Anyone have example of dumble type OD on to tweed 5F6A-part II

[adamG]

Hi Guys,

http://el34world.com/Forum/index.php?topic=9968.msg90850

Above topic was posted in 2010, but as you can see, someone has been inclined to buit it...that is me
Normal and Bright channels are beautiful, but  there's a problem to fire up the distortion one.
When I activate it by the footswitch I can hear a big hum with the very quiet guitar audio sound ,but there's no any distortion.
I wonder ,whether it is the proper point of cathode signal tone stack ,to get enough portion of the overdrive?!
Usually ,the clean signal is taken from the anode through a cap into the gain stage.
Anyway ,I deeply ask for some assistance? It is a pity to leave that great amp in present state.   
If it is necessary ,I'll put another info.
Another story is Reverb, but I'll take care of it later on. For now, distortion is the main thing.
Any suggestions will be very appreciated?

Thanks in advance.

Regards,

adamG

[jojokeo]

That's a very clean BUT tight build there Adam. Looks terrific, yet beauty means nothing if there's something that doesn't work as it should. I've seen this case many many times. Your hum/quiet signal issue sounds like you have a ground, solder contact issue, wrong/mislabeled part, or other initially but it could also be a grid return resistor or just a complete mis-wiring of a relay or wiring going to/from it? Really hard to pin down when not in front of a person w/ no schematic and limited pictures to see. BTW, love those good ol' Tung-Sol 5881s!

[tubenit]

Don't know if you have seen the D'Mars ODS?

With respect, Tubenit

[tubenit]

Is this what you are building?  IF so,  compare it to the D'Mars.

with respect, Tubenit

[adamG]

That's a very clean BUT tight build there Adam. Looks terrific, yet beauty means nothing if there's something that doesn't work as it should. I've seen this case many many times. Your hum/quiet signal issue sounds like you have a ground, solder contact issue, wrong/mislabeled part, or other initially but it could also be a grid return resistor or just a complete mis-wiring of a relay or wiring going to/from it? Really hard to pin down when not in front of a person w/ no schematic and limited pictures to see. BTW, love those good ol' Tung-Sol 5881s!

Yes, that's tight build, but you should see my previous one-Tweed Twin. That chassis' space is veery restricted.
Till now I'm quite sure I haven't made such mistake as cold solder, wrong part,etc.There's a couple elements only, that I checked two,three times. But after some resting time, I'll go back to check again. After all ,it might be a idiot mistake;)
I agree, Tung-Sol 5881s are really good.   
I consider to record the hum I mentioned. I must finalize that amp.

Thank you.

Regards,

Adam

[adamG]

Is this what you are building?  IF so,  compare it to the D'Mars.

with respect, Tubenit

Hi Tubenit,

Yes ,this one " Bassman & Dumblish" I've been following.
The thing is I've build it already, therefore what can I change now? I wouldn't like to rip everything I've done.
Could you suggest me what I've made wrong or what other possibility I have or what kind of info you would need to assist?
Big thanks for your concern.

Regards,

adam

[adamG]

Is this what you are building?  IF so,  compare it to the D'Mars.

with respect, Tubenit

...Actually, I followed two of schematics.
The idea of only two inputs I took from "Bassman & Reverb" and gain stage from "Bassman & Dumblish".   

Regards,

adam

[tubenit]

Please don't gut it and start over.  IF the clean channel is good, then the OD channel is the issue.  Let's get the OD sounding good also.

What we need to do is eliminate different aspects of the amp to narrow down the problem area.

1) I want you to change the 220uf on the clean channel to a 2.2uf to 10uf value, please.

2) Then you need to bypass the switching completely and go from the clean into the OD into the LTPI phase invertor. (IF you
     know how to do this safely, you can simply use insulated alligator clipped wiring.)

3) (IF possible change out the OD drive from a 1M to a 50ka to 100ka.)

Then report back the results.  Main thing is to do steps #1 & #2.   The amp should sound good on the OD channel also and not have a hum and low distortion.

IF bypassing the switching does not eliminate the problem, then you have a bad solder joint or something miswired on the OD channel. IF bypassing the switching resolves the issue, then it's your switching/relay

With respect, Tubenit

[adamG]

Please don't gut it and start over.  IF the clean channel is good, then the OD channel is the issue.  Let's get the OD sounding good also.

What we need to do is eliminate different aspects of the amp to narrow down the problem area.

1) I want you to change the 220uf on the clean channel to a 2.2uf to 10uf value, please.

2) Then you need to bypass the switching completely and go from the clean into the OD into the LTPI phase invertor. (IF you
     know how to do this safely, you can simply use insulated alligator clipped wiring.)

3) (IF possible change out the OD drive from a 1M to a 50ka to 100ka.)

With respect, Tubenit

Tubenit,

I'm gonna do what you suggest.
Actually ,regarding the inputs issue of two sockets only (my buid), I followed the below layout - Bassman & Reverb.
Therefore, shall I change individual cathodes caps pin3 and pin8 for common 5uF? Of course, I'll change them ,if necessary.
I believe the relay/switching mode is ok. I measured its coil voltage, contacts changing over. They're quite ok.
Anyway, I also thought to myself to provide the bypass switching before.I did it with same ham as initially, unfortunately.
I also changed pot.1MA for 250kb, with no success, but now I'm gonna be comply with your instructions of cathode cap and 100kA pot.
I'll report you;)

Big thanks!

Regards,

adam

[tubenit]

there's a problem to fire up the distortion one.  When I activate it by the footswitch I can hear a big hum with the very quiet guitar audio sound ,but there's no any distortion.

One can have a relay that does switch and has the correct voltage and that relay can still induce a significant amount of hum.  I have had that happen!  That is the reason I suggested bypassing the relay switch as illustrated in the previous schematic about trouble shooting.

Is your jack for the footswitch isolated from the chassis?

Lowering the cathode cap value on the clean channel will simply allow the OD channel to sound smoother & less distorted but probably will not
lower the hum.

On the layout you followed, there needs to be a 220k to 330k range resistor from the side terminal of the reverb pot going to the other side of the 100k resistor into the LTPI.

It might help if you had a photo directly over the layout board. Maybe we could see something amiss with that? 

It would be even more helpful if you could post the EXACT layout that you are using.  Not something similar to what you are using but the exact layout.

With respect, Tubenit

[tubenit]

Adam,

You done a VERY nice looking build. It looks very professionally done and I think you can get this to work and sound great.  You will have to eliminate areas around the OD section to pinpoint the exact area of the problem.

I hope this will encourage you.  My Tweed BluezMeister wiring is a total mess and I am using 3 relays, ...... AND it is quieter then the original Princeton Reverb I owned.  It is very cramped also similar to yours.  Yet, it is amazing quiet.  No hum issues. The amp sounds beautiful to me and I love it.

So, IF my amp works well .............. then there is NO reason your amp should not work and sound great  and perhaps even better then mine. 

With respect, Tubenit

[tubenit]

IF you are NOT able to resolve the issue doing other things, I hope you will try bypassing the switching.  IF that doesn't resolve it, then try bypassing the second gain stage of the OD, then try bypassing the first gain stage of the OD. 

One of those should reveal where the problem lies.

With respect, Tubenit

[adamG]

IF you are NOT able to resolve the issue doing other things, I hope you will try bypassing the switching.  IF that doesn't resolve it, then try bypassing the second gain stage of the OD, then try bypassing the first gain stage of the OD. 

One of those should reveal where the problem lies.

With respect, Tubenit

Hi Tubenit,

I'd like to thank you very ,very much.
I am affraid I do not have good news. Perhaps I've been making a idiot mistake.
None of above solutions solved my problem.
You suggested to present the layout I followed. There's no completed one. I adopted a couple ideas. Eyelet board was made with cad soft. Bias and invertor sections were adopted from...i can not mention the company name;) You'll figure out. Additional power sec "D" is also added, after the "C" cap.
On attached photos now, you can easly see what I did.
Today I recorded the sound of the amp with the signal runing through OD stage.
May I send it to you by PM?

Once more, big thanks my friend. You're the good man.

Regards,

adam

[adamG]

...tomorrow I'll take some photos of the amp internals and put them here.

adam

[jojokeo]

I recognize a cereal tone when I see one 
Adam - one suggestion: never take shortcuts and build circuits on the fly or copy others work without confirmation that it's proven/verified good. Or else you will be the victim sooner or later of a lot of wasted time, money, and/or frustration. I personally don't enjoy wasting any of those. The other thing is that it's best practice to work from a schematic and then a layout. Doing things on the fly is the quickest way to failure. Then you are rolling the dice if what you did will work or not at the expense of a smoke and fireworks show. Lastly, how do you tweak or troubleshoot it afterwards in any constructive and meaningful way?

[tubenit]

I am affraid I do not have good news. Perhaps I've been making a idiot mistake.  None of above solutions solved my problem.

Let me make sure I am understanding you correctly?

1)  The clean channel sounds beautiful and you like it?   Correct?

2)  You bypassed the switch and went straight from the clean to the OD to the LTPI & the problem still existed?  Correct?

3)  You bypassed the switch and went into the first stage of the OD, bypassed the 2nd stage of the OD and the problem still existed?  Correct?

4)  You bypassed the switch and went into the 2nd stage of the OD, bypassing the 1st stage of the OD and the problem still existed? 
     Correct?

5) The clean channel sounds good using the relay switching AND bypassing the switch?  Correct?  * see schematic

Please confirm that all of the above are correct? !!    IF you did not do one of those in your trouble shooting, please state what trouble shooting effort you skipped?

One of those should have narrowed the area of the problem in the OD area IF you are always bypassing the relay switch in the trouble shooting?   

What exactly did you experience and hear when you bypassed those stages? 

With respect, Tubenit

[tubenit]

There is nothing that stands out to me regarding the layout or layout board that you posted.  I don't see any obvious errors.  I don't see anything in that layout that would concern me for causing a hum.

I am very puzzled why the bypassing OD stages and bypassing the switch did NOT pinpoint where the problem is?  That doesn't make sense to me unless you have a problem on both gain stages of the OD section which seems to be unlikely?

You're positive that you bypassed the relay switching each time? And that you bypassed the first gain stage of the OD and then bypassed the second gain stage of the OD?

You've tried different OD tubes correct?  Have you swapped a known good tube into the OD section?

I am not saying you should do this, but I probably would personally go straight from an input jack into the OD section into the LTPI and see what that sounds like?  If that doesn't sound right  BUT the clean channel into the LTPI sounds right that further pinpoints the problem as being in the OD section somewhere OR in the switching.

with respect, Tubenit

[jojokeo]

With what little I could see and make out of your only blurry gutshot photo I circled a few things that catch my eye that gives cause for concern. With the relay, it looks really close to those parts it's almost sitting on top of and there's contacts underneath it.
 

[adamG]

Let me make sure I am understanding you correctly?

1)  The clean channel sounds beautiful and you like it?   Correct?
Yes, clean channels sound great, of course when I activate them by direct connection into PI.

2)  You bypassed the switch and went straight from the clean to the OD to the LTPI & the problem still existed?  Correct?
Yes, problem still exists.
                       
3)  You bypassed the switch and went into the first stage of the OD, bypassed the 2nd stage of the OD and the problem still existed?  Correct?

Acc.to trouble shootin#2 - no sound at all.

4)  You bypassed the switch and went into the 2nd stage of the OD, bypassing the 1st stage of the OD and the problem still existed? 
     Correct?
trouble shooting#3 - initial problem went back.

5) The clean channel sounds good using the relay switching AND bypassing the switch?  Correct?  * see schematic
Yes,that's correct.I both mods of relay swithing and bypassing, clean channels sounds great without problems.

What exactly did you experience and hear when you bypassed those stages? 
As written above,trouble shooting#2 - no sound ,trouble shooting#3 - "clean" sound appears back on low/"normal" level with some portion of hum.

I can send you recorded files, may I?

Thank you very much for this rescue action;)

Regards,

adam

[adamG]

With what little I could see and make out of your only blurry gutshot photo I circled a few things that catch my eye that gives cause for concern. With the relay, it looks really close to those parts it's almost sitting on top of and there's contacts underneath it.

Yes, your're right.Relay board is almost sitting on top of two resistors underneath, but is it a real problem of missing OD sound from OD stage?

Yesterday, I took several photos. Would you have a look on ,if I post them?

Thank you for your assistance;)

Regards,

adam

[adamG]

You're positive that you bypassed the relay switching each time? And that you bypassed the first gain stage of the OD and then bypassed the second gain stage of the OD?
Yes,I am positive. Everything you suggested me to follow on, I've made very carefully. So, my mind tells me that I haven't made any mistake;)

You've tried different OD tubes correct?  Have you swapped a known good tube into the OD section?
Of course, I swapped other tubes.

I am not saying you should do this, but I probably would personally go straight from an input jack into the OD section into the LTPI and see what that sounds like?  If that doesn't sound right  BUT the clean channel into the LTPI sounds right that further pinpoints the problem as being in the OD section somewhere OR in the switching.
Today I'll try reconecting imputs ,as you put that on trouble shooting#5

I wonder, maybe I shall provide sreened cable from and into gane stage,also? I mean that one from Treble pot into gain stage and the going into PI?
--
Maybe there's a problem with voltage aplied into G.S. plates? I measured that on pin 1 it is 150V, on pin 6 - 174V.O cathode pin 3 - 1,96V, pin 8 - 1,55V. Should the voltages be same ?I mean that Plates same and cathodic also same?
Hum might be accessory issue but "missing" OD is strange thing ,even to as newbie;)

Big thanks T.;), very much!

Regards,

adam

[adamG]

I recognize a cereal tone when I see one 
Adam - one suggestion: never take shortcuts and build circuits on the fly or copy others work without confirmation that it's proven/verified good.

I'd like to be such smart and successful in every case I challange. In this issue of my Bassman Plus nobody has buit it before but the temptation to me was huge;)

Or else you will be the victim sooner or later of a lot of wasted time, money, and/or frustration. I personally don't enjoy wasting any of those. The other thing is that it's best practice to work from a schematic and then a layout. Doing things on the fly is the quickest way to failure. Then you are rolling the dice if what you did will work or not at the expense of a smoke and fireworks show. Lastly, how do you tweak or troubleshoot it afterwards in any constructive and meaningful way?

You see, my activity on tube amps is a kind of journey into my far past. A couple decates ago, when I was young man, such hobby was absolutely impossible. The reason was that there was nothing to purchase in stores ,together with no schematic, with no layouts,etc. At that time I only could dream about Dumbles and Marshalls. Today, I'm not a guitar player any more ,but the passion for music, for tube amps remained......

Regards,

adam

[tubenit]

3)  You bypassed the switch and went into the first stage of the OD, bypassed the 2nd stage of the OD and the problem still existed?  Correct? Acc.to trouble shootin#2 - no sound at all.

Adam,

I am understanding "no sound at all" to be different then "  a big hum with the very quiet guitar audio sound ,but there's no any distortion"?

IF I am understanding you  correctly, you are saying that when you bypassed the 2nd stage of the OD but sent a signal into the first gain stage of the OD, then you had NO sound at all?   ( not sure what "Acc. to trouble shooting #2" means?)

IF that is correct, then I would look for the main problem being somewhere in the first gain stage area of the OD.  Measure voltages, check continuity of all your wiring, "chopstick" the area, triple check wiring to pots, make sure there is not a loose ground  wire from shielded wiring that is sending the signal directly to ground, ....... etc.......

The voltages on the OD tube are reasonably OK, correct?   And check the wiring right at the OD tube socket to make sure there is not a loose wire from one pin touching another pin.

Given that the clean into the LTPI works just fine, then we know "the" problem is specifically in the OD area. The main concern is to figure out what section of the OD is the main problem.  Is it the relay switching?  Is it the first gain stage?  Is it the second gain stage, is it a potentiometer problem and so on.   

I would personally continue to bypass small sections of the OD until I pinpoint the exact area.

I am suspicious that something is wired incorrectly or you have a bad potentiometer or that the signal is being sent to ground somehow or that a pot is not appropriately grounded or something like that is going on.

Can you post a sound sample on sound cloud or sound click or something like that & provide a link?  Do you have easy access to be able to do that?  I am not that great in diagnosing problems from hearing a sound clip but maybe one of the other guys on the forum could?

with respect, Tubenit

[tubenit]

After checking wiring, continuity, chopsticking, etc ...................  IF you have not located the exact area of the problem, then I would continue to bypass areas in the OD wherever you can to narrow your search and find the exact area of the problem.

There is just not much in the OD section, so I think you will find the problem and correct it.  I am understanding that the reverb is not being used when you are playing thru the clean section and it sounds good.

Let's make sure you are getting a good OD signal through first & then we can look more at reducing hum in the OD section.

Tubenit

[jojokeo]

Adam, can you post a few more pictures? Use the "macro" setting on your camera so that the close-ups are clear to see.

[adamG]

You're positive that you bypassed the relay switching each time? And that you bypassed the first gain stage of the OD and then bypassed the second gain stage of the OD?

You've tried different OD tubes correct?  Have you swapped a known good tube into the OD section?

I am not saying you should do this, but I probably would personally go straight from an input jack into the OD section into the LTPI and see what that sounds like?  If that doesn't sound right  BUT the clean channel into the LTPI sounds right that further pinpoints the problem as being in the OD section somewhere OR in the switching.

with respect, Tubenit

There's something positive;)
Today I followed your Trouble shooting #4.OD sound appered ,but with huge OD signal.It is too high, because after a moment of pure OD signal , cranch and clatter appers.
I turned off the amp, pulled out the tube and put it back into socket and swithed the power on. The amp responded same with cranch and clatter, after the while.
I returned to the initial state ,which is preamp reconnected back, but without the trim pot. With the Trim there's huge hum with weak guitar signal. Now, there's tone stack, Level and Drive together with "garbage",as above mentioned.
BTW, relay has been removed temporarily, for the purpose of reduction potential source of hum.
How to balance signals? How to make the whole amp normally working without "exciting" fireworks?;)
Your today's posts I'll read tomorrow morning. For now ,it's time to go to bed;)

Thank you very much!

Regards,

adam

[tubenit]

There's something positive;)   Today I followed your Trouble shooting #4.OD sound appered ,but with huge OD signal.

Reading your description, I am thinking that is some possibility that your tube socket may be bad??   IF you can get someone to strum a guitar while you place your finger on the top of the OD tube carefully and wiggle it ..................... does that produce a strong OD tone at all even if momentary?

IF wiggling the tube in the socket playing a guitar creates an OD signal,  first check your wiring and if it looks OK, then replace the tube socket or retension the tube socket springs.  I would personally just replace the tube.

IF the tube socket is not the problem then bypass the OD trim pot using a 27k resistor to ground as illustrated and then report back, please.

You will get this issue resolved!  The quality of your build looks quite good from the pictures & you have easily followed some trouble shooting guidelines .................. so you are smart enough to conquer this problem and get the amp working just fine.

With respect, Tubenit

 

[tubenit]

OK,  let's say you have replaced the tube socket for the OD or at least ruled it out.

AND,  removing the trim pot into the OD and using the 27k resistor to ground did not resolve the issue either.

I am thinking on of those above will resolve the issue and you will have OD sound.

Then I would try going from the input jack straight into the 2nd gain stage of the OD.  IF that works then the problem is the first OD gain stage area.   troubleshooting #6  attempt

IF that doesn't work then I would go from the input jack into the first OD gain stage, then bypass the 2nd OD gain stage into the LTPI.  IF that works, then the 2nd gain stage is probably the issue.  trouble shooting #7 attempt

With respect, Tubenit

[adamG]

I am thinking on of those above will resolve the issue and you will have OD sound.

Then I would try going from the input jack straight into the 2nd gain stage of the OD.  IF that works then the problem is the first OD gain stage area.   troubleshooting #6  attempt

IF that doesn't work then I would go from the input jack into the first OD gain stage, then bypass the 2nd OD gain stage into the LTPI.  IF that works, then the 2nd gain stage is probably the issue.  trouble shooting #7 attempt

With respect, Tubenit

The socket is changed. I just did it to be sure that future noise would not com.
Now the report....following trouble shooting #7 - no OD sound,only clean with some noises.  I've nocited a big hum when pin 2 is touched by wooden bolt. That is strange because there's no such on pin 7?! Trim pot reacts like a volume one.So, the first OD stage doesn't work at all,I think.

Following trouble shooting #6 -  there's very low OD level sound. Drive and Level pots adjusted on full.
In both cases I aplied extra resistor 68K ,as you instructed.
You know, making decision of building this amp I was a little skeptical, sensing minor problems. I mention that because on previous three builds I was almost sure I had been successful. And that was success after all.
The low of attraction;)     

My friend, you might be tired of following me? ;)
What now?

Thank you very ,very much!

Regards,

adam

P.S. Could it be a issue I layed down power wires into supply points A,B.C together with the others(pot's wires,ground ones), bunch underneath pots?

[tubenit]

I think you have narrowed it down to the first gain stage of the OD section.  Double and triple check every connection for continuity, check to make sure the trim pot is grounded,  check  to make sure any shielded wiring is not grounding the inner signal wire to ground.

I think you have also narrowed this down to the grid pin 2 given the hum when touching pin 2 .   CHECK every thing from the clean channel treble pot to the grid pin 2 of the OD first gain stage.  Maybe something under the layout board is shorting down to the chassis and sending signal straight to ground?  There has to be a wiring error somewhere between the treble pot to the OD tube on pin 2.

Check the heater wire voltages on the OD tube.  They're probably fine but just make sure they are.

As bizarre as it may be,  I wonder if the new socket that you put in has a problem also?

I once had a problem where inside a brand new resistor the wire had broken but you couldn't see it when I checked continuity cause it showed continuity.  I eventually discovered it was bad when I tugged on both legs of that resistor and saw some wire move.  Maybe something like that is going on? 

I think you will find the problem.  You are intelligent and you did a very neat build.  The problem is a wiring one I think and it's up to you to find it.

It would be helpful at this point if you posted some chassis interior layout board photos for us to look at.

With respect, Tubenit

[jojokeo]

The problem is a wiring one I think and it's up to you to find it.

It would be helpful at this point if you posted some chassis interior layout board photos for us to look at.

Exactly. He may not even know not to ground both sides of a shielded cable? Or re-wired the new pot incorrectly, just like the old one could've been? W/out photos I'm surprised you got this far.

[adamG]

I think you have narrowed it down to the first gain stage of the OD section. 

Hi Tubenit,

I needed amount of time to rest from Bassman.
Today ,I came back and found reasons of two faults. First,which might be painful is that the power tubes are not ok.I just swapped Tung-Sol 5881 for a couple of NOS Russian ones and...noises stopped. 
Second "discovery" is that the trim pot was out of order.
Here is the present situation with gain issue. I came back to initial state of the whole assembly, with switchable possibility. Relay works ok.Overal signal level going through OD stage is huge with the weak OD sound! I changed drive pot stepping 100KA, then 250KB and finally 500KA. With all of three pots adjusted on maximum, there's some but not sufficiently gained signal but as said ,the overal signal level is almost as 100% of power;).
I also swapped level pot for 250KB to improve OD signal. There is some score but as said, the overal signal...
Can you explain me the major idea of OD circuit in this particular issue, please? Maybe is it necessary to change the whole OD circuit elements' values?
I'm "blind", I'm afraid;)   

One general impression of my own is that The Fender amps of Tweed era have small hum problems/issues derived from the power supply. Tube rectifier and small capacity filtering cap,right?

Thanks in advance!

Best regards,

adam

[tubenit]

Adam,   

In reply #2 of this thread,  I posted a schematic of a D'Mars ODS.  It is NOT much different then your Bassman with an OD circuit.

On my D'Mars,  I can get the OD channel MUCH louder than the clean channel. Additional gain stages increase the potential of gain/volume.

When an amplifier is wired correctly,  the additional gain stages (such as the two OD gain stages) add much more gain and volume.  Something is wired incorrectly around the OD section.  IF the clean channel sounds great then there is no reason for the OD channel to not be working IF it is wired  correctly.

With respect,  Tubenit

[tubenit]

You have never posted a schematic in this thread that is an accurate representation of what your amp is.  I have posted numerous schematics as illustrations to you.

In order to help you any further, you will need to either post a schematic that is a completely EXACT representation of what you are using AND/OR post more detailed photos above the layout board and chassis area.

If I were there with you, I am confident I could trouble shoot this and make this work for you.  However, not being there & not having a true schematic and more accurate pictures ............. I am only guessing what could be wrong?

IF it were wired correctly, I don't see any reason why it would not work?   My D'Mars amps have all worked and they are similar.

Please hear this respectfully as I intend it to be this way.  I am cheering for you and wanting your amp to work and sound good to you.
I want you to be successful with this and believe it is possible to achieve.

Best regards and with respect, Tubenit

[adamG]

You have never posted a schematic in this thread that is an accurate representation of what your amp is.  I have posted numerous schematics as illustrations to you.

In order to help you any further, you will need to either post a schematic that is a completely EXACT representation of what you are using AND/OR post more detailed photos above the layout board and chassis area.

Hi Tubenit,

As written above, today I publish photos as an accurate representation of what my amp is now ,after several operations of soldering ,bypassing ,etc.
I followed the schematic put in your post on 10th may. There isn't any other I applied for this build.
The "layout"/main board is put in my post on 13th may. That's the main component ,where I would make a "hotchpotch". If needed ,further/all connections will be indicated on it. Just give me such feedback. I'll do that immediately.
Nevertheless of final score, I thank you very much for your willingness to help!
I'll put another photos tomorrow(posting capacity limits).
I'm gonna accomplish this build sooner or later;).

Best regards,

adam


 

[tubenit]

Adam,

THANKS for letting us know that you are using that 5-10 schematic for the Bassman & OD.  I also appreciate your posting the photos. 

Overall,  your build looks very professionally done with very neat wiring and decent solder joints.  I think you can get this build up working correctly!

We know that the clean into the LTPI sounds good per your previous posts.  The OD has consistently been the problem with low and distorted volume. 

You've done such a good job wiring this up, I somewhat regret asking you to change and try things messing up your wiring.  Having said that,
I personally would try the following:

1)  double and triple check to make sure that you do NOT have something shorting to ground.  Make sure signal wires (in shielded wires) are not
     shorting to ground by touching a braided shield wire strand.  Using your meter make sure signal path is not shorted to ground/chassis
     underneath the board

IF you can not find a short to ground then I would proceed to the next two steps

2)   completely remove the relay board and hard wire the clean into the OD into the LTPI. Rather then bypass the relay,  remove it completely
      from the amp chassis

3)   I would remove the 470k to 250p to ground that is between the relay and the OD trim pot (entrance in OD section).  It is not critical to have
      that there so let's take it out for now.

Is the relay switch itself in a relay socket?

IF you post some more pictures, please post the following:

-  overhead photo of the entire amp chassis

-  photo of the pots wiring especially around the OD pots

-  photo of the OD tube socket wiring to the board.

There is something shorting to ground ............ or something miswired ................ or a bad component.

I am presuming you have used a non-conducting chopstick or something to tap around the OD section?  Does anything crackle or pop when you do that?   If so,  you have a bad solder joint?

Also with the amp drained of voltage,  gently tug on the wire leads to all your resistors around the OD section and the wire leads to the caps around the OD section.   I once had a resistor wire broken inside the resistor body.  It tested OK with my meter, but when I gently tugged on the wire lead to the resistor, the wire moved revealing it was broken inside the resistor. 

I am cheering for you to have success with this build!  Don't give up!

With respect, Tubenit

[tubenit]

I am NOT sure you have the wiring right on the relay?  Looks like you're missing a wire and I want you to recheck that you wired the 220k between the relay and the trim pot correctly, please and report back.  I don't know how it's wired under your layout board so it may be fine OR it may be wired incorrectly?

It may be totally wired correctly,  I just want you to triple check it.  Also check the value of that 220k resistor  please.

With respect, Tubenit

[tubenit]

Is this how you had your relay wired?   Note that I am not saying this is correct wiring!  I am asking if that is how you wired yours?   And why is one of the relay wires missing?

I think what I am showing in the illustration is how your relay should be wired up?   Can you please confirm that it is wired that way? 

And can you offer some explanation why it appears to be missing a wire?  Maybe you made the connection under the relay?

Tubenit

[tubenit]

Notice both the similarity and  the difference in how yours is wired and how I wired mine using one of Doug's relays. 


Again,  this may be another good reason to actually remove the relay switch out of the chassis altogether and temporarily hardwire the clean into the OD into the LTPI.

To have a quieter amp, my suggestion is to have the OD connected as normally closed and the clean as normally open. The OD will be quieter that way compared to OD connected as normally open which is noisier.

With respect, Tubenit

[adamG]

Adam,
IF you post some more pictures, please post the following:

-  overhead photo of the entire amp chassis

-  photo of the pots wiring especially around the OD pots

-  photo of the OD tube socket wiring to the board.

Tubenit,

Here is few photos with descriptions...
I believe they go without saying;)
Filament voltage is 12,6V with pin 9 grounded.
Tomorrow, I'll put a photo of relay connections. Today limit is over. One desription instead, relay's NC pin on the left is bridged to NO pin on the right. With such solution ,I've go OD stage connected to ground when clean one is activated. Is it proper?
I'll implement the instructions that you suggested.
Allow me express myself? Two times american gentlemen helped me a lot. First, I was very generous man giving me an OT theory lectures. Second such person is....you!
Thank you very much! 

adam
 

[tubenit]

One desription instead, relay's NC pin on the left is bridged to NO pin on the right. With such solution ,I've go OD stage connected to ground when clean one is activated. Is it proper?

Yes, that is correct.

I think a signal path is shorted to ground.  OR a resistor value is incorrect.  Or something is wired wrong.

Is there anyway to get a small mirror and flashlight to check under the layout board to make sure a wire isn't touching the chassis around the OD section?

I am hoping removing the relay and temporarily wiring the clean straight into the OD into the LTPI will allow the OD to work properly?  I am wondering IF something under the relay switching board is touching something on the main layout board and shorting to ground or to a component? 

For example, if the bridged wire from normally closed (left) to normally open (right) is touching something like the cathode resistor wire or cathode cap wire, that could be the problem?

I know it's going to be an effort to remove the relay board and temporarily hardwire the clean to OD to LTPI, but IF that is where the problem lies, then it will be worth it?

I think your wiring is VERY neatly and professionally done.  The only thing that looks suspicious to me is the relay area or the 250p and 470k to ground going to the trim pot.

with respect, Tubenit

[tubenit]

In photo 2240295,  what is the DPDT switch between the V1 clean tube and the V2 OD tube?  Is that a manual switch to activate the relay switching?

I know you've already done this trying a "good tube" in the OD , but could you try a couple of different 12A_7 type tubes in the V2 position?   Try a 5751, 12AT7,  12AY7, 12AV7 or any of those in the V2 (if you have others to try?).  Let's try to get the OD working at a good volume first, then we can tweak the gain for the OD.

I have always run my heater wiring at 6.3v instead of 12v.  So if there is something unique about the 12v heater wires on the OD, I am not knowledgeable enough to know what that would be?

With respect, Tubenit

[tubenit]

Maybe here is another thing to try before removing the relay.

Post & record  the voltages for the OD tube  V2-1,  V2-3,  V2-6,  V2-8.    And for the heater voltages on the OD tube.

When the relay is switched, do any of those voltages change?   Does the heater voltage for the OD tube change when relay is switched?

With respect, Tubenit

[adamG]

I think a signal path is shorted to ground.  OR a resistor value is incorrect.  Or something is wired wrong.
Equipped with photo, you will easly get a view of relay connection philosophy.

Is there anyway to get a small mirror and flashlight to check under the layout board to make sure a wire isn't touching the chassis around the OD section?
Actually, I lifted up the board weeks ago.There wasn't anything suspicious underneath.But, I'll do it for my own confidence. I Also assume to provide extra electric isolation under the layout board.

I am hoping removing the relay and temporarily wiring the clean straight into the OD into the LTPI will allow the OD to work properly?  I am wondering IF something under the relay switching board is touching something on the main layout board and shorting to ground or to a component? 
I think ,there's a proper free space underneath relay board. I made a spacer by few flat washers;). I'll temporarily remove the board anyway to test the "clean" signal way via clean channel and OD stage.

The only thing that looks suspicious to me is the relay area or the 250p and 470k to ground going to the trim pot.
Initially ,they were withing the OD circuit acc.to schematic, but now they only exist on board not connected.

[adamG]

In photo 2240295,  what is the DPDT switch between the V1 clean tube and the V2 OD tube?  Is that a manual switch to activate the relay switching?
Yes, that's the manual switch to drive OD stage.

I know you've already done this trying a "good tube" in the OD , but could you try a couple of different 12A_7 type tubes in the V2 position?   Try a 5751, 12AT7,  12AY7, 12AV7 or any of those in the V2 (if you have others to try?).  Let's try to get the OD working at a good volume first, then we can tweak the gain for the OD.
I've got different above mentioned tubes, so I'll try them on.

I have always run my heater wiring at 6.3v instead of 12v.  So if there is something unique about the 12v heater wires on the OD, I am not knowledgeable enough to know what that would be?
The reason of 12,6 V was to reduce cross sec.of winding wires withing the power transformer and to minimaze the supply hum. I got such solution viewing an old tube laboratory intrument;)

With respect, Tubenit

[adamG]

Post & record  the voltages for the OD tube  V2-1,  V2-3,  V2-6,  V2-8.    And for the heater voltages on the OD tube.
V2-1 - 150V,V2-3 - 1,96V, V2-6 - 174V, V2-8 - 1,55V. They suppose to be almout equal,right? I measured those voltages right after assembling ,what made me suspicious a little bit.

When the relay is switched, do any of those voltages change?   Does the heater voltage for the OD tube change when relay is switched?
I'll check that, but during assembling with all tubes placed into their sockets, I did not record any voltage drop with full power consumption. But ,I'll check that on the relay switching on/off.

Thank you Tubenit!

[tubenit]

Adam,

You've done so much right already with this amp, it is truly puzzling why you aren't getting a strong OD tone.   

On reply #25 you said:

Today I followed your Trouble shooting #4.OD sound appered ,but with huge OD signal.It is too high, because after a moment of pure OD signal , cranch and clatter appers.

That is an indicator to me of a bad connection or a short or faulty part.

Here is the order of what I personally try:

1)  safely & vigorously chopstick around the OD section & include the OD pots, OD sockets, and relay.  Anything crackle
     or do you get noise increase?  IF you have a volume jump, then there is a short or something.

2)  check voltages when switching relay.  Does anything change?   (Your reported voltages look OK to me)

3)  with amp turned off and power drained,  I'd gently pull on all the wire leads of resistors and caps in the OD section.
     Do any wires slide from inside a cap or resistor?  Maybe there is a broken wire inside the resistor or capacitor body?

4)  I'd disconnect each shielded wire at each OD pot (trim, drive, level) and test continuity to make sure your signal wire
     isn't shorted to ground

     Also check continuity with the shielded wire signal path on both ends of the shielded wire.  I have had several
     occasions that the fragile signal wire inside the shielded wire was broken.  You can use your meter to check this
     and you can safely bypass the shielded wire by paralleling an insulated alligator clipped wire in parallel to the
     shielded wire.  Yes, that would be noisey BUT if you had a huge volume increase, it would indicate that you
     need to replace that shielded wire as it had a short in it.

5)  While you have the shielded wire disconnected on each pot,  you might consider creating a "test" to see if the pot is
     bad in some regard. I have had a couple of pots go bad on me and not allow signal to go thru.  See below.  What you
     are doing is bypassing each pot to see  if that pot was the problem?

6)  Try all the different 5751, 12AT7, 12AY7 tubes ............. etc ...........

7)  completely disconnect the 470k & 250p from the signal path to the OD trim pot

8)   Completely remove relay switching from the chassis  &  temporarily hardwire  clean to OD to LTPI

I would try everything possible prior to removing the main board.  Your wiring is so neat, that I hate to see you remove the main board.

With respect, Tubenit

[tubenit]

Adam,

When you look at the relay and OD section of your layout, there is not a lot there.  IF you are thorough in your trouble shooting and continue to check for continuity,  shorts, bad components & use techniques like bypassing a section to isolate the problem area .................... then you will find the problem and get it fixed!

I am cheering for you and I am confident if you stick with it, that you will find the solution!

With respect, Tubenit

[tubenit]

IF none of those steps above resolve the issue, then go back to bypassing the first gain stage of the OD and see if it works.  AND this time bypass it by directly wiring from treble pot wiper to 2nd gain stage of the OD and then from that gain stage directly wire to the .02 cap into the LTPI. 

IF the amp works like that and you have reasonable volume, then the problem is either the relay or the first gain stage.

With respect, Tubenit

[adamG]

1)  safely & vigorously chopstick around the OD section & include the OD pots, OD sockets, and relay.  Anything crackle
     or do you get noise increase?  IF you have a volume jump, then there is a short or something.
I did as you instructed. I got a suspicion on shielded cable into pin2. It's been changed together with 3 other ones for drive and level pots.

2)  check voltages when switching relay.  Does anything change?   (Your reported voltages look OK to me)
No, the voltage didn't change during switching.

3)  with amp turned off and power drained,  I'd gently pull on all the wire leads of resistors and caps in the OD section.
     Do any wires slide from inside a cap or resistor?  Maybe there is a broken wire inside the resistor or capacitor body?
Everything seems fine. Here is a conclusion...

6)  Try all the different 5751, 12AT7, 12AY7 tubes ............. etc .
That's today's point. Whole day I had a convenience to test several tubes such 12AT7,12AY7,12AU7,12AX7 on higher sound volume:) .The last one is too sensitive/powerfull to my OD stage.In my opinion, for this particular circuit, that tube has too big amp.factor. 12AU7 is too weak.My choice is among of 12AY7 and 12AT7. With both of them I receive a good balance between distortion level and overall sound volume-clean channel. I forgot that this amp hasn't got master vol, so volume pots need to be at least on 3-4 to get amount of overall satisfactory amp distortion. With that approach I think that amp might be a great classic amp with additional OD stage.

7)  completely disconnect the 470k & 250p from the signal path to the OD trim pot .
Yes, I've removed them.

I would try everything possible prior to removing the main board.  Your wiring is so neat, that I hate to see you remove the main board.
As said above, It wasn't necessary to lift the board up. Generaly, I moved back into 100kA as drive pot and 100kB as level pot, and amp seems to be ok now. But one thing might be still an issue. It's level of hum/noise when OD stage is activated.My PT's filament 6,3V is grounded with two 100R resistors. Do you think that grounded centr.tap is better solution?Or the reason is somewhere else?

Anyway ,the Bassman is great construction! Leo did a very good job ;)
Tomorrow I'll be going back to reverb stage. So, don't worry, you'll be got annoyed with another issues;)))

Thank you very ,very much!

Best regards,

adam