First amp build, tweed deluxe 5e3, not working!

[Duelling Banjo]

Looks like the problem is to do with the area around the rectifier tube. After a pause in my efforts, I had another go at it just now. Initially no guitar sound and only a very faint mains hum. The rectifier didn't look to be glowing, so I switched off, unplugged the tube and plugged it in again, then switched the amp back on. Now I had guitar signal coming through the speaker at significant volume, but...also a VERY loud mains buzz and smoke and burning smell coming from what seems to be the rectifier tube socket, or wires connect to it. I didn't want to leave the amp on any longer so switched off before I could pinpoint the problem. I guess this would suggest a short circuit between two of the pins on the socket. Does this sound like the probable cause? I don't know if you guys would know exactly what would need to be shorting to cause this though I will of course have a good look with a magnifying glass and check my wiring is correct as per the diagram. Could be a simple case of sloppy soldering!

 

[Duelling Banjo]

Pins 7 and 8 I'm guessing though difficult to see. I might just bend pin 7 away or even snap it off as it's not being used.

 

[milocj]

The pins on the rectifier socket look like they could use some more solder. Maybe you've got an intermittent connection on one of those wires.

 

[Duelling Banjo]

Perhaps it wasn't the rectifier after all. Bent pin 7 away from pin 8 then turned it on. Still mains hum and smoke so I was staring at the circuit from a few inches away trying to pinpoint the source of the smoke whilst thinking I better turn this off before something worse happens... Lucky I wear glasses as I'm still picking bits of that capacitor off my face and out of my hair.

 

[2L man]

After cleaning I recommend you measure and test circuits first before installing new capacitor without all tubes. Then install capacitor and test and measure voltages. Then rectifier and measure. Then power tubes and measure. Few minutes testing after each significant build step test save more time in the end.

I believe there are building instructions which explain the way to proceed. If not someone should do them or "we" as comminity should make them. A while ago I recall I saw a table where was average resistances of tested and function amp between tube sockets etc. and possibly it was 5E3?

I test both transformers before screwing them to chassis. Filament voltages when they are wired. PS voltages when PS is done. I use Variac to bring Mains voltage up and without Variac I say a light pulb limiter is essential.

 

[Kev-wilson]

x2 for a 'light bulb limiter' recommendation! light bulb limiter

 

[YellowBoots]

Thank you for sharing. You just improved safety for further generations, and that's honorable. Now let's see if we can find out what happened so we can keep it from happening again.

 

[YellowBoots]

First off, I propose we badger @robrob to add your photo in #64 , along with a paragraph about eye protection, to his well-trafficed web pages.

Second off, I'm not jumping to the conclusion you did anything wrong. To get to the bottom of this, we need more info. Can you describe any changes the were made between #46 (when the amp was reportedly working) and now?

 

[Duelling Banjo]

No changes @andrewRneumann, I moved the amp and the jolt must have made it work, it was briefly fine when I reported it working. Then I mounted the chassis in the combo and left it for a while. When I turned on and plugged in today my experience was as per my posts today, so I guess the brief period of a few seconds when it was working was just a lucky moment when the short circuit wasn't happening, rather than anything actually being fixed. New capacitors on order!

 

[chas.wahl]

Amp startup sequence guides:

Amp Startup

Tube Amplifier Startup

robrobinette.com

http://paulrubyamplifiers.com/info.html#FirstPowerUp {older, some links in it no longer work}
Maybe someone knows of one, or a thread, where sequence has been followed/tailored for a 5E3 specifically; I don't.

Read both carefully; pick one and follow it, informed by your reading of the other one.

Somewhere near the beginning, after double-checking circuit with schematic and layout, I'd suggest going through @andrewRneumann's resistances table found in his post #5 on this thread; and @D'tar's input resistance chart posted by @King Fan in post #8. I know you've already been through this, but best to start here again, with no power.

As far as "typical" 5E3 voltages, your Modulus instructions may have that info, or you can refer to this:
https://robrobinette.com/How_The_5E3_Deluxe_Works.htm {and search for "Standard 5E3 DC Voltages"} where @robrob has annotated a layout. DC voltages measured to a chassis grounding point.

Lightbulb limiter is key, and for a 5E3, I've heard that a 100 W (actual, incandescent or quartz, no "equivalent") load is about what you want (based on its expected current draw). Read up on how to use one for the initial power-up steps.

I'm no expert, but the soldering of connections to the rectifier look dodgy to me, from what I can see. After doing the resistance tests, at least (to see if something appears wrong around this area) I would probably unsolder those, take out the socket and examine it carefully, and redo the connections to get shiny ones with sufficient solder. Others are much more expert at this, and may disagree.

 

[YellowBoots]

No changes @andrewRneumann, I moved the amp and the jolt must have made it work, it was briefly fine when I reported it working. Then I mounted the chassis in the combo and left it for a while. When I turned on and plugged in today my experience was as per my posts today, so I guess the brief period of a few seconds when it was working was just a lucky moment when the short circuit wasn't happening, rather than anything actually being fixed. New capacitors on order!

Well I'm really glad you are okay and this didn't cause you any personal injury.

My guess is that a short in the rectifier tube cause full AC to be applied to the first filter cap. That caused a lot of current and polarity reversals and eventual overheating and explosion of the first filter cap. This is only a hypothesis. Your rectifier socket wiring looks correct to me, but that doesn't preclude a hidden defect or stray whisker.

When you said it was humming loudly, was that from the speaker or from the transformer?

 

[Duelling Banjo]

Well I'm really glad you are okay and this didn't cause you any personal injury.

My guess is that a short in the rectifier tube cause full AC to be applied to the first filter cap. That caused a lot of current and polarity reversals and eventual overheating and explosion of the first filter cap. This is only a hypothesis. Your rectifier socket wiring looks correct to me, but that doesn't preclude a hidden defect or stray whisker.

When you said it was humming loudly, was that from the speaker or from the transformer?

Good question, now you mention it I can't be sure, especially as I was facing the back of the amp, if transformers hum then that's probably where the noise was coming from.

 

[Duelling Banjo]

Amp startup sequence guides:

Amp Startup

Tube Amplifier Startup

robrobinette.com

http://paulrubyamplifiers.com/info.html#FirstPowerUp {older, some links in it no longer work}
Maybe someone knows of one, or a thread, where sequence has been followed/tailored for a 5E3 specifically; I don't.

Read both carefully; pick one and follow it, informed by your reading of the other one.

Somewhere near the beginning, after double-checking circuit with schematic and layout, I'd suggest going through @andrewRneumann's resistances table found in his post #5 on this thread; and @D'tar's input resistance chart posted by @King Fan in post #8. I know you've already been through this, but best to start here again, with no power.

As far as "typical" 5E3 voltages, your Modulus instructions may have that info, or you can refer to this:
https://robrobinette.com/How_The_5E3_Deluxe_Works.htm {and search for "Standard 5E3 DC Voltages"} where @robrob has annotated a layout. DC voltages measured to a chassis grounding point.

Lightbulb limiter is key, and for a 5E3, I've heard that a 100 W (actual, incandescent or quartz, no "equivalent") load is about what you want (based on its expected current draw). Read up on how to use one for the initial power-up steps.

I'm no expert, but the soldering of connections to the rectifier look dodgy to me, from what I can see. After doing the resistance tests, at least (to see if something appears wrong around this area) I would probably unsolder those, take out the socket and examine it carefully, and redo the connections to get shiny ones with sufficient solder. Others are much more expert at this, and may disagree.

Thanks for all that info @chas.wahl. Clearly a more thorough testing and start up approach is what I need or it will continue to be guesswork.

 

[Duelling Banjo]

So after a cleanup, here's where the capacitor did it's 'thing', also blowing a resistor off its leads, though otherwise not much visible damage. Although it doesn't look terribly clean, with plenty of debris still visible, it's a huge improvement if you compare it with my photo from yesterday just after the event. I'm not overly 'chassis-proud' so this will do me from a visual point of view, though I'm wondering if it "needs" to be cleaner. I did spend a good hour or so cleaning it up using a brush, tweezers and a vacuum cleaner but that stuff is very stubborn, it's a bit sticky so just brushing and vacuuming doesn't do it and I don't really fancy picking every single fibre off with a magnifying glass and a pair of tweezers. Is that stuff conductive? If so then I have little choice but to replace the affected parts i.e. turret board and sockets which would be a huge setback in the build. What do you think I should do?

 

[2L man]

I recall electrolyte fluid is not corrosive or conductive but because it is sticky it might collect dust which then can come conductive. Together with high voltage dust can make small leak currents but which then current will "wear/smoke out" when power supply is capable to deliver current. I have cleaned quite many blown electrolytes just to look about clean and that has been fine.

Tube sockets are which you should concentrate because there voltage is high and grid current is very low and leaks can screw biases and then cause irratic operation. On power tube sockets the Anode voltage sweep and flyback spike voltages can be many times the power supply voltages high they can be prone to sparks. There are electronics cleaner spray bottles which you can use because they are safe for plastics.

 

[Duelling Banjo]

Thanks @2L man, I guess I'm after a consensus as to whether my cleanup "will do", or if I would be wasting my time to replace the damaged components, then resume the testing procedure i.e. checking continuity, then voltages with tubes out, then adding in the rectifier etc. No desperate hurry because I'm not going to proceed any further until my lightbulb current limiter components arrive and the device is assembled

 

[2L man]

I think that remaining does nothing for actual circuit but if it change bias/operating point it might cause something. Amplifiers are known to be wetted by bar liquids and puke and still keep operating

 

[Duelling Banjo]

I think that remaining does nothing for actual circuit but if it change bias/operating point it might cause something. Amplifiers are known to be wetted by bar liquids and puke and still keep operating

That's good enough for me!

 

[chas.wahl]

Isopropyl alcohol or ethanol and Q-tips? Think like old master painting restoration/cleaning (though that would not involve solvents unless incredibly proven).

 

[Duelling Banjo]

Isopropyl alcohol or ethanol and Q-tips? Think like old master painting restoration/cleaning (though that would not involve solvents unless incredibly proven).

That did occur to me but I also thought maybe drink the ethanol in a beverage of my choice whilst remembering this is no old master, just a novice build of an old amp.