First sounds of the 18W TMB tremolo build

18watt-specific Tech Talk - Building, Fixing, Parts, Mods...

Moderators: CurtissRobin, colossal, zaphod_phil, Daviedawg, Graydon

Post Reply
User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 455
Joined: Mon 02/10/20 8:24 am

First sounds of the 18W TMB tremolo build

Post by Bieworm »

Build is done and checked first without tubes with lightbulb current limiter. All was fine, just as expected the HV was high.
So put some tubes in... it has sound!!

BUT... a very loud hum. Ok that is traceable..so I don't worry about that.
Voltages are ok. More or less.. but tweakable

BUUUT...it distorts immediatly, not nice, it chokes on the guitars input signal. When I strum hard the sound mushes and fades away real quick and then comes back..oscillating a little. With or without trem engaged. When I clean it up on the guitar volume knob..like volume between 1 and 5 there is No trace of the choking. It sounds ok then,but dark ofcourse. As of there is too much input signal to be processed and the amp can't handle it.

And BUMMER... The tremolo doesn't work.
15855030897481380446932608716726.jpg
Sound clip:
https://www.dropbox.com/h?preview=Spraak+010.m4a
You do not have the required permissions to view the files attached to this post.
0 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 455
Joined: Mon 02/10/20 8:24 am

Re: First sounds of the 18W TMB tremolo build

Post by Bieworm »

Bump
0 x
"THIS should be played at high volume..preferably in a residential area"

Daviedawg
Superior Amp Tech
Superior Amp Tech
Posts: 612
Joined: Fri 01/08/10 2:00 am
Location: Scotland

Re: First sounds of the 18W TMB tremolo build

Post by Daviedawg »

Is this the first time this circuit has been built? It may be worthwhile bypassing V1 and connecting V2 to the input to check the signal is clean of hum at that point? If not then proceed with fault finding. If it is then you have limited the source of the issue to stage one.

Most likely it is time for the dreaded fault finding. Sorry if you know all this already but this is my approach to it. (The hum and poor signal may be the same problem.)

Firstly with the amp off do a visual review of all connections with a magnifying glass if possible looking for shorts or cold "unshiny" solder joints. Especially look for whiskers shorting between valve pins. Poke about at the same time while amp is off moving wires watching for bad joints. Look for anything else unusual like a component that has been hot.
Secondly tap around with your chopstick with the amp on, listening for unexpected noises trying to identify the part of the circuit with a problem like a poor joint.
Then if no joy, print a copy of the schematic (not layout) get a marker pen then go through the whole amplifier following from one end or the other but in this case doing the power supply last as the voltages seem about right. Check the wiring and the component values carefully then mark off methodically.

I hope that gives you some direction to go.

Dd
1 x

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 455
Joined: Mon 02/10/20 8:24 am

Re: First sounds of the 18W TMB tremolo build

Post by Bieworm »

Thx DD

As far as I know this is the first build being posted. I now have my 18W classic fully operational, so I can enjoy that one without dismantling it for the TMB tremolo build ;-) and work on that without stress of having ruined my amp
So I ordered and received all the parts for a complete chassis build (that I finished obviously)

The highlighting was done prior to the lightbulbtest, and everything's in the right place with the right components.
Also did the checkup with the chopstick. No oddities found there.

I didn't follow the footswitch connections from the lay-out, instead I used an inputjack that grounds directly on the chassis. Do you think that's a wrong approach? ( I also put a 150pf cap between tip and ground, saw that on another schematic to avoid switching pop?) The tube sure doesn't oscillate. Maybe it's because of the low voltages of the first amplification stage.
It's as if the first amplification stage gives a too large boost and gives the sound a cardiac arrest.
I remeasured today and the value of V1 pin 1 was about 82V,while pin 6 was 133.
As for the powertubes ... I put in some older EL84 ruby tubes.. The cathode voltages were 11.84 on these..so ...bueno!
PI looks pretty on spec. Altough,... the voltage measured on pin 2 and 7 are supposed to with the DMM set on AC, right? Otherwise the DC values are around 35V :roll:

Wall voltage is pretty high at the moment. 245V AC
Maybe I'll have to up the 150R/25W rectifier resistor to 200R to be more on spec. Unfortunately the PT HV are rated 300V instead of 290V. But hey.. The amp has to live with that. And now with that high wall voltage of 244V for a 230V PT primary it lifts those secondaries up...

BTW I already tried different 12AX7 tubes with no effect. In case you would advise me to try that and rule out the possibility of a bad tube
You do not have the required permissions to view the files attached to this post.
0 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 1977
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: First sounds of the 18W TMB tremolo build

Post by JMPGuitars »

Your voltages look a little weird to me. Your power tube plates are high, but the preamp plates are low. You mentioned an oscillation, I assume you mean a parasitic and not tremolo? Try chopsticking the wires a bit and see if you can get rid of it that way, and how it affects the voltages. Remember that the plate wires shouldn't be close to or parallel with grid wires. Please also post some more high res photos of the build.

If that doesn't help, there's a couple things we can try next. It's possible we may need to decouple the preamp tubes from each other, and/or add a voltage divider attenuator between them.
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 455
Joined: Mon 02/10/20 8:24 am

Re: First sounds of the 18W TMB tremolo build

Post by Bieworm »

JMPGuitars wrote:
Mon 03/30/20 6:44 am
Your voltages look a little weird to me. Your power tube plates are high, but the preamp plates are low. You mentioned an oscillation, I assume you mean a parasitic and not tremolo? Try chopsticking the wires a bit and see if you can get rid of it that way, and how it affects the voltages. Remember that the plate wires shouldn't be close to or parallel with grid wires. Please also post some more high res photos of the build.

If that doesn't help, there's a couple things we can try next. It's possible we may need to decouple the preamp tubes from each other, and/or add a voltage divider attenuator between them.
I think the wire placement is ok in crossings or parallels. I was moving them all over the place yesterday, just to hear if there was anything oddplaced. But there was no difference in doing that..
I didn't mean tremolo oscillation, just the sound clipping like a diode fuzz and choking out on the low frequencies..from loud to no volume at all..then slowly coming back, swirling / resonating/ but not really oscillating. Did you get to hear the soundclip in the first post?

V1
You do not have the required permissions to view the files attached to this post.
Last edited by Bieworm on Mon 03/30/20 7:26 am, edited 1 time in total.
0 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 455
Joined: Mon 02/10/20 8:24 am

Re: First sounds of the 18W TMB tremolo build

Post by Bieworm »

V2
You do not have the required permissions to view the files attached to this post.
0 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 455
Joined: Mon 02/10/20 8:24 am

Re: First sounds of the 18W TMB tremolo build

Post by Bieworm »

V3
You do not have the required permissions to view the files attached to this post.
0 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 455
Joined: Mon 02/10/20 8:24 am

Re: First sounds of the 18W TMB tremolo build

Post by Bieworm »

V4+5
You do not have the required permissions to view the files attached to this post.
0 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 455
Joined: Mon 02/10/20 8:24 am

Re: First sounds of the 18W TMB tremolo build

Post by Bieworm »

Board etc
You do not have the required permissions to view the files attached to this post.
0 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 1977
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: First sounds of the 18W TMB tremolo build

Post by JMPGuitars »

First, please read and watch the videos in the solder technique thread: viewtopic.php?f=4&t=25396

Here's a couple tips on how I do things...

I strip the wire further back, and then use heat shrink tubing for jumping tube socket pins:
socket-jumpers.jpg
You might also notice that I saved the Pin 9 heater connections for later. This makes it much easier to keep the socket neat, and avoid hitting anything with the soldering iron by mistake.


For short resistor leads across cathode caps, I combine and solder them, then only connect the cap leads to the turrets:
leads-and-solder.jpg
Also note that I avoid using the turret hole whenever possible. If the turret tube has available space, that always gets used first. Try to avoid the leads of one component touching other components.

You have melted caps and things all over the place. Even if they read correctly on a simple meter, that doesn't mean they'll work correctly, or be reliable for the long run. Always work the soldering iron angles patiently, and avoid touching anything it shouldn't. I wire my boards before I put any components on them. That makes it much easier to reduce risk of burning anything.

The easiest way to make a clean and reliable amp, is to literally make it as clean as you can during the build process.

Thanks,
Josh
You do not have the required permissions to view the files attached to this post.
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 455
Joined: Mon 02/10/20 8:24 am

Re: First sounds of the 18W TMB tremolo build

Post by Bieworm »

JMPGuitars wrote:
Mon 03/30/20 7:44 am
First, please read and watch the videos in the solder technique thread: viewtopic.php?f=4&t=25396

Here's a couple tips on how I do things...

I strip the wire further back, and then use heat shrink tubing for jumping tube socket pins:
socket-jumpers.jpg

You might also notice that I saved the Pin 9 heater connections for later. This makes it much easier to keep the socket neat, and avoid hitting anything with the soldering iron by mistake.


For short resistor leads across cathode caps, I combine and solder them, then only connect the cap leads to the turrets:
leads-and-solder.jpg

Also note that I avoid using the turret hole whenever possible. If the turret tube has available space, that always gets used first. Try to avoid the leads of one component touching other components.

You have melted caps and things all over the place. Even if they read correctly on a simple meter, that doesn't mean they'll work correctly, or be reliable for the long run. Always work the soldering iron angles patiently, and avoid touching anything it shouldn't. I wire my boards before I put any components on them. That makes it much easier to reduce risk of burning anything.

The easiest way to make a clean and reliable amp, is to literally make it as clean as you can during the build process.

Thanks,
Josh
Crap! I have to resolder just about everything then...
The only ones touched are the oscillator caps, so I will replace them. The other 2 caps with a small burn mark were probably some hot flux droplets , but very superficial and look much worse on pics than in real.
You also suggest soldering the hookup wires from the valves to the turrets with a J-shaped hook instead of through the hole?
You think the low voltages on the preamp tubes are caused by the soldering?

Maybe I'd better order another board and better turrets. These turrets are hell. The turrets on my 18W classic were so nice to solder! Hook up the component, heat for a few seconds and apply the solder..it flows nicely around the wire and seemlessly onto the turret. These turrets seemed to reject the soldering tin...I ahd to flux an burn the hell out of them to make connections.
Man, I'm so disappointed right now
0 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 1977
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: First sounds of the 18W TMB tremolo build

Post by JMPGuitars »

Bieworm wrote:
Mon 03/30/20 8:15 am
You also suggest soldering the hookup wires from the valves to the turrets with a J-shaped hook instead of through the hole?
You think the low voltages on the preamp tubes are caused by the soldering?

Maybe I'd better order another board and better turrets. These turrets are hell. The turrets on my 18W classic were so nice to solder! Hook up the component, heat for a few seconds and apply the solder..it flows nicely around the wire and seemlessly onto the turret. These turrets seemed to reject the soldering tin...I ahd to flux an burn the hell out of them to make connections.
Man, I'm so disappointed right now
Yes, only use the hole when a j-hook isn't going to fit nicely.

I don't know why your voltages are as they are. It could be the tubes, it could be lead dress causing an oscillation keeping the voltage in the wrong place, or it could be solder technique to some extent. For example, the reason I have pin 2 on the EL84s always included on my voltage tests is because bad soldering between pin 2 and ground can cause big problems. If there's a voltage reading above low mV, then that's a sign that the path to ground isn't cleanly soldered.

Yes, I recommend redoing the board with better turrets, but before you do, let's sort out the sound issues. Chances are I'm going to modify the layout more (I already made one change I haven't published yet).
1 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 1977
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: First sounds of the 18W TMB tremolo build

Post by JMPGuitars »

Let's do the easy experiment first. Look at V1 Pin 7 on my Superlite TMB Layout: files/JMPGuitars_18_Watt_Superlite_TMB_Layout.pdf

Make V2 Pin 7 look the same on your Tremolo TMB and let me know if that helps the issues you described. So remove the 10K grid resistor, replace it with a 470K, and from pin 7 connect a 2nd 470K resistor to ground. If this helps a lot, but not enough, you can also try adding a 10K grid resistor to V3 Pin 2.

These are all changes I had to make to another amp I designed with an extra gain stage. I also had to decouple the preamp tubes from each other, but that was a much higher gain build, so maybe not necessary, or needs to be inserted differently? I guess we'll find out. Or maybe somebody more knowledgeable than me will chime in. ;)

Of course, none of this may be necessary if lead dress or solder joints are causing the problems. But that voltage divider/attenuator is a simple enough experiment to see what the effect is considering we don't have any other completed builds of this circuit to compare it to.
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 455
Joined: Mon 02/10/20 8:24 am

Re: First sounds of the 18W TMB tremolo build

Post by Bieworm »

JMPGuitars wrote:
Mon 03/30/20 9:13 am
Let's do the easy experiment first. Look at V1 Pin 7 on my Superlite TMB Layout: files/JMPGuitars_18_Watt_Superlite_TMB_Layout.pdf

Make V2 Pin 7 look the same on your Tremolo TMB and let me know if that helps the issues you described. So remove the 10K grid resistor, replace it with a 470K, and from pin 7 connect a 2nd 470K resistor to ground. If this helps a lot, but not enough, you can also try adding a 10K grid resistor to V3 Pin 2.

These are all changes I had to make to another amp I designed with an extra gain stage. I also had to decouple the preamp tubes from each other, but that was a much higher gain build, so maybe not necessary, or needs to be inserted differently? I guess we'll find out. Or maybe somebody more knowledgeable than me will chime in. ;)

Of course, none of this may be necessary if lead dress or solder joints are causing the problems. But that voltage divider/attenuator is a simple enough experiment to see what the effect is considering we don't have any other completed builds of this circuit to compare it to.
Any harm in using a 470K 0.5W resistor from pin7 to ground? I have only got 1x 470k 2W left in my spare parts stash
0 x
"THIS should be played at high volume..preferably in a residential area"

Post Reply