ArtS
Joined: May 09, 2008
Posts: 1401
Isle of Kent, MD
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Posted on Jun 10 2019 12:40 PM
All,
I finally decided to swap the tubes out for a re-issue unit I bought and seldom use. I noticed the following:
Tube sticker inside unit reads "Diagram L-R"
6V6GT,
12AT7,
7025
Actual tubes
1st one I can't read any number,
ECC81,
12AX7
I think I'm okay with the 12AT7 replaced by ECC81 and 7025 replaced by 12AX7.
Can someone verify?
Also, can someone suggest best Tube configuration. She has been sounding very un-reverby...
Thanks!
— Surf.The most dangerous of genres...
Surfcat
MARCH OF THE DEAD SURFERS! (2024) - Agent Octopus
THE JOURNEY HOME - Free download (2025) - Agent Octopus (Single)
BANDCAMP - Agent Octopus
YOUTUBE - Agent Octopus Surf
BANDCAMP - Reverb Galaxy
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DaveMudgett
Joined: Mar 17, 2019
Posts: 162
Central PA
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Posted on Jun 10 2019 03:19 PM
SG101 has a useful reverb unit FAQ here - http://wiki.surfguitar101.com/ReverbFaq - you can see a circuit and physical layout diagram here - https://www.thetubestore.com/lib/thetubestore/schematics/Fender/Fender-Reverb-6G15-Schematic.pdf
The original 6G15 had 12AX7/7025 in position 1, 12AT7/ECC81 in position 2, and 6K6, not 6V6, in position 3. The reissue subsituted a 6V6. While I mostly have had vintage units over the years, I had a reissue at one point. I didn't care for the 6V6, and so put in a 6K6 and was much happier.
I think the main subminiature preamp tube issue is that they should be strong and not unreasonably microphonic. Anything else as far as tube recommendations are mostly a matter of personal taste. In any piece of tube equipment, I just try some appropriate tubes until I find ones I like. I keep a lot of spares around.
— The Delverados - surf, punk, trash, twang - Facebook
Chicken Tractor Deluxe - hardcore Americana - Facebook and Website
The Telegrassers - semi-electric bluegrass/Americana - Facebook
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Stormtiger
Joined: Dec 12, 2006
Posts: 2687
Ventura, CA
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Posted on Jun 10 2019 03:24 PM
You are correct.
12AT7 = ECC81
12AX7 = 7025 = ECC83
Most people replace the 6V6 with a 6K6 like the older units.
Check your reverb cables, make sure they are snug and well connected to the tank. I have to check mine occasionally when the reverb sounds weak and that fixes it.
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ArtS
Joined: May 09, 2008
Posts: 1401
Isle of Kent, MD
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Posted on Jun 10 2019 03:30 PM
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DaveMudgett
Joined: Mar 17, 2019
Posts: 162
Central PA
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Posted on Jun 10 2019 03:46 PM
Definitely - if changing tubes doesn't fix your issue, check your cables. I also suggest making sure the reverb cable plugs are making good contact with the jacks, and all contact points are not oxidized. This goes for tube pins and tube socket contacts too. I generally use De-Oxit D5 spray to clean all electrical contact points if I'm noticing issues in any electronic equipment.
If that doesn't do it, there could be something going on with the reverb tank.
None of this exhausts all possible issues. But pretty much anything beyond trying different tubes, reverb tank, and making sure these kinds of contact points are clean and secure requires knowledge of servicing tube amps, since it is not hard to do damage to the equipment or yourself dealing with the high voltages inherent in tube circuits.
— The Delverados - surf, punk, trash, twang - Facebook
Chicken Tractor Deluxe - hardcore Americana - Facebook and Website
The Telegrassers - semi-electric bluegrass/Americana - Facebook
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DeathTide
Joined: Apr 13, 2018
Posts: 1379
New Orleans
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Posted on Jun 10 2019 06:10 PM
The ‘63 and ‘64 tanks were ridiculously microphonic, until I changed tubes. The 7025 sounded better than the 12AX7s somehow, but the 12AT7 in V2 never sounded right. In either tank. Put in another 7025 and it sounds great and is not microphonic. I tried NOS 12AT7s and brand new 12AT7s but they all sounded bed.
One thing I’d love to see explicitly explained is the chopstick trick. I think one of the tanks may need that, but the existing tutorials have too many words and not enough photos. Maybe yours needs the chopstick fix...
— Daniel Deathtide
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ArtS
Joined: May 09, 2008
Posts: 1401
Isle of Kent, MD
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Posted on Jun 11 2019 07:52 AM
Ordered new tubes yesterday from Viva Tubes.
Electro-Harmonix 12AT7 ECC81 Gold Pins Vacuum Tube
Gain Tested Sovtek 12AX7WA / 7025 / ECC83 Vacuum Tube
Tests NOS Sylvania Leaf USA 6K6G Round Black Plate D Foil Get Tube
Will get De-Oxit 5, and shoot it up. If that doesn't fix it.. to the shop.
THANKS TO ALL!
— Surf.The most dangerous of genres...
Surfcat
MARCH OF THE DEAD SURFERS! (2024) - Agent Octopus
THE JOURNEY HOME - Free download (2025) - Agent Octopus (Single)
BANDCAMP - Agent Octopus
YOUTUBE - Agent Octopus Surf
BANDCAMP - Reverb Galaxy
Last edited: Jun 11, 2019 08:33:31
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ArtS
Joined: May 09, 2008
Posts: 1401
Isle of Kent, MD
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Posted on Jun 11 2019 07:52 AM
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Badger
Joined: Nov 16, 2013
Posts: 4537
Wisconsin
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Posted on Jun 14 2019 09:02 AM
DeathTide wrote:
One thing I’d love to see explicitly explained is the chopstick trick. I think one of the tanks may need that, but the existing tutorials have too many words and not enough photos. Maybe yours needs the chopstick fix...
Only thing I keep a chopstick around for is poking into electrified places without killing myself. It is often used as a non-conducting probe to tap on the tube while running, or connections, and see if a source of harmonics or tube going bad will reveal itself. Not aware of any "fix"... Be interested to hear about that too.
— Wes
SoCal ex-pat with a snow shovel
DISCLAIMER: The above is opinion/suggestion only & should not be used for mission planning/navigation, tweaking of instruments, beverage selection, or wardrobe choices.
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DeathTide
Joined: Apr 13, 2018
Posts: 1379
New Orleans
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Posted on Jun 14 2019 03:25 PM
All I could find in a quick search was this, but many folks here have praised this and explained it without providing photos that I understood. And everyone says how the pans are super sensitive and can break easily.
https://www.guitarplayer.com/miscellaneous/righteous-reverb-tweaks
"A great-sounding reverb pan is also essential to having great reverb. Here is a modification to improve the sound of any reverb pan. The reverb pan (also called the “tank”) resides within a vinyl bag on the inside floor of the amp. Remove the bag, open it, and slide out the pan. There’s a cardboard cover on the bottom of the pan that is held by four small screws. With the cardboard removed you’ll see that there are two transducers inside the pan—one drives the springs, and the other is a pickup that transforms the reverberated sound back into a signal voltage. Both transducers consist of a coil of fine wire wound around a small bobbin, with a steel laminated core inside the bobbin. Nearly always, the bobbin is loose on the laminated core. This results in the bobbin moving somewhat instead of all the movement going to the springs. To fix this, you need only to insert a small shim between the steel core and the plastic bobbin. I cut these shims from a bamboo chopstick using a razor utility knife. It looks something like a miniature saxophone reed, and once in place, the shim makes the bobbin tight and secure on the core. Now, all the energy will drive the springs, and none will be wasted on moving the coil. And the same for the pickup transducer—all of the return energy will go into making signal, instead of being wasted by moving the coil."
— Daniel Deathtide
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Badger
Joined: Nov 16, 2013
Posts: 4537
Wisconsin
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Posted on Jun 14 2019 05:16 PM
Interesting thanks!
And yeah, while the big pieces in a pan are pretty tough, those transducers are the weak link & need TLC.
— Wes
SoCal ex-pat with a snow shovel
DISCLAIMER: The above is opinion/suggestion only & should not be used for mission planning/navigation, tweaking of instruments, beverage selection, or wardrobe choices.
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DeathTide
Joined: Apr 13, 2018
Posts: 1379
New Orleans
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Posted on Jun 14 2019 09:59 PM
Lemme know if you figure it out, and please post close photos! I'm using a vertical pan but it looks similar.
— Daniel Deathtide
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