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

[Bosses]

Hi all,
I have (tried to) built the metroamp jtm45. 
Now finished and measuring.......hmmmm...something is wrong.
Voltages:
Pin   V1   V2   V3   V4   V5   V6
1   70   44,6   63         
2                         3,3    3,3    5,2AC,88DC
3   4,4   3,5   3,6   88   88   
4   3,3   3,3   3,3   88   88   393
5   3,3   3,3   3,3   -75   -75   
6   70,9   72   61   88   88   321
7             45            
8   4,4   3,5   3,6   3,3   3,3   5,2AC,88DC
9   3,3   3,3   3,3         
Wall   229               
Bias            0   0   


Also the GZ34 gets REALLY hot.

I checked and triplechecked wiring etc. so im kind of lost right now :(

Any suggestions on how to troubleshhot from here?

Regards,   

[Papa Jim]

First off take all the tubes out.
Others will tell you how to put a load on the output.
Are you powering up with a current limiting light bulb in series with your wall ac.?https://www.thegearpage.net/board/index.php?threads/light-bulb-current-limiter-build-thread.1607972/

When you have those two things in place you need to leave the tubes out and power up, and give us your power supplies B+ Voltages.

[Bosses]

Tubes out - check
Current limiter- not doable in my country since that kind of lightbulbs are prohibited (Denmark)
B+:307 and 103
Already have a load on the output

[Papa Jim]

Go underground to get ya a bulb 

[Bosses]

 

[Papa Jim]

Does your amp kit tell you what the B+ voltages are supposed to be. I can't see them on the schematic. I am assuming that 307 is the vdc at point A on the schematic.

[Papa Jim]

You said you are providing an output load. How are you doing that. Without tubes check for B+ Plate voltage and filament voltage at the tube sockets for us. Notice I said us because this is about as far as I can go with my amp knowledge other than once all those things are correct I would power down, drain the ps. caps, take the schematic and visually step thru it checking off each wire as I verify it is wired correctly. All wires, and no extras. Then put the preamp tubes in first and power back up and measuring again the plate voltages, and filament voltages at the sockets for us. Once satisfied with that power off and add the output tubes and repeat those two measurements for us. Next step is to do an output tube bias procedure before going any further. These all have to be correct before proceeding. Does your instructions tell how to bias the output tubes.

[Bosses]

Thanks a lot papa
B+ at pin 8 of rectifier socket is 421VDC
Filament voltage at v1,2,3,4,5 is 3,3 VAC

As stated in my first post i checked, rechecked, triplechecked the wiring, but still :)
I will go over all wiring again tomorrow - for now its bedtime

Thanks again,

[Papa Jim]

Ok. don't worry about the amp. These dudes  on here will help ya get it working. Pretty much a guarantee if you follow directions.

[Bosses]

I sure hope so
Oh and the load I’m providing is an 8 ohm speaker @100 w

[Papa Jim]

That load is good as long as you know the ot tranny is wired correctly to the ot tubes and is a good tranny. Chances are it is but re-check your wiring to the socket and maybe do an ohms check of the input and output windings. 

[Ed_Chambley]

For a JTM 45 your voltages are off considerable. If 70 vdc on V1 plates you are about 100 vdc low.
Check voltages beginning with ht ac and if ok move to after rectifier. If ok, with rectifier tube  only continue without tubes in. Voltages should now seem high since no tube load.


Keep in mind the Metro Amp has under board wiring.  Did you insert enough lead to completely go through the turret and bend it  down the side to insure it  cannot fall out.


Unloaded v1 should be over 200vdc as it is in both I have. You either have wiring error or resistors that is too large somewhere. Sometimes jumping the rectifier tube with diodes is less expensive for testing especially if your rectifier tube is a NOS amperes or mullard.


The general rule is if it were wired correctly using proper component values it would work.

[Ed_Chambley]

Thanks a lot papa
B+ at pin 8 of rectifier socket is 421VDC
Filament voltage at v1,2,3,4,5 is 3,3 VAC

As stated in my first post i checked, rechecked, triplechecked the wiring, but still :)
I will go over all wiring again tomorrow - for now its bedtime

Thanks again,

Always measure filament voltages across, not one to ground, but one on each tube connection. This will give you an accurate measurement of close to 6.3 vac.

[purpletele]

I sure hope so
Oh and the load I’m providing is an 8 ohm speaker @100 w

Bosses,

In order for the group of guys to be able to help you it is important that you provide the information that they need to analyze the issues.

1. I highly recommend posting a readable pdf of the schematic and layout.

2. Review the Hoffman section for posting photos and take some clear photos.  If you don't reduce the photos pixel count and you type a long message then you might lose the message if you don't save it somewhere.

3. If you do that in a very structured manner it makes the process much more pleasant for you and more satisfying for the moderators.


4. I just finished a JMP/JCM  designed by Sluckey.  I'll post my voltages now that I have the amp working well.

BV

[Bosses]

I sure hope so
Oh and the load I’m providing is an 8 ohm speaker @100 w

Bosses,

In order for the group of guys to be able to help you it is important that you provide the information that they need to analyze the issues.

1. I highly recommend posting a readable pdf of the schematic and layout.
 
2. Review the Hoffman section for posting photos and take some clear photos.  If you don't reduce the photos pixel count and you type a long message then you might lose the message if you don't save it somewhere.

3. If you do that in a very structured manner it makes the process much more pleasant for you and more satisfying for the moderators.


4. I just finished a JMP/JCM  designed by Sluckey.  I'll post my voltages now that I have the amp working well.

BV

Schematic and pictures attached. (sorry for the wiremess, it will be cleaned up when amp is working  )

I just realised that i only get 78 VAC through the fuseholder (116VAC on other side). It has a 2A slowblow fuse which should be suitable for 230VAC.
When i bypass the fuse i get filamentvoltage and lamp turns on, but not when going through fuse?!? Bad holder perhaps?
I tried several different holders but no luck.....

/bosses

[Papa Jim]

Do you have some way to jump around the fuse holder but still go thru the fuse in order to determine if it is the fuse or the holder. Auto parts stores usually carry a universal fuse holder with pigtail wires on it for a couple bucks. You could use for testing then throw in your amp tool kit. .

[Bosses]

Do you have some way to jump around the fuse holder but still go thru the fuse in order to determine if it is the fuse or the holder. Auto parts stores usually carry a universal fuse holder with pigtail wires on it for a couple bucks. You could use for testing then throw in your amp tool kit. .

I tried 3 different holders - brand new, straight out of the bag, with 6 different fuses, also brand new - no change 

[Papa Jim]

I would probably remove the fuse and try to measure the the resistance of the tranny input side then. And it looks like that tranny has multiple taps so double check that you are using the right one. After that you have already powered it up without a fuse so I would probably put a 3 amp in and see if that helps. Don't know for positive if that will make a difference or not but that is what I would do. Then a 4, 5,  Just kidding   I'm not sure  but others will know if problems after the secondary side of a power tranny will affect the primary side. On ot's it does.

[Bosses]

I would probably remove the fuse and try to measure the the resistance of the tranny input side then. And it looks like that tranny has multiple taps so double check that you are using the right one. After that you have already powered it up without a fuse so I would probably put a 3 amp in and see if that helps. Don't know for positive if that will make a difference or not but that is what I would do. Then a 4, 5,  Just kidding   I'm not sure  but others will know if problems after the secondary side of a power tranny will affect the primary side. On ot's it does.

But....as per this pic all of this is happening before the PT and as stated before : I get heaters on, lamp on and some kind of voltage on the tubes (not the right ones though  )
I already tried a 3A fuse - no luck 
I also doublechecked that it is the right tap - and it is, and the blue (from fuse to PT) is common and the orange on the PWS is 230V tap.
Im kinda confused here - not my first build but this one i cant figure out 

Maybe you're right that something on sec is affecting pri?!?!?

but thanks for your inputs so far 
/bosses

[Papa Jim]

Sounds like you have done all the right things. The territory now is beyond my understanding so I am gonna step back from here and watch to learn from the knowledge base on here. I think that a slo blo may have some resistance to it and not a dead short. Seems that the extra voltage needed to light your pilot lamp and bring up the filaments is getting dropped across that fuse but not quite enough to blow it. Only thing I know of at this point is measure the voltage drop across that fuse and everything else in the input circuit. May even be a wire due to a poor solder joint.  Just my theory. Waitin to learn something here because I could be all wrong but not too much.  I hate to be fooled by Ohms law.  but often am.

[shooter]

built the metroamp jtm45

need a schematic to help,
did the kit come with "options" for 230 vac /120 vac?
did it come with a troubleshooting section in the directions? 

[Papa Jim]

Hey, Shooter I googled and found this. Maybe this is what he has? http://valvestorm.com/sites/default/files/JTM_45_KIT_V2.1.pdf

They even have their own forum for builds.
http://forum.metropoulos.net/viewtopic.php?t=10853&start=15

Although the knowledge base here probably far exceeds that. 

[Bosses]

Hey, Shooter I googled and found this. Maybe this is what he has? http://valvestorm.com/sites/default/files/JTM_45_KIT_V2.1.pdf

Exactly! 

[Bosses]

built the metroamp jtm45

need a schematic to help,
did the kit come with "options" for 230 vac /120 vac?

Yes

did it come with a troubleshooting section in the directions?

Nope - just a voltage chart

/bosses

[pdf64]

...Current limiter- not doable in my country since that kind of lightbulbs are prohibited (Denmark)...

I think you can still find them if you look a bit harder, eg specialist electrical suppliers.
If you can't find regular domestic type bulbs, then try a search for R95, PAR38, anything with a ~100W element.

[sluckey]

That's the best build instruction document I've ever seen. Even better than the old Heath Kit stuff. You just need to start at page one and move forward again until you find what you did wrong.

[purpletele]

That's the best build instruction document I've ever seen. Even better than the old Heath Kit stuff. You just need to start at page one and move forward again until you find what you did wrong.

I agree, that is a very nice document. I am going to print that out, it will probably burn out my ink put that is a nice document to have on hand.

[Bosses]

That's the best build instruction document I've ever seen. Even better than the old Heath Kit stuff. You just need to start at page one and move forward again until you find what you did wrong.

Hi sluckey,
Already rebuilt twice 
Well, at it again hehe
What I’m confused about is that there’s not enough voltage going through the fuse?
As I wrote I can get good readings - or at least some readings when I bypass the fuse.
That seems weird to me 
It is difficult to troubleshoot further down the line when the problem starts before I even get current flowing in to the pt.
I’m not an expert on this just a happy diy-builder who have a passion for tubes and guitars 

[st]

What I’m confused about is that there’s not enough voltage going through the fuse?
As I wrote I can get good readings - or at least some readings when I bypass the fuse.

I suspect you have a discontinuity somewhere in the primary circuit: mains line 1-- mains switch -- primary transformer winding -- mains neutral (or line 2). The 70-odd volts you are measuring could be phantom voltage (or one mains line to earth, instead of between two mains lines). Triple check continuities and solder connections in this section, check against schematic. Post detailed pics so we can help you netter.

[st]

... also, the 116vac and 78 vac are measured to ground, correct? Just to be sure, re-measure  between those points and neutral/line 2 (which in your country may not be at the same potential as earth ground)

[Bosses]

... also, the 116vac and 78 vac are measured to ground, correct? Just to be sure, re-measure  between those points and neutral/line 2 (which in your country may not be at the same potential as earth ground)

Yes measured to ground
I get 233 between L and N which is correct here
I will just go redo the whole AC part and take some pics along the way 

[st]

No need to redo everything. Just check, double-check, then triple-check, then measure some more and post results here.

What might be insightful is if you
- break the connection at the fuse holder (e.g. by removing the fuse), than power up and measure voltage across the fuseholder;
- find a way to eliminate the possibility that the power switch is playing games. If you find a safe way to jumper the terminals (amp unplugged of course), do this and then plug it in;
- with the amp unplugged, switch on, fuse in place, measure resistance between line and neutral pins on your mains plug. Then take out fuse and to the same from fuse tip to orange wire on power switch.

[Bosses]

No need to redo everything. Just check, double-check, then triple-check, then measure some more and post results here.

What might be insightful is if you
- break the connection at the fuse holder (e.g. by removing the fuse), than power up and measure voltage across the fuseholder;

233 vac across

- find a way to eliminate the possibility that the power switch is playing games. If you find a safe way to jumper the terminals (amp unplugged of course), do this and then plug it in;

No change

- with the amp unplugged, switch on, fuse in place, measure resistance between line and neutral pins on your mains plug.

Nothing

Then take out fuse and to the same from fuse tip to orange wire on power switch.

7 ohms

[st]

- with the amp unplugged, switch on, fuse in place, measure resistance between line and neutral pins on your mains plug.

Nothing

Then take out fuse and to the same from fuse tip to orange wire on power switch.

7 ohms

This is your problem. You should read a value there. The 7 ohms you read is through your transformer primary winding. So between those two points everything is fine. That leaves the switch (which you also say is ok), the fuse or fuseholder, and everything from those two points to your mains plug (including the solder connections on your iec connector and any wire-to-wire connections you may have made). Are you 100% sure the fuse itself is okay, as in not popped? Take it out and measure resistance across it. Are you sure you're not putting a 5x20mm fuse in a 6.3x32mm fuse holder?

To rule out the iec connector, unplug the amp, and measure for continuity between one of the pins on your mains plug, and the two outer terminal on the back  of the iec socket in your amp. One should read open, the other zero ohms, the other way around for the other pin.

[Bosses]

- with the amp unplugged, switch on, fuse in place, measure resistance between line and neutral pins on your mains plug.

Nothing

Then take out fuse and to the same from fuse tip to orange wire on power switch.

7 ohms

This is your problem. You should read a value there. The 7 ohms you read is through your transformer primary winding. So between those two points everything is fine. That leaves the switch (which you also say is ok), the fuse or fuseholder, and everything from those two points to your mains plug (including the solder connections on your iec connector and any wire-to-wire connections you may have made). Are you 100% sure the fuse itself is okay, as in not popped? Take it out and measure resistance across it. Are you sure you're not putting a 5x20mm fuse in a 6.3x32mm fuse holder?

To rule out the iec connector, unplug the amp, and measure for continuity between one of the pins on your mains plug, and the two outer terminal on the back  of the iec socket in your amp. One should read open, the other zero ohms, the other way around for the other pin.

Fuse not blown - tried two others, same result. And it is the right size for that holder 
Full continuity on pins on the IEC.
I've narrowed it down to somewhere around the fuse/holder because when i bypass it, as shown in pic, the amp "works"  - or rather i get lamp on and filament voltage (6,2VAC)
An odd thing is that now i get around 50VAC on heaters on rectifier.....
Now, I dont want to run without a fuse so i somehow need to figure out what is going on.
I also tried another fuseholder - no-go 

[sluckey]

Can you post some pics that clearly show the power cord, PT, power switch, indicator lamp, and fuse holder, and wires between these components? Several angles if needed to clearly see how it is all connected.

The only way to measure the rectifier tube 5VAC filaments is with one meter probe on pin 2 and the other meter probe on pin 8. If you had one meter probe connected to chassis then that 50VAC reading is bogus and meaningless.

[st]

Fuse not blown - tried two others, same result. And it is the right size for that holder 

Don't take this the wrong way, but it is not because you tried a few different fuses, that they are all fine. If there are other problems (i.e. shorts) in your amp as well, which appears to be the case, then any fuse you put in there will pop. Have you actually measured continuity of the fuse? (I ask again because you do not say so unambiguously). Popped fuses would explain both why a different fuse holder doesn't work and why you do get power when you bypass the fuse (which I didn't advice you to do and which you shouldn't do!) As Sluckey suggests, when you measure something, be a bit more precise about what and how you measured.

[Bosses]

Can you post some pics that clearly show the power cord, PT, power switch, indicator lamp, and fuse holder, and wires between these components? Several angles if needed to clearly see how it is all connected.

The only way to measure the rectifier tube 5VAC filaments is with one meter probe on pin 2 and the other meter probe on pin 8. If you had one meter probe connected to chassis then that 50VAC reading is bogus and meaningless.

Here you go :)

[Bosses]

Fuse not blown - tried two others, same result. And it is the right size for that holder 

Don't take this the wrong way, but it is not because you tried a few different fuses, that they are all fine. If there are other problems (i.e. shorts) in your amp as well, which appears to be the case, then any fuse you put in there will pop. Have you actually measured continuity of the fuse? (I ask again because you do not say so unambiguously). Popped fuses would explain both why a different fuse holder doesn't work and why you do get power when you bypass the fuse (which I didn't advice you to do and which you shouldn't do!) As Sluckey suggests, when you measure something, be a bit more precise about what and how you measured.

Sorry i forgot to say - yes i did measure all the fuses i tried for continuity before and after i tried. No fuses blown.

[Papa Jim]

That's what I understood is he has never blown a fuse just can't totally power up when a fuse is in there but can when fuse is bypassed..

[Papa Jim]

Why do you have 2 fuse holders out the side of the chassis?  Even the kit instruction picture page 13 shows only one black one thru the chassis side then a exposed glass fuse one inside the chassis.

[Bosses]

Why do you have 2 fuse holders?  Even the kit instruction picture page 13 shows only one.

There is also one on page 8, internal one i moved from chassis to side ;-)
It is the H.T. Fuse

[Bosses]

That's what I understood is he has never blown a fuse just can't totally power up when a fuse is in there but can when fuse is bypassed..

Correct 

[Papa Jim]

Just asking for the heck of it, and probably a really stupid question because I don't think you would get as far as you have if you did this. But you for some reason didn't wire the pilot lamp in series instead of parallel. I have no idea what that would do either. 

[Bosses]

Just asking for the heck of it, and probably a really stupid question because I don't think you would get as far as you have if you did this. But you for some reason didn't wire the pilot lamp in series instead of parallel. I have no idea what that would do either. 

Pilot lamp is wired directly to v5 because its a 6,3V not 120V.
So, no it is out of the AC circuit. 

[Papa Jim]

ok good

[sluckey]

The wire colors for your PT are different from the colors specified on page 28 of the instructions pdf. ie, the filament wires are orange rather than green. So, what color is the filament center tap wire? Did you possibly mix up one of the orange filament wires with the primary common orange wire? Can you post a diagram of the actual transformer you are using?

It appears that the EIC, fuse holder, power switch, and PT primary are connected correctly, although you have been swapping PT primary orange and blue wires between snapping pics. This should work unless that fuse holder is bad. Try this...

Put a fuse in the holder and turn off the power switch. Disconnect mains EIC plug/cord. Set meter to measure resistance. Connect one meter probe to Line 1 of the EIC socket. Connect the other meter probe to Line 2 of the EIC socket. The resistance reading should be infinity, open circuit. Now turn the power switch on. Meter reading should now be some small resistance value. What have you?

[Bosses]

The wire colors for your PT are different from the colors specified on page 28 of the instructions pdf. ie, the filament wires are orange rather than green. So, what color is the filament center tap wire? Did you possibly mix up one of the orange filament wires with the primary common orange wire? Can you post a diagram of the actual transformer you are using?

It appears that the EIC, fuse holder, power switch, and PT primary are connected correctly, although you have been swapping PT primary orange and blue wires between snapping pics. This should work unless that fuse holder is bad. Try this...

Put a fuse in the holder and turn off the power switch. Disconnect mains EIC plug/cord. Set meter to measure resistance. Connect one meter probe to Line 1 of the EIC socket. Connect the other meter probe to Line 2 of the EIC socket. The resistance reading should be infinity, open circuit. Now turn the power switch on. Meter reading should now be some small resistance value. What have you?

Yes i swapped the wires for testing if it was a bad wire (blue). It wasnt and now it is back to original.
Attached are the wiring of the PT.
I get OL in both instances when measuring line 1 & 2

[sluckey]

Now bypass the fuse as you did earlier and repeat the resistance check. What have you. If you now get a low resistance reading, that indicates the fuse holder is bad. Replace it.

[st]

As I said earlier, you have a discontinuity in the primary. If your sure it's not the switch and fuse, check wiring again. I pointed out there wire-to-wire connections before. I can see them in yellow heatshrink. Are you sure these are sound? Maybe you moved one when you bypassed the fuse holder and made a connection in doing so (so not actually by bypassing the fuse), breaking it again when you moved everything back to where it was.

Also investigate the possibility that the transformer is wired incorrectly, as sluckey suggested.