Problems with my Tweed Deluxe 5E3 rebuild

[Mike_J]

Just finished rebuilding my Tweed Deluxe 5E3 amp. Looked through the amp before startup and everything looked good. Plugged it into a speaker cabinet turned it on and couldn’t hear anything coming through the speakers. Plugged guitar in and there was weak sound with a lot of hair. Turning the amp way down reduced the hair substantially but the amp doesn’t have the volume it had before. Additionally, when I turn the standby switch to off I hear a buzzy hum. Anyone have any suggestions?

[sluckey]

Start here...


     http://el34world.com/Forum/index.php?topic=19361.0

[Mike_J]

Here are the voltages:


Tube 1 (12AY7): V-1-1 = 76.5 vDC, V-1-3 = 1.42 vDC, V-1-6 =100.2 vDC, V-1-8 = 1.56 vDC
Tube 2 (12AX7): V-1-1 = 130.6 vDC, V-1-3 = 1.00 vDC, V-1-6 = 160.9 vDC, V-1-8 = 35.77vDC
Tube 3 (6V6): V-3-3 = 310.1 vDC, V-3-4 = 250.4 vDC, V-3-5 = 0 vDC, V-3-8 = 29.7vDC
Tube 4 (6V6): V-4-3 = 292.5vDC, V-4-4 = 245.6vDC, V-4-5 = 18.04vDC, V-4-8 = 29.7vDC


Seems peculiar that V-3-6 shows no voltage whereas V-4-5 has a voltage of 18.04vDC. Will start my search in this area, if it doesn't fix it I will use the yellow highlighter method again.

[sluckey]

Pin 6 is not used by the 6V6 tube. But it is often used by the builder as a convenient tie point for components. Do you have anything connected to pin 6 of your tubes? Which layout are you using?

[PRR]

> peculiar that V-3-6 shows no voltage whereas V-4-6 has a voltage of 18.04vDC.

Both should be ZERO (+/-1V). Also the cathodes are typically 20V not 30V.

So why does V4 pin 6 (actually pin 5; p6 is a tie-point for p6) have 18V on it??

> Just finished rebuilding

Just new rings and gaskets? Or pistons crank cam bearings and accessories? "What you touched" is where to look for trouble after you touched it.

[Mike_J]

Pin 6 is not used by the 6V6 tube. But it is often used by the builder as a convenient tie point for components. Do you have anything connected to pin 6 of your tubes? Which layout are you using?

Yes, running 1.5K resistor on the tube socket to from pin 6 to pin 5. Grid wire goes into pin 6. Should have listed pin 5 as my voltage source. Will correct.

[Mike_J]

> peculiar that V-3-6 shows no voltage whereas V-4-6 has a voltage of 18.04vDC.

Both should be ZERO (+/-1V). Also the cathodes are typically 20V not 30V.

So why does V4 pin 6 (actually pin 5; p6 is a tie-point for p6) have 18V on it??

> Just finished rebuilding

Just new rings and gaskets? Or pistons crank cam bearings and accessories? "What you touched" is where to look for trouble after you touched it.

Pin 5 on tube 4 has volts of DC on it. I turned it off as I don't want to damage the tube if it hasn't been already. Could the voltage on pin 5 be contributing to the high cathode voltage? I am using a 270R cathode resistor which should give me the 20 volts theoretically. Will look to see why there is voltage on pin 5. Should be obvious.

[Mike_J]

Only possibility I see is the .1 mF cap is leaking a whole lot of DC. Is that possible?

[sluckey]

Only possibility I see is the .1 mF cap is leaking a whole lot of DC. Is that possible?

That's a good possibility. Wiring error is about the only other possibility. Needs to be corrected before going any further.

[Mike_J]

Only possibility I see is the .1 mF cap is leaking a whole lot of DC. Is that possible?

That's a good possibility. Wiring error is about the only other possibility. Needs to be corrected before going any further.

Changed the coupling cap between V-2-6 and V-4-5 with no change in DC on the grid of the power tube. Looked at the wiring and can not see anything wrong with it. Will tackle it again tomorrow. Going to resolder all wiring on V4 although I am not confident that will fix the problem. Can anyone think of a way DC would get on the grid of a power tube other than through the coupling cap of the previous stage? Can it be a tube or another issue?

[sluckey]

Can it be a tube or another issue?

Maybe. Not likely. Pull the output tubes and see. I still think it's probably a wiring error. Post some hi rez pics and we'll take a look.

[Mike_J]

Can it be a tube or another issue?

Maybe. Not likely. Pull the output tubes and see. I still think it's probably a wiring error. Post some hi rez pics and we'll take a look.

Can I pull the output tubes and turn the amp on to check for DC on pin 5? You are most likely correct about the wiring error. Have had some pretty strange wiring issues in the past that were very difficult and sometimes impossible to see. Working on the pictures.

[sluckey]

Can it be a tube or another issue?

Maybe. Not likely. Pull the output tubes and see. I still think it's probably a wiring error. Post some hi rez pics and we'll take a look.

Can I pull the output tubes and turn the amp on to check for DC on pin 5? You are most likely correct about the wiring error. Have had some pretty strange wiring issues in the past that were very difficult and sometimes impossible to see. Working on the pictures.

yes

[PRR]

The wiring is wrong. 18V dropped to 4V across 1.5k says 10mA flowing to grid. I can't imagine where 10mA "should" be coming from.... most of the small-tube stages work at 1mA-2mA and can't be much over 3mA since they typically ("should") have 100k plate resistors.

Tip (not that I always take my own advice) : if stuff in a build is hard to see, *change it* so it can be seen clearly. I always "tried" to do that in electronics. I spent days in my cellar re-routing the builder's electric cables so I can know what is what without putting my hands in spider-nests and splinter-forests. Along the way I found a fair number of bad splices, explaining why the kitchen outlets tripped-out a lot. In my last house I found connections that were WRONG, explaining why breakers were NOT tripping as they should.

[sluckey]

Measure resistance from V4-5 to chassis. Do the same for V3-5. What have you? Hint... should be 220KΩ for each reading.

[Mike_J]

Measure resistance from V4-5 to chassis. Do the same for V3-5. What have you? Hint... should be 220KΩ for each reading.

You were correct, both measured 220K.


The only difference I see in the wiring of my amp versus the Hoffman layout is I terminated the heater center tap at the positive end of the cathode cap. I also ran just one wire from the same area to pin 8 of tube three and daisy chained it over to pin 8 of tube four. Do you think either of those issues could be causing the problem with the voltage on pin 5 of tube 4?

[sluckey]

V-4-5 has a voltage of 18.04vDC

Look closely at your meter. Is it possible that it is displaying 18.04mV instead of 18.04V?

[Mike_J]

V-4-5 has a voltage of 18.04vDC

Look closely at your meter. Is it possible that it is displaying 18.04mV instead of 18.04V?

Looks like you might be on to something. Just had both lenses replaced and laser surgery to eliminate cataracts. Thought I could see well, supposedly 20/15 now, but I still have the same brain to process the information. Doing the best I can with what I have to work with.


Measured V-4-5 and it is now reading in mV and probably was before as you suggested. However, V-3-5 has a zero rating whereas the V-4-5 reading keeps rising as I keep my meter on it up to 106mV and rising. My meter has worked well in the past but is no Fluke. Wonder if it is contributing to the issue?


Measured the above without tubes in. Will switch tubes around and take measurements just to see what happens.

[sluckey]

Call it good and move on to chasing the real problem.

[Mike_J]

Measured V-4-5 with tubes in. Now it is 22 vDC not mV. When the standby switch is turned off there is a noticeable hum that is not there when the standby switch is in the on position. Don't know how one can have anything to do with the other. My experience has always been the standby switch in the off position can reduce hum not increase it. Need to work on pictures.

[sluckey]

Disconnect the .1µF coupling cap for V4. Still got 22V on V4-5? If so, swap the 6V6s . Still got 22V on V4-5?

[Mike_J]

Disconnect the .1µF coupling cap for V4. Still got 22V on V4-5? If so, swap the 6V6s . Still got 22V on V4-5?

Don't have 22V but have in excess of 1V on one tube and 4V on the other tube.


I am thinking it might be a good idea to try moving the heater center tap to the main ground point. Do you think this is worth trying?


Is there still a 1 meg file size limit on this site? My high rez pictures exceed 1 meg.

[sluckey]

Your readings seem to be all over the place. Disconnect BOTH .1µF coupling caps and recheck pin 5 for both tubes. What have you?

The heater center tap should not be a factor.

Attachment Restrictions: 4 per post, maximum total size 2048KB, maximum individual size 1024KB. Adjust your file size accordingly.

[Mike_J]

Your readings seem to be all over the place. Disconnect BOTH .1µF coupling caps and recheck pin 5 for both tubes. What have you?

I have 0V on V-3-5 and 28Vdc on V-4-5. Let me know if you need specific pictures.

[Mike_J]

By lifting the coupling caps feeding signal to the power tubes pin 5 of both power tubes are connected to essentially nothing if I am not mistaken. Therefore there should be no voltage on pin 5. Removing tube 4 did not eliminate the voltage on pin 5 entirely. As I recall there was about 4V on it with the tube out and it was rising.


Is there any place other than the tube socket where DC can be leaking into pin 5? Seems to me that replacing socket 4 may be warranted. Maybe there is some voltage leaking across the socket. Can't see any other place it would come from.


Thanks
Mike

[sluckey]

I want you to totally remove the two .1µF caps (brown one and yellow one). And unsolder/lift the bottom end of both of those blue 470Ω screen resistors. Take another pic of the board. I want to clearly see the turrets that are underneath the brown and yellow caps that you removed. Pull the 6V6s and lay them aside for now. Recheck the voltage on pins 5 of each 6V6 socket? What have you?

[Mike_J]

Measurements showed zero volts on both power tube grids. Took the picture you requested along with a picture of the new tube socket for V4. It is quite a bit easier to see now.


Thanks Mike

[Mike_J]

I want you to totally remove the two .1µF caps (brown one and yellow one). And unsolder/lift the bottom end of both of those blue 470Ω screen resistors. Take another pic of the board. I want to clearly see the turrets that are underneath the brown and yellow caps that you removed. Pull the 6V6s and lay them aside for now. Recheck the voltage on pins 5 of each 6V6 socket? What have you?

Forgot to put your quote in the previous post.

[sluckey]

OK. I suspect your circuit board or sockets have some leakage between the screen connections and the grid connections. Use some denatured alcohol or mineral spirits to clean up that flux crud on the board. (I use small acid brushes but a tooth brush works pretty good too.) Clean the crud off the tube sockets as well. Then neatly reconnect the screen resistors and coupling caps. Recheck the voltage on pins 5 of each socket. What have you? If zero on both sockets, plug in the tubes and recheck voltage. What have you?

[Mike_J]

OK. I suspect your circuit board or sockets have some leakage between the screen connections and the grid connections. Use some denatured alcohol or mineral spirits to clean up that flux crud on the board. (I use small acid brushes but a tooth brush works pretty good too.) Clean the crud off the tube sockets as well. Then neatly reconnect the screen resistors and coupling caps. Recheck the voltage on pins 5 of each socket. What have you? If zero on both sockets, plug in the tubes and recheck voltage. What have you?

Cleaned circuit board and tube sockets with denatured alcohol. Have zero volts on pin 5 with or without tubes. The voltages with tubes in all in DC are as follows:


V1 - 1    92.2
     - 3      1.714
     - 6   120.0
     - 8      1.884


V2 - 1   155.4
     - 3       1.241
     - 6   193.2
     - 8     44.3


V3 - 3   343.5
     - 4   303.1
     - 5       0
     - 8     20.47


V4 - 3   344.5
     - 4   303.4
     - 5       0
     - 8     20.46


Thanks for your help with this. Learned a few lessons.


Still have hum when I turn the standby switch off. That is probably a wiring problem. Will take picture. Also, the voltages on the plates seem a little low to me. Does anyone have an optimal target range for plate voltages for a Tweed Deluxe?

[sluckey]

Here are my voltages...

http://sluckeyamps.com/5e3/5e3.pdf

[Mike_J]

Here are my voltages...

http://sluckeyamps.com/5e3/5e3.pdf

Pretty close. My voltage for V-1-1 is a little lower because I used a 220K plate load resistor ala the RobRob lead channel mod.


Thanks
Mike

[Mike_J]

Here is a picture of the standby switch which is on the far left of the chassis. The standby switch is connected to pin 8 of the rectifier tube on one lug and to the positive side of the first power cap on the other lug, in this case a 30mF cap. One of the black wires from the PT are connected to one lug on the main a/c switch and the other black wire is connected to the white a/c wire coming from the wall. The black wire from the wall is connected to the top of the fuse socket. The other end of the fuse socket is connected to the remaining lug on the main a/c switch. Seems pretty simple. Not sure why there is hum when I turn off the standby switch. Can you suggest anything? I had a death cap on the rectifier tube side of the standby switch but removed it with these modifications. Wonder if I need to put it back.

[Ed_Chambley]

Try chopsticking your filter caps and the higher voltage section of your B+ is close to the back of the pots.  Can you hear a change in the hum?  Get louder sometimes?  Quiet others?  Compare Sluckeys filter cap layout to yours.  Take a look at the Fender layout.


Both layouts work, it is just sometimes a little massage is in order.

[Mike_J]

Try chopsticking your filter caps and the higher voltage section of your B+ is close to the back of the pots.  Can you hear a change in the hum?  Get louder sometimes?  Quiet others?  Compare Sluckeys filter cap layout to yours.  Take a look at the Fender layout.


Both layouts work, it is just sometimes a little massage is in order.

The only time it hums is when the standby switch is in the off position. Have been reading and it may have something to do with the PT radiating into the OT when they are too close. The OT wires are pretty close but the transformers seem to have a reasonable distance between them.

[sluckey]

Remove both wires from the STBY switch and tape the ends. Does the amp hum now?

[Mike_J]

Remove both wires from the STBY switch and tape the ends. Does the amp hum now?

Removed both wires from the standby switch and taped the ends. No hum at all. I am guessing this probably eliminates the PT to OT theory.

[Mike_J]

Try chopsticking your filter caps and the higher voltage section of your B+ is close to the back of the pots.  Can you hear a change in the hum?  Get louder sometimes?  Quiet others?  Compare Sluckeys filter cap layout to yours.  Take a look at the Fender layout.


Both layouts work, it is just sometimes a little massage is in order.

Do you think these layout points could be causing the hum while the standby switch is off? There isn't any voltage going to the filter caps that I can see. The amp is quiet when the standby switch is on. Makes me think the best move would be to put a wire across the two lugs on the standby switch which would mean the standby switch would always be on no matter where it is set. Or maybe not if the switch is causing the problem. As you can plainly see I am confused.

[sluckey]

Remove the solder on the switch and clean it up with denatured alcohol. Then reconnect the wires to the switch, but this time wrap the wire around the lug and crimp before you solder. IE, make a good mechanical connection, don't just poke the wire in the hole and hope the solder will make a connection. Does the amp hum now? If so, replace the switch.

[Mike_J]

Remove the solder on the switch and clean it up with denatured alcohol. Then reconnect the wires to the switch, but this time wrap the wire around the lug and crimp before you solder. IE, make a good mechanical connection, don't just poke the wire in the hole and hope the solder will make a connection. Does the amp hum now? If so, replace the switch.

Cleaning the switch didn't fix the hum so I will order a new switch as I can't seem to find one around here. Love the amp. Spent the last hour laying down a Little Wing rhythm track on my looper and playing over it. A little Jimi, a little SRV and a lot me. Tone is great. The kind that makes it hard to put your guitar down.


It makes me realize why I like to build these amps. Had two heart attacks, a AAA rupture that kept me in the hospital for seven weeks getting everything a hospital can offer, controlled high blood pressure and type 2 diabetes and my lower back screams at me every time I do anything that is the least bit strenuous. But for the last hour I was young again with a tone that just made me happy.


Thanks
Mike