Results 1 to 15 of 15

Thread: Another Deluxe Reverb Request - 1981

  1. #1
    Member
    Join Date
    Jun 2017
    Location
    Ontario, Canada
    Posts
    325
    Thumbs Up/Down
    Received: 18/0
    Given: 33/0
    Rep Power
    2

    Another Deluxe Reverb Request - 1981

    Hi, I need schematic for a 1981 DR with pull boost on the vibrato channel volume knob. This amp has a blackface panel but it is not the Deluxe Reverb II model. It does not have a master volume. It has jacks on the back panel for "line/recording" and "boost pedal". I've hunted high and low and haven't been able to find it. There is a file floating around called deluxe_reverb_boost_schem.pdf but there is no boost circuit in sight on that drawing. Unfortunately there is no circuit number indicated on the tube chart. I will be eternally grateful if someone knows where this obscure document is hiding.

    B.

    p.s. I'm interested mostly in the pull boost function, so a schematic for a different amp that has the same circuit would also be helpful.

    0 Not allowed! Not allowed!

  2. #2
    Supporting Member
    Join Date
    Jan 2018
    Location
    Michigan
    Posts
    184
    Thumbs Up/Down
    Received: 16/0
    Given: 43/0
    Rep Power
    2
    just eliminating the obvious , have you contacted Fender ?? They have a Deluxe reverb w/boost schematic in the archive, not sure if it's the same pdf you mentioned ,you have to email them to get it.
    https://support.fender.com/hc/en-us/...-Copy-Archives

    0 Not allowed! Not allowed!

  3. #3
    Member
    Join Date
    Jun 2017
    Location
    Ontario, Canada
    Posts
    325
    Thumbs Up/Down
    Received: 18/0
    Given: 33/0
    Rep Power
    2
    Quote Originally Posted by shortcircuit View Post
    just eliminating the obvious , have you contacted Fender ?? They have a Deluxe reverb w/boost schematic in the archive, not sure if it's the same pdf you mentioned ,you have to email them to get it.
    https://support.fender.com/hc/en-us/...-Copy-Archives
    Thanks, I'll try that. I'll post it here if I get it.

    0 Not allowed! Not allowed!

  4. #4
    Don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    10,877
    Thumbs Up/Down
    Received: 927/21
    Given: 2,253/8
    Rep Power
    21
    Quote Originally Posted by bobloblaws View Post
    There is a file floating around called deluxe_reverb_boost_schem.pdf but there is no boost circuit in sight on that drawing.
    Look at the line coming off the reverb drive transformer. (yes it's an odd spot for boost )
    Attached Files Attached Files

    4 Not allowed! Not allowed!
    Just because they don't have tubes doesn't mean they don't have feelings! - glebert

  5. #5
    Member
    Join Date
    Jun 2017
    Location
    Ontario, Canada
    Posts
    325
    Thumbs Up/Down
    Received: 18/0
    Given: 33/0
    Rep Power
    2
    Quote Originally Posted by g1 View Post
    Look at the line coming off the reverb drive transformer. (yes it's an odd spot for boost )
    Oops, I feel pretty silly now. But yeah, I was looking in the area of the volume pot.

    0 Not allowed! Not allowed!

  6. #6
    Member
    Join Date
    Aug 2015
    Location
    Edmonton, AB
    Posts
    180
    Thumbs Up/Down
    Received: 164/3
    Given: 94/3
    Rep Power
    4
    I have a 78-79 Deluxe Reverb Silverface with that pull volume boost.

    The circuit matches the schematic above.

    FWIW that pull boost is a poorly conceived idea.

    Yes... it does give a volume boost... if you like shrill, harsh and all round horrible.

    It's well known by owners of these amps with the pull boost... to never pull that knob.

    I converted mine to a tone stack lift.
    This accomplishes the same thing (volume boost) but in a much more usable way.

    I installed a push/pull pot with a DPDT switch.

    One of these... https://www.amplifiedparts.com/produ...5-bushing-dpdt

    I took the new pot apart and put the 1Meg wafer from the original pot in there, so it's the same as original.

    Wired the switch so I can select the stock 6.8k mid resistor on the bottom of the tone stack. (switch pushed in)

    Switch pulled out selects a much larger resistor (forgot what value I used) to basically "lift" the tone stack.
    I found with the tone stack completely lifted (disconnected from ground) there was too much boost. YMMV

    p.s. I'm interested mostly in the pull boost function,
    I assume you intend to find out why it sounds so bad? and try to fix it?

    1 Not allowed! Not allowed!
    The world is full of people that are right.

  7. #7
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    14,294
    Thumbs Up/Down
    Received: 1,266/5
    Given: 1,378/0
    Rep Power
    28
    I'm a fan of the treble cap bump. Fender did this also on some amps. Later Mesa Boogie did it. If I were changing the "boost" switch (which I definitely would) I would make it an extra 500p cap parallel to the existing treble cap when switched in.

    JM2C

    1 Not allowed! Not allowed!
    "...less ear-friendly but handy for jazz." Leo_Gnardo

    "A pedal, any kind, will not make a Guitar player more dangerous than he already is." J M Fahey

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  8. #8
    Member
    Join Date
    Aug 2015
    Location
    Edmonton, AB
    Posts
    180
    Thumbs Up/Down
    Received: 164/3
    Given: 94/3
    Rep Power
    4
    Quote Originally Posted by Chuck H View Post
    I'm a fan of the treble cap bump. Fender did this also on some amps. Later Mesa Boogie did it. If I were changing the "boost" switch (which I definitely would) I would make it an extra 500p cap parallel to the existing treble cap when switched in.

    JM2C
    That sure sounds easier than what I did.

    With the tone stack lift, the mids get pushed up more.
    Mines not foot switchable, so not easy to kick it on during playing.

    0 Not allowed! Not allowed!
    The world is full of people that are right.

  9. #9
    Member
    Join Date
    Jun 2017
    Location
    Ontario, Canada
    Posts
    325
    Thumbs Up/Down
    Received: 18/0
    Given: 33/0
    Rep Power
    2
    Quote Originally Posted by galaxiex View Post
    I have a 78-79 Deluxe Reverb Silverface with that pull volume boost.

    The circuit matches the schematic above.

    FWIW that pull boost is a poorly conceived idea.

    Yes... it does give a volume boost... if you like shrill, harsh and all round horrible.

    It's well known by owners of these amps with the pull boost... to never pull that knob.

    I converted mine to a tone stack lift.
    This accomplishes the same thing (volume boost) but in a much more usable way.

    I installed a push/pull pot with a DPDT switch.

    One of these... https://www.amplifiedparts.com/produ...5-bushing-dpdt

    I took the new pot apart and put the 1Meg wafer from the original pot in there, so it's the same as original.

    Wired the switch so I can select the stock 6.8k mid resistor on the bottom of the tone stack. (switch pushed in)

    Switch pulled out selects a much larger resistor (forgot what value I used) to basically "lift" the tone stack.
    I found with the tone stack completely lifted (disconnected from ground) there was too much boost. YMMV



    I assume you intend to find out why it sounds so bad? and try to fix it?
    Yes, mine matches as well.

    Agree on the sound, unusable to my ears. In my case I want to fix it even if it never gets used, it belongs to a friend. Currently it hisses like crazy with the boost engaged and the noise increases when the volume control is turned up. For that reason I want to think the source is pre-volume control, even though I have to wonder why the hiss wouldn't be apparent in non-boost mode as well. Maybe it is present but barely noticeable. Does this boost circuit have a substantial gain factor?

    0 Not allowed! Not allowed!

  10. #10
    Member
    Join Date
    Jun 2017
    Location
    Ontario, Canada
    Posts
    325
    Thumbs Up/Down
    Received: 18/0
    Given: 33/0
    Rep Power
    2
    Quote Originally Posted by Chuck H View Post
    I'm a fan of the treble cap bump. Fender did this also on some amps. Later Mesa Boogie did it. If I were changing the "boost" switch (which I definitely would) I would make it an extra 500p cap parallel to the existing treble cap when switched in.

    JM2C
    Hmmm, that might be the way to go, thanks for the tip!

    0 Not allowed! Not allowed!

  11. #11
    Member
    Join Date
    Aug 2015
    Location
    Edmonton, AB
    Posts
    180
    Thumbs Up/Down
    Received: 164/3
    Given: 94/3
    Rep Power
    4
    Quote Originally Posted by bobloblaws View Post
    Yes, mine matches as well.

    Agree on the sound, unusable to my ears. In my case I want to fix it even if it never gets used, it belongs to a friend. Currently it hisses like crazy with the boost engaged and the noise increases when the volume control is turned up. For that reason I want to think the source is pre-volume control, even though I have to wonder why the hiss wouldn't be apparent in non-boost mode as well. Maybe it is present but barely noticeable. Does this boost circuit have a substantial gain factor?
    The hiss is there in boost mode because the boost is using V3 reverb driver as an extra gain stage.
    The signal from V3 is very "trebley" thanks to that 500pf cap feeding V3 grid.
    You don't hear the hiss thru the reverb when the boost is OFF because the tank can't "send" the hiss thru to the reverb recovery stage V4B.

    Have a look at the schematic, all they did to add this boost circuit is, add 1 wire with a switch on it.
    From the reverb transformer output, to a voltage divider, to the grid of V4A.

    The signal feeding V3 reverb driver has most of the lows gone, so it boosts the highs and mixes that into the signal path at V4A.
    Hissy and screechy.

    I don't know what the gain of V3 is, but I'm sure it can be calculated.

    To "fix" this... disconnect that wire from the reverb transformer output, and do "almost anything else" to get a volume increase.

    Switch out the NFB.
    Do a switchable tone stack lift.
    Or as Chuck suggests, add a switchable treble cap.

    2 Not allowed! Not allowed!
    The world is full of people that are right.

  12. #12
    Member
    Join Date
    Jun 2017
    Location
    Ontario, Canada
    Posts
    325
    Thumbs Up/Down
    Received: 18/0
    Given: 33/0
    Rep Power
    2
    Quote Originally Posted by Chuck H View Post
    I'm a fan of the treble cap bump. Fender did this also on some amps. Later Mesa Boogie did it. If I were changing the "boost" switch (which I definitely would) I would make it an extra 500p cap parallel to the existing treble cap when switched in.

    JM2C
    Do you mean the existing 250p cap at the top of the tone stack? I put a 500p cap in parallel but I didn't hear a difference.

    0 Not allowed! Not allowed!

  13. #13
    Member
    Join Date
    Jun 2017
    Location
    Ontario, Canada
    Posts
    325
    Thumbs Up/Down
    Received: 18/0
    Given: 33/0
    Rep Power
    2
    Quote Originally Posted by galaxiex View Post
    The hiss is there in boost mode because the boost is using V3 reverb driver as an extra gain stage.
    The signal from V3 is very "trebley" thanks to that 500pf cap feeding V3 grid.
    You don't hear the hiss thru the reverb when the boost is OFF because the tank can't "send" the hiss thru to the reverb recovery stage V4B.

    Have a look at the schematic, all they did to add this boost circuit is, add 1 wire with a switch on it.
    From the reverb transformer output, to a voltage divider, to the grid of V4A.

    The signal feeding V3 reverb driver has most of the lows gone, so it boosts the highs and mixes that into the signal path at V4A.
    Hissy and screechy.

    I don't know what the gain of V3 is, but I'm sure it can be calculated.

    To "fix" this... disconnect that wire from the reverb transformer output, and do "almost anything else" to get a volume increase.

    Switch out the NFB.
    Do a switchable tone stack lift.
    Or as Chuck suggests, add a switchable treble cap.
    So I tried the NFB mod and I like it. The only problem is I can't figure out how to implement it with the current open/close switch without it working in reverse. In other words, it's easy to use the switch to switch out the NFB but the volume is boosted with the switch in/open and not boosted with the switch pulled/out/closed, which is the opposite of how a user expects the function to work. Is my only option to replace the switch with DPDT?

    0 Not allowed! Not allowed!

  14. #14
    Member
    Join Date
    Aug 2015
    Location
    Edmonton, AB
    Posts
    180
    Thumbs Up/Down
    Received: 164/3
    Given: 94/3
    Rep Power
    4
    Quote Originally Posted by bobloblaws View Post
    So I tried the NFB mod and I like it. The only problem is I can't figure out how to implement it with the current open/close switch without it working in reverse. In other words, it's easy to use the switch to switch out the NFB but the volume is boosted with the switch in/open and not boosted with the switch pulled/out/closed, which is the opposite of how a user expects the function to work. Is my only option to replace the switch with DPDT?
    Yeah, pretty much need a DPDT switch for that. ( A SPDT would work too)

    I tried to puzzle out a way to use the stock switch, and the "opposite" function was all I could get.

    0 Not allowed! Not allowed!
    The world is full of people that are right.

  15. #15
    Bent Member Chuck H's Avatar
    Join Date
    May 2007
    Location
    pacific north west
    Posts
    14,294
    Thumbs Up/Down
    Received: 1,266/5
    Given: 1,378/0
    Rep Power
    28
    Quote Originally Posted by bobloblaws View Post
    Do you mean the existing 250p cap at the top of the tone stack? I put a 500p cap in parallel but I didn't hear a difference.
    No kidding? I suppose if your treble control is down really low or if you're cranking the amp you may not hear much difference. It boosts the upper mids which is a good way to make clean and slightly distorted tones stand out and it adds gain and roundness to distorted tones that you can "feel" more than hear. Mesa uses a 750p cap and Dan Torres uses a rotary switch with several values up to .01uf. So you could try a bigger value cap. When I used the Torres circuit I likes the .0022uf cap position best for the amp it was in.

    But I'm really surprised you didn't hear a difference between a 250p treble cap and a 750p treble cap.?. If you have Duncan TSC you can simulate it and see that it's a pretty big shift.

    0 Not allowed! Not allowed!
    "...less ear-friendly but handy for jazz." Leo_Gnardo

    "A pedal, any kind, will not make a Guitar player more dangerous than he already is." J M Fahey

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. 1981 Peavey Special combo amp question about filter caps
    By Slobrain in forum Maintenance, Troubleshooting & Repair
    Replies: 1
    Last Post: 01-04-2014, 07:32 PM
  2. Lifco 630-2 Reverb Information Request
    By clarked in forum Music Electronics
    Replies: 6
    Last Post: 08-04-2012, 04:36 PM
  3. Peavey Bandit (1981) loud hum
    By JimmyTolson in forum Guitar Amps
    Replies: 31
    Last Post: 06-10-2012, 10:43 AM
  4. channel 1 on my 1981 ampeg V3 is only barely audible
    By deanamite in forum Maintenance, Troubleshooting & Repair
    Replies: 0
    Last Post: 09-27-2010, 06:15 PM
  5. 1981 Peavey Renown amp question for Enzo
    By Slobrain in forum Maintenance, Troubleshooting & Repair
    Replies: 2
    Last Post: 03-16-2007, 07:43 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •