How long should grid resistors last?

[pbman1953]

In 2015 you all helped me convert , in a Traynor YBA-3 (not Super) , EL34's to 6550's. Ed always put a bug in my ear that if you hear noise like bacon frying , that could be bad grid resistors. Any opinions?


Also, when filters caps go, is the hum even with the volume off? What does it mean if you get hum when you increase the volume & gain controls?


Thanks

[shooter]

if you hear noise like bacon frying

typical is bad solder joint, sloppy sockets

What does it mean if you get hum when you increase the volume & gain controls?

the problem is usually "left" (before) those pots

[pbman1953]

This is upsetting if it's a cold solder. I purposely held each connection to the terminal and watched them solidify before letting go. Plus last year I installed all new Beldon sockets.

[shooter]

the frying bacan is pretty easy;
bench the amp, plug in a signal, and chop-stick, wiggle jiggle, thump, rotate knobs quick, and the gremlin can't resist showing itself
hum, Identify if it's 60 or 120hz 1st
60 is filaments, 120 is PS

[pbman1953]

will do!

[pbman1953]

Just from memory it's a 60 cycle. Sounds like a low bass tone

[shooter]

If so;
start at 1st tube, (V1) Pull, hum, if yes, next tube.  STOP before the PI.  That should eliminate stuff and point you to the right ballpark

[pbman1953]

With V1 out, no noise

[pbman1953]

I'm noticing a low level 120 hz hum too, all tubes in

[shooter]

roll a few tubes into V1, check heater wires at the socket


for the 120hz, parallel an E-cap (~~~47uf 450vdc) with each "tap" Ecap, walk it down the line, so PA, PI, Pre
CAUTION, shock hazard, caps stay charged so make sure you bleed 'em down

[pbman1953]

This morning I listened closer to the 120 and it's only slightly noticeable with the volume and gain at zero. I think we could move on and hone in on the hum.


I installed a couple more tubes with the same result. The hum goes up and down with the volume

[pbman1953]

I measured the heater wires. They start out at 6.32 volts at the standby and at V1 it's reading 6.02. The line starts at V7 and V1 is last in line.
Is the drop  a concern?

[shooter]

Is the drop  a concern

are all the filaments glowing in both standby and operate?

With V1 out, no noise

Still the same?

if so;
look there, all the wires, the solder connections, the tube socket pins, components, ground connections, input jack, shielded cables......
post a schematic so everyone's on the same page

[tubeswell]

Check all solder joints around V1 carefully (closely) for cracks or improper contact. Sometimes a joint can look soldered but if you grab the wire with needle nose pliers (with the power off) and wriggle it, and it moves, hey presto!
Or maybe a loose tube socket pin clamp on V1 (retension clamp - with power off).
Or could be a dogdy plate resistor on V1 (chopstick these)

[pbman1953]

All tubes light up.

[proaudioguy]

I have a similar issue on a DRii.  V5 is humming on the plate side, but if I probe the actual positive of the capacitor feeding that (and other) tube, its clean and quiet.  I grounded the grid and it made no difference.  I disconnected the NFB and it got a little louder as well as the noise.  Humdinger is set for minimum hum.  Pulling V1-V4 makes no difference.  Pull V5 and the amp gos silent, so the PI itself is clean and quiet.  Tube rolling has had no impact.  So I’m looking forward to your solution although its probably something different since yours happens before the volume and that triode is really high gain.

[pbman1953]

Sorry to sound ignorant, for tube rolling. Do you mean swap out different tubes

[HotBluePlates]

... if you hear noise like bacon frying , that could be bad grid resistors. Any opinions? ...

Maybe you moved on from resistors, but any of them could be bad/noisy.  It helps if you use a signal tracer or scope to find the location of spurious noises.

Below is a demo of the Noise Test found on some old signal tracers (generally best done on parts not in-circuit).  Apparently when voltage is applied to resistors, some will really act up.  There is a complete amplifier after the resistor being tested.  Skip to 1:45:12 in the video; the bookmarked time is not rendering when posting a video here.

=6312

[acheld]

PBMan, yes tube rolling is swapping various tubes into the circuit.

[Willabe]

Ed always put a bug in my ear that if you hear noise like bacon frying , that could be bad grid resistors.

Are you sure he didn't say plate R , not grid R?

Plate R's are usually the culprit for going bad and making bacon frying noise, hiss/snap/crackle/pop sounds.       

[pbman1953]

Ed always put a bug in my ear that if you hear noise like bacon frying , that could be bad grid resistors.

Are you sure he didn't say plate R , not grid R?

Plate R's are usually the culprit for going bad and making bacon frying noise, hiss/snap/crackle/pop sounds.     

You have a point here. Maybe Ed would be watching this. Which pin is the plate?

EDIT... fixed quote, sluckey

[sluckey]

Which pin is the plate?

Which tube? The answer you seek can easily be found here...

     http://tdsl.duncanamps.com/tubesearch.php

[shooter]

With V1 out, no noise

[PRR]

> Skip to 1:45:12 in the video; the bookmarked time is not rendering when posting a video here.

The code is not handling the time parameter sensibly. You can try to hide it:

click me for the movie!

(I shifted back to 1:45:10 to allow for opening a new window and getting the eyes in gear.)

[pbman1953]

Which pin is the plate?

Which tube? The answer you seek can easily be found here...

     http://tdsl.duncanamps.com/tubesearch.php

Great resource! thanks!




So is Willabe referring to the preamp tube plates? Because the power tubes don't have a resistor connected to them. Each side of the power tubes #3 is connected to the OT.
 

[HotBluePlates]

So is Willabe referring to the preamp tube plates? ...

Ed was probably talking about a plate resistor.  It has upwards of 100v or more dropped across it, which happens to also align with the ~100v placed across the resistor for the signal tracer's Noise Test.

The implication is that while grid reference resistors have higher resistance & might be noisier due to one cause, they generally have little or no d.c. volts across them.  Probably why there's the general suggestion of "replace plate resistors" when encountering noise.

    NOTE: a member here wound up finding his cathode resistor was noisy, when the noise remained after swapping the plate load resistor.

[shooter]

How did you get to the power amp tubes since V1 stops the noise????
were there bad solder joints, loose socket pins, swap the plate R with a new one, 10 minutes

[pbman1953]

Ok, I'll retract the power section of my reply. The sockets are new. The original socket were old and loose. Months ago I spent time replacing all of the sockets. The worst ones were the power tubes. I used 7 new Beldon sockets. Everything is nice and tight!
Yes, I will replace both plate resistors.


Thanks

[pbman1953]

I replaced both resistors for pins 1 & 6 on V1. Seems a little better. The I made more tests. I removed v2 and it was the same result zero noise. I removed v3 and with this removal I heard the crackle in full bloom.


This must be the PI, so is that common if PI is removed?

[pbman1953]

Here's a side question about heater wire connection. I've noticed on the schematic that one wire connects all the pin 2's and & 9's . the other wire feeds the 7's and the 4/5's. If they cross, does it matter? Meaning if the leave  a pin 2 and goes to the next tube's 7.

[HotBluePlates]

... I removed v2 ... zero noise. ...

Which seems like the noise must be at/before V2, right?

... I removed v3 ... I heard the crackle in full bloom. ...

Remove the tube and the noise is there.  Seems like it must be plate resistors for V3 or something after the phase inverter, where there is still a continuous circuit all the way to the speaker.

If I understand your tests/results, you have multiple noise sources.

Simplify:
Remove the phase inverter (V3) and make sure the amp is quiet.  If it isn't, find/fix the reason it makes noise.

Reinstall V3 but remove V2.  Find/fix any noise problems (which must be between V2B's plate & V3).

Reinstall V2 but remove V1.  Find/fix any noise problems, which could be anywhere from Input jack to V2B's grid (as stuff attached to V2A up to V2B grid couldn't be evaluated with the tube out of the socket).

... heater wire connection. ... If they cross, does it matter? ...

IMO, no.

Some people will tell you yes, but when I've tried to swap/fix-swap in heater wires I never heard a difference. 

[pbman1953]

I have to cap to understand the fixes-


V1 removed- no noise


V2 removed- no noise


V3 removed- plenty of noise- Are you saying to replace r23 & r22?

[pbman1953]

Plus I just found a mistake . When I went through the amp years ago, in the r22 position, I used a 82k instead of 52K. Is that an issue?  The 5 on the print out was weird so I just enlarged it to compare another 8 on the schematic and it's really a 5.

[HotBluePlates]

When V1 is out of the amp, V2 and V3 are still in the amp?  And able to pass sound to the output tubes?

I'm not understanding a fault mechanism where "all the tubes in the amp" = "no noise" but removing only V3 causes noise to appear.

[pbman1953]

yes,


with v1 removed all other tubes are still in- no noise


with v2 removed, v1 and v2 are in- no noise


with v3 removed v1  & v2 are still in- noise

[shooter]

maybe we go back to OP 
you have noise, it changes with volume
with V1 out the noise goes away;  "no noise"


NOW;
after changes you made;


with V1 in...  Do you still have the original noise?

[pbman1953]

after the v1 the plate resistor replacements (for pins 1 & 6) , it seems to be a bit quieter with v1 in, and all other tubes in

[HotBluePlates]

after the v1 the plate resistor replacements (for pins 1 & 6) , it seems to be a bit quieter with v1 in, and all other tubes in

And if you have all tubes in then remove only V2, there's no noise?

[pbman1953]

after the v1 the plate resistor replacements (for pins 1 & 6) , it seems to be a bit quieter with v1 in, and all other tubes in

And if you have all tubes in then remove only V2, there's no noise?   correct, no noise

[pbman1953]

Does the phase inverter tube control the power tubes not to red plate? With v3 out they glow a bit , but I shut it down as soon as I saw that. I put the PI back in and they were better

[shooter]

see reply #6


EDIT:
Until you are happy with the noise V1 in creates, don't go downstream!
when you go down stream, do it 1 tube at a time

[pbman1953]

You're right, up to v2 but not taking our v3, the hum is lower after replacing the plate resistors for v2. Should I replace the plate r's for v2?

[PRR]

> in the r22 position, I used a 82k instead of 52K. Is that an issue?

This is clearly a 82k. 52k would be far too little gain. 3/4 of similar Fenders use 82k. You can do math and find an "exact" value to balance the stage, which is an odd value near 82k.

[pbman1953]

> in the r22 position, I used a 82k instead of 52K. Is that an issue?

This is clearly a 82k. 52k would be far too little gain. 3/4 of similar Fenders use 82k. You can do math and find an "exact" value to balance the stage, which is an odd value near 82k.

You may be right but after finding clearer versions to look at, compared to other 8's on the page it looks like a 5. But an 82k is still in there, thanks for the heads up

[thetragichero]

i doubt you'll find a 52k resistor anywhere in most amps when 51k is a standard E24 series value

[pbman1953]

I took a close up of the schematic , do you think Traynor made a mistake on the schematic? You can see that it's a 5. Looking at r48 you can see the difference. Plus I took a picture of the 3A super which has the 82K. I think the 3 Custom schematic was wrong.

[ac427v]

I was confused by symptoms that don't seem to match your troubleshooting steps. Then there is the mysterious 52k plate resistor on the pi. So I went back to look at the full schematic you posted near the beginning of the thread and now I am really confused. Clearly says 52k. PI grid leak resistors of 100k? 100k grid stopper on the pi input? 47 ohm plate resistors on two power tubes and none on the other two? Fed by 536 volts? The whole power section looks wonky to my no-formal-training brain. I hope some of the folks here who really understand theory weigh in the unusual aspects of the design and whether that may complicate your troubleshooting. I know it is way beyond me.

[pbman1953]

I think, because PRR, brought up the case that it should be a 82k. You can see from my last post that Traynor showed the 82K on YBA -3a super which is a close cousin but uses different tubes. Plus the 47's are now 1K's 5W per tube ( Sluckey's suggestion) so I could use 6550's

[pbman1953]

Well my friends I decided to bias to see where I was and a soar thumb stuck out, a bad JJ 6550. At first I thought there was a bad connection at the socket but I moved the suspect tube in 3 other locations and the issue followed it. By lightly tapping with a finger nail it exhibited noise, plus tapping the tube next to it exhibited noise though the bad one. Fortunately I had a Winged C 6550 , same dissipation of the JJ. I slipped that in and there's a slight crackling noise , which I suspect could be another JJ but all 4 remaining tubes are quiet to the tap.


The only item left is the hum which only comes up with increased gain or master volume. I've made many 12ax7 tube swaps with no change. But the v1 plate resistor replacements did help some. Maybe 10% or so

[pbman1953]

Any other ideas to help this hum?