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#47
11-17-2008, 10:56 PM
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BTW it did look like Crate screwed up the reverb circuit in the V18: the V33 uses a 100k feedback resistor in the reverb recovery circuit, while they switched that to a 220k resistor in the V18 for over twice as much gain in the signal coming back from the springs. (That is reference number R38 in the V18). The Accutronics tank sounds like a great upgrade but if someone doesn't have the bucks (~$40?) replacing R38 with a 100k resistor, and R40 with a 470k resistor goes a long ways towards making the stock reverb a lot more usable. Actually I have 3 of those Accutronics tanks in various Peavey amps so I could try swapping one in to see how my mods work with that tank... BTW have you upgraded any of the tubes? Steve Ahola P.S. If it seems like I am mod crazy, that's probably because I am...  I bought 3 of the V18-112's specifically to screw around with, trying out different designs in them. I'll be testing out a Soldano SLO design in one of them and a Maz Junior in another... But it's really great that you did a few mods to your amp and are very happy with it- it's *your* amp now, not just something that you bought in the store. :BEER Last edited by steeve_a; 11-17-2008 at 11:10 PM. 
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#49
11-18-2008, 08:26 AM
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Crate emailed me the schematics for the v50. The schematic for the v50 appears to be the same as the v33 except for around the power tubes and R77 being dropped. R4 is the same, is it a good idea to change R4 to the 2.2M value? Since R77 isn't there for the v50 I was wondering what it's purpose was in the v33 head? I guess changing the slope resistor would also be beneficial for the v50 since the circuits are nearly identical? Haven't received the amp yet, ordered it last week from Music123, looking forward to trying these mods out.
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#50
11-18-2008, 09:59 AM
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It sort of depends on what the amp sounds like to begin with for whether or not you should do them. R77 in the V33 (R10 in the V18) sends some of the signal to ground. It reduces the gain at the second gain stage a bit and that helps to clear up that muddy OD. I guess Crate thought the V50 doesn't need that. If you really needed to you could probably rig up a custom R77...
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#51
11-18-2008, 10:26 AM
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There's an empty spot on the board of the v50 for the R77 resistor. If I put the R4 into the this R77 spot will the resistor now become part of the circuit assuming that all the circuit traces are the same for both boards, be it v33 or v50?
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#52
11-18-2008, 11:46 AM
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I would just go to radio shack and get a pack of 2.2m resistors (if they have them) and some 1m resistors too. 1/2 watt. While you're there you could get some 100k resistors for the slope resistor (R17 on the V33). Then you could try a 2.2m in R4 or a 1m if you can't get a 2.2m. You can always order 2.2 meg resistors from someplace. Then again you could be different and try a 1m in R4 and R77 and see how that is. So many possibilities.... Also, it would be cool if you could email that schematic to Steve at blueguitar.org so he could post it for all to enjoy!
Last edited by dvnator; 11-18-2008 at 12:01 PM.
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#54
11-19-2008, 09:38 AM
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OK something is wrong. I went to play a bit now and the and will give me nothing but clean, no matter where the gain knob is. all the gain knob does is alter the volume a bit (teeny weeny bit). I haven't changes anything since I last wrote here. And it was playing fine when I last turned it off. Now I turn it on and its like this? Doesn't make sense. The only variable is that its a pretty cold day now. I thought that might have something to do with it and left the amp on for a while and played with it for a while just in case it warming it up was gong to make any difference but it did not. I also swapped out V1,2 and 3 just to make sure I hadn't blown a tube but no. Any ideas?
BTW the I cant get the volume to go up with the gain low. with the gain at about 3 I can max out the volume and I get a living room music volume at most. This sucks,I finally find the tone Im looking for and now its gone. I hope its not for good. Last edited by Helder22; 11-19-2008 at 10:37 AM.
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#55
11-19-2008, 11:19 AM
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I would check all the soldering you did. The slope resistor because it was the last thing but especially the 470k resistor at R4. That resistor sends some signal to ground. It could be it's sending a lot more signal to ground than it should be. I would go ahead and replace that 470k resisitor with a new one and make sure it soldered in nice and neat.
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#56
11-19-2008, 11:51 AM
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I can't believe this didn't dawn on me before about the resistor swap but after looking at the v33 and v18 schematics, and the differences in the numbering, R4 really is swapped.
In the stock v33 the resistor labeled R4 is part of the high pass filter with C5. (R10 in the v18) In the v18, R4 is the resistor to ground (R77 in the v33). I'm probably not explaining this very well but if you look at the schematics you'll see what I mean. Maybe it's just a coincidence with the numbering but, still, sort of strange...
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#58
11-19-2008, 12:20 PM
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If it makes you feel any better sh*t like that happens to all of us! So you go back in and double check all of your solder joints. I'd leave the back off when I fire it back up and if I was still having problems I would measure the voltages at all of the tube pins. You might also ohm out the gain pot to see if maybe something inside is shorting it out to ground. Good luck- once you find and correct the problem your good tone will be back! Steve Ahola
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