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Post subject: stand alone reverb unit
Posted: Thu Dec 06, 2012 12:21 am
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Back to the Weber 5G15, a fullwave 6G15 knock-off. Do I need to shift forums? Art

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Post subject: Re: stand alone reverb unit
Posted: Thu Dec 06, 2012 12:31 am
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Art, no I think this is a cool place. I would love a write-up on this DIY kit. There was quite a bit of electrical acrobatics I needed to do, to get a RI '63 Reverb Unit to sound anything like the 6G15 I have.


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Post subject: Re: stand alone reverb unit
Posted: Fri Dec 07, 2012 11:42 pm
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Yeah man, it's the intermittment reverb signal problem. I'll get the voltage readings ASAP. It's pretty strange. Tubes aren't the problem-a straight signal flows,quite well, through the unit. The tank tests fine(as do the cables). It's almost as though, a cap charges or not. The scenario is: the signal flows in the non-reverb fashion(no loss of volume); following maybe 30-40minutes, the reverb kicks in and remains for the duration of playing( 1.5 hrs). Yeah, cleaned all the pots, jacks, tube sockets, and R&R all tubes. All the components are stock Weber. I do have an upgrade supply of all components, but was just giving the OEM parts a chance. The circuit is the same as the 6G15, except a full wave rectfier and a thermistor. Any advise is welcome!!! Art.....Oh Yeah, the guy is about 2.5 yrs old, and the problem surfaced about a year ago.

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Post subject: Re: stand alone reverb unit
Posted: Sat Dec 08, 2012 8:29 am
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Art, you have a schemo of this DIY unit? What is that thermistor doing? Current limiter on the PT? I've heard of issue using a thermistor for this function. You really don't need on for this small unit. But, a CL-40 or some such beast would work a lot better.

Gotta check this out, when I get home.


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Post subject: Re: stand alone reverb unit
Posted: Sat Dec 08, 2012 8:36 am
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BMW2002Ti wrote:
Art, you have a schemo of this DIY unit? What is that thermistor doing? Current limiter on the PT? I've heard of issue using a thermistor for this function. You really don't need on for this small unit. But, a CL-40 or some such beast would work a lot better.

Gotta check this out, when I get home.


Schematic:

https://taweber.powweb.com/store/5g15_schem.jpg

Layout:

https://taweber.powweb.com/store/5g15_layout.jpg

RT1 in the schematic is the thermistor.

I notice that the Fender Blues Deluxe/Deville Reissues use a thermistor but on the primary side of the PT vice the secondary side as used in the Weber. Not sure if this makes a difference.

http://support.fender.com/schematics/gu ... _Rev-A.pdf

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Post subject: Re: stand alone reverb unit
Posted: Sat Dec 08, 2012 10:11 am
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For really big amps with big PTs and good sized rectifier diodes and caps --- prolly need some sort of current limiter circuit, on cold starts. But in a Reverb Unit? I known that CL were a big fad maybe 5-10 years ago, as a "slow-start" simulator. But, really, they are not designed to be slow-start all the time. Only when they are cold and the resistance is low.

I have heard of many DIY amp blowing CLs. Or sounding poor with intermittent problems due to poorly designed circuitry or improper CLs or both.

I'll need to hunt down those specific references. But, I'd email Weber and ask about the function of that CL past the bridge. I can't imagine the current draw being so high on this unit, that it warrants a CL.

A little blurb on CLs:

http://www.diyaudio.com/forums/tubes-va ... imary.html


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Post subject: Re: stand alone reverb unit
Posted: Mon Dec 10, 2012 11:13 am
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Wasn't able to get back to thank you guys( computer problems)!!! I should have some time to check the unit out this afternoon. Art

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Post subject: Re: stand alone reverb unit
Posted: Thu Dec 13, 2012 11:18 pm
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Yeah, internet service broke down. Anyway, voltage after the thermistor is 350 VDC, all plate, screen, cathode, grid voltages are pretty much in line, considering the high B+. Resistors tested within specs. Have yet to start pulling coupling and bypass caps for tests or R&R. All ground circuits test very good as do all wiring continuity tests. BTW Just to show my ignorance, since this is a 1 Watt amp, I did plug it into a 5 watt amp(no volume or input source), for the voltage tests. Better check the Pots? Art

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Post subject: Re: stand alone reverb unit
Posted: Fri Dec 14, 2012 10:08 am
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Art, just for giggles, try running a wire parallel to that current limiter. My bet is the unit will sound better.

Just a WAG and-a-half. :D


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Post subject: Re: stand alone reverb unit
Posted: Fri Dec 14, 2012 10:15 am
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BMW2002Ti wrote:
Art, no I think this is a cool place. I would love a write-up on this DIY kit. There was quite a bit of electrical acrobatics I needed to do, to get a RI '63 Reverb Unit to sound anything like the 6G15 I have.


I'll take a well built clone of a RI any day!

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Post subject: Re: stand alone reverb unit
Posted: Sat Dec 15, 2012 6:35 pm
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Beemer, pulled the thermistor and installed a permanent wiring scenario for the B+. Sound wise, it might be a little mellower with absolutely no hash and very quiet!!.....Detroit, I respect your preference. I have playing experience with both the original 6G15 and the reissue. It's just that a hand-wired unit is more up my alley. The eyelet board is on 3/4" stand offs(allowing pretty good ventilation), decent ceramic tube sockets, Switchcraft jacks, CTS pots, USA Accutronics tank, solid core wiring, decent flame-proof resistors. The only short coming IMO is the cap choice. F&T, Auricap, and Hovland are ready for an R&R. Just wanted to give Weber's choice a chance. Tubes, at this time are: NOS- Raytheon 6K6GT, Phillips JAN 12AT7, RCA 7025. I did make a slight ground scenario change, in order to keep the unit quiet. Overall, I say the Weber is a great alternative to the original 6G15. Art

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Post subject: Re: stand alone reverb unit
Posted: Sat Dec 15, 2012 6:49 pm
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Very cool! I had this feeling about that current limiter. My personal feeling is that the less superfluous components, esp solid-state stuff, the better. It's one of the reason why simple single-ended amps sound so vintage. And that reverb unit is a single-ended amp.

For a bit more "bite," go for the most potent 6V6GT you have on hand. The JJ 6V6S is the most potent new issued 6V6 type around.

Have a good one!


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Post subject: Re: stand alone reverb unit
Posted: Sat Dec 15, 2012 9:57 pm
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Yeah Man, it's cruisin' right along(3 hrs of playing)!!! If any thing the guy has a thicker sound. I really like the 6K6GT. Had that Pope in there and only swapped to see if that was the weak point. But no, the 6K6''s seem to trip my trigger! Tried a nice 6V6, a while back. But it offered too much punch(gain through out). Who needs no stinkin' thermistor???? Tanks Mon!!! Art

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Post subject: Re: stand alone reverb unit
Posted: Sat Dec 15, 2012 10:39 pm
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Glad everything worked out. :D

Hmmmm. Wonder if I should pull the thermistor out of my BDRI? :!:

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Post subject: Re: stand alone reverb unit
Posted: Sun Dec 16, 2012 2:12 am
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What I tell ppl: if the filter caps & PT are good (meaning not old & overspec'ed) , try bypassing the CL and listen to the tonal changes. You may need to measure B+, as some apps the B+ may change slightly with the limiter in or out of the circuit.

You can bypass it by placing a temporary jumper across the leads of the NTC, in parallel. I leave the amp on the bench and A/B it with the jumper in and out of circuit. Amp hooked to a known cab. That way you don't need to solder to do the test. If you like the tone without the limiter, you can then clip it out and hard-wire the connection.

Good luck!


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