5E9 Tweed Tremolux Build Thread: Pics on Page 11

[Racing]

Look. That Geloso a couple of posts down. EZ-81 tube rectifier socket to the far left. A F&T 47uF capacitor bolted to the shortside wall. HT taps are the red n yellow. In between them the centertap in black. See how that centertap is run for the groundlug,together with the heater CT,on the shortside wall where that capacitor grounds too?
That´s the way to do it.

Mains voltage in turn. See that green/yellow wire from the mains wire harness? It heads for a lug completely of its own on the longside wall,just next to where the mains wire enter. See how long i´ve left it?
This is for a reason. As the amp uses a solid installed mains (in contrast to a jack (An IEC for instance)) the idea here is that IF the amp falls over still attached to mains wall socket the absolute LAST thing to be ripped out of the amp shall be that safety ground. Thus..it´s way longer,from a "stretch" POW than the other two (phase and zero)

[Racing]

´Nother example. In this case an IEC jack equipped amp. Thus,the safety ground just needs to be in the mix as the cord will rip out of its jack before any such damage needs to be considered.
However. Notice the mains fuse holder and how the wires for it are ty-wrapped in place. This is as IF them solderjoints would ever become loaded beyond reason (for instance some idiot replaced the mains fuse with a 10A one) the wires can´t really go anywhere and hurt anyone.

Failsafe...ALWAYS think as far as you can when it comes to this crap. Think WAY WAY WAY down the line and anticipate the worst case moron there is...at all times.
No. You can not safeguard for all...but you can do your damndest trying..



Yet another example. By know i guess your starting to see a picture emerge here...
FWIW,you might not have considered this but...all of them amps above are tube rectified units. I ALWAYS use fuses for both wires handing the high tension AC for the rectifier. Main reason for this is to safeguard the PT should the tube rectifier go Harrisburg on our asses. Fuses are cheaper than a new PT... In turn i always use "saver diodes" ahead of the TR. This diminishes the load on the TR per se,but still lets the TR present its mA max capacity and voltage drop. IOW...belt and suspenders.

[Racing]

Btw.
Never ever assemble an amp as were you putting out a fire. Let it take the time it needs and do it once.
Electronics like law n order. Hand it that. A proper layout is in turn not only easier on the eye,it makes it a HELL of a lot easier for the schmuck needing to repair the thing one day to understand the logic of the layout,thus cutting bench time and cost.
Be anal about it. When pulling work off,do so at a pace that suits YOU. Think three times,cut once.

MTBF becomes lower as you get more seasoned at doing this. IOW leave room to grow. What you don´t know,ask. There´s always those of us around all to happy to help out when we can.

[wproffitt]

Racing,
Thanks for the responses! I'll go ahead and rearrange my grounds on the power end of the amp on Monday. The photos of the Geloso were very helpful, by the way. Even if I know what something is, seeing a picture of a concept in action is very useful for me putting that concept into practice.
As for separating the resistor from the cap next to the end of the board, how far apart should they be? I know from reading other threads that that resistor will be QUITE hot!

[Racing]

I guess the correct answer is that the farther spaced apart that resistor and cap is,the better.
Be aware that what that capacitor actually does is work as AC ground. Ie;it´ll stop the DC voltage at the resistor end from going any further but it will let AC voltage through and thus increase power accordingly.
That brings up a viable question. Does the capacitor need to be next to the resistor? No. If you wish you can solder that capacitor directly onto the sockets,where they are joined by a wire or whatever,and in turn head that capacitor for ground basically anywhere.
If you wish bolt in a one prong solder support and just run a wire from there to resistor ground. Be aware that THAT ground passes power.

Then a note on groundloops. It is very easy to miss out...and very easy to check IF you´ve got your grounding scheme down.
If you have there will be ONE wire,of whatever variety,heading for chassis ground. Thus,if you solder that wire loose ground connection for that stage will disappear. Ie; off THAT wire comes and when you measure from chassis ground to the point where that wire connects to whatever it is supposed to ground your DMM should read OL or resistence in kOhms at least.
If it does not but reads zero Ohms or very low resistence,you have a ground loop and this needs to be remedied.

Therefore each "part" of the amp (read-each node and thus e-cap) should have its circuit "floating" before it hits that e-caps ground. Ie; as you remove the ground wire for for instance the phaseinverter from its e-cap the phaseinverter should loose contact with ground. In this manner diagonising is a breeze....

[wproffitt]

c/ read the part about the golden rule again. Do NOT sum all grounds as you´ve described. The centertap runs to the groundlug of the 1st hit e-lyte FIRST,before hitting the chassis. Again..for ample reasons (Kirchoff). Kirchoffs current LAW applies. At all times. Closed "power circles" does it.
.

In this case, should I run the red/yellow CT wire over to the turret where the wire runs to ground for the Electrolytic cap rather than having the two wires meet up at the chassis?

[sookwinder]

Wow ... I go off line for 12 days (business trip to Germany) and the amp is almost there.
great read so far !

[wproffitt]

Thanks for the encouragement, David! With any luck, I'll have this thing ready to test out in the next couple of days.

[Racing]

c/ read the part about the golden rule again. Do NOT sum all grounds as you´ve described. The centertap runs to the groundlug of the 1st hit e-lyte FIRST,before hitting the chassis. Again..for ample reasons (Kirchoff). Kirchoffs current LAW applies. At all times. Closed "power circles" does it.
.

In this case, should I run the red/yellow CT wire over to the turret where the wire runs to ground for the Electrolytic cap rather than having the two wires meet up at the chassis?

To comply with the golden rule,to the e-lyte first. Then to chassis.

[wproffitt]

Thanks, Racing!
I redid my grounds today and finished up those last few connections from the board to the preamp section. I do t have time to run through the startup protocol today, but will do so tomorrow. Wish me luck!

[sookwinder]

You are now at the point in an amp build that gives me both good and sad feelings.
This is where the build has finished and I really enjoy building amps.

Now the amp will either work first time and many of my builds have been like that or it won't work and obviously you will then need to assess where the issue is or the mistake is. I have had some real bad periods where I was totally out of my depth but I struggled through and the amp in question eventually worked well and I learnt a lot.

Trouble shooting an amp that isn't working is just a matter of first just looking at the build and then looking at the schematic/layout drawings.
can you see any that is wrong (do this with the power off).
Have you traced the hookup wire the wrong way as iut moves across another wire and so some connections are wrong.
are the electrolytic capacitors in the correct direction.
Is the fuse in the fuse holder (yes I have done that one before)
Have you connected a speaker to the amp
Is the volume turned all the way down
Can you see glowing filaments in the valves
Have you mistakenly swapped around the rectifier with a power valve

Use a multimeter to check continuity of earth/grounds

Once you are happy everything looks ok and that you haven't down something stupid or forgotten to do something, then set about checking voltages.
Don't be worried if the voltages are 5, 10 20 volts out on the high values, just as long as they are in the ball park.
I always check in the first instances the cathode voltages
For the pre amp valves (pins 3 and :
12AY7 1.8 - 2.6V ...remember just look at ballpark comparisons ... if it read 1.6... just move on if it read 2.5 move on for the moment. If it reads 10 volts then there is an issue, likewise if it read 0.5 V
12AX7; 1.2 - 2.2 V
6V6GT: (the combined cathodes) 22 - 28V

the start with just the voltages elsewhere in the circuit, both going into the valves and at locations in the circuit.
I just checked the Fender 5E9 schematic and there are no voltages listed , but the 5G9 schematic does have some voltages, so similar design areas can be used. Note the 6V6s are cathode biased in the 5E9 and not in the 5G9, so that is something to watch out for and not use that.

Another thing you can do is put a constant signal into the input and see how it gets amplified along the way (or doesn't as the case maybe)
a signal generator can be used... I have used white noise or a tone off AM radio band ... but you will also need a scope of some sort.

and don't forget ... ask questions !

[wproffitt]

Hello again,
This afternoon, I plugged the amp in with tubes and speaker. After several seconds, the tubes were all glowing nicely, and there was a quiet hum which was encouraging because it is easily as quiet or more quiet than my PR. However, when I plugged in my guitar, no sound came from the speaker! When I touched the guitar cable to the jacks, there was none of the usual racket, either. Yes, the speaker was plugged in. Yes, the right tubes were in each spot. Before I get out the voltage meter (which I've never used, btw), what should I be checking after I look over the diagram and compare it to what I've done? Also, here are some pictures of the inside of the chassis. Does anything jump out at you about the way the jacks or pots are wired up?

[sookwinder]

My first response would be to check if there was a short to earth somewhere.
SO WITH THE POWER OFF AND THE AMP LET TO SIT FOR AN HOUR OR SO ... get the DVM and set it to "continuity check" where the DVM using beeps when there is a perfect connection between two point.
So if you measure between the two ends of a resistor, no beeping will occur because there is a resistance.
If you measure between the "bottom" end of the capacitor/resistor on the cathodes of the small preamp valves (pins 3 or 8 ) and the chassis 9anywhere on the chassis, then DVM should beep. this is because the chassis is ground and the bottom end of the cathode cap/res is meant to be connected to earth.

So with the cable plugged into the amp but not the guitar, I would then check the continuity between the hot tip of the cable and the start of the 68k res.
Then go from the other side of the 68k res and compare that to ground
Then go from the other side of the 68k res and check the continuity to pin7 of the 12AY7.

If your DVM doesn't having the beeping continuity check, just look for zero ohms between the locations you are checking.

Go through the amp and just do a sense check that various locations should not be the same as earth (for example pins 1 2 3 6 7 8 of the small valves and some locations should be connected to earth.

A couple of times I have forgotten to trim the excess wire that is pushed through the eyelet or turrets, and this wire shorts out with something else.

Once you exhaust this idea, so it on with out the cable connected and start checking voltages.
I have just seen on the Fender layout drawing for this amp there are voltage values listed, so you should be able to see pretty quickly of the amp is firing up as you8 want it,

[Racing]

Well get you through this.
READ ALL OF THE FOLLOWING BEFORE DOING ANYTHING ELSE!

First up. You need to learn how to work a DVM/DMM. That´s short for either digital voltmeter or digital multimeter. As that meter can most likely measure more than just volts the correct nomer,and abbreviation,is DMM.
Please take a pic of YOUR DMM and post.

With the amp on the bench set the DMM to volts DC. If autorange that´s it,if not you need to set it to an appropriate range. As you´re probably aware that amp of yours can sport several hundred volts both when live and when off. As you can not damage a modern meter (in contrast to old analogue ones) try different setting but start at the 200 to 2000 volt DC setting. Reset range downwards as you go until you get reasonable voltage readings.
Be aware that some cheaper meters will have to inser the red probe into different jacks depending on if measuring Ohms or Volts. Make sure the probes are connected to the appropriate jacks on the DMM of yours.

First thing´s first tho. Check,physically,that the mains cord is out of the wall socket. This is safety rule No1 at all times. Cord out,flip the standby switch to on(!!!!). Leave the mains switch off. THIS IS IMPERATIVE.

Now. Seing that groundbus bar is attached to the chassis (more on that later) set the black probe of the DMM to the chassis. Use the red probe to probe the positive lead of the electrolytic caps. As WE can´t see if there´s ground for the first hit e-lytes,check all of them. If residual voltage is below approx 30VDC you´re good to go. If this measuring comes to nil for the first two hit e-caps we need to find out why. In such a case set DMM to Ohms and check for resistance between first hit e-lyte negative lead and chassis ground. This should be zero. If not,find out why and remedy.

As a cathode bias amp is turned off (as for fixed bias amp to a degree) if and when the powertubes have been running the powertubes will continue to digest current albeit the amp is turned off. That means that if the powertubes were running residual voltage will be low to very low. Expect along the lines of a few volts DC or so and that´s it.
Anyways.
If residual voltage checks out to be less than 30 volts DC you´re good to go and the amp is now safe to touch and handle within.

This procedure you ALWAYS go through before commencing work. It doesn´t matter if hell freezes over,this HAS to be done for your own safety.
If residual voltage is up...you can drain this by placing a ceramic resistor between the B+ line and chassis. Any value from 470 Ohms up will do. The higher the value resistor the longer it takes to drain,that´s all. Ceramic resistor as it´s large enough to hold without risking getting in touch with its lead as you work it.

That done.
As has been described per above reset DMM to Ohms. Insert a guitar cable into one of the jacks and check for DC resistance to where that jacks ends,at the actual tube socket. (Ie;pin 2 or pin 7. Btw. We count pins of sockets from inside the chassis (underneath socket) and do so in a clockwise manner. From the "opening" in the pins and from left to right).
Jacks are paired. This means that the one socket should show approx 34k Ohms from the hot tip of your guitar cable to the pin of V1 it serves. The other jack should show 68k.
Now DC check from hot tip to chassis. The 34k jack should show approx 1M Ohm to chassis and the 68k one just shy of 140k Ohms if all is well. Do this for both jacks.
If this doesn´t check out,i can understand if the wiring of closing jacks is confusing,we´ll get to that too.

If it checks out,probes,fingers and what there is out of chassis.... Now reattach the black probe to the chassis,firmly. Use a hole in the chassis or whatever that´ll keep the probe in place. Make sure the point/metal of that black probe is in good solid contact with the chassis.
Insert the speaker wire into speaker out jack of amp.

Mains voltage to the wall and fire the thing up again.

Let the amp come up on voltage and setttle. This time out though.. ONE hand and ONE probe is what you use. Ie; red probe in hand... Set DMM to handle 500VDC or more (if not autorange). Other hand in backpocket or whatever.
Take the red probe to the positive lead of the first hit e-lyte. This should show your B+ voltage. Ie;the highest reading voltage in the entire amp. We need to read this to determin if the tube rectifier is up and running and doing its fair share. Me not knowing the specifics of the 5E9 expect to read approx 400 volts DC or so seing there´s 6V6s onboard.
If it doesn´t we need to find out why. If so,hold and report back.

If this checks out probe from the powertube cathodes to ground. IOW leave the black probe be where it resides in its hole in the chassis. Just move the red probe. Cathode is pin 8 for 6V6´s.
Octal sockets you "count" from the recess. Ie;the locating pin cutout-what references where the tube ends up in its socket. Pin 8 is then the last pin of that socket.
Now.
Both pin 8´s are supposed to be tied together of the the powertube sockets. Voltage should hoover around the twenty volt mark or so vs ground. If it does this means that the powertubes are working. If voltage is off by any fair amount (lower) chances are the ONE powertube isn´t doing its job and we need to find out why. If so we´ll get into that. If so,hold and report back.


If ok proceed.
As has been mentioned above you now measure voltage between cathodes of the remaining tubes and chassis. For the novals at hand that means pin 3 and 8. For sake of ease leave the workings of the tremolo tube out for now. If it runs or not isn´t a part of this ATM as far as sound goes.

The phaseinverter is of paraphase style in this case. If you want to understand how it works look the Valve Wizards pages up (google) and check the paraphase heading.
No matter.
As the cathodes of the phaseinverter is tied together we first up check voltage between cathodes and ground. This should be a few volts DC. If present we check to see voltage drop across each plate resistor. Common voltage,to both sides,BEFORE the plate resistors(where they´re tied together) and a substantially lower voltage AFTER each plate resistor. If we see this behavior for each triode we´re good to go. That means that the tube in case is firing and up and running.

Then for the entry stage tube. Same deal. Between cathode and ground...and before and after each plate resistor.

Cathode voltage in this case should come to a few volts while the plate measurements should hand you several hundred volts before each plate and...like 30% less or so voltage after each plate.

Remember...when working on a live amp ONE probe in ONE hand at all times. Other hand in your backpocket or whatever.

If this all checks out that means all of your tubes are firing. This HAS to be checked as a "pre flight checklist" in this case. If not,hold and report back.


Right. Now physically yank the mains wire out of the wall socket. Do NOT engage any switches. Check how DC voltage drops at the first hit e-lyte as you do. This little excersize to make you understand how the residual voltage is arrived upon. When residual voltage is under 30VDC..you´re good to go. Again.

Now.
That groundpoint for the preamp of yours. The one installed to the short side wall. This is wrong. As i wrote,Kirchoff. This means that your preamp and PI should PHYSICALLY be attached to the groundlug of one of the input jacks. NOT "close by" but physically the wire should head for and be soldered to the grounds of the jacks. There are no shortcuts. Remedy this.

That done reset your DMM to VAC. Yeeees....alternating current voltage. The point here is that your DMM is more than qualified to handle VAC and see...signal is measured in VAC.
No. The DMM won´t give you accurate readings but at this stage.. you don´t need accurate readings.

Again. Black probe to chassis. Mains to wall and fire the thing up. If you haven´t touched the mains or standby switch be aware that voltage will be present as soon as you put the jack to the wall.

Let the amp come up on voltage and settle.

Lay your guitar down on the bench,or similar. Just make sure it´s planted firmly. Open the volume pots of it up and leave it there. Insert the telejack between the guitar and amp.

Probe between each powertubes pin 5 and ground with DMM set to VAC as you strum the strings of the guitar.
Imperative part here is IF there´s voltage present at pin 5 or not. If this voltage passes a threshold of approx 200mVAC to 300mVAC you´ve got an issue. A few mVAC though amounts to nothing and is perfectly normal.
IF there is,back off right there and then. If there´s signal present at pin 5 and you have no sound chances are that you can ruin your output transformer otherwise. In that case turn the amp off and check out why. If so,hold and report back.


Be aware of which pair of jacks serve which side of V1. Now. At the plate resistor there´s a coupling cap. In your case orange drops. Find the solderlug AFTER each cap. One lead of each cap heads for the plate resistor for said stage,the other heads for a volume pot. Set both volume pots to max.
Probe the side of each capacitor that heads for the volume pots for volts AC while you strum the strings of your guitar.
Do this for both pair of jacks.

Readings should show around 2-4VAC approx and this reading should be dependant of how hard you hit the guitar. Ie;soft-lesser voltage,hard-more voltage.
If this checks out then your V1 is doing its job. If not,we´ll get into that.

Now. The two volume pots and the tone pot are tied together. See (probe) to make sure you have AC voltage outbound of each pot too. This is the voltage that should show up on the leading grid of the phaseinverter tube.

Checking the phaseinverter for signal is done in the same manner. Capacitors...and measure at the end that heads for the powertubes. Signal for powertubes should in this case be present at pin 5 of each socket on the powertubes.

In an ideal world the AC voltage outbound of the phaseinverter should be the same for each powertube. In reality it is not. The perfectly balanced phaseinverter simply doesn´t exist,so no fret.
Imperative part here is IF there´s voltage present at pin 5 or not.

In this manner you "follow" the signal through the amp. No. At this point there´s NO need for an oscilloscope...none. Your DMM will do just fine as long as you understand/know how to swing it.

Go through this checklist of mine and report back where the amp fails.

[wproffitt]

Here's my voltage meter. I'll be in meetings ALL day and have a late night at work so I won't be able to think about this until tomorrow. In the meantime, thanks, Racing and David, for your helpful, concrete advice to get a new guy through this!