help with new amp

[bnew63]

Just finished putting together a Ceriatone 36 watt ef86
This is my first el84 amp
Started it up with a current limiter,then full power.
I'm getting an slight hum from the speaker which varies with the volume and master volume.
I'm not getting any sound when I plug a guitar into the input.
I rechecked the wiring and everything seems okay.
Thought I'd post the voltages to see if they are okay.
All voltages are to the star ground.
  Pin         1      2      3     4      5     6     7     8     9
el84#1             1      26       6.5            368         349
     #2             1      11       6.5             368        349
     #3              1     11       6.5             368        350
     #4             1      26       6.5             368        350

12ax7#1   290   53                         419   30   56
       #2    150    0     1                   269  150  150
       #3                                        160          1
 ef86       260

ez34               825        564   305   570   305  825

As stated above this is my first el84 amp.Do the el84's always run so hot.I've had many 6v6 amps and the tubes never run this hot.
I'm using second hand iron and the PT secondaries are 305-0-305 which is 15 volts above the 290 in the schematic.
any help would be appreciated

 Cheers Brian

[DummyLoad]

I rechecked the wiring and everything seems okay.

respectfully, barring a faulty component, if it were wired right, it's likely that it would be working.
since this is a new build, with (i assume?) new components, i'd gamble on a wiring error. you're getting hum that varies with volume control so it would seem that at least the output stage and some of the pre-amp stages are functioning.

looking at voltage chart - 12AX7#1 pin 6 - 419V - really? how is that possible if plates are 368V

mistype? 319V is believable.

the voltage chart formatting is difficult to read. would you check and re-format. also, kindly take some voltage measurements of each of the three 22uF 450V caps. please review attached commented layout. it would be immensely helpful if you could post some hi-res pics of guts  from several viewpoints.

with all controls up 1/2; when you probe each of the probe points with meter set to read DC volts, do you hear a pop noise in speaker? where do you lose pop noise?

--DL

[stratele52]

If you ear hum wich varies with volume this mean amp is "working". No guitar sound this mean wiring FROM input jack are open or missing .
and / or wiring and faultly components in this signal chain.

Tubes voltage could be all good in this case of open signal circuit with no guitar sound in speaker.
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A scope and signal generator is THE tools to fix this problem . I assume you don't have it ?

You don't have the schematic of this circuit ? It is easy to follow the sound path with schematic. Can you found it and show to us ?

Is there a chance that some wiring or part is missing on this Ceriatone sketch ? I see that some time, but not very often not in Ceriatone  but in other electronic kits.
________________________________________________________________________________________

What you could do for now ?

1-Be SURE all your wiring AND solder are good . Be sure you follow the layout with no error. This is almost all trouble I had in building projects.

a) No wiring is missing or broken .
b) You are connected a tube's RIGHT pins
c) Tubes are good AND GLOW.
d) All solder are good.
 
2- All components , specially all signal capacitor are good .

Take your time , be patient and do not be discouraged.

A few closes pictures of your amp could help.

Good luck.

[Boots Deville]

If I was faced with this issue, I'd get out my "Listening Amplifier" that Doug describes here:
http://www.el34world.com/Hoffman/tools.htm

Cheaper than a scope and signal generator and for this job, just as useful in tracking down the problem.

I have a couple amps around that I've put passive loops in.  I just run the signal into the power amp input on one of those - works great.

[HotBluePlates]

Or...

Clip your meter's black lead to the chassis or ground point of your choosing. Use the red probe, set to measure voltage, to lightly touch each plate/grid with the amp on, turned up and with a speaker load.

Start near the output of the amp; phase inverter should work fine. If you probe the phase inverter plates, you will hear a slight pop through the speaker. When you move "backwards" through the circuit to the phase inverter grids, the pop will be somewhat louder. That's due to the gain of the phase inverter.

Keep stepping backwards through the circuit, probing plate then grid of each preceeding stage, until you find the point you don't get a "pop." You will have found at least one wiring error location.

For example:
12AX7 #2 in your amp - probing the plate (pin 1) gives a pop, probing the grid (pin 2) gives a louder pop.
12AX7 #1 - you probe pin 6 (second stage plate), you get no pop.
   - Between 12AX7 #1, pin 6 and 12AX7 #2, pin 2 there is a coupling cap, the volume control and a 1M resistor/500pF cap. There must, therefore, be a wiring error, poor solder joint, or shorting of the signal in/around those components between the two tubes.

If you were doing this in conjunction with measuring your amp's tube voltages, you'd also look to see evidence of cathode circuit wiring errors/opens, such as one triode's cathode being 0v (or very close) and its plate being at B+. That would indicate no current through the triode, and an open circuit between the tube cathode and cathode resistor, or cathode resistor and ground.

[bnew63]

Thanks guys.
I'll be the first to admit I can check something three time and still do it wrong.
I spend today rechecking

Thanks Brian

[stratele52]

+1 HotBluePlate

[bnew63]

Had a little time to recheck the wiring.
Found that I had missed two wires(preamp tube #1 & 4,pin 3 to 8)
voltages on the 22uf caps from right to left are 286,262,279
Pin 6 on preamp tube 1 reads 188
The amp now makes a louder hum and a squeel if the ef 86 is turned up.
The wire going from the .0022 cap to the  volume pot is highly sensitive to touch,the hum increases two fold if I touch it.Should I wire it with shielded wire??
Started reviewing my electronics for dummies book so I can follow you guys better

Took some pics of the wiring,I know it's a little messy,I'll be neater on the next build.
I'll have more time tomorrow to go over it again.

Thanks Brian

[Rev D]

 I'm one of those guys on here that is more likely to use a Layout rather than schematic, I can read the schematic, but for building the layout is my friend for sure. I usually use a highlighter and check each wire on the layout to ensure its going where it supposed to. After I've done that I just x-off the wire as correct and proceed to the next. I'm assuming your doing likewise.


 One of our mentor/proprietor of this site Doug Hoffman's most notable saying and I'm paraphrasing, if it was wired correctly it would be working. Its ALWAYS 100% correct when it comes to wiring issues. I can't recall how many times I was SURE it was wired correctly and it wasn't. The wire I KNEW was correct was miss-routed or miss-wired. The above idea's are all excellent, the guy's here are probably the best remote amp debuggers I think I've seen on most forums and I frequent or at least lurk on a awful lot of them.


 Grounds are the undoing of many projects, a ground missing somewhere or a bad ground can cause many problems. Check all of those, particularly the input jacks. Once we (or more likely THEY) get the project going you may need to further do a few things to remove some hum by moving wires, or shortening them and cleaning up your lead dress (wire routing/path to they're components) because in a amp the more gain a circuit has the more potential for oscillation, the EF86 has quite a bit of gain and they're prone to microphonics as well. I think if you eliminate any wiring errors and follow hotblueplates instruction I'll bet things will come together for you. I apologize in advance if your knowledge of electronics is such that it sounds like I'm telling you basics which you already know. I don't always know the extent of someone's knowledge unfortunately. Heck I was chasing a problem for months on a old build of mine that worked for years and suddenly was showing a problem. Turns out I guess the aluminum chassis must have corroded under a ground wire, by moving and tightening it up it all works great again. These amps are fickle beast they are..  

Regards,

Don

[TIMBO]

Hi Brian,Every amp has its owns quirks and most times its the simple things that makes the quirks easier to find. If you look at the Ceriatone layout there is some basics that they have found to work well for their kits and this also applies for scratch builds. If you look at the layout it plots the positions for components and hardware,this makes for short wires.Coloured wires for easy tracing between components.A ground buss wire that is used for grounding gain stages in the preamp and star points for other grounds. A single ground for the IEC ground. Shielded wire for the more sensitive areas such as wires from the inputs to valves and any long runs that might pickup unwanted noise from high voltage wires. Heater wires should be twisted together and kept away from sensitive wires and elevated  by connecting heater CT to power tube cathode. Use the layout supplied and try to copy this as close as possible and this will help you learn good building techniques and neat builds.Hope this helps   

[stratele52]

bnew63

Good you find some wiring missing

About the hum , IMO it look you're wiring need to bee clean . Proper lead dress is a must to have a no hum , no noise amp. An "easy" way is to use shielded wire on ALL preamp 's tubes input grid.
Those shielded wire must be shielded at ONE end only.

You must run all wire close to the metal chassis. Also best is signal wire cross another one in 90 degree  , not in parallel .

On your first post , you show us the Ceriatone complete amp's chassis ; this is the way your wiring should look,  should be,
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Rev D

You are right about the use of layout to built the amp ; that the use of the layout; building the amp
Shematic is a must l for trouble shouting .

Shematic is like a road map.
bnew63 is lost somewhere in is trip  ( to have a working amp).
But we don't have the road map to help him. Not easy.

[bnew63]

Rewired my inputs today and retraced all the wiring and highlighted each wire when traced as suggested.
I did find a few error's
One question I have is to do with the feedback switch.It shows the feedback switch being wired from the 16ohm tap from the OPT.
I only a 4ohm tap from my OPT.Will this present a problem?
D.L.   I will report back when I probe those suggested locations.Wanted to get the wiring right first

Thanks Brian

[PRR]

> Will this present a problem?

No.

[bnew63]

Thanks prr
found the layout drawing for the speaker jacks was wrong after they were rewired correctly it produced sound.The amp worked in half power but still blows fuses in full power.
Sorry for not being able to produce a schematic.Ceriatone doesn't make them available( a lesson learned).The closest I've come was a schematic for an A30 but the drawing was so small it is unreadable.
I still have quite a hum which is affected by the master volume.I've put shielded wire on the volume pots but that didn't reduce the hum.
Probed with a stick but didn't notice any appreciable change in the hum level.
Probing pin seven of the el84 tubes 3&4 with the voltage meter on DC produces a very loud squeel and the dc volts which reads 362 on the first two tubes,reads (3.6.2).I'm not sure if this means the voltage reading is off the scale or if it's some kind of ocillation.
Could this be a faulty OPT.I did test this before I installed it.

Brian

[Ed_Chambley]

Brian, my first build was a 5F4 and I began not knowing very much about building (still don't know much).  I built everything from forming the chassis to drilling my own board and staking turrets.  During the building process I was so excited to get the thing working I made many mistakes everywhere.  My wiring looked like a rats nest and most of it was the same color.  I finally decided I wanted to learn how to really build amps and do it nice and thought just as you that I would do a better job on the next one.
Long story short, if I wanted to build nice amps I needed to do it now so I disassembled everything as I began to understand that there is not one way to build an amp, but there are much better ways to build.  I cleaned all old solder and began again.  I asked the guys here what color scheme they used for wiring and this let me understand each component and what it does.  When I finished rebuilding the 5f4 it had short wiring, which was color coded which I recorded.  Needless to say my second attempt at my first build was very successful and the lead dress looks very professional.  When I fired it p for the first time the only ting I had to do was change the OT wires as they were reversed and the squealed.  It takes time and newbies like me get so excited to play the amp, we let important things go.
The best answer I ever got to one of my questions was very direct and it hurt a little, but it help me the most.  I was told "If it was wired correctly, it would work"!  When I got over being mad at the comment, I knew he was right and I was either going to build nice amps or not.