How would you salvage a Peavey Delta Blues

Discussion in 'Shock Brother's DIY Amps' started by wtk0315, Apr 21, 2019.

  1. wtk0315

    wtk0315 Tele-Holic

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    Just like my Hot Rod Deluxe years ago, my Delta Blues has lost some functionality. Trem and reverb are both out. I've never opened the DB, but from what I remember of the old Peavey Classic 30 mod site, it's a 3 layer board with ribbon connectors between the boards. A PITA to work on, in other words.

    But me being the frugal guy I am, I hate to see perfectly good transformers, speakers, cab and chassis go to waste. I'd like to rebuild it to a classic circuit and do away with the PCB board.

    So what to do with 4xEL84 and 3 12*y and SS rec? I've thought about a vox, but I don't know if how it would be with SS rec. The JCM800 is a known and loved design that came with SS rec. I could do a JCM800 pre with a 4xel84 power section, but again I don't know how it would sound with el84s instead of el34s. I could even do Bassman/JTM45 pre with Rob's mods.

    Y'all have any Frankenstein ideas?
     
  2. drlizardo

    drlizardo Tele-Meister

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    I'm going to watch your thread because i also have a dysfunctional Peavey Delta Blues. A member here turned on into a Trainwreck Liverpool I believe. He may have a thread on here still.
     
  3. wtk0315

    wtk0315 Tele-Holic

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    I'll google-ley it. Thanks.
     
  4. schmee

    schmee Poster Extraordinaire

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    Make it into a Carmen Ghia clone, it'll be just as loud!
    But seriously, you might as well open 'er up and see if anything is evident, burned etc. A friend and I did decide to scrap a Classic 30 a couple years ago though, it was just one thing after another, and it owed him nothing...
     
  5. Papa Joe

    Papa Joe Friend of Leo's

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    I don't know if they still do it but I sent one to the Peavey repair and they restored it to better than new at a very good price..
    I spoke to Jim Brown on the steel guitar forum and he got me in touch with the repair department..It was easy..and fast..
     
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  6. sds1

    sds1 Tele-Afflicted

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    Here is my Classic 30 to Liverpool conversion build thread:
    http://www.tdpri.com/threads/build-trainwreck-liverpool.761381/
     
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  7. Dacious

    Dacious Poster Extraordinaire

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    It's probably as simple as reflowing some solder joints. Possibly some ICs. Getting it fixed is probably a better idea.

    If you want a boutique amp, move it on and get one secondhand. Building yours into something will cost a lot which you will lose most of. It's neither here nor there. Not stock, not boutique.
     
  8. dkevin

    dkevin Tele-Meister

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    I bought a minimally-functional Delta Blues just to see what all the fuss was about. It needed 7 pots to be replaced. It was challenging but not super difficult to do. The amp works fine. I got a lot of help (and much-needed encouragement!) from a lot of people on this forum. If your amp was mine, I would not be afraid to take a look inside. The issues might be fairly easy to fix . I agree that any value the amp has would be greatly diminished by gutting it and installing a homemade circuit.
     
  9. wtk0315

    wtk0315 Tele-Holic

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    Well anyone who likes P2P/terminal strip construction and frankenstein projects stay tuned. Parts have been ordered.

    Oh and it won't be a Trainwreck...
     
  10. wtk0315

    wtk0315 Tele-Holic

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    Ok. So I thought I had this thing in the bag, but I'm gonna redo it. It's promising but not quite there. Here's the findings:

    1. No tubes, put it through light bulb limiter. Voltage was around 362 on power tubes screens and 364 on plates. Light bulb limiter did what it was supposed to.

    2. Put tubes in. Voltages dropped absurdly low, like down to 170 on the HT. I didn't get good measurements on the tube pins but light bulb limiter was burning dim, good sign.

    3. Took off light bulb limiter, fired it up, tubes were redplating. Checked bias voltage, only -1 volt (Merlin says I need about -15) at this point my meter is starting to fail me.

    4. Researched bias supply some more. It seems setup I was using only works with a center tapped transformer and the Peavey doesn't have one.

    5. Fixed bias supply. Repowered, tubes no longer redplate.

    6. Meter is no longer working, but tubes weren't redplating so I did tubes swaps all tubes including all four power tubes. Sound oscillates in and out and makes odd ball noises but it's surprisingly quiet at idle. Doesn't sound quite right until...

    7. Flip power switch off and while playing with just the leftover power from the caps, it sounds glorious! So I'm close.

    I refuse to show pictures because it's such a rats nest I'm frankly embarrassed. I'm going to redo it with a proper board and see if that helps with the strange oscillation/thin signal. They way I have it now, I've got the tubes about half covered. It makes it difficult to chopstick and measure voltages.

    Does anyone have an idea of why it would sound good as the power drains but weird with it powered up?
     
  11. Commodore 64

    Commodore 64 Friend of Leo's

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    The main thing you will want to sort is the power supplies. I think Peavey wires heaters in series, so you are limited to the tube complement that is there. What is that, 7, 6V tubes?

    I dunno what they do with the main B+ as far as doublers or whatever. Sort that, too. But schematic is looking for ~330V on the plates. So that puts you square in EL84 power tube territory. Maybe 6K6GT power tubes.

    Then you can do whatever you want as far as circuit.

    If need be, you can cut pins off of tubes so that you can just run the heaters if you end up with something that has less tubes than the original circuit (given the heaters).

    --------------------------------------------------------------------------------------------------------
    Edit: Sorry, I responded before realizing you undertook to wire it yourself already. Have you got a schematic of what you tried to do?

    And get a working DMM. You absolutely must have this.
     
    Last edited: Aug 12, 2019
  12. tubeswell

    tubeswell Friend of Leo's

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    The PV DB and C30 are a real PITA to work on and harder to fix. Even if you get it going, vibration and heat can warp and flex the boards and crack traces and pads and undo your hard work . I’ve spent many days of my life in toil on these amps that I won’t get back again. And I’m refuse to fix them anymore.

    Good on you for perseverance.

    If I was looking for a project and had a broken one, I’d rip the boards out and start from scratch. The chassis is cramped but you should be able to wire up a PTP/ eyelet board setup with a bit of forethought.
     
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  13. D'tar

    D'tar Friend of Leo's

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    I feel your pain!!!

    Life is too short to be singing the Delta Blues if you dont have to!!!:)
     
  14. wtk0315

    wtk0315 Tele-Holic

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    Ok. So I'll bring ya'll up to date.

    So I pulled my weird split board/rats nest back out. Did a little research since I reported my findings in post #10. I've been dead in the water with no meter though.

    I don't know how I'm going to post a schematic as I have no computer to make one. I basically married a 1987 preamp to 4 el84s, with 1987 HT filtering and choke setup. I used vox values for power tube grid and screen resistors. I used Rob rob's fixed bias for bridge rectifier (no PT center tap). I followed advice from sds1 and installed a 6.3v transformer to simplify heater wiring.

    Proposed changes to first try:
    1) Turret board instead of Hodge podge rats nest

    2) Use Delta Blues low voltage secondary tap to create -36 volt bias supply. Originally this tap powered all of the relays and solid state devices. I'll have to play with dropping resistor values because the schematic only calls for -14 volts of bias voltage. Peavey originally wired it fixed adjustable, I'd like to install a pot.

    3) I saw in a post on el34 world about the 2 tube 1987 and 4 tube 1959 having different value NFB resistors. I'll play with that resistor value on the rebuild and see if it was contributing to the odd sound.

    4) I'll rework the cap can grounds to follow Merlin's scheme. I'll put the rectifier bridge ground directly to reservoir cap can. Run jumper to next 2nd cap can ground and ground that can to the chassis. Put the prescence control and phase inverter grounds with the power grounds.

    5)Use voltage divider off of B+ (or B++, etc.) supply for DCV reference on my 6.3v transformer CT. I currently have that the 6.3v transformer CT wired straight to the positive node of a FWB rectifier that is fed by the low voltage secondary tap (36V). Not sure if I was supposed to put a cap there, but it's moving anyway.

    6)Most 4 tube layouts (1959, Vox AC30) I see have V4 plate strapped to V5 and V6 plate strapped to V7. I did the opposite, thinking the plate wires twisted together would cancel noise, but I ended up with 4 plate wires out to join up with OT leads. I think I should have done the conventional method of wiring a jumper from one plate to the adjacent tube's plate and running only 2 plate wires to the OT junction turret. Also I did not try swapping plate leads when everything was sounding weird.

    So my 5 guesses as to why the thing sounded crazy.
    1) plate leads needed to be swapped, although it wasn't howling
    2)biased power tubes down into cutoff. Couldn't check because meter gave out.
    3)NFB resistor was poor match for 4 tube setup.
    4) 6.3V CT hooked directly to positive node of 36 V supply with no filter cap at all. Can't say. DC heater elevation is fairly slim on info because it either gets taken off voltage divider on B+ supply or off power tube cathodes. I've yet to see anyone attempt to build a supply just to provide a DC reference. I had the tap though so it was easy, but I have no way of knowing if it was right.
    5)General lead dress issues. My previous doo doo partial board covered the tube pins and made it hard to diagnose cold joints and the like.
     
  15. wtk0315

    wtk0315 Tele-Holic

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    That last post was huge.

    Quick question: if I took two coated pieces of wire and one stripped piece of wire, twisted them together and put them all in a piece of heat shrink would it function the same as shielded cable. Assuming I ground the naked wire of course.

    The little bit of shielded cable I have is messy. If what I proposed would work, I could have the ends pre stripped all nice and neat, run my home made shielded input wire pairs straight down to V1A and V1B, and put my 2 grid stoppers straight on the pins like Merlin suggests. The first try I put the grid stoppers on the jacks and ran a single wire to the V1A and V1B grids.
     
  16. W.L.Weller

    W.L.Weller Tele-Meister

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    No.

    I will mail you 10' of shielded cable for the cost of postage just so you don't try what you are proposing.
     
  17. Commodore 64

    Commodore 64 Friend of Leo's

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    Last edited: Aug 13, 2019 at 9:24 PM
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  18. wtk0315

    wtk0315 Tele-Holic

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    I have miles of coax but I don't know how many conductors. And I can't make clean connections, which is aggravating.

    My proposal would be more or less that fender method, but with a fat piece of heat shrink around the whole set up. After reading a little more it seems the proper way to do it would be to use copper tape. Again that would end up being messy because I'd still have to solder a wire to the copper tape.

    I'll dig around and see if I have some shielded with two conductors. I really don't want four fat coax wires running down to V1. I have a little bit of single conductor shielded from the reverb connections on the Peavey I suppose I could get creative with the heat shrink to make everything look nicer. It's not as fat as coax individually so I could probably shrink wrap two pieces together.
     
  19. D'tar

    D'tar Friend of Leo's

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    Rg174 is less than 3mm diameter.... just what the doctor ordered:)
     
  20. W.L.Weller

    W.L.Weller Tele-Meister

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    Do whatever you want but don't come back asking about strange noises.
     
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