Going to try and finish my Cornet II after a long summer break...

pretzel_logic · « **on:** 26 Aug 2009, 08:41 pm »

I am finally going to get back to work on what I started late last winter. As usual I get so occupied with other things once the weather warms up I'm rarely inside enough to do much other than relax.

Basically I just have the chassis work to do, maybe the scariest part for me and one reason I put it off in the first place. One modification I'm making to the chassis is putting the on/off switch on top near the transformer. I ordered a chassis that's a little longer than spec so hopefully that won't create a problem with a few longer wires, won't be that much different.

Brian

pretzel_logic · « **Reply #1 on:** 27 Aug 2009, 01:26 am »

Well, I screwed up my first try at the top chassis plate, didn't have the template in the right spot, was too far forward so tried again using the bottom plate. Everything looks fine now, a little filing to remove burrs and should be good to go. Was actually easier than I thought once I had everything centered properly. Tomorrow or the next day I'll actually mount the board, do some wiring and see where I'm at but in reality I should be close to firing this bad boy up by the weekend.

Brian

Demsy · « **Reply #2 on:** 28 Aug 2009, 04:02 am »

Hi Brian, good luck with the project. Btw, what chasis are using?

D

pretzel_logic · « **Reply #3 on:** 28 Aug 2009, 01:37 pm »

I'm using a lansing chassis, nice but unfortunately I goofed on the first go cutting the top. Used the bottom and it turned out fine, though a couple minor mars in it now. I have everything ready to go except hooking up the power leads, can't find the lug to the ground terminal, if it was ever there. Went through the garbage and no luck so will make something or find something that will work. I also have to hook up the RCA's to the board, not using the spec'd version, bought some Vampires on Jim's recommendation.

I started this project back in January and just ran into a lot of other things going on, the board has been done for months. Once spring arrived I had a lot to do outside, landscaping and what not. Hopefully I'll be able to put power to this tonight and see if I have fire or music.

Brian

pretzel_logic · « **Reply #4 on:** 28 Aug 2009, 10:23 pm »

Well I finished up my Cornet II today, plugged it in and no smoke, good start. After checking voltages I found they were all within spec but I had a problem checking the heater voltage to the EH 5Y3GT I used. Pin 2 was showing 270+ volts and pin 7 nothing. I immediately shut the unit down trying to figure out what's going on but have had no luck yet.

When I turn the unit on it immediately goes to green on the LED, no red at all.

Any suggestions? I have been looking for different tubes to try, have a GZ 34 and a couple 5U4 on hand but not sure I shoule try them, can't remember if they're compatible.

Brian

pretzel_logic · « **Reply #5 on:** 28 Aug 2009, 11:42 pm »

I tried the GZ 34 in the unit and got a better reading, 6.47 on the heater but still high it seems. I am thinking I was reading the wrong pins but all the other readings were within 10 volts of spec.

I gave it a listen to see if there was hum and sure enough there is, changes with the volume so I'm not a happy camper. I don't see any bad solder joints but I could be wrong there.

Any suggestions would be much appreciated, especially with the hum. I do have some NOS tubes on the way as well.

Brian

tubesforever · « **Reply #6 on:** 29 Aug 2009, 08:31 am »

First and foremost, remove the back bell cap on your transformer and remove the wire that goes to the housing. Cut this off, strip it back and solder on a longer lead wire. This needs to go straight to the ground point you selected as the main circuit ground. Think of this as how will the signal reach ground. Each point of the circuit needs a fresh and immediate grounding option or you will hear hum.

Make sure none of the Vamps is touching the case work. The RCA ends must float.

Also, sever any ties between the RCA ground plugs. Take each right and left ground individually back to the board and from the board out to the output RCA's. Otherwise you run the risk that the signal will loop before it ever hits the circuit or loop on its way back out to the IC's. .

I bet this will solve the hum.

Cheers!

pretzel_logic · « **Reply #7 on:** 29 Aug 2009, 12:33 pm »

Thanks for the suggestions Jim. Regarding grounding the transformer to a point I selected as ground. I'm showing my ignorance here but where would that ground point be? Should I use the earth tab on the board, I didn't actually pick a spot for a ground, just went by what the manual said.

I do have the RCA grounds tied together so I'll make separate runs for those.

As far as heater voltage goes, what it the optimum voltage if there is one? I have a Sylvania 6106 rectifier on the way among some other tubes. I am going to order a couple different values in the R223 position, I have a 1.5 in now and a 1.8 on hand.

I will say I liked the sound of the unit for the little while I had it running. Obviously the hum was bad but in general the sonics seemed good compared to my original Cornet.

Thanks again,

Brian

pretzel_logic · « **Reply #8 on:** 29 Aug 2009, 01:37 pm »

Just saw the post by OMalley about his hum issues, can't believe I didn't see it before but didn't. Anyway, great source of info there. I have my bell covers off and will be running a longer ground wire to the ground lug on the chassis.

pretzel_logic · « **Reply #9 on:** 29 Aug 2009, 07:39 pm »

Well, I got rid of about 95% of my hum, made sure the RCA's were isolated from the chassis, 2 weren't, ran the transformer housing ground out to the grounding post on the chassis and wired the RCA grounds separately instead of tieing them together. I do still have a little bit of hum that changes with the volume but it's hardly audible. I also have some new tubes coming as well, was hoping they'd be here today, so maybe that will help as well. I would like to eliminate the hum altogether obviously, my original Cornet was completely quiet.

Thanks again Jim, and I suppose the Piccolo will be next, may source a few different caps for that.

Brian

pretzel_logic · « **Reply #10 on:** 30 Aug 2009, 12:59 pm »

Gave the Cornet II a good listen last evening and liked what I heard. I can only compare to my original Cornet but with only a few hours listening time, and with pretty basic "new" tubes, Sovteks in the AX7 and AU7 spots, and a Phillips 5V4GA, it sounded very good.

I don't know how the Sylvania 6106 compares to the Bendix version but I have a Sylvania on the way as well as a cleartop RCA 12AU7 and a couple RCA longplate AX7's.

I do still have a little hum issue to contend with, not sure what to do about that yet, will see if it subsides once I get some different tubes. I also wonder if I should be concerned about the LED going straight to green, it never turns red. Should I worry about that???

Anyway, I'm glad to finally have this finished and running, only took me about 7 months!

Brian

GRD · « **Reply #11 on:** 30 Aug 2009, 06:09 pm »

I believe only Bendix made the 6106. Some of the Bendix production was re-branded (I have an example). The other designation for the 6106 is 5Y3 WGTB. I've also seen pictures of 6106 tubes described (in error I believe) as WGTA.

Bottom line - if it's a 6106, it's a Bendix (but there were some changes over time in the 6106 internals during production eg. the center steel sleeve - holding the ceramic tube that is heated by the filament - can look a little different).

Very interesting tube.

pretzel_logic · « **Reply #12 on:** 30 Aug 2009, 10:28 pm »

I'm not sure about the 6106, I thought only Bendix made them also. It is from a reputable dealer and should be here tomorrow along with several other tubes, going to roll my amp and preamp as well.

Demsy · « **Reply #13 on:** 31 Aug 2009, 04:08 am »

Using the Philips 5Y3, the red LED will glow for approximately 3 seconds before jumping to green, now I'm using the POPE 5AR4/GZ34, it takes about 15 seconds. I think the 5Y3 is directly heated and the 5AR4 indirectly, please correct me if I'm wrong. This means the 5Y3 supplies the rectified voltage quicker than the 5AR4. I have a pair of 6106 on it's way, and according to the people that has used it, it will even take longer before it works.

Quote from: pretzel_logic on 30 Aug 2009, 12:59 pm

I do still have a little hum issue to contend with, not sure what to do about that yet, will see if it subsides once I get some different tubes. I also wonder if I should be concerned about the LED going straight to green, it never turns red. Should I worry about that???

pretzel_logic · « **Reply #14 on:** 31 Aug 2009, 01:21 pm »

I actually did notice a slight red hue through the green on the LED at startup, it was there but very faint. I'm not concerned as the unit sounds fine so far and my voltages were pretty close to spec. I'm going to check voltages again today and see if anything varies from my initial check.

Another question, will changing the rectifier create any changes in voltages? I know some tubes like a little higher voltage, I came in at 5.7 volts with the JJ GZ34 after having problem with the 5Y3 EH I originally installed. I then popped in a Sylvania 5V4GA that was in my original Cornet. Not sure I like how that sounds, a little too much in the low end for my tastes but I also swapped in a 5814 in the AU7 spot, could be that tube. And yes, this unit has a lot of break-in to go, only about 4 hours on it yet.

The other tubes I'm going to try, I have a couple 5751's on hand, am waiting on a couple RCA longplate, a RCA 12AU7 cleartop and the 6106 as well.

I wish I had a tube tester. I have some vintage Mullard and Tele 12AX7's but I know at least a couple of those crackled in my other Cornet.

I'll also try to post a few pics in the next day or two as well. Lots of upgrades in the capacitors thanks to suggestions from tubesforever.

Brian

Brian

GRD · « **Reply #15 on:** 31 Aug 2009, 09:20 pm »

The 5Y3, GZ34 and 5V4 all are spec'd at 2 amps heater current, so there should be no material difference in the final heater voltage. The 6106 is spec'd at 1.9 amps, but that's pretty close to 2 amps so maybe a hair higher heater voltage. You should get a somewhat higher B+ with the GZ34 and the V4 - but I never measured the difference. The 6106 and 5Y3 should have similar B+. They will all sound a little different. Interested in finding out what you finally settle on (which will also depend on what you settle on for the other 3 tubes).

pretzel_logic · « **Reply #16 on:** 31 Aug 2009, 11:58 pm »

Thanks for the info GND. I did get my tubes in the mail today, retubed sections of my amp and preamp, tried the supposed to be 6106 which was labeled Zenith 5Y3GT/6109 not 6 but supposedly made by Sylvania, as well as the RCA cleartop 12AU7 and the RCA AX7's. I liked the sound a lot but went out for a bit only to come back and find the 5Y3 cold, the other tubes were still warm.

Anyway, tried the 5V4 again and am back to a little more weight in the low end. Will be making a call to the guy I got the tubes from but he said on his website they were the same as the Bendix 6106. I may have just gotten a bad tube but I do want to try the 6106, has gotten a lot of rave reviews on here. He was out of the Bendix so I may hunt around for one.

Brian

WGH · « **Reply #17 on:** 1 Sep 2009, 01:43 am »

I use a 5V4GA RCA (branded CBS) NOS and also like it's weight and sound. Also in the mix is a 12AU7A GE branded CBS NOS black vertical rib plate and a pair of Sovtek 12AX7LPS.

I bought my all tubes from Jim McShane.

Ain't this fun?

Wayne

GRD · « **Reply #18 on:** 1 Sep 2009, 02:59 am »

For what it's worth, I've settled on the RCA 5Y3. Sovtek LPS AX7 and a CBS 5814. The 5y3 type sound the best in my system. The 6106 sounded a little too soft in my system and the 5V4 and GZ34 were too bright. But that's just for me. You can find the 6106 for not outrageous $ and they are a very interesting design with a history.

tubesforever · « **Reply #19 on:** 1 Sep 2009, 06:28 am »

I used the stock rectifier on my Cornet 2 and got about 10% below the values on the board test points. I used a Bendix 6106 and the Mullard rectifier and they are about 6% above the values on the board.

While I could live with this, I decided to change the step downs. I ended up just changing the values by a few thousand ohms and got the test points dead on.

I love the 6106 and the Mullard rectifier so I am sticking with these tubes. Just think slam, space and cohesion and you get what I am hearing.

I love this topic, and remember that this might be system dependent so what's best in my system might sound too raw or two loose in other systems.

I just love the C2 and I figure it is possibly the steel of the century in its price range.

Cheers.