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Author
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Topic: Schematic For Supro???
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Dave Zielinski
Member From: Pennsylvania, USA
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posted 09 February 2006 08:45 AM
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I have a clean 1964 Supro amp. 2 6L6,, 5u4, 3- 12AX7s, single 15" speaker. Cosmetically it is perfect. 100% original, however lacks a bit in tone and volume. Has no model number anywhere. I'm looking for a schematic for this guy and can't seem to locate anything similar! Anyone out there think they can help out?? |
Jay Fagerlie
Member From: Lotus, California, USA
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posted 10 February 2006 05:44 AM
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Dave,
Is that the one with two preamp channels?
Tremolo on one channel?If so, I have one, too. It too is cosmeticaly perfect, I even have the amp cover for it.
So far, I've never found out what the model # is or found a schematic for it....
Good luck on your quest, if you find out anything, please let me know Jay |
Blake Hawkins
Member From: Land O'Lakes, Florida
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posted 10 February 2006 06:42 AM
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Dave, If you just want to restore it, you can do it without a schematic.
All the caps and resistors are marked with their values. You can replace the caps and measure the resistors with an ohmmeter, replacing those that are out of tolerance.If you want to check out the circuit, just get a schematic from an amp with the same tube line up, follow the connections and make corrections.
The Supro amps I've seen used pretty standard circuits.
Blake |
Dave Zielinski
Member From: Pennsylvania, USA
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posted 10 February 2006 07:44 AM
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Yup, its the same amp. cool amp, but I'm gonna make it have more guts. I don't really NEED a schematic, more than I just want one to mark up and know what model it is. I've already increased the power supply caps, and bypassed all the preamp cathodes, raised preamp voltage. It is now a screamer! I'll try it out at tonights gig. Thanks,
Dave |
Brandin
Member From: Newport Beach CA. USA
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posted 10 February 2006 10:20 AM
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It sounds like a Supro "Thunderbolt", made
by Valco. I have one, and I love it. I
wish I could get it back from my son.
GB
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Jay Fagerlie
Member From: Lotus, California, USA
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posted 11 February 2006 07:34 AM
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Yes Brandin, the power section is just like a Thunderbolt, but it has a two channel preamp.
Normal channel and tremolo channel.
It looks like a Thunderbolt.
Great amp.
Jay |
Jay Fagerlie
Member From: Lotus, California, USA
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posted 11 February 2006 08:38 AM
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Dave,
Is this like the one you have?
click here
Mine is like it.(I just found this on eBay, I don't have anything to do with the auction) Jay |
Dave Zielinski
Member From: Pennsylvania, USA
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posted 12 February 2006 06:18 PM
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Yes, thats the one.I'm actually working on mine right now. For anyone interested in soem of the things I've done to it.... 1. Changed all cathode resistors to 1K Ohms. Added 47uF bypass caps across all of them. THis increases gain. I originally did 820 Ohms, but it made this thing sound like a Marshall! 2. Increased preamp plate voltages = More gain out of the 12AX7s. I did this by reducing the 10K resistor in the power section to the preamp to 4.7K/2W. 3. INcreased main filter to 80uF. more "oomph" on the lows. 4. Put NOS 6L6GCs in. RCA black plates. Checked th ebias at 72mA per tube! THis amp is cathode-biased and will run more current that way. I have the volume up enough that is gets smokin about 1/2 way up. When I turn the volume higher, i get more dynamics. Im going to try a new speaker to, as this one is in pretty bad shape. I also redrew a schematic for it today. It is the same power section as the Thunderbolt- just verified that. Preamp is done very similar to a Gibson GA-30 amp, or Tweed Tremolux. My "mods" optimize the gain out of the preamp. It still isnt a super loud amp, but I will try it out this weekend. anyone intereste din my schematics. email me.
Dave
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Ken Fox
Member From: Ray City, GA USA
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posted 13 February 2006 06:51 AM
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I sent a schematic in Acrobat format for the Supro Thunderbolt. Check your email![This message was edited by Ken Fox on 13 February 2006 at 06:51 AM.] |
Jim Sliff
Member From: Hermosa Beach California, USA
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posted 13 February 2006 07:01 AM
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"Yup, its the same amp. cool amp, but I'm gonna make it have more guts."Just please don't do anything that's non-reversible. Those amps are classics, and IMO should be left stock. I don't have a huge problem with reversible mods though - just don't drill holes or cut things! Personally, if amp doesn't have enough punch or the wrong gain structure, I think the best solution is to get an amp that's right for you rather than modding a vintage piece. |
Dave Zielinski
Member From: Pennsylvania, USA
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posted 13 February 2006 09:10 AM
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I agree 100%, an DO NOT mod anything permanently. no holes, just updated filter caps and such. added a few parts, never really REWIRE soemthign to make it what it is not. like making a supro into a marshall. I simply increased the gain structure in the preamp to get giggable volume out of it. it still sounds like a supro, just with more "oomph"I keep all the old parts and marked up drawings, sometimes pics, so i can return it to stock if i sell it. im a player, not a collector. I have more guitars and amps that were pieced together from someone elses screw ups, than i like to admit. for the sake of playability, ANY old tube amp is better off with updated filter caps. is changing a speaker a "mod"? most old amps sound bettter with new, more efficient speakers. My 1960 tweed bassman has the originals, but i replaced them with reissues just cause i dont want to blow the original ones. i think that is a wise "mod". |
J Fletcher
Member From: London,Ont,Canada
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posted 16 February 2006 03:58 PM
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You might want to be careful exceeding the recommended value of 40 uf as the first filter cap. The good old "RCA Receiving Tube Manual" has this to say..." Higher values of capacitance than indicated (40 uf in this case) may be used, but the effective plate supply impedance may have to be increased to prevent exceeding the maximum rating for peak plate current".
You might also try a GZ34 in there. That will probably raise the high voltage 20 or 25 volts. At that point you would need to ensure that you are not exceeding the voltage ratings for capacitors, or the plate dissipation rating of any tubes. As usual, just my 2 cents..Jerry |
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