Reverb Tank: Project

[dubtrub]

I made quite a bit of progress, so I thought I'd share where I'm at the present. I have material for several different tolex coverings including tweed, plus grill cloth to accompany certain Fender tolex colors. I haven't quite decided whether to go with tweed to accent my tweed Deluxe, black to go with my '65 Bandmaster, or brown to go with my '63 reissue Vibroverb. I like them all. Suggestions are welcome, but you have to give a reason why.


Did I say before how good this thing sounds?

[Dennisthe Menace]

Danny, that's looking pretty sweet

[Don]

Got the 60 cycle hum problem temporarily resolved.

Danny, what was the cause of your hum? My homebuilt does the same thing.

[Desert Surfer]

Got the 60 cycle hum problem temporarily resolved.

Danny, what was the cause of your hum? My homebuilt does the same thing.

Don: As I mentioned, Danny is away for a few days. I am sure he will reply you when he gets back. (He asked me to watch the store a little while he is away.. )

[dubtrub]

As I mentioned, Danny is away for a few days. I am sure he will reply you when he gets back. (He asked me to watch the store a little while he is away.. )

Vincent, thanks for helping keep and eye on the forum. Much appreciated to both you and Dennis for keeping the activity going.

Got the 60 cycle hum problem temporarily resolved.

Danny, what was the cause of your hum? My homebuilt does the same thing.

The cause is determined to be 'ground loop' effect. Not smart enough on the technical side of the equation to describe it, and have not yet learned the proper permanent cure for it, although when my technician friend get's back in town I will get a more definitive answer. For the time being the simple solution is to use a two prong adaptor on the plug. The two prong breaks the phenomenon of ground loop.

[dubtrub]

Don,

I have been asking questions about the cure for the hum and have been given the advise to use a star grounding system. Rather than try to explain what it is and why it is, here is a link that gives a great overview. http://aikenamps.com/StarGround.html

Additionally, reading the Weber forum, it is apparently a common problem in kits and home made projects especially in reverb units due their high gain design. http://www.tedweber.com/cgi-bin/yabb/YaBB.pl

I will be opening up my reverb and try changing a couple of the grounding points. In particular I will use a heavier gauge grounding wire from the filter caps and from the buss plate and run the two directly to the ground point of the power transformer grounding wire point. Here's an example for the Weber AddVerb. https://taweber.powweb.com/store/addverb_layout.jpg

If you have photo's of your reverb, I'd sure like to see them posted here on the forum.

[Don]

Thanks for the info, Danny. For the record, I think you've done a great job on yours! Mine is not as exciting in that it is mostly a Weber kit...




I'm in the middle of a big home remodel so I haven't had time to troubleshoot and repair mine yet, but we're about 2-3 weeks from being done with the house so it will hit the bench soon. The hum is annoying but not bad enough to keep me from using it in the meantime. In fact I can't hear it at bedroom levels...only when I turn the amp up a ways and, even then, only when not actually playing. But it's one of those things that will bother me until I fix it.

I considered isolating chassis and circuit grounds ala the Fender Reissue while building it, but heard so many success stories with the Weber kit that I decided it wasn't needed. That will be my last resort since it would require a fairly big rebuild effort. The few quick attempts I've made to eliminate potential ground loops, like with the 2-prong adapter, haven't changed the hum at all.

Let me know if make any more discoveries with yours.

[dubtrub]

Let me know if make any more discoveries with yours.

Don, that is a great looking unit and looks like a real clean wiring. Love the logo.

I changed the grounding on the filter caps as mentioned before and used an 18 gauge wire. Like you, I really don't want to do a complete major rebuild, so I left it at that. I was surprised that it eliminated about 85% of the hum. Also I did not do the brass buss plate ground as of yet. I will have to pull it away from the chassis in order to get it hot enough for the solder to flow. However, it still runs pretty quiet with the two prong.

I think the right idea would be as you mentioned earlier with the isolated chassis circuit ground. As stated in one of the links I posted, the chassis in itself creates grounding 'eddies' as in water running in a river. The running of a heavy copper ground wire and connect each phase of grounds according to the wiring layout in the AddVerb, I feel is the answer to the problem.

[Don]

Danny, thanks for the compliment.

My filter caps are already grounded at a PT bolt via 18ga wire. In fact, all my ground wires are 18ga and would be easy to move around for testing. You're probably right about what will ultimately fix the problem, but I'm gonna try some more easy things first!

More questions for you...
Are you using the Accutronics pan? How did you mount yours?
What tubes are you using? Mine started with all JJ's as in the picture, but I was really happy with the difference when I changed the 6V6 to an old 6K6.

[dubtrub]

Are you using the Accutronics pan? How did you mount yours?

I am using the same inexpensive Belton pan that's in the Weber kit that I purchased from Antique Electronic Supply for 19.95. I have mounted my home built chassis in my Fender reissue cabinet that uses the Accutronics 4AB3C1B, and found that the Belton sounds better with the capability of a much longer decay and has a better splash back. To my ears the Accutronics has more of a tinny sound that is not as pleasant. I only have the pan temporarily mounted screwed directly to the face board, but I will be changing it to spring mounting as it is dampened some what by being mounted solid.

What tubes are you using? Mine started with all JJ's as in the picture, but I was really happy with the difference when I changed the 6V6 to an old 6K6.

I am using old stock RCA 6k6, 12AX7 and 12AT7, although I tried the Fender 7025 and AT7 and couldn't tell any difference at lower (house hold) volumes. I have not tried a 6V6 but will give it a go and see if it's any different. They are suppose to have about a 50 volt plate voltage difference on the lesser side so it may help with the hum also. I know that in my Fender reissue, it sure sounded a lot sweeter with the 6K6 so that's why I haven't tried the 6V6. I've checked the schematics of the original 6G15 and the 5G15 and the B+ voltage is about 35 volts higher in my 5G15 copy. This is possibly the source of the hum.

BTW, the amp I've been testing my reverb with is a Weber 5E3 amp kit that I built a couple of years ago. It was my first electronics project. I really dig what Ted Weber is doing by making affordable projects. But, one has to upgrade some of the parts to get really quality final results.