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Post subject: Modding a 79 Deluxe Reverb to pre 65 specs ? Worth it ??
Posted: Thu Apr 20, 2017 8:22 am
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I've got a chance at a very clean 1979 Deluxe Reverb for around 1K or less
Just wondering if I can get the amp back to prefered specs without too much craziness ?
Removing the pull boost , real bias adjust etc.......
Anyone here mess with this circuit ? ( Steve, Arjay, other ........)
Thanks

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Post subject: Re: Modding a 79 Deluxe Reverb to pre 65 specs ? Worth it ??
Posted: Thu Apr 20, 2017 8:41 am
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I do on fews Siverface amp.

Do you have any skill and experience in electronics ?
Yes,
Just follow the amp layout you want .

No skill or experience in electronic, leave it original.

Worth it ?
IMO, only if you can do by yourself


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Post subject: Re: Modding a 79 Deluxe Reverb to pre 65 specs ? Worth it ??
Posted: Thu Apr 20, 2017 10:38 am
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I know Stratele52, however I was hoping someone here had already done the process of removing the pull boost, I've done many true Bias mods on many Fenders

You know I've been elbow deep in many amps, from Super Reverbs to bassmans etc...... but never to pull boost circuit 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


Last edited by blues bondsman on Thu Apr 20, 2017 2:06 pm, edited 1 time in total.

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Post subject: Re: Modding a 79 Deluxe Reverb to pre 65 specs ? Worth it ??
Posted: Thu Apr 20, 2017 12:09 pm
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Pre 65 specs are more than remove the pull volume boost and another bias circuit.
These mod do not change tone to a pre 65 DR amp and your amp still a '79

Volume boost ; just remove the wires on the pull switch side and circuit side.
Bias '65 circuits easy to find on web, look a '65 layout


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Post subject: Re: Modding a 79 Deluxe Reverb to pre 65 specs ? Worth it ??
Posted: Thu Apr 20, 2017 6:47 pm
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Hiya Chris!

You know the pull-boost DR circuit is not far from the AB763 circuit. The "boost" seems to come from adding pre-vibe gain back into the pre-amp, at V4A. My guess is if you don't pull the boost, the circuit more-or-less acts like an AB763.

I believe all DR from BF through SF era had bias pots. The SF era circuits having oddball caps added to the 6V6GT tubes, to reduce potential high-frequency instabilities. Seems pretty easy to remove.

Pull Boost schematic:

http://ampwares.com/schematics/deluxe_reverb_boost.pdf


AB763:

http://ampwares.com/schematics/deluxe_reverb_ab763.pdf


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Post subject: Re: Modding a 79 Deluxe Reverb to pre 65 specs ? Worth it ??
Posted: Thu Apr 20, 2017 8:04 pm
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The pull boost isn't so much a problem as how it was done. Fenders can use a boost, but the signal is sourced from the reverb driver tube and is a nasty clipped square wave. Nobody seemed to like the tone, so I started modding that circuit.
As you've heard me harp on it before, the reverb balance resistor is a choke point in the signal path. So I comandeer the boost switch to bypass that resistor to a certain extent. Its free. Its clean. Its easy.
It pushes the reverb into the background, but that's usually OK. Fenders have plenty.
Here are the old notes I have on the Deluxe Reverb. No guarantees if it matches yours.
Cut the orange wire to the reverb input jack and connect it to the 3.3M/10pF near the edge of the board. If your amp has the boost footswitch jack, then add a 5.6K resistor between the white wire and the Jack. This maintains the level, but pops a bit.
The effect is a boost that looses the reverb as it switches in. Its less of a drive channel as a boost in dynamics. Good for surf music and such.

Tone-wise, the silverface has a lot more sub-sonic bass than the BF originals.
A new reissue output transformer would get you a lot closer to the BFs of old. They have the same low inductance as the originals. They cancel a lot of the bass with the low inductance.
These factory reissues easily go up to 36Khz and sound great. Cost is about the price of a pair of output tubes. But it doesn't wear out.
A less expensive method is to change out the 25/25 cathode caps on the input stages. A 2.2uF poly cap limits bass to about blackface levels, but doesn't have the same characteristic as OT saturation at high power levels.


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Post subject: Re: Modding a 79 Deluxe Reverb to pre 65 specs ? Worth it ??
Posted: Fri Apr 21, 2017 2:50 am
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Thanks !
I'll let ya know if I'm able to negotiate the deal.

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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: Modding a 79 Deluxe Reverb to pre 65 specs ? Worth it ??
Posted: Fri Apr 21, 2017 3:00 am
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TimsAudio wrote:

Tone-wise, the silverface has a lot more sub-sonic bass than the BF originals.
.



+1


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Post subject: Re: Modding a 79 Deluxe Reverb to pre 65 specs ? Worth it ??
Posted: Fri Apr 21, 2017 8:10 am
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blues bondsman wrote:
Thanks !
I'll let ya know if I'm able to negotiate the deal.


Think, if you can get the DR for around $1K --- and it starts and runs okay --- you'll won't lose $$$. DR's are fairly easy to revert to blackface standard. Well, let's just say a TON easier than a silverface Bassman. :lol:

I love my 1968 drip-edge. Clean tone. Good vibrato. Great reverb.

Tim has some interesting circuit mods, for the pull switch. Worth trying out.

:mrgreen:

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Post subject: Re: Modding a 79 Deluxe Reverb to pre 65 specs ? Worth it ??
Posted: Sat Apr 22, 2017 12:53 pm
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Nice !
I love amp guts pics !!

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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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Profile
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