positive ground.  Put in 470ohm.

Now to your current question.  I cannot get the bias pots to work independant.  Turning one changes the negative value on BOTH Control grids.  With the speed knob at 0 it just jumps so much you cannot even see a reading.  If you turn it up all the way the Control grid will stabilize. Either pot you turn will change the negative reading of the control grid.  I have checked the continuity of the under-board wiring and it checks out.

Also, those voltage reading are with tube out.  Even preamp tubes.
  

[Ed_Chambley]

Since the pots were in the path, I checked them.  They seem ok, but I think I need to remove the wires from them.  Since they interact with each other I do not know for sure if they are ok, but they all sweep.  I have a 1 meg resistor at the inputs and shielded wire grounded and the input jacks with 68k resistor and a 33k on a switch for input 2.  That was in the path and I have not checked these as the bias issue seems priority.

The 250 Dual Intensity pot only reads half that at full turn, but it is grounded differently and not in direct line with the ground bus.  Grounding the B+ has to effect everything.  It seems as tho the speed pot is not reverse, but all the way off I get a reading of 3M3.

I am frustrated and very close to pulling the board and taking it to my table saw and cutting off the second bias.  Put octal sockets in and 6v6's, but it should work.  I was very meticulous with everything.  All vishay 1 watt metal resistors.  Teflon wire. Sozo blue caps.  Took my time and double checking along the way.  I could understand it if I had never done this before.

All I know is at one point the bias section was stable.  Now it is not and I cannot see how grounding the B+ can affect the bias caps.

[John]

If your bias did work before you grounded the B+, something in there must have gotten messed up. I have yet to mess with the fixed bias, but what I would try is clipping in a fresh e-cap at the bias pots. Also, Tubenit just said something about he had a brand new resistor with the lead broken just inside the ceramic part, took him weeks to find it. I'm thinking that the juice to the ground buss may have broken a lead somewhere and is making it funky? I dunno, trouble shooting isn't my strong suit, but I have found plenty of errors (cause I've made plenty) with a chopstick and meter. I keep whacking on things till something goes zzzt. 

[Willabe]

I am frustrated and very close to pulling the board and taking it to my table saw and cutting off the second bias.  Put octal sockets in and 6v6's

NO, don't you do that.   

Come on Ed, slow down a little, you'll find it.

Divide and conqure as the guys say.



                              Brad     

[Ed_Chambley]

If your bias did work before you grounded the B+, something in there must have gotten messed up. I have yet to mess with the fixed bias, but what I would try is clipping in a fresh e-cap at the bias pots. Also, Tubenit just said something about he had a brand new resistor with the lead broken just inside the ceramic part, took him weeks to find it. I'm thinking that the juice to the ground buss may have broken a lead somewhere and is making it funky? I dunno, trouble shooting isn't my strong suit, but I have found plenty of errors (cause I've made plenty) with a chopstick and meter. I keep whacking on things till something goes zzzt. 

The B+ was grounded from the beginning.  At one time the bias worked, but the amp never has.  I haven't gotten there yet.  I never install a part before checking it.  Mainly because with resistors I cannot see the stripes.

The problem here is I am building something I have never seen and I have never had a bias vary tremolo build.   You are correct in the part department tho.  Steve is great at zeroing in on a particular section and he has helped me many times to locate the problem area.

The most frustrating part of this is I have really put my heart and soul in this build.  I cut no corners and used the best parts.  Made the chassis and had it chromed, cabinet, 2 smaller cabinets for extensions.  It is really a work of art as I have never put so much effort into a build.  Then to make such a stupid mistake.  As soon as I put my meter on 4vb plate and had noting I turned everything off and walked away to calm down.  Waited a day and looked into the chassis and saw what I had done.  I still cannot believe I did it.  All the main parts, the expensive ones are fine.  I am just deciding now if it is worth finishing it as planned or pull the board and make it like Binwitt did.

Just feeling a little beat up right now.  I have no doubt I will get it going, but if not for such a stupid mistake I would be plaing it instead of writing about it.

[Ed_Chambley]

I am frustrated and very close to pulling the board and taking it to my table saw and cutting off the second bias.  Put octal sockets in and 6v6's

NO, don't you do that.    

Come on Ed, slow down a little, you'll find it.

Divide and conqure as the guys say.



                              Brad    

Thanks Brad, you don't know how much help you guys are.  Maybe I will get out the tele and play some through my Bassman.  That always helps when I feeling down.  I just can't believe I grounded the B+

[Willabe]

Sounds like a good idea.    


                      Brad        

[Willabe]

I turned everything off and walked away to calm down.  Waited a day and looked into the chassis and saw what I had done.  I still cannot believe I did it.  All the main parts, the expensive ones are fine.  I am just deciding now if it is worth finishing it as planned or pull the board and make it like Binwitt did.

Like you said, no expensive parts burned up. It was a mistake and we all make mistakes.   

Main thing is you didn't get hurt.     

When my trem wouldn't wiggle, I gave my self a little time to think about and then went back in and got it working.



                              Brad       

[John]

I would keep track of the stupid things I do, but it's embarrassing. 

What helps me a lot when I've got a problem like this is to let it be for a couple days, sometimes most of a week. Work usually makes that easy to do anyway. And at some point, the way becomes clear. I almost guarantee you if you take a break from staring at it for a while, something will occur to you to check and that'll be it. And for sure, if you've done the layout etc, no reason to tear it down. There's simply a faulty part somewhere or a wire that's not going where you're absolutely positively sure it is (ask me how I know) and you'll find it without destroying all your hard work.