MetroAmp JTM45 build - no sound, help please ;-)

[sluckey]

That blue PT wire with the splice is long enough to reach the power switch. I suggest cut out that splice and connect the blue to the power switch and connect the orange to the fuse holder. Oh, and one more test on the fuse holder. Just measure resistance from side lug to end lug. If it ain't zero ohms (or real close to zero) replace it. Otherwise move on.

[purpletele]

In reply #14 photo 1019, it looks like the tip of the first fuse has a black wire that goes straight to a ground post.

Am I seeing that correctly? 

[Papa Jim]

In reply #14 photo 1019, it looks like the tip of the first fuse has a black wire that goes straight to a ground post.

Am I seeing that correctly?

Sure looks like it.
 And in that same area why is that tiny tiny black wire going to that big filter cap?

[Bosses]

In reply #14 photo 1019, it looks like the tip of the first fuse has a black wire that goes straight to a ground post.

Am I seeing that correctly?

Yes, that is the HT fuse

[purpletele]

In reply #14 photo 1019, it looks like the tip of the first fuse has a black wire that goes straight to a ground post.

Am I seeing that correctly?

Sure looks like it.
 And in that same area why is that tiny tiny black wire going to that big filter cap?

That's a ground wire coming off of the cap, I looked on George's instructions and he does it just like that.

I looked for a photo of how he hooks up the fuses, he doesn't clearly show how that fuse is hooked up.

[Bosses]

In reply #14 photo 1019, it looks like the tip of the first fuse has a black wire that goes straight to a ground post.

Am I seeing that correctly?

Sure looks like it.
 And in that same area why is that tiny tiny black wire going to that big filter cap?

That is the choke wire

[purpletele]

In reply #14 photo 1019, it looks like the tip of the first fuse has a black wire that goes straight to a ground post.

Am I seeing that correctly?

Yes, that is the HT fuse

I think it should go to a positive terminal and definitely not to ground.  Let others verify that, but I pretty sure that is your issue.

[purpletele]

Here is a drawing that Steve Luckey did for me a couple of weeks ago.

I am most uncomfortable in this area and I have a pile of transformers to verify my fears.  This drawing helped me in my last build, there are different ways about routing, I look for the method that the EYES can recognize when I raise my hand for help.

I hope this helps.

You don't have to change your wiring, but focus on the fuse hook up only

[Bosses]

Oh good riddance
I changed the fuseholder and now i get filamentvoltage and lamp voltage
Funny thing is I did that last night as well with no results.
As per the wiring on the other fuse: I just rechecked it and that way is the way George is doing it. I can’t believe he would mess that up?

[Papa Jim]

Oh good riddance
I changed the fuseholder and now i get filamentvoltage and lamp voltage
Funny thing is I did that last night as well with no results.

Throw all your extra fuse holders in a lake somewhere. 

[Papa Jim]

Now don't forget to start over giving the guys measurements with your tubes out before going any further.

[Bosses]

 

Now don't forget to start over giving the guys measurements with your tubes out before going any further.

 

[Bosses]

Thanks a bunch guys - this is incredible!!!   

Now, voltages without tubes:

V1,V2,V3,V4,V5 Filament: 6,22
V6 : 5,21
Anything else before i throw in the gz34?

[sluckey]

As per the wiring on the other fuse: I just rechecked it and that way is the way George is doing it. I can’t believe he would mess that up?

He didn't mess it up. He copied that from the original JTM45. It's fine with that fuse wired to ground. Don't get sidetracked by that drawing purpletele posted. That's a different amp. You're building a JTM45. Stick to the excellent plan George gave you.

[sluckey]

Anything else before i throw in the gz34?

Yes. Measure the AC voltage on pins 4 and 6 of the rectifier socket. Then measure the -dcv on pin5 of each output tube socket.

Then turn to page 20 of the instructions and follow George's excellent testing procedures. If you get hung up, just ask another question.

[Bosses]

 

As per the wiring on the other fuse: I just rechecked it and that way is the way George is doing it. I can’t believe he would mess that up?

He didn't mess it up. He copied that from the original JTM45. It's fine with that fuse wired to ground. Don't get sidetracked by that drawing purpletele posted. That's a different amp. You're building a JTM45. Stick to the excellent plan George gave you.

[Bosses]

Anything else before i throw in the gz34?

Yes. Measure the AC voltage on pins 4 and 6 of the rectifier socket. Then measure the -dcv on pin5 of each output tube socket.

Then turn to page 20 of the instructions and follow George's excellent testing procedures. If you get hung up, just ask another question.

Pin 4 : 300V
Pin 6 : 95,6V
pin 5 of V4,5: -0vdc (shouldnt this be around -50 to 70

[sluckey]

You got more work to do. Pin 6 should be the same as pin 4. And you must get a good negative voltage on pin 5 of both output tubes.

DON'T PLUG IN ANY TUBES UNTIL BOTH THESE ISSUES ARE RESOLVED!

[Bosses]

You got more work to do. Pin 6 should be the same as pin 4. And you must get a good negative voltage on pin 5 of both output tubes.

DON'T PLUG IN ANY TUBES UNTIL BOTH THESE ISSUES ARE RESOLVED!

Ok - just ran over every soldering, reflowed a few, checked component values (ok) and measured continuity on sec. (77,6Ohm)
Still no go - 300v on pin 4 and around 100 on pin 6.
Could it be the sec thats fried?
Still no neg. dc on pin 5 of v4 and v5

[sluckey]

The data sheet you posted for that PT says the voltage should be 345VAC on each of those red wires attached to pins 4 and 6. Disconnect that white wire from pin 6 and recheck the voltages. What have you? And post some pics that show the half of the circuit board closest to the PT.

[Bosses]

The data sheet you posted for that PT says the voltage should be 345VAC on each of those red wires attached to pins 4 and 6. Disconnect that white wire from pin 6 and recheck the voltages. What have you? And post some pics that show the half of the circuit board closest to the PT.

Already tried that and the voltage rised about 4-5 v

[sluckey]

Already tried that and the voltage rised about 4-5 v

According to that statement you need a new PT. There's nothing else you can do until you do that.

So, is this really a Metro kit? Or did you source all the parts and scratch build this using the metro plans?

[purpletele]

[/quote]According to that statement you need a new PT. There's nothing else you can do until you do that.[/quote]

Bosses, welcome to the club, I could do transformer replacements in my sleep now. (As long as I have a diagram)

[Bosses]

Already tried that and the voltage rised about 4-5 v

According to that statement you need a new PT. There's nothing else you can do until you do that.

So, is this really a Metro kit? Or did you source all the parts and scratch build this using the metro plans?

Not a metro kit. Valve storm is in the us and with customs and all it’s too expensive

[Bosses]

*Sigh*
Well, new PT it is then 
Luckily it is only 250$ here in Denmark 

[pdf64]

That’s a shame, it a bad feeling to realise that an expensive component has been damaged. Be assured that we’ve all been there. The best thing you can do to avoid it ever happening again is to build yourself a light bulb limiter, while you’re waiting for a new PT.

[Papa Jim]

+1

[Bosses]

So:
Got the new pt, slammed it in and......no neg dc on pin 5 of v4+5 
Approximately 400 vac on pin 4, 110 vac on pin 6 of v6.

What the hell is going on here 

[sluckey]

So:
Got the new pt, slammed it in and......no neg dc on pin 5 of v4+5 
Approximately 400 vac on pin 4, 110 vac on pin 6 of v6.

What the hell is going on here 

Most likely a wiring error/s. Show us the new transformer wiring diagram.

[Bosses]

Most likely a wiring error/s. Show us the new transformer wiring diagram.
[/quote]
Same as the other PT:

[sluckey]

Connect a red wire to pin 4. (Doesn't matter which one)
Connect the other red wire to pin 6.

Now for the tricky part. You have two black wires.

***YOU MUST CONNECT THE CORRECT ONE TO CHASSIS GROUND.***

Use your ohm meter to determine which black wire is the correct one. Connect one probe of your ohm meter to a red wire. Doesn't matter which one. Connect the other meter probe to the other red wire. You should have a resistance reading. Make a note of what that reading is. Now leave one probe connected to a red wire but move the other probe to a black wire. One black wire should show no resistance reading (This is the wrong black wire!). The other black wire should show a reading that is approximately half the reading between the two red wires. This is the correct black wire. Connect it to chassis ground.

[Papa Jim]

Sluckey, correct me if wrong, but on this schematic wouldn't that correct black wire (sec.red wires blk c.t) go to the fuse? https://el34world.com/charts/Schematics/files/Marshall/Marshall_jtm45_readable.pdf

[sluckey]

That's correct. And the other side of that fuse connects to chassis ground. I hope this is not confusing.

[Papa Jim]

Sorry Sluckey I see that point now,

[Papa Jim]

I was thinking in physical terms and you were thinking electrically (continuity) terms. 

[Bosses]

Connect a red wire to pin 4. (Doesn't matter which one)
Connect the other red wire to pin 6.

Now for the tricky part. You have two black wires.

***YOU MUST CONNECT THE CORRECT ONE TO CHASSIS GROUND.***

Use your ohm meter to determine which black wire is the correct one. Connect one probe of your ohm meter to a red wire. Doesn't matter which one. Connect the other meter probe to the other red wire. You should have a resistance reading. Make a note of what that reading is. Now leave one probe connected to a red wire but move the other probe to a black wire. One black wire should show no resistance reading (This is the wrong black wire!). The other black wire should show a reading that is approximately half the reading between the two red wires. This is the correct black wire. Connect it to chassis ground.

Measured between the two reds : 71 Ohm
Measured between one red and the black(already connected to ch.gr.): 40,8 Ohm

The other black wire (120VAC Tap) : Nothing

That must be correct, right?

[sluckey]

OK, we are back to the same point we were when you ordered a new PT. Before, I asked you to disconnect the white wire from pin 6 and recheck the voltage at pin 6. (My suspicion was that something on that white wire was dragging the voltage on pin 6 down.)You said you already did that and the voltage at pin 6 only went up a few volts. And that was your statement that lead to you ordering a new PT. I'm gonna take a slightly different approach this time.

Disconnect the RED PT wire from pin 6 on the socket. Just let that red wire dangle in the air without touching anything. Now measure the voltage on the dangling wire. Should be the same as the voltage on the other red wire that is still connected to pin 4. What have you?

[Bosses]

OK, we are back to the same point we were when you ordered a new PT. Before, I asked you to disconnect the white wire from pin 6 and recheck the voltage at pin 6. (My suspicion was that something on that white wire was dragging the voltage on pin 6 down.)You said you already did that and the voltage at pin 6 only went up a few volts. And that was your statement that lead to you ordering a new PT. I'm gonna take a slightly different approach this time.

Disconnect the RED PT wire from pin 6 on the socket. Just let that red wire dangle in the air without touching anything. Now measure the voltage on the dangling wire. Should be the same as the voltage on the other red wire that is still connected to pin 4. What have you?

256 vac on pin 4, 109 on the loose wire

[Papa Jim]

For my own sanity and nothing else. Trace that dangling wire back and make sure there is nothing else connected to it and also that it is in fact the red wire from the transformer.

[Bosses]

For my own sanity and nothing else. Trace that dangling wire back and make sure there is nothing else connected to it and also that it is in fact the red wire from the transformer.

Hehe - it’s fresh from the box, no cut wires and yes it IS the red from pt 

[sluckey]

Measure the voltage BETWEEN the two red wires, ie, one probe on a red wire, and the other probe on the other red wire. What have you?

[sluckey]

BTW, your voltage readings are all over the place. Earlier you had ≈400V on pin 4. Now you have 256V on pin 4. Either you are not operating the meter correctly or the meter is lying or just bad. What brand and model number meter do you have?

[Bosses]

Measure the voltage BETWEEN the two red wires, ie, one probe on a red wire, and the other probe on the other red wire. What have you?

699 - 700 vac

[Bosses]

BTW, your voltage readings are all over the place. Earlier you had ≈400V on pin 4. Now you have 256V on pin 4. Either you are not operating the meter correctly or the meter is lying or just bad. What brand and model number meter do you have?

Elma bm811

[sluckey]

700V is a good reading. Now measure the voltage between the black wire (not chassis) and each red wire. I want two numbers. What are they?

[Bosses]

700V is a good reading. Now measure the voltage between the black wire (not chassis) and each red wire. I want two numbers. What are they?

347 and 348 vac

[sluckey]

Perfect! You have another one of those crappy fuse holders. Just connect that black wire directly to chassis ground at the filter cap ground lug for now and reconnect the dangling red wire to pin 6. Now recheck AC voltages on pins 4 and 6 and negative DC voltage on pin 5 of each output tube. At this time you do not want ANY tubes plugged in. What have you?

[Bosses]

Perfect! You have another one of those crappy fuse holders. Just connect that black wire directly to chassis ground at the filter cap ground lug for now and reconnect the dangling red wire to pin 6. Now recheck AC voltages on pins 4 and 6 and negative DC voltage on pin 5 of each output tube. At this time you do not want ANY tubes plugged in. What have you?

347/348 vac, -40,21vdc on both
 :worthy1:I bow in respect

Lol 2 out of 2 brand new fuse holders faulty - way to go   

[sluckey]

I bet your original PT is good too.

[Bosses]

I bet your original PT is good too.

Yes - might be but on the other hand i measured no resistance on the windings but I will check it for sure