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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sat Apr 13, 2013 5:40 pm
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Rock Star
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Chris,

Sorry about that one 6072A. Try this trick. Get a small radio or some such thing. Place it next to the noisy tube. Turn on both radio and guitar amp. Now, enjoy the tunes of the radio through your cab. :lol:

I'll look for another 6072... :mrgreen:

As for the snubber cap to help reduce arcing and noise across a SBS:


"Because the B+ voltage from the transformer needs to be dissipated somewhere, we installed a 4000V 0.033 µF metallized mylar film capacitor just upstream of the standby switch. Also, if I ever decided to use a solid-state rectifier solution to take the place of a rectifier tube, I would need a standby switch in order to protect the tubes because of the solid-state rectifier’s extremely quick power-up time. "


You can see this cap in the schemo that Bluesky used. But, it is before the SBS (cap C1). Get the highest voltage rated cap you can find. Anything from 0.02 mfd to 0.068 mfd is fine. I usually use Srague Mylar 1.6 KV to 2KV rated caps.

https://taweber.powweb.com/store/java_schem.jpg


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sun Apr 14, 2013 5:50 am
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Hey, I'm thankful to have a friend willing and able to hunt some down for me !!!
Thanks for all of your efforts !

I'm fairly sure I'm going to build a 5E3 this year unless I find work in Texas and have to move.
I'm trying desperately to find work in a more southerly direction 8)
Then I'll need at least one more 12AY7 .

I'm real surprised the Tung-Sol reissue guys have yet to put out a good 12AY7, must not be nearly the demand ????

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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Sun Apr 14, 2013 5:29 pm
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Chris,

Well, New Sensor's Electro-Harmonix (NS owns the rights to both TungSol Ri and EH labels), has the gold 12AY7/6072. Not the most toneful 12AY7. But, not bad.

http://newsensor.com/ProductHighLight.aspx?ProId=38


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Mon Apr 15, 2013 6:06 am
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I tried the EH and found it far from what I had in a vintage 12AY7.
That first valve is so critical in the tone of any amp and so having some NOS or good used vintage glass is worth the hunt in any amp in my opinion.

On the other hand, I have yet to find an amp that runs 12AX7 in v-1 that didn't like that Tung-Sol RI 12AX7 so...... Go figure !

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2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Mon Apr 15, 2013 4:42 pm
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Chris, I just replaced the V1 6072, with a (GE 6072 black plate, 5 star) in my Bassman, last week. The RCA 6072 started having an intermittent "pop", still sounded fine when playing. But was irritating, when not playing, so....Anyway, You can take a look at Gregg Levy's selection at: http://hitestguitars.com/ Art

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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Mon Apr 15, 2013 5:06 pm
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Rock Star
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Art,

Try this trick. Spray a brass wire brush with Deoxit D5 or GN5. Polsih the pins of the "popping" 12AY7. Then, try it.

Good luck!

:mrgreen:


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Mon Apr 15, 2013 5:12 pm
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Cleaning pins and sockets is a great way to clean up crackles !

I don't mean to keep this thread on here forever but it is so full of great tips from the Vintage amp guys that well ..........
and every time I have an issue or find a cool solution, this seems to be a good spot to plant it, that and it gets a few hundred reads a week.

As long as the powers that be don't mind, I would like to open it up to anyone wanting to post vintage amp fix tips, ask for suggestions on fixes in progress etc....

Thanks

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Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Mon Apr 15, 2013 10:40 pm
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Thanks for the advice, my friend!!! But no amount of cleaning seemed to help that guy. I don't know what it is. But I can't seem to keep 12AY7's or 6SN7's to last more then a year or so. They just like to become microphonic or get noisy. Not to say they don't sound good, while playing. But between songs, they like to let you know they're there. Art

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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Tue Apr 16, 2013 4:08 am
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Art,

You know, 12AY7 should be idling with less anode plate voltage than either 12AX7 or 12AT7. If you look at the tweed Bassman setup, Fender ran the plate voltage between 130 to 180 VDC per plate. You can run them at slightly higher cathode bias to get more idle wattage output.

You may have noticed that gain stage tubes tend to get noisier, faster with higher plate voltages. Yes, you get more swing with higher plate voltages and less idle bias current ( shift in curve characteristics ). But, the higher plate voltages seem to reveal the tubes to inherent noise.

:D


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Tue Apr 16, 2013 7:52 am
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Hey
Art has an amp using 6SN7 tubes
I know someone with a box of good uns just waiting for someone who can use em. :mrgreen:

Check your e-mail Brother. 8)

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Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Tue Apr 16, 2013 8:07 pm
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Thanks guys!!! I'll check that plate voltage, Beemer. Chris my '55 Valco uses two 6SN7's. Art

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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Wed Apr 17, 2013 3:27 am
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blues bondsman wrote:
Cleaning pins and sockets is a great way to clean up crackles !



How to clean the sockets? :oops:


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Wed Apr 17, 2013 6:48 am
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This is what I use. A pipe cleaner sprayed with Deoxit. Just be sure amp's caps have been discharged of stored voltage.

http://www.amazon.com/gp/product/B004QK ... UTF8&psc=1


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Wed Apr 17, 2013 6:59 am
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Art those 6SN7's are all yours if ya want em !
I have no need and so......

Pipe cleaners !!! Excellent idea !
I just sprayed them with un lubed deoxit and inserted the tubes a few times.

Love this forum !!!

_________________
Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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Post subject: Re: 68-69 drip edge Bassman /circuit changes
Posted: Wed Apr 17, 2013 9:16 am
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Thanks Chris!!!!! Very generous offer!!! Beemer, you're absolutely right. The plate voltage is around 250VDC. I'll have to look at some options, to lower that. Thanks for the heads-up on that!!! Art

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