HELP!! ENGL Powerball trouble.

[trikmorgan]

Hello all!

I recently decided to completely retube my ENGL Powerball and I am unhappy with the result. Now I'm in a real pickle.

The amp seems lifeless. Volume is lacking. The high-mid and high frequencies have dropped off. It sounds altogether muddy. I went through several experiments and had no results. I resorted to putting the old tubes back in and it seems to have had little effect! It's still lifeless! Can anyone help??

I have "played" with the bias and it is also having little effect. I am in the process of setting up so that the bias can be adjusted for both the full set of power tubes AND each one individually so any that I feel are too far mismatched (even though they're meant to arrive matched....some peoples idea of matched is more loose than others) they can be adjusted. Taking some readings and calculating, something seems wrong. The lowest mA from one tube is 19mA and the highest is 32mA! Now I know thre is a tolerance but shouldn't it be no more than a few mA?? One person has suggested something may have happened during tube swapping or even before and could have blown a screen resistor or resistors.

Anyway, can anyone help? suggestions? point me to a forum with amp techs? anything?

[punkykatt]

Was the amp sounding bad before you installed the new tubes?

[trikmorgan]

No the amp sounded normal. The retubing was being done due to the amp never having had new tubes (8 years or so!!!!). I was having some slight noise issues and hoped new tubes would help with noise and breathe new life into the amp. (I was also having sustain issues and a little deadness in the sound but nothing like this!)

[SILVERGUN]

Anyway, can anyone help? suggestions? point me to a forum with amp techs? anything?

You don't need to go anywhere else....the guys on this site will help you

There are a couple of things that will need to be clear......1st is safety!!...do you have amp repair experience and are you familiar with the safety precautions you must take?

Do you have a schematic for the amp?...Does this one look correct?
http://www.el34world.com/charts/Schematics/files/engl/engle_powerball.pdf

The amp seems lifeless. Volume is lacking. The high-mid and high frequencies have dropped off. It sounds altogether muddy

Are your tone controls turned up?  ......on the guitar?
Are you using a guitar with active pickups?....check the battery
Do you have anything plugged into the effects loop?
Have you tried a different speaker/cabinet?
This is all troubleshooting 101

You'll be asked for voltage readings off of the tube sockets,,,,so make sure you're comfortable with that process...
Otherwise, because of the complexity of that amp, I would consider taking it in to a repair tech......he might save you A LOT of time

Good luck,,,,don't assume anything,,,and just give these guys all the info you have, including exactly how you are "playing" with the bias

[trikmorgan]

I don't have much amp repair experience no but I am working with my dad who is an electronics engineer (with some audio electronics experience).  He is well versed in safety and I too have learned much.  I understand that capacitors hold potentially lethal voltages (even while switched off and/or unplugged).  I have watched some Gerald Weber videos on amp repair, one tip I would have missed is to never run the amp without a load (speaker cab plugged in).  I am very cautious about going anywhere near the circuit while the amp is live.  I have gotten reasonably comfortable taking readings on a multimeter. 

About the schematic.  I do have this very schematic but I have read here and there that they are untrustworthy, mainly in terms of missing components but also possibly having incorrect component values! .....why bother releasing a bloody schematic in the first place :/.  Also, the front face of the PCB is underneath the metal casing (looking down onto the amp head) so without actually removing the board, 95% of components aren't visible so no simple comparisons can be made with the schematic.

Tone controls on the amp are all centered and then adjusted during testing to different settings. Guitar volume(s) and tone(s) are up full. All passive pickups.  I have an effects loop with a dry/wet mix pot.  It is set to dry.  Nothing is connected anyway which shorts this circuit sending a direct dry signal.  Also a noise gate on the amp which is off.

I haven't tried a different cabinet no.  I would have to borrow one if I wanted to try this.  Never say never but I seriously doubt a speaker problem here :/.

As far as biasing, I measured the voltage on pin 8 and used the formula voltage(bias)/resistance(according to the schematic each tube has a 4.7k resistor)=current to determine the mA of each tube.  We are waiting for a socket to arrive so we can make a bias probe and do this properly but using the method I just explained it seems that the bias is set cold.  After several adjustments I got up to three quarters towards max on the trim pot and got values that started at .09 (calculating to 19mA) to .15 (calculating to 32mA).  This doesn't seem right to me, even assuming no faults anywhere, I thought matched tubes should be capable of simultaneous biasing with only a few mA tolerance.  This is a 13mA gap!  Also reading the plate voltage (pin 3 of each tube) gives 470-475V (the multimeter isn't the best, my dad has a better one at work should we need it).

Any readings/ratings that anybody requires, as long as I am clear on the method I can give them, for example, reading the voltage from tube sockets...do you want the voltages from the pins with all the tubes IN or all the tubes OUT as I understand there is a voltage drop when the tubes are in.

So...I hope that clears up some things and thank you so much for posting a reply, I really appreciate it!!  I hope someone can help.  I really can't afford an amp tech as much as I would really love to just take it to someone and have them take care of it!

Thanks again, keep posting!

[punkykatt]

I resorted to putting the old tubes back in and it seems to have had little effect! It's still lifeless!  Are the tube sockets mounted on the chassis or are they on a PCB?  If on a PCB see if you can find where maybe when installing the new tubes you may have  broken a tube socket pin solder joint on the board? Also pull the tubes and check all the tube pin gripers in the sockets make sure they all look  the same and will make good contact with the tube pins. When voltages are taken all the tubes must be installed.

[SILVERGUN]

punkykatt's suggestion is a great place to start....(with the amp off) gently wiggle the tubes in the sockets and see if you see any movement of the pins in the soldered connections on the board

Is this pic what you are seeing of the tube sockets?

Use the supplied numbers in the pic to provide us with voltage readings off of every pin on every tube if possible....(with the amp on, all tubes in, and a dummy load or speaker connected)

Connect the black multimeter lead to a good solid ground point with a clip on test lead,,,,and take your readings with the red lead, using one hand

Plenty of guys here are capable of helping you, and this is a great place to start......I'll be away from my computer for a while,,,but hang in there and some bigger fish will be along soon enough....post your findings, and whatever you do, DONT try taking the board out, or solder anything on the board without showing your dad or posting a couple pics

Be safe

There are some good pics here:
http://forumusica.com/topic/113285-engl-powerball-ajuste-do-bias/

[trikmorgan]

Thanks for replying guys, and quick too! I'm so grateful I really really am.

I have checked the sockets and solder joints. Everything seems fine there.  I also cleaned the sockets again (i'd done this once when I got all new tubes but thought why not)

I will take the readings with my dad for all the pins on all the tubes and post them in the next 12 hours.  Bearing in mind I'll be doing this with all the original tubes (I have put the new tubes back in their box and will try them when the amp is functioning properly and re-bias etc)

Thanks Silvergun, I hope whatever has got you busy goes well! :)

[trikmorgan]

OK, here are the readings I took.  I soldered a wire to the mains ground point in the amp and wrapped the other end around the black probe (have no aligator clips handy, put the amp on and left it in standby for a few mins.  Then switched the standby into play mode put one hand in my pocket and took the readings.

They are in order of position i.e. facing the front of the amp left to right, tubes 1-4 (power tubes obviously). The "pin numbers" are as shown in the picture that Silvergun posted (1-7 clockwise). I have made a note alongside my readings though showing the "actual" pin numbers so I can easily refer to it should anyone post refering to actual pins, just be sure to mention that please :).

Tube 1;
1 - 3.55V     2 - 117mV     3 - 0     4 - 3.55V     5 - 470V     6 - 467V     7 - -48.6V

Tube 2;
1 - 3.5V       2 - 191mV     3 - 0     4 - 3.55V     5 - 470V     6 - 465V     7 - -48.8V

Tube 3;
1 - 3.46V     2 - 155mV     3 - 0     4 - 3.54V     5 - 473V     6 - 467V     7 - -49.1V

Tube 4;
1 - 3.5V       2 - 93mV       3 - 0     4 - 3.54V     5 - 472V     6 - 468V     7 - -49.1V

Hope to hear something soon!

[punkykatt]

What tubes are in this amp?  The voltages don`t make any sence. Most tubes Im used to seeing are eight or nine pin.

[trikmorgan]

6l6GC's. The ones that are in are the originals (with an ENGL stamp on them so not sure who the manufacturer is).  The new ones i bought are JJ/Tesla 6l6GC's.

[trikmorgan]

Don't forget the pin numbers correspond to the picture posted earlier.  The socket has 7 pins and a gap. The tube has 6 pins (two gaps). Pin 1 on the tube is located at the pin numbered 3 on the picture.

I'm not sure if the layout is exactly as mine is, I will take some pictures today as no doubt I will need to post some.

[punkykatt]

WOW! thats confusing.  So #1 is actually pin 2 heaters 3.5 vac, #2 is pin 1 or pin six no connection?, #3 is pin 8 cathode 0v,  #4 is pin 7 heater 3.5 vac, #5 is pin 3 plate 470v, #6 is pin 4 screen grid 467v, # 7 is pin 5 control grid -48.6v.  in that case for a 6L6GC the voltages look to be normal.
Now we need the preamp voltages.

[SILVERGUN]

Hey guys....sorry for the confusion....the pic that I posted was off of that website link I gave you..
The problem is that ENGL only used the 7 pins necessary on the board (so they are really 8 pin sockets, but only 7 solder connections on the board)
The biggest problem is that the guy numbered the pins incorrectly,,,,sooo, the label for #1 actually is for tube pin #7 (and so on)

So, I went and adjusted the pic to reflect the correct tube pins, so we will all be speaking the same language.....

If you get a minute please adjust your voltage chart to reflect these changes.....

The good news is that the voltages look OK  
The bad news is, you're going to have to try to get to the preamp tube pins

[SILVERGUN]

WOW! thats confusing.  So #1 is actually pin 2 heaters 3.5 vac, #2 is pin 1 or pin six no connection?, #3 is pin 8 cathode 0v,  #4 is pin 7 heater 3.5 vac, #5 is pin 3 plate 470v, #6 is pin 4 screen grid 367v, # 7 is pin 5 control grid -48.6v.  in that case for a 6L6GC the voltages look to be normal.
Now we need the preamp voltages.

Sorry pk, I was posting while you were,,,so it's actually even more confusing than you thought,,,,check the pic above for the correct pin # labels

(#1 on the original pic is actually pin 7 and so on)  

[trikmorgan]

here it is with the proper pin numbers.
Tube 1;
7 - 3.55V     8 - 117mV     1 - 0     2 - 3.55V     3 - 470V     4 - 467V     5 - -48.6V

Tube 2;
7 - 3.5V       8 - 191mV     1 - 0     2 - 3.55V     3 - 470V     4 - 465V     5 - -48.8V

Tube 3;
7 - 3.46V     8 - 155mV     1 - 0     2 - 3.54V     3 - 473V     4 - 467V     5 - -49.1V

Tube 4;
7 - 3.5V       8 - 93mV       1 - 0     2 - 3.54V     3 - 472V     4 - 468V     5 - -49.1V

[SILVERGUN]

OK, thanks trip.....that looks good,,,and before you go any further,,,,I may have had a moment of clarity whilst in the shower....
3 years ago I had a JCM800 on my bench, with a similar complaint........and after staring at it and taking V measurments, I was prodding around and pressed the signal tab on the "Cliff" style input jack,,,and BAM, full volume restored......

So,,, I ask you to check and see if you have a plastic, Cliff input jack, and is it accessible......if it's loose, or your cable feels loose inside of it, then it's worth replacing............if you're full guitar signal isn't making it to the tubes then, that would definitely cause your complaint

I hate to guess on stuff like this,,,,,but this might be a "no-brainer"

[trikmorgan]

Well Mr.Silvergun, further I have gone lol. Here are my preamp readings!
(pins are in their proper location  )
Tube 1;
1 - 250v     2 - 0     3 - 2v     4 - 14mv     5 - 14mv     6 - 230v     7 - 0     8 - 1.5v     9 - 6.9v

Tube 2;
1 - 241v     2 - 0     3 - 2v     4 - 11.5mv     5 - 11.5mv     6 - 175v     7 - 0     8 - 2v     9 - 6.9v

Tube 3;
1 - 262v     2 - 0     3 - 2v     4 - 6.2mv     5 - 6.2mv (not sure about 4 & 5 as the probe picked up 3-4mv at idle so...barely any change)
6 - 231v     7 - 0     8 - 1.75v     9 - 7v

Tube 4 (Phase inverter);
1 - 273v     2 - 66     3 - 76v     4 - 3.5v     5 - 3.5v     6 - 285v     7 - 68     8 - 76v     9 - 3.44v

I will check on your theory asap and of course present the results asap!

[punkykatt]

Pins 4,5 and 9 are the heaters on these tubes. You should be getting 3.3 volts AC. Red meter tip on pin black meter tip to ground.

[punkykatt]

Woops, looks like they are running those three tubes heaters on DC.  Im just guessing but it appears the tube voltages are good. To bad the voltages are NOT listed on the schematic.  Question is: What caused the amp to take a dive when you installed the new tubes?? Something had to change. It sounds bad even with the original tubes reinstalled..

[trikmorgan]

That's right PK. DC on AC on power tube heaters and phase inverter heater, DC on the first three preamp tubes 

Yes I have become unhappy with the frequency response of the amp but the main problem here is that the volume has dropped significantly. Who knows, if the problem is fixed maybe the actual sound will be too. Either way something is certainly not right.

I tried checking the input jack, cleaned it, wiggled the plug and had my dad prod around the amp with a chopstick while playing to see if we could find any loose joints, bad spots on the board, pins etc etc. Not a peep.

[SILVERGUN]

I am concerned about pins 4+5 on the 3 preamp tubes....
If you lost the heater path on those pins,,,that might explain it....

Have your dad try to trace the path from the power transformer through to the sockets and see if you're losing your heater voltage somewhere....

Check for a burnt path on the board near the power transformer or a loose/ burnt wire in a connector to the board coming off of the PT

[PRR]

> If you lost the heater path

Then he wouldn't have the perfectly-reasonable Plate Grid Cathode voltages he reports.

P - 250v     G - 0     K - 2v    (H  H)  P - 230v     G - 0     K - 1.5v     (H)

A dead heater would give Plate stuck near supply voltage (perhaps +350V), Cathode stuck at Zero.

The apparent 6.9V on the "6.3V" connection on most heaters is entirely acceptable, and NOT gonna hurt tone/loudness.

The 3.5V 3.5V 3.44V on the Phase Inverter tube heaters ..... ah, this tube is heated with the AC stuff. We expect oddball "DC" readings, check again with AC setting and measure *across* the heater (pin 4/5 to pin 9). However the phase inverter's other pins are showing very reasonable numbers, and certainly not zero. So this tube is heating fine.

[trikmorgan]

Hey guys, we checked heater voltages and all seems well. What has you worried silvergun?

I'm unsure if there should be a drop in mV through preamp tubes 1-3, maybe its normal? (tube 1-pin 4&5; 14mv.    tube 2-pin 4&5 11.5mv.     tube 3-pin 4&5 6.2mv, again barely registering)

[trikmorgan]

Just asked my dad about these readings and he says that pins 4&5 don't matter, they're "floating" and as mentioned he checked heaters across pins so everything seems fine there.......what next 

[SILVERGUN]

Thank you PRR..........sorry trik 
I am working on someone else's kitchen and trying to help at the same time,,,,,so I appreciate someone checking my work...(that's my excuse) 

trik,,,I was expecting to see voltages on pins 4+5 similar to the phase inverter tube running on AC,,,and when I saw the mV readings, I immediately flashed back to when I had a Mesa Boogie amp fail on me on stage, when the heaters went out due to a burnt and lifted heater supply trace, and the amp lost volume and sounded horrible   .....it was a PC board amp, and a pain to repair..
So, as I glanced at "your" schematic and saw those 3 pre-amp tubes running off of the same DC heater supply,,, I took a quick shot,,,,,,and now I'm embarrassed......

trik,,,,it might be time to start looking for a repair tech in your area....
Unfortunately,,,,,amps with PC boards in them can be difficult to repair,,,even if we were able to find the problem here online.....but it sounds like your dad is doing a fine job of trying to help....

Think of it like this:
If you drive a 1987 Chevy pickup, you could probably save yourself some money by working on it yourself,,,,but if you drive a 2007 BMW,,,get ready to take a beating when something goes wrong

ENGL= BMW (at least for the purpose of over-emphasizing my point)

Sorry I couldn't be of more assistance, and I wish it was just the input jack, cause that would've saved you a lot of time and money....
Good luck, and if you guys figure it out, please post your findings.......

[punkykatt]

Try this if you havent already:  Get a insulated glove that wont burn when you touch hot glass or burn your fingers,  connect your guitar to the amp,  put the guitar in a guitar stand so you can strike the guitar strings with one hand to make noise through the amp while you grab the hot tubes one at a time with the gloved hand pushing down and pulling up without removing the tube all the way. What you will be doing is flexing the PCB and hopefully locating the possible trouble area. Be careful.  

[trikmorgan]

OK guys, its been a while but basically, there were a few problems.
1) I had an intermittent connection, couldn't see which solder joint was bad (on the v4 socket) but I re-soldered all pins and that seems to have solved that.
2) I also RE-RE-RE cleaned and scraped the tube socket pin gripes and tightened them to ensure good connection which helped with the preamp tubes. The first preamp tube (v5) is a little temperamental but seems ok for the moment after cleaning/tightening. If it is still problematic I'll swap the socket.
3) ...it's a little embarrassing but in the interest of knowledge for whom it might help;  I make my own cables ya see, now, for the most part (here's my best tony the tiger impression) THHEEEEEEEEY'RE GREAT!.....BUT just out of curiosity I used a multimeter on all the cables I was using and found that there was some resistance across some of them.  This was weird,    I thought they either worked, didn't work or cut in and out from a dodgy connection.  I re-checked connections and checked any pressure points e.g. in the right angle plugs where the wires run through the right angle and all is well with the cables now, completely open circuit which basically solved the REMAINING volume issue.
5) Amp was ok for the most part and I'm playing away for about....3 hours. Anyway, I switch the standby and decide to let it cool before switching off when I noticed that the filament in v8 was not glowing and the tube was stone cold :S, somehow I was running on 3 tubes. The tube failure circuit didn't light the warning LED so...not sure what was happening there.  With some persuation (wiggling etc) the filament would light and the tube would warm but after 10 mins playing it would be off again.  Suspecting the tube socket that I'd re-soldered I swapped the tube to another position and to my surprise it did the same in the other position so, I sent the tube back and after 2 weeks I finally have the new one, plugged in, warmed, played for 10 mins, no problems and the amp has plenty of life again so....I think problem (or more accurately, problems) solved!.

Now...it could just be me but since I took the head out of the enclosure I'm pretty sure there is more mechanical rattle than usual (if there was any to start with, I'm not sure) and some "fizz" for lack of better description from the cab. No it isn't crossover distortion, the amp is properly biased for good headroom but not particularly cold. The rattle sounds like its coming from the input transformer (possibly also the output transformer). Could this have happened while trying the get the amp head out? It was stuck in there pretty good!! so....I'm startin to think I'm just lookin for trouble now :S

Cheers guys! Sorry for the essay, thanks for reading and for any and all of your help!!  I am humbled.

Keep posting 

[silverfox]

For what it's worth- I had a Carvin MTS3200 that fits this scenario somewhat. The last thing I found was a dead tube and all the voltages present on the tube socket pins. PC board construction. A couple places where diodes had over-heated. I checked the socket, checked the tube and couldn't figure it out.

It did work. Just never sounded right.

That was in November of 2012. The Carvin chassis has been stripped and the second power amp build is in progress, didn't like how the first build sounded. Funny thing, I used the Carvin schematic.

Don't be surprised if one day you find yourself on the Topic trying to scare up some designs for your first build.

Anybody want to comment on how the Engl Powerball tone stack is: Good ??? Might be a good design for a build I'm thinking of...


Silverfox.

[punkykatt]

Is this a head or a combo amp? Check for any loose screws , rivits, wires, etc that could vibrate anywhere inside or outside the amp.  Are you sure the sound is coming from the amp and not something vibrating in the room?