Print Page - New 5X3 build no sound help

Hi, I just finished the 5X3 build and am getting no sound from guitar input, maybe just light distorted sound with full volume. I've gone over the wiring and don't see anything loose or not soldered, and have gone over everything with a chopstick to no avail. Here is what happens when I turn on the amp:
pilot lamp lights
as amp warms up it begins to emit a hum from the speakers while still in standby
once I switch from standby to play the hum goes away
plug in guitar to any jack and bet no sound at all.

any ideas of where to begin to trouble shoot?

thanks
Dave

I put a signal tracer on it and I have signal throughout the circuit, pins 5/6 of 6L6's and I get signal at volume and tone pots and a weak signal at output jacks. I do have hum also and it seems the 12AX7 amplies it.
When I turn on the power switch it is quiet until the gz34 heats up and then it starts to hum, when I turn on the standby to play the hum goes away for a bit but then comes back. As I trace the signal occasionally I touch a spot and the hum goes away, then slowly comes back.
I'm missing two input jacks for channel 2 so the 2 feeds off the 68K resisters are not tied to anything but the 2 jacks from channel 1 are connected and the ground is tied to the volume pot.

Quote from: davohilts on February 20, 2011, 12:39:57 AM

Do you just not have the other jacks right now?

First thing is attach those 68K to Ground for the time being.

Not sure what jacks Nik uses, but on a traditional 5E3 build, you use switching jacks that ground the tip of the jack when not in use, its to reduce hum. I doubt it will fix the big issue, but it may handle that hum.

Nik does a bit of disservice by not posting schematics (I[m sure he has his reasons), but the closet schematic I know is Weber's 5E3P (similar to the 5X3)... here it is for reference....note the switching jacks.

https://taweber.powweb.com/store/5e3p_schem.jpg

I'm waiting to get the additional jacks in the mail. Can't find any in town. I believe I have the two I have installed wired correctly but don't know how to test with an ohm meter. The other leads from the 68K resisters I have taped off in the chassis. Should these be tied to ground until I get my additional jacks.
Thanks guys for your help, I know i'm not giving you much help by explaining what the issue is. I've built a couple of amps from kits, an 18watt and a Deluxe Reverb. I've been building this one with my son and between the two of us we have really created a problem here. He wants to use it in a show on Thursday and we have been rushing to finish it and you know what happens when you rush.....

Quote from: davohilts on February 20, 2011, 04:01:28 PM

Ground those 68K's, even simply with Alligator clips for the time being and check the affect on the hum.

But my guess is the hum is coming from wherever your input problem is.

Insert a cord in one of the jacks, power does not have to be on. And check connectivity from the other cable end...make sure the sleeve is connected to ground and then make sure the tip is connected through to the input (checking on the leg of the correct 68k resistor is fine).

grounding the 68k's didn't help on the hum. I checked the input jacks and they work as they should. I get signal undistorted to the 12AY7 but the sound out of the 12AX7 is overdriven and distorted.
the grounding on the pot side is sort of strange I think. The schematic doesn't show any direct grounding, everything seems to be connected to the 16uF caps w/out a direct to ground connection. I might try adding a ground here to see if I can get rid of some hum.
the weber schematic seems like a better layout with a bias adjustment.
i don't see a bias adjustment capability with the 5X3 circuit.
How would I adjust the bias on the 5X3?

okay, I added a ground to the circuit because the grounding scheme on the layout didn't ground the big resister and cap, they were not grounded. When I added the ground the amp sprung to life! The hum is gone and the guitar input goes through and all knobs work. Now my issue is that although I get good throughput on the signal the amp sounds more like a deluxe not the super deluxe. It is not loud enough to play along with a drummer. I'm disappointed because I have a deluxe reverb that is louder.
Any ideas as to what to do the get more out of this amp?
Thanks,
Dave

Quote from: davohilts on February 20, 2011, 11:03:57 PM

What speaker and what are your B+ and plate voltages?

Quote from: davohilts on February 20, 2011, 11:03:57 PM

okay, I added a ground to the circuit because the grounding scheme on the layout didn't ground the big resister and cap, they were not grounded. When I added the ground the amp sprung to life! The hum is gone and the guitar input goes through and all knobs work. Now my issue is that although I get good throughput on the signal the amp sounds more like a deluxe not the super deluxe. It is not loud enough to play along with a drummer. I'm disappointed because I have a deluxe reverb that is louder.
Any ideas as to what to do the get more out of this amp?
Thanks,
Dave

You mean the places on Nik's layout where it shows a green line going to "X" and "X" being the Ground lug?

Yeah, that's the problem with layouts, they make certain omissions based on assumed common knowledge and that you would have the schematic available. They really are for assembly instructions and not troubleshooting.

As for the current crisis....

Use Weber's bias calculator to figure out your dissipation.

The 5X3 and 5E3P differ in the bias. The Weber uses fixed bias to get about ~35 watts, the Ceriatone is cathode bias, and should give around 25 watts (of top of my head).

If you are getting low output, it may just mean tweaking the bias resistor for more dissipation.

Which 6L6GC's are you using? You can figure many Chinese and the Tesla for 30 watt tubes and assume Russian tubes are 25 watts max. dissipation.

If the recone was done right, you should have a very sensitive 103db speaker in there. So, you should be getting more output than you are implying.

Okay, I've been working on the amp again as I was able to buy a couple of input jacks from a repair place that was open today. I installed the 2 input jacks and that has improved my sound and volume very much. The plate voltage on pin 6 of before I connected the second pair of inputs was 86v and now is 140v. There must be some connection thru the jacks that was missing.
I get a good sound now although compared to the Bell Pacemaker PA head I modified which uses 2 6L6 power tubes, this circuit doesn't have near the same amount of power.
We built the cabinet out of canary wood and we were expecting this thing to blow our sox's off but it is a little dark and not as loud as my Magnatone MP1. I'm using a pair of Silvertone 6L6's which test good until the JJ 6L6's arrive. I will check into the bias issue and report back what I find out, not too sure what the silvertone tube manufacturer was. The bias thing has always seemed mysterious to me so this should be a good learning experience.
I appreciate the help.
Dave

I bet it's a matter of weak power tubes.

As for tone, dark is the Tweed Deluxe vibe.

Some people buy Tweeds and clones assuming they are getting that classic signature "Fender Tone" in cooler clothes.

Tweed Tone is midrange heavy, with big, loose bottom end and the high-end rolls off very early (earlier on the smaller amps), and they generally break up early, a side-effect of the midrange and low-voltage preamps. Tweeds are really part of the Marshall family of amps tone-wise.

By a little dark, I mean cotton in ears dark, even dark for a deluxe in my opinion.
the schematic called for a 270 ohm 10 watt cathode resister and all i could find was a 250 ohm 10 watt resister. I went through and ran the calcs on the weber site and got the following:
2 tubes, 32.5v across cathode resister, 250 ohm resister actual, 403 volts across cathode and plate of 6L6's, giving me a calculated 25 watts plate dissipation per tube and an approximate plate current in each tube of 62 milliamps.
There you go. Now what if I went to a 200 ohm cathode resister? That should kick up my plate dissipation to around 31 watts, is this the direction I should go or does that set the bias too hot?
Thanks,
Dave

I definitely think you want to go the other direction. Try a 270, 280, or 300 ohm cat resistor.
That will get you current down a bit, without going to "thin" I think.
70% of a 30 watt tube is 21 watts. And, are you sure about your numbers.? 65mA per tube is almost double the "normal" current for a 6L6.
JMO of course....
Best

Hi, and thanks for the help.
The 62milliamp was generated by the Weber calculator I was using. I measured the milliamps on my power tubes and they are 52 which I thought was high but then not really understanding what I'm doing I was unsure which way I should go. The spec on the build I'm doing calls for a 270 ohm 10 watt resister but I couldn't find one so I went with the 250 ohm. I could probably use a couple of resisters in series to get into the range which would lower the current down into the mid range.
Thanks for the shove in the right direction.
Dave

Would it be financially hard for you to order some high power resistors from Mouser.?
I do not mean to pry. You can email or PM me if you want to take this off-line.
I can mail you some 10 watt resistors if there is a need.
Keep in mind, the 270 on the schematic is somewhat of a "theoretical" value. In the end, you need to use what works to get the amp working properly.
To back track for a minute....are you sure about that 32.5 VDC across the cat resistor.?
Anyway, if I can help, let me know.
Wyatt is the one with a lot of knowledge about this stuff. He got you started, I should probably just let him get you through this.
Best

Quote from: davohilts on February 22, 2011, 03:24:19 AM

the only thing that was stopping me from getting the proper value or range of values for the resistors is my own stupidity. I looked around several months ago and couldn't find the right value so ordered one I could get. Considering the amount of stress this has put me through all for a 69 cent part, I'm beginning to think I need to seek professional help.
I have checked the voltage across the cat. resistor and am certain of the 32.5v value.

The main issue I think is my old silvertone 6L6gc's. They test very strong so I thought they would be a good choice while I await the JJ's coming wednesday, however, when I test the current on pin three I get 51 mV on one and 63 on the other. I'm thinking they are not well matched (they came out of an old Silvertone 1484 that I'm in the process of rebuilding and since they tested so well I thought I'd pop them in and use them.

My son is wanting to use this amp when he play in a blues club on thursday and he is pushing for more volume out of the amp. Compared to my 40 Watt pignose this amp is very quiet and it would be a stretch to play over drums with this amp which suprised us both since it has 2 6V6 power tubes.

Anyway, thanks for your input and concern about my sanity.
Dave

Hey Dave....
Help on the forum is free, but my therapy rates are 300 dollars/hour. It is 9AM straight up right now. Shall I start with your obvious hate for your parents.....:-)
Anyway...maybe get some 10 watt resistors ordered for those new JJ's you have coming. BTW, the mA difference you see on your old tubes in not "huge"and may not even be enough to cause any kind of ghosting or any other problem. The benefit of "matched" tubes is still debated. A lot of guys prefer un-matched tubes. Whatever, I think for your purposes, a pair that is within 6 mA will be fine.
If you need something in a hurry, just let me know. I can see what I have and get them in the mail from USA CA 94585. You can send me some replacements when you get a chance. Just an offer. No big deal.
Best...
Chip

6mA is getting pretty far apart, not a deal breaker with a 6L6GC, but it would be be huge for a 6V6GT or EL84. These tubes are being biased with the same resistor, so you are talking about one tube burning at nearly10% more dissipation. That's fine if the hotter tube isn't running above 80% dissipation, but rough on the tube if it's not.

As for the tubes testing good...that's a matter of which tube tester and how well it's been calibrated and what that particular manufacturer considered "good."

Wait for the JJ's...and try them with the stock 270 first.

Also what preamp tubes are you using, the problem may be a preamp tube choking signal off early.

8-ohm speaker, correct?

thanks for the input!
8 ohm JBL Speaker
JJ 12AX7 in #2 position
12AY7 6072 box plates 1950s GE-made/say Sylvania in #1 position
I'm hoping the JJ 6L6's come today and the cat. resistor will come tomorrow.
If I want to brighten up the tone a little can I use a 25mf 25 volt cap to bypass the cat resistor?
or if not what might I do to give the amp a little more treble for leads but not lose the nice bottom and mid of the deluxe.
thanks!
Dave

got the tubes and resistors and have done the following:
installed 270 ohm cat resister with 22mf 63V cap
installed JJ 6L6 power tubes
replaced the 22mf 40v cap bypassing the 820 resistor on pin 8 of 12AY7 with 2mf 50v cap
replaced the 22mf 40v cap bypassing the 1K5 resistor on pin 3 of 12AX7 with 2mf 50v cap

amp has more bite to it by far and I think when the speaker gets broken in more it will sound fantastic

the tubes are still running at 52 mA each, now balanced but still a little hot. I might drop in a 300 ohm 10 W cat resistor to see what happens but my son is playing it tonight for the first time!

Well, Mystery solved!! It turns out that the newly reconed JBL speaker has a badly rubbing voice coil! I discovered this when I plugged in a silvertone 1484 twin 12 cabinet to my 4 ohm load jack and the amp sprung to life. OMG the tone is really over the top and the volume is what I was originally expecting. I then tried a new speaker wire feed to the JBL thinking mine must be defective but still no go. I pulled the speaker and popped in an old JBL that had a repaired cone tear and fired it up and it sounds even better than I had hoped!
Thanks to all who helped advise, I think the mods I made were great adding some brightness to the tone but it is really a Deluxe on steroids now and my son is in loving the sound!
Dave

Ceriatone Forum

American Style => 5E3 Tweed Deluxe => Topic started by: davohilts on February 19, 2011, 08:24:51 PM