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Post subject: stand alone reverb unit
Posted: Thu Jan 26, 2012 12:10 am
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OK guys, it's my turn for your help! Got a 3yr old Weber 5G15, basically a 6G15 with a full wave rectifier. This unit has plenty of hours, tubes are fine. Noticed the reverb fade maybe 30 seconds after playing, now it's almost gone even with the dwell and mix cranked(tone control doesn't have much push). It passes the input signal quite well on to the host amp, with the expected gain. So, how do you guys check the tank? I'm getting no ohmage reading from the tanks input and across to the output side. Haven't pulled the tank yet. It's the 4AB3C1B. Not getting any splash when the unit is moved. Just didn't think the tank should fail in 3yrs. The unit stays at home, mostly. And yeah, call me lazy, I haven't done the voltage check yet. Art

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Post subject: Re: stand alone reverb unit
Posted: Thu Jan 26, 2012 3:42 am
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I have a 4AB3C18 at home , working fine .

Input 1.1 ohms , output 213 ohms. wire between thank and circuit are allright ?


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Post subject: Re: stand alone reverb unit
Posted: Thu Jan 26, 2012 9:18 pm
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Stratele, thanks for your experience and advice. Pulled the tank and checked the transducers. They were OK, 1.6 and 209ohms. Cleaned the transducer connectors inside the tank, outside connectors, hook-up cables, and tested the cables. Put it back together and it works better. Just wondering if the transducers wear down over time? I know the springs can get sloppy. Oh well, it's doing OK for now. Thanks again for the help! Art

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Post subject: Re: stand alone reverb unit
Posted: Fri Jan 27, 2012 2:31 am
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I never see or heard of bad transducer. They are like pick up coil , IMO they can't wear down normaly but if the small wire are too tight when built it it can break maybe.


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Post subject: Re: stand alone reverb unit
Posted: Fri Jan 27, 2012 11:17 pm
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Stratele, after trying a couple of different power tubes, I found the RCA 6K6 to be the weak point. How come I didn't suspect that tube, considering the fade symptom? Oh well, the cleaning and inspection process was a good thing. Stay well and warm, up there in the Great North Country! Art

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Post subject: Re: stand alone reverb unit
Posted: Sat Jan 28, 2012 3:40 am
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Great you find it and unit work well.


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Post subject: Re: stand alone reverb unit
Posted: Sat Jan 28, 2012 11:23 pm
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Art, one other thing you may want to do (if it isn't already done) on that 6G15: tie the output 12AX7's (or 7025) grid to ground with a 1meg ohm resistor. The original 6G15 didn't have this. This helps stabilize the load onto the grid and keeps that 12AX7 in a better idle bias position. It's one thing that the new RI model has that the original didn't.

It's R13 on the new RI model's schematic:

http://www.studiosoundelectronics.com/s ... manual.pdf

http://www.webphix.com/schematic%20heav ... _schem.pdf


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Post subject: Re: stand alone reverb unit
Posted: Sun Jan 29, 2012 12:25 pm
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Thanks for the tip, Beemer. I'll do that soon! Art

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Post subject: Re: stand alone reverb unit
Posted: Sun Jan 29, 2012 10:29 pm
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aclempoppi wrote:
Thanks for the tip, Beemer. I'll do that soon! Art

Help me here,which pin is that ground tied to?


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Post subject: Re: stand alone reverb unit
Posted: Sun Jan 29, 2012 10:56 pm
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Pin 2 on the first half of the 12AX7, Reb. Hey, I got a question for you guys. What are your feelings on the use of a 6K6 vs 6V6 in these units? Art

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Post subject: Re: stand alone reverb unit
Posted: Sun Jan 29, 2012 11:18 pm
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Hey Art! You know, I like the tone of the 6K6GT. Not that the 6V6GT is all that bad.

Whether it be Sylvania or RCA or whatever US made NOS. Very nice tone. Really a lot wider range of depth than the 6V6GT ones I've heard. But both are better than most onboard units. To me, the black plate are the best. Some guy I know uses a Ken-Rad mil spec black plate/black glass VT-152. Really, a very smooth midrange tone. [Yeah, the USAAF had reverb units in their B-17's during WW2. Betcha didn't know that] :wink:

https://www.tubeworld.com/6k6gtkr.jpg


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Post subject: Re: stand alone reverb unit
Posted: Mon Jan 30, 2012 6:23 am
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aclempoppi wrote:
Pin 2 on the first half of the 12AX7, Reb. Hey, I got a question for you guys. What are your feelings on the use of a 6K6 vs 6V6 in these units? Art

Thanks Art,that's what I thought looking at the schematic but I wanted to be sure.
I have an original '63 unit that I bought last year,and I already had some 6K6 tubes in my stash just waiting to use when I got one....I would think like BMW said it would sound better and smoother than a 6v6...there should be some available at some of the online tube stores or eBay.


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Post subject: Re: stand alone reverb unit
Posted: Mon Jan 30, 2012 5:54 pm
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That was my line of thought when I built the guy. I put the stock tubes aside and used NOS tubes instead. Since the RCA 6K6 wore out, the stock 6V6 is in there. It works fine, but I will order a 6K6. Thanks for the input. Art

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Post subject: Re: stand alone reverb unit
Posted: Tue Jan 31, 2012 1:53 pm
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Art, Yeah no issues running either the 6V6Gt or 6K6GT in the Reverb Unit. The circuit is a single-ended, cathode-biased amp... similar to the Champ. Glory of this is the unit is somewhat self-biasing. The real issue is the current needed to warm the heater filaments. I would not recommend a 5881 or 6L6G(_) sub for this reason.


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Post subject: Re: stand alone reverb unit
Posted: Tue Jan 31, 2012 7:23 pm
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Yeah, ordered up a couple 6K6's, from AES, but they are not brand specific. So I'll see what turns up. Beemer, I remember reading that the reverb was used on the bomber, many moons ago. But can't remember what the heck they used it for. Enlighten me! Art

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