Author Topic: Power Transformer (Read 37814 times)

taylorc315 · « **Reply #150 on:** May 22, 2015, 05:48:06 am »

Yes EL34's, very little sound as in I have to turn it up all the way to get anything. with 14.61watts the tubes shouldn't get so hot should they? maybe because of having to turn all the way up had something to do with it. I will check everything again, any suggestions?

Thanks once again.
Tracy

John · « **Reply #151 on:** May 22, 2015, 07:44:03 am »

There's a wiring error somewhere.

Double check the filter cap connections, make sure each "node" on the power supply rail is going to the right one. (made that mistake)

Check your grid leak resistors on the power tubes, make sure they're not say 2.2k instead of 220k (or whatever the schem says)

Are your power tubes actually glowing red, or just getting hot very quickly? Because power tubes do get much much hotter than your preamp tubes.

taylorc315 · « **Reply #152 on:** May 22, 2015, 08:05:49 am »

Yeah they are glowing red, I will check the resistors, I did notice that the voltage from board A,B,and C was much higher than D&E don't know if that could be an issue. I will check them again after work but they seemed to be at least 100vdc difference.

John · « **Reply #153 on:** May 22, 2015, 04:08:06 pm »

Hmm. I'm tapped out of ideas (my knowledge is a thimble compared to Sluckey's bucketful)

I can't understand why your power tubes are redplating when, if your math is right, they're only dissipating ~ 14 watts per tube at the plates. You're measuring across a 1 ohm resistor? Are you sure that's a 1% tolerance 1 ohm, like Doug sells?

This is why I like cathode bias.

taylorc315 · « **Reply #154 on:** May 22, 2015, 04:11:35 pm »

Yes I got everything from Doug. I will check again and post as soon as I get home from the work thing.
Thanks
Tracy

John · « **Reply #155 on:** May 22, 2015, 05:01:29 pm »

That darned work thing! It keeps my ouput to 2 a year, if I'm lucky.

taylorc315 · « **Reply #156 on:** May 22, 2015, 05:59:11 pm »

I have 5.6k resistors on the tubes, that's what it calls for. It stands to reason that board A has more voltage now that I look at it duh on my part. I do have the bias tap wired to the 220k 3 watt resistor from the pt red output. And the feedback wired from the 8ohm switch to the 47k resistor as it shows in the diagram. I'm going to keep looking this damn thing over maybe I'm just not seeing something.

taylorc315 · « **Reply #157 on:** May 22, 2015, 06:30:31 pm »

Should I be getting 470+vdc out of all tabs on the filter caps?

AZJimC · « **Reply #158 on:** May 22, 2015, 06:59:46 pm »

Quote from: taylorc315 on May 22, 2015, 06:30:31 pm

Should I be getting 470+vdc out of all tabs on the filter caps?

No, look at your schematic, there is the first node, highest voltage, then choke, which drops some voltage, so it's cap would be just a little lower, then dropping resistor, and another cap, which should be lower voltage, (assuming a normal loading with all tubes in place and functioning). Then another dropping resistor and cap, with lower voltage. Each power supply resistor drops the voltage a bit.

taylorc315 · « **Reply #159 on:** May 22, 2015, 07:06:19 pm »

OK great that's what I'm getting. Thank you

taylorc315 · « **Reply #160 on:** May 22, 2015, 07:20:32 pm »

Thought I might have found a problem, it was in the preamp tube thought I had wire's touching but wasn't it. This is kind of like golf very humbling. Still red plaiting damn.it

John · « **Reply #161 on:** May 22, 2015, 07:35:34 pm »

Quote

This is kind of like golf very humbling.

But way more fun.

John · « **Reply #162 on:** May 22, 2015, 07:43:21 pm »

Okay, you've probably already done this and posted the answers, but if not: with the amp turned off (and unplugged), measure resistance from each pin of the power tubes to ground. On both tubes, the pins should measure pretty much the same, but probably not exact.

And, you're not using pin 1 on either tube as a tie point, are you? IIRC the EL34's have an internal connection with something there.

taylorc315 · « **Reply #163 on:** May 22, 2015, 08:06:57 pm »

Yes I have pin 1 tied in with 8. Maybe Bingo?

John · « **Reply #164 on:** May 22, 2015, 08:13:23 pm »

That might be the problem! BUT, I don't know enough to say for sure, so wait until someone else chimes in.

*edit* No, that's not it. It is supposed to be tied to the cathode.

taylorc315 · « **Reply #165 on:** May 22, 2015, 08:18:57 pm »

Dang it

taylorc315 · « **Reply #166 on:** May 22, 2015, 08:25:32 pm »

I will check the resistance on all.pins and.see what I get and post.

taylorc315 · « **Reply #167 on:** May 22, 2015, 09:09:01 pm »

V4
Pin1&8=1.2ohm
Pin 2=50.1ohm
Pin 3=O.L
Pin 4=O.L
Pin 5=297.2k
Pin 6=291.6k
P 7=50ohm
V5
Pin 1&8=1.4ohm
Pin 2=50ohm
Pin 3=O.L
Pin 4=O.L
Pin 5=297.1
Pin 6=291.5
Pin 7=50.1

John · « **Reply #168 on:** May 23, 2015, 04:55:46 am »

Check the little 1 ohm resistors again. When you set your DMM to check ohms, touch the leads together first; that should give you a 0.00 reading. Those resistors should be reading 1 ohm, or 1.01 at the most.

Otherwise, the one is 20% off and the other is 40% off. That'll give you bad math for sure.

And hey, somebody that knows more than me (which is everybody)... should pin 6 be showing those resistance readings?

sluckey · « **Reply #169 on:** May 23, 2015, 05:32:43 am »

Quote

should pin 6 be showing those resistance readings?

Yes. The 5.6K grid stopper is mounted between pin 5 and pin 6.

taylorc315 · « **Reply #170 on:** May 23, 2015, 07:51:42 am »

Thank you I'm on it.

taylorc315 · « **Reply #171 on:** May 23, 2015, 08:17:20 am »

I get 1.0 on one and 1.1 on the other, it's not 1.01 does that make a difference?

taylorc315 · « **Reply #172 on:** May 23, 2015, 08:26:29 am »

John, remember I'm on here so I would be the one that doesn't know anything ; )

sluckey · « **Reply #173 on:** May 23, 2015, 08:40:21 am »

I don't worry about a 1Ω 1% precision resistor being exactly 1Ω. If it reads close to 1Ω, I always assume it is correct. Such things as lead resistance, connectors and even the pressure you put on you probes can cause a seemingly out of tolerance reading.

taylorc315 · « **Reply #174 on:** May 23, 2015, 08:56:55 am »

Thanks sluckey,do you have I suggestions as to the red plating in the tubes? What I can check?

sluckey · « **Reply #175 on:** May 23, 2015, 11:06:50 am »

Power tubes (may have been damaged earlier), voltages on power tubes, especially the - bias on the grids, wiring to the power tubes, components in the power tube circuit.

Disconnect the NFB wire. Does that help? Leave it disconnected for now.

Pull all the little tubes and leave them out until the red plating condition is solved. Post a few hi-rez pics of the power tubes and board near the power tubes. We need to be able to clearly see a wire that leaves the board and connects to a pin on the power tubes. We need to be able to see resistor color codes and cap values.

taylorc315 · « **Reply #176 on:** May 23, 2015, 03:56:36 pm »

I should know this,. But what is NFB? Thanks. I will try to get some decent pictures posted as soon as I can.

Willabe · « **Reply #177 on:** May 23, 2015, 04:00:46 pm »

There's a wire that goes from the amps speaker output jack to a R then it goes to the PI. (NFB = negative feed back)

Brad

taylorc315 · « **Reply #178 on:** May 23, 2015, 04:18:14 pm »

R=? PI=? Sorry still really new at all the hyphens. And thanks again

Willabe · « **Reply #179 on:** May 23, 2015, 04:27:46 pm »

Ok, sorry. R = resistor, PI = phase inverter. Sometimes LTPI = long tail phase inverter. C = capacitor.

E-cap or e-cap = electrolytic capacitor, B+ filter cap or cathode (= K) bypass cap. CCR (no not the band

) = carbon composition resistor, MFR = metal film R. The plate of a tube = anode = A or P.

Switches, SPST = single pole, single throw = on/off switch. SPDT = single pole, double throw. DPDT = double pole double throw. It goes on as there are any # of poles and throw combinations. Also the switch will be listed as maybe center off or on/on/on....... (The pole is the 'common' of the switch and the throw is what the switch switches to.)

Also you will see NFB as -FB or FB. (There's also positive FB.)

Brad

taylorc315 · « **Reply #180 on:** May 23, 2015, 04:36:13 pm »

CCR are you sure its not the band : ) To funny! Thank you very eye opening. I pulled the pre amp tubes now when I take readings on the power tubes I get pretty much nothing, is that normal?

taylorc315 · « **Reply #181 on:** May 23, 2015, 04:45:16 pm »

I believe that I may have a problem Houston, I don't have any resistors connected to my output jacks. The diagram that I have and maybe I'm reading it wrong, which is entirely possible doesn't show any.

Willabe · « **Reply #182 on:** May 23, 2015, 04:47:46 pm »

I don't know if you've seen this but it is an excellent way to double check an amp build with it's schematic.

We've seen a good number of guys who couldn't find what was wrong with their build and using this method they found it.

Doug did a great job on this example;

http://el34world.com/Forum/index.php?topic=17701.0

Brad

Willabe · « **Reply #183 on:** May 23, 2015, 04:48:51 pm »

Can you post your diagram?

taylorc315 · « **Reply #184 on:** May 23, 2015, 05:24:03 pm »

It's page 2 in the library of information plexi 50 watt
That's the easiest way for me to post because I suck at computer stuff

sluckey · « **Reply #185 on:** May 23, 2015, 06:30:39 pm »

Quote

I pulled the pre amp tubes now when I take readings on the power tubes I get pretty much nothing, is that normal?

Say what!!!

taylorc315 · « **Reply #186 on:** May 23, 2015, 07:31:10 pm »

Yeah, I have 0 volts on pins 1&8
3.4 vac on pin 2
5.74vdc on pin 3
5.74vdc on pin 4
-49 vdc on pins 5&6
Great huh : (

Willabe · « **Reply #187 on:** May 23, 2015, 11:51:07 pm »

Here, red arrows, shows NFB wire from OT (output transformer, secondary side) speaker output jack, going to the series NFB R.

taylorc315 · « **Reply #188 on:** May 24, 2015, 09:56:38 am »

OK I have the 8ohm wire from the output going to the 8ohm selector switch from the selector switch to the resistor from the resistor to the 5k pres switch.And thank you again

taylorc315 · « **Reply #189 on:** May 24, 2015, 10:06:36 am »

About not having power to the power tubes, I had a blow.5 fuse. It's good now

taylorc315 · « **Reply #190 on:** May 24, 2015, 11:31:47 am »

I found a resistor that I soldered in the wrong way, it's the 330/16v that is in with the 820. That's probably not good. I switched it around don't know if that is my issues but it has to caused some of my headaches.

shooter · « **Reply #191 on:** May 24, 2015, 12:21:34 pm »

Quote

it's the 330/16v that is in with the 820

Are you talking C1a - R7a, coming off pin 3 of V1a? That would be a cap - capacitor, in || - parallel, with 820 ohm R - Resistor. If so, you might want to replace it, caps usually don't do well when they're hooked up backwards, and, ya, that will give you problems. Do you know WHY your fuse blew?

taylorc315 · « **Reply #192 on:** May 24, 2015, 12:37:20 pm »

No I don't, I can only assume that I did something to cause. Of course we all know what assuming does.; ) I will replace and see what happens. Thank You

taylorc315 · « **Reply #193 on:** May 26, 2015, 10:22:29 am »

https://www.flickr.com/photos/131879876@N08/17937088129/in/album-72157651167916813/

Please see if this works.Pictures
Thanks
Tracy

sluckey · « **Reply #194 on:** May 26, 2015, 10:55:43 am »

Doesn't work. Requires log in.

taylorc315 · « **Reply #195 on:** May 26, 2015, 11:02:57 am »

try tra412000 then taylor for pass

Willabe · « **Reply #196 on:** May 26, 2015, 11:20:17 am »

Clicked on link says, 'page not found'.

taylorc315 · « **Reply #197 on:** May 26, 2015, 11:35:17 am »

Try tra412000 and use password taylor or maybe if you could go to flicker and search for taylorc315.

taylorc315 · « **Reply #198 on:** May 26, 2015, 12:09:54 pm »

Any Luck?

sluckey · « **Reply #199 on:** May 26, 2015, 01:02:03 pm »

I see the pics.

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Author Topic: Power Transformer (Read 37814 times)