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5e3 troubleshooting assistance needed
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vulture



Joined: 01 Mar 2008
Posts: 4503
Location: Chicago

PostPosted: Mon Jul 10, 2017 9:27 pm    Post subject: 5e3 troubleshooting assistance needed Reply with quote

Scoured the internet of all amp and 5e3 sites and trouble shooting to no avail came up zilch.
Amp was built by a member here about 5 years ago with new components.
Here's the deal. Was playing it the other day sounds great. Powered it up and got a severe volume drop, fizzy distortion almost like it is unbiased sounding. Only can get barely any sound through its turned up past 7 and hitting low notes/chords.

Tried the following with zero change:
Another Speaker
Another guitar
Another guitar cable
Progressively switched out all tubes with known working ones.
Checked the output transformer, readings looked good.
Tried another output transformer regardless.
Chopstick test on solder joints and wiring.
Tested all resistors
Tested pots
Cleaned jacks
Cleaned tube sockets
Tested all capacitors, filter caps, tone caps etc.

Haven't tested the power transformer yet, I'm guessing if there was any problem with it it wouldn't power on.

Any amp gurus got suggestions? Would like to deal with this myself and save some $$$'s on amp tech fees. Much thanks in advance.
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statorvane



Joined: 21 Aug 2003
Posts: 1950
Location: Upstate New York

PostPosted: Tue Jul 11, 2017 2:54 am    Post subject: Reply with quote

Almost sounds like the rectifier went south. Are you using a tube or SS rectifier? Can you post the power rail voltages?
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vulture



Joined: 01 Mar 2008
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Location: Chicago

PostPosted: Tue Jul 11, 2017 6:53 am    Post subject: Reply with quote

Tube rectifier. Tried two other reliable rectifiers with no change.
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Kregg



Joined: 22 Apr 2008
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PostPosted: Tue Jul 11, 2017 11:15 am    Post subject: Reply with quote

http://www.geofex.com/ampdbug/ampdebug.htm
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vulture



Joined: 01 Mar 2008
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PostPosted: Tue Jul 11, 2017 4:05 pm    Post subject: Reply with quote

Thanks. I scoured that link based on the diagnosis and still came up empty handed. My gut was telling me at first it was the cathode bypass caps, maybe i will triple check them again. Cathode resistors measure there rated ohms. Rolling Eyes
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statorvane



Joined: 21 Aug 2003
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Location: Upstate New York

PostPosted: Tue Jul 11, 2017 5:40 pm    Post subject: Reply with quote

Here is an annotated Weber 5E3 layout you can use to check your voltages:

https://robrobinette.com/images/Guitar/5E3P_Build/5E3_Voltages.png

Rob has some pretty good amplifier information on his site. Posts over at AX84 on occasion.
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vulture



Joined: 01 Mar 2008
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Location: Chicago

PostPosted: Tue Jul 11, 2017 9:23 pm    Post subject: Reply with quote

statorvane wrote:
Here is an annotated Weber 5E3 layout you can use to check your voltages:

https://robrobinette.com/images/Guitar/5E3P_Build/5E3_Voltages.png

Rob has some pretty good amplifier information on his site. Posts over at AX84 on occasion.


Thanks for this. I have been using Rob's awesome tutorial its great. I did take some readings most are close within 5 to 15v. below are the most drastic compared to his.
Power tubes pins 4 is at 382V
Secondaries on power tubes 380V
The readings between the filter caps l to r is 398 384 369
Pin 1 and 6 off of V1 is 107V

Update: Swapped out Cathode Bypass cap and resistor, No Change.
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statorvane



Joined: 21 Aug 2003
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Location: Upstate New York

PostPosted: Wed Jul 12, 2017 2:51 am    Post subject: Reply with quote

Yes, Rob's got some great information, he really put a lot of time into his website.

The rail voltages look pretty high, even allowing for the increase of line voltages over the last 50 years or so. Is your rectifier a Sovtek 5Y3GT, or a 5U4GB? These are fairly stiff, don't have as much of a voltage drop compared to the original 5Y3GT, which can lead to higher power rail voltages.

The voltage after the last dropping resistor there should be around 250 volts, and if I read you response correctly you are getting around 369 volts. The dropping resistor there should measure around 22K Ohms.

What do you get for your heater voltages?

The voltages at the preamp, V1 plates look a little low.

I would focus on the power rail voltages, looking for a wonky component (filter cap or dropping resistor), and verify the heater voltages too.

Hope this helps.
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vulture



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PostPosted: Wed Jul 12, 2017 6:22 am    Post subject: Reply with quote

Thanks statorvane. Yes its a 5Y3 i have to check on what brand but its a NOS. I will take a reading on the drop down resistors again as i figured 369 is too high and should be at least closer to the 250 to 280v range. Though last test i ran on all resistors read stable, no open readings. Very possible that it may be a filter cap. Will look at the heater v as well. The lower v on the v1 was alarming too. I will swap out the 12ay7(again) and see if it changes.
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statorvane



Joined: 21 Aug 2003
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Location: Upstate New York

PostPosted: Wed Jul 12, 2017 6:21 pm    Post subject: Reply with quote

Chances are if you have a NOS 5Y3GT it's fine.

Yes, I'd look at filter caps - they are the most likely components to go south. I'm pretty sure you have to measure the capacitance out of circuit.

Good luck and keep us posted. 5E3 is a great sounding amp.
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vulture



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PostPosted: Wed Jul 12, 2017 11:27 pm    Post subject: Reply with quote

I figured the next step would be to take them out of the circuit. But before I do that i checked for the heater voltage between 4/5 and 9 on the preamps with AC and there all at 3V, doesnt it suppose to be closer to 6V?
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statorvane



Joined: 21 Aug 2003
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Location: Upstate New York

PostPosted: Thu Jul 13, 2017 2:46 am    Post subject: Reply with quote

Measuring from pin 4 to 5 and you should see 6.3 volts. Within 10% is okay. Your heater wiring is center tapped right?
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vulture



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PostPosted: Thu Jul 13, 2017 7:14 pm    Post subject: Reply with quote

yes, center tapped at 3V off both preamps 4/5 Confused
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Johnson82



Joined: 27 Aug 2007
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PostPosted: Fri Jul 14, 2017 6:17 am    Post subject: Reply with quote

Just to clarify on the measurement: You should be measuring from pin 4/5 to pin 9, not from 4 to 5 (or to ground). If you measure from pin 9 (or pin 4/5) to ground, you should get around 3 volts.
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vulture



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PostPosted: Fri Jul 14, 2017 8:44 pm    Post subject: Reply with quote

Embarassed Yes your right half the current. I have been taking so many readings off this amp to ground via DC I for got to measure off the 9. Yes it is in fact 6.3V

I'm going to have to heat up the iron and take these filter caps out to test them.
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