5E9 Tweed Tremolux Build Thread: Pics on Page 11

[Racing]

Usable,but not all that much more.
I doubt the probes of that thing is insulated to really take 500 volts,but if not i guess you´ll notice .

Anyways. You don´t have to worry about swapping jacks for the probes for various measurements. Just run what ya brung.

Start with voltage DC selector set to 500VDC,then work your way downwards when checking CATHODE and RESIDUAL voltage. Selector needs to be in 500 mode to measure B+ and rail voltages.

For measuring signal set selector to 200VAC.

In all honesty though i think you should invest in a higher Q meter somewhere down the line. Preferably an autorange one. Expect that one to run like 50-100 USD.

[wproffitt]

Racing,
There's a lot to digest in your helpful directions here. This is what I got when I measured some voltages with the amp on:
1st E cap- 340
2nd 6v6 pin 8 26,
Pin 3 306,
Pin 4 280

1st 6v6 pin 8 28,
Pin 3 333,
Pin 4 286

I did not get Into the preamp tubes because they sent noise right through the speaker when probed and imy daughter is sleeping upstairs right now.

As for the grounding, are you saying in need to have a wire going from the ground bus on the preamp side to the ground lug of each of the 4 jacks?


David,
the continuity tester gave me a beep from the cable to the top of each 68k resistor. From he bottoms of these, I got beeps at pins 2 and 7 of the 12ay7, respectively.

I did not get a beep between any of the 12ay7 pins and the chassis. I what's up with that?

Thanks in advance for all of the help you are providing!

P.S., I also have this meter

[Racing]

Your powertubes are up and running.
This means a few things,that all are good.

First up it means that the powertransformer and rectifier tube are doing their job. Amp is per that definition working. In short it means that the entire powerstage is doing its thing,the phaseinverter apart.

Next.
That you get static out of the speaker as you probe the preamp tubes is good. This means that the tubes,and pots,are passing signal
No.
It does not suffice to ping the inputjacks and their workings. Read my instructions above. You have to set that DMM to first up 200k. Remember that the jacks are paired. You need to have an instrument cable inserted as the jacks are of the switching kind.
Check from hot tip to inbound grid for V1,both channels. The one jack should show approx 34k and the other 68k.
Now set the DMM to 2M. Measure between each jack,still hot tip,but this time vs ground. For the 34k jack you should see 1M Ohms vs ground and the 68k one approx 130-140k-ish.
V1 NEEDS that connection vs ground otherwise the tube can not establish bias. IOW that ground reference is essential.

No. You do not have to run 4 separate wires. All them inputjacks should have their groundlugs connected. Ergo,they should all measure the same from a ground reference point of view why ONE wire from the entire preamp will suffice.
That red striped wire in your photo above though heads for the short side wall,and not the jacks. The ground wire has to physically run for one of the groundlugs of the jacks.
Also.
Physically measure resistence between groundlugs of jacks and chassis. This should come to zero Ohms. To the letter.

From the little you´ve told here it sound to me at least that you have an issue at V1. Most likely the jacks ain´t providing a ground path (reference) for either of V1´s grids,which will make V1 dead as a doornail. In other words...handle that there with groundreference,which will be a matter of how the input wires are wired,and most likely you´ll be good to go.

[Racing]

Btw.
Need be,if and when the time comes,to measure signal set that second DMM of yours to 20VAC.

[wproffitt]

Racing,
I'll try to get the grounding of the preamp/jacks sorted out in the next couple of days. If my daughter takes a nap this afternoon, perhaps I'll do it then. From every other photo I've seen online of how to ground one's jacks, it looks as though this is a MAJOR thing that I missed in wiring this up. While I'm at it, I'll also run grounds to the bus bar from the ground lugs of my volume pots. I'll report back with photos when I have something to show for my efforts. Until then, thanks for answering my questions and for letting me know about things like proper settings for the DMM that I'm using for this project. I really appreciate your time and expertise.

[wproffitt]

Hello again,
Here are the latest pics of the chassis in its current state. I did run the ground from the bus bar to the ground lug of one of the inputs. I also ran ground wires from the volume pots to the bus bar while I was at it. I fired it up this afternoon and it performed exactly as it had before. I guess I need to check out the voltages on my preamp tubes, right?

[Racing]

Your input jacks are wired dead wrong.

http://el34world.com/charts/images/cliffjacks.gif

Now. These are "floating" Cliff jacks and how they wired for a Marshall. Thus,what you can disregard is the ground bus and how it´s connected.
That´s NOT to say that you can disregard the wiring for the prong that grounds the signal completely when the jacks are empty. Notice how ONE of the paired jacks can hit ground via its switched solderprong. ONE.

Now. At the same time V1 needs to see groundreference at its grids. Both of them. That brings that the 1M Ohm resistor set to handle this needs to be run for the "hot tip" prong of the "hi" jack (-s). As is them 1M Ohm resistors hit the switching prong of each pair and this is wrong. Thus the grids of V1 will not see ground reference and as a result won´t be able to establish bias and thus won´t fire.

Study the scetch in the link. Working principle is exactly the same as for your amp,it´s just that the groundbus isn´t needed in your case as the jacks ground directly to the chassis where they´re installed.

That green wire running for a ground lug is now correct.

I bet that if you fix that jack setup there the amp will work just fine.

[Racing]

For a Switchcraft style jack fwiw...
You have three solderprongs. On one side we see the groundlug. Opposite side...hot lug. The middle one in turn is the switched lug.

[wproffitt]

Thanks, Racing!
I'm going to rewire the jacks either later this afternoon or sometime this weekend. I'll let you know how it turns out. If this isn't THE problem, at least we'll be able to say that it isn't A problem, right?

[Racing]

Right.
When done check to see that when you insert an instrument cable the resistence between pin 2 and 7 respectively shows either 1mega Ohms or around 140k Ohms approx.
That done V1 should fire up at least.

[wproffitt]

Wasn't able to check anything with the DMM, but I did rewire the jacks. No sound yet. I'll get back to you on what I'm seeing at pins 2 and 7 of V1 later.

[Racing]

Looks reasonable but still check DC resistence vs pin 2 and pin 7 from telejack tip.
In turn check resistence vs tip of telejack to ground and ditto from pin 2 and 7 (just to make sure of continuity)

Then fire the amp up. The voltage drop between pin 3/8 and ground. Should show a volt DC or so.
Then check voltage drop across the two plate resistors. Reason for this is that with the cathodes tied together you need to measure if both triodes are firing.

[wproffitt]

Hello again,
I checked my resistance coming from the jacks to pins 2 and 7 of V1:

On the normal channel, input 1, I got 35.8. For input 2, I got 71.8
On the bright channel, input 1, I got 36.3. For input 2, I got 69.8

Don't yell at me when I tell you this next thing:
-as for the voltage drop between pins 3 and 8, I think I discovered a problem that I might have created. I I do NOT have a wire jumper between these pins. This is because I conflated the 5e3 layout I was using for reference (better detail on the wiring of the PT, etc) with the 5e9 layout. The 5e3 does NOT have pins 3 and 8 of V1 jumpered, so I followed suit. There's no voltage at the point where these go to ground.

See what I did?


I also didn't get to the grid resistors because I noticed this:



Should my second 6v6 be glowing like this? I turned it off right away until I had more info to go on. Thoughts? Thanks in advance for your help.

[sookwinder]

On the normal channel, input 1, I got 35.8. For input 2, I got 71.8
On the bright channel, input 1, I got 36.3. For input 2, I got 69.8

Yeah that seems OK

-as for the voltage drop between pins 3 and 8, I think I discovered a problem that I might have created. I I do NOT have a wire jumper between these pins. This is because I conflated the 5e3 layout I was using for reference (better detail on the wiring of the PT, etc) with the 5e9 layout. The 5e3 does NOT have pins 3 and 8 of V1 jumpered, so I followed suit.

On the original Fender 5E3 circuit/layout drawing pins 3 and 8 are connected, just like on the 5E9.
Scott are you using the original Fender layout drawings or modern versions?

There's no voltage at the point where these go to ground.

where exactly are you measuring?
One probe should be on earth/ground , the other should be on the valve side of the "25uF capacitor / 820R resistor" .. at the point where the wire(s) come from pins 3 and 8

I also didn't get to the grid resistors because I noticed this ...

these can wait

Should my second 6v6 be glowing like this? I turned it off right away until I had more info to go on. Thoughts? Thanks in advance for your help.

Well no I think is the answer ... a nice blue is OK , but pink is problematic (correct RACING ??)
For the moment do you have spare 6V6s ? Just replace that valve for the moment... even if you have two new 6V6s ... because at this stage we are just getting the amp to come to life. When I build amps I never put my final quality valves in, I just use old ones or modern one that I have lying around..
We can sort out later what that 6V6 is doing.
Now if you replace that RED 6V6 and the replacement also glows red then you have wire something up incorrectly... but let's not cross that bridge yet

[ziess]

When the plate glows red it's never good, it'll fairly quickly meltdown (and potentially take other parts out when it dies). Swap the tubes in the sockets, that way you'll be able to tell if it's the tube (s) or an issue with the wiring.

For reference, blue glow is fluorescence and is the result of strat electrons hitting the glass. It doesn't usually indicate a problem.

Tommy.